KR20120082912A - Dimmable lighting system - Google Patents

Abstract

A lighting system is disclosed that operates using a light adjuster circuit 1 comprising a triac TR1 connected to a load. The load includes a driver circuit for supplying current to a light source comprising one or more LEDs LED1-4, the current being determined at least in part by an adjusted setpoint value. The system comprises a setpoint filter circuit 20 for obtaining a light adjuster setpoint value 21 and for generating an adjusted setpoint value 24 at least partially determined by the setting of the light adjuster circuit 1. It further includes. The sensitivity of the adjusted setpoint value to changes in the illuminator setpoint value is low at the lower of the illuminator adjuster values.

Description

Dimmable Lighting System {DIMMABLE LIGHTING SYSTEM}

The present invention relates to a dimmer triggering circuit for low load applications such as LED-based light sources. The present invention further relates to a light adjuster system comprising such a light adjuster triggering circuit.

In general, phase-controlled dimmers include a triode for alternating current, also referred to as triac. Triacs are bidirectional switches that conduct current in either direction when triggered, ie when turned on. This can be triggered by the positive or negative voltage applied to its gate electrode, ie when a small current is applied to its gate. This current only needs to be applied for a short time period, ie approximately microseconds. In other words, the triac needs to be triggered or 'fired'. Once triggered, the device causes the current through it to be below a certain threshold, such as at the end of the half-cycle of an alternating current (AC) mains supply, also referred to as zero-crossing. Continue to conduct current until it descends. As a result, the triac is then 'turned off'.

These dimming regulators are effective at dimming incandescent light bulbs that draw relatively high currents. When these dimming regulators are used with smaller loads, such as light sources based on light emitting diodes (LEDs), they face various problems. This occurs especially when replacing standard incandescent bulbs with LED retrofit bulbs in situations where a conventional triac dimming regulator is installed for use with the bulb.

The LED light source may not draw enough current so that the triac in the dimming regulator is turned on as needed, which may result in dimming for light or irregular operation of the dimming regulator. Small resistive loads on the dimming regulator can cause oscillation of the voltage at the dimming regulator output caused by multiple firings of the triac and can cause inaccurate dimming behavior. In low dimming settings, the LED driver circuit can cause a short flash of light from the LED light source while naming. Moreover, the human eye generally senses light intensity along a logarithmic curve, such that the LED has a nearly linear response and the light intensity emitted is almost proportional to the current flowing through the LED. When operated using a conventional dimming regulator, the LED light source does not smoothly dimming and the change in sensed light intensity does not have an intuitive relationship with the knob position of the dimming regulator. Small changes in power supply voltage can also cause visible flickering of light emitted by the LED light source.

The present invention attempts to solve various of these problems, in accordance with various embodiments. According to one aspect, the invention relates to a lighting system operating using a dimming circuit comprising a triac connected to a load. The load includes a driver circuit for supplying current to a light source comprising one or more LEDs, the current being determined at least in part by the adjusted setpoint value. The system further includes a setpoint filter circuit for obtaining the illuminator setpoint value that is at least partially determined by the setting of the illuminance regulator circuit and for generating the adjusted setpoint value. The sensitivity of the adjusted setpoint value to changes in the illuminator setpoint value is low at the lower of the illuminator setpoint values.

The setpoint filter circuit can be configured to increase the adjusted setpoint at a lower rate at lower values of the dimming set point value and at a higher rate at higher values of the dimming set point value. The change in the adjusted setpoint value in response to changes in the illuminance controller setpoint value is preferably close to the exponential response. The setpoint filter circuit preferably generates a full range of adjusted setpoint values over a full range of illuminance setpoint values, and preferably generates a adjusted setpoint value having a minimum value greater than zero.

The setpoint filter circuit also has a first substantially constant value during the dimming set point value in the first range, increases at a low rate during the dimming set point value in the second range, and sets the dimming set in the third range. It may be configured to increase at a high rate during the point value and generate an adjusted setpoint having a second substantially constant value during the dimming set point value of the fourth range.

The setpoint filter circuit may also include a second or higher order low pass filter that filters the received dimming set point value. The setpoint filter circuit may include a differential amplifier for generating an intermediate setpoint value, which controls the transistor to generate an adjusted setpoint value.

The driver circuit can be designed using a voltage control circuit and a current control circuit, where the voltage control circuit controls the voltage at the output of the driver circuit in accordance with the voltage set point, and the current control circuit in accordance with the set point voltage set point. Change The current control circuit can be designed to operate within a predetermined range, where the voltage setpoint is maintained at the boundary value when the current control circuit is at the boundary of its operating range.

The setpoint filter circuit may obtain a light adjuster setpoint value from the voltage at the output terminal of the light adjuster circuit. The setpoint filter circuit can alternatively derive the dimmer setpoint value from the firing angle of the dimming regulator triac, which is a time delay between zero crossing of the supply voltage and the first triggering of the triac after the zero crossing point. Can be derived from

The lighting system may also include a dimming triggering circuit that triggers the dimming triac, wherein the dimming setpoint value is one or more occurrences of rising and / or falling edges of current flowing through the dimming triggering circuit. It may be determined at least in part by time or by the voltages associated with the rising and falling edges. Thus, the dimmer setpoint value may be determined at least in part by the time delay between the rising and falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges. The illumination system of the present invention can be designed to operate when the current through the dimming circuit is less than the holding current of the dimming regulator triac when the dimming regulator triac is on.

The lighting system can include a dimming triggering circuit that triggers a dimming triac, wherein the dimming triggering circuit includes a voltage-level detector for detecting whether the input voltage of the dimming triggering circuit is below a threshold, and a voltage-level detector. A bipolar current source circuit that provides a current if the voltage detected by the threshold is below a threshold and is otherwise deactivated. The lighting system can be designed such that the maximum current through the dimming trigger triggering circuit is less than the holding current of the dimming regulator triac and the current through the dimming trigger triggering circuit is less than the holding current of the triac when the dimming regulator triac is on. The dimming triggering circuit can be designed such that the dimming triggering circuitry loses less than 100 kW average power during operation.

In another aspect, the invention also uses in a lighting system that includes a triac dimming circuit, a light source comprising one or more LEDs, and a driver circuit for supplying current to the one or more LEDs. And a current is determined at least in part by the adjusted setpoint value. The setpoint filter circuit includes an input circuit for obtaining a light adjuster setpoint value determined at least in part by a setting of the light adjuster circuit, and an adjusting circuit for generating an adjusted setpoint value, wherein the light adjuster set The sensitivity of the adjusted setpoint value to changes in the point value is low at the lower of the dimming set point values.

The setpoint filter circuit may be designed to increase the setpoint adjusted at a lower rate at lower values of the dimming set point value and at a higher rate at higher values of the dimming set point value, the dimming set point value. The change in the adjusted setpoint value in response to the changes in may be close to the exponential response. The adjustment circuit may be configured to generate a full range of adjusted setpoint values over a full range of illuminance setpoint values, and may generate a adjusted setpoint value having a minimum value greater than zero. The input circuit may include a second or higher order low pass filter to filter the received dimming set point value. The adjustment circuit includes a differential amplifier for generating an intermediate setpoint value, which controls the transistor to generate an adjusted setpoint value.

The setpoint filter circuit can derive the dipper setpoint value from the voltage at the output terminal of the illuminance regulator circuit. The dimmer setpoint value may also be derived from the firing angle of the dimming regulator triac, which determines the dimming setpoint value from the time delay between zero crossing of the supply voltage and the first triggering of the triac after the zero crossing point. Can be obtained by deriving.

In another aspect, the invention is directed to an illumination system operating using a dimming circuit comprising triacs, wherein the system is adapted to trigger a dimming triac, and a light source comprising one or more LEDs. A load comprising a dimming regulator triggering circuit and a driver circuit for supplying current to one or more LEDs (LED1-4), wherein the current supplied by the driver circuit is at least by a value of the dimming set point; Partially determined, wherein the illuminator setpoint value is derived at least in part from the firing angle of the illuminator regulator triac.

The driver circuit preferably derives the dimmer setpoint value from the time delay between zero crossing of the supply voltage and the first triggering of the triac after the zero crossing point. The dimmer setpoint value may be determined at least in part by the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges. The dimmer setpoint value may be determined at least in part by a time delay between the rising and falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges.

The driver circuit may include a voltage control circuit and a current control circuit, where the voltage control circuit controls the voltage at the output of the driver circuit in accordance with the voltage set point, and the current control circuit in accordance with the current set point. Change The current control circuit preferably operates within a predetermined range and the voltage set point is maintained at the boundary value when the current control circuit is at the boundary of its operating range. The lighting system can be configured such that when the dimming triac is on, the current through the dimming circuit is less than the holding current of the dimming triac, and the maximum current through the dimming triggering circuit can be less than the holding current of the dimming triac. have. The lighting system can be configured wherein the current through the dimming triggering circuit is less than the holding current of the triac when the dimming triac is on and the dimming triac is off. The lighting system may also include a setpoint filter circuit for generating an adjusted setpoint value from the dimming set point value, wherein the sensitivity of the adjusted set point value to changes in the dimming set point value is Low at the lower of the dimming set point values.

A further aspect of the present invention relates to an illumination system operating using a dimming circuit comprising triacs, the system comprising a light source comprising one or more LEDs, and an illuminance for triggering the dimming triac A load comprising a regulator triggering circuit and a driver circuit for supplying current to one or more LEDs, the driver circuit including a power factor correction circuit, the current supplied by the driver circuit being a dimming set point value. Determined at least in part by the dimming set point value derived at least in part from the firing angle of the dimming regulator triac.

Figure 1 schematically shows a conventional dimming regulator connected to an incandescent bulb.
2A is a diagram of an exemplary waveform of an AC supply voltage across the dimming circuit.
2B and 2C are diagrams of exemplary waveforms of voltage across the dimmer load at different dimmer settings.
3 is a schematic diagram of an illumination system according to an embodiment of the present invention including a dimming trigger triggering circuit connected to an LED light source.
4 is a schematic diagram showing additional details of a dimming trigger triggering circuit for use in an illumination system according to an embodiment of the invention.
5 is a schematic diagram of another embodiment of the dimming triggering circuit.
6 is a simplified circuit diagram of an embodiment of the dimming regulator triggering circuit.
FIG. 7A is a diagram of voltage-current behavior between terminals of the dimming trigger triggering circuit of FIG. 6.
7B is a diagram of voltage-current behavior between terminals of an embodiment of a dimming regulator triggering circuit including a microprocessor.
8 is a simplified circuit diagram of an embodiment of a setpoint filter circuit.
9A is a diagram illustrating an example of a change in the adjusted set point with two slopes.
9B is a diagram illustrating an example of a change in the adjusted setpoint approaching an exponential response.
10 is a simplified circuit diagram of the secondary side of an embodiment of an LED driver circuit.
FIG. 11A shows an example of the dimming regulator output voltage when the dimming regulator triac current exceeds the holding current of the triac. FIG.
FIG. 11B is a diagram showing an example of the dimming regulator output voltage when the dimming regulator triac current does not flow or is less than the holding current of the triac.

The following is a description of specific embodiments of the present invention, which are provided by way of example only. Figure 1 schematically shows a conventional dimming regulator 1 connected to a load 3, which is generally an incandescent bulb. The illuminance regulator 1 comprises a triac TR1 connected in parallel to a series variable resistor R1 and a capacitor C1. In this description, the combination of resistor R1 and capacitor C1 will be referred to as an RC circuit or a timer circuit. In addition, the illuminator includes a triggering component, i.e., a component suitable for triggering the triac TR1. In general, a diode for alternating current (diac) is used for this purpose. A diac is a bidirectional trigger-diode that conducts a current after a diac threshold voltage, also referred to as a diac trigger voltage, is exceeded. Diaak maintains the conductivity while the current flowing through it remains above the threshold current. If the current decreases below the threshold current, the diaak switches back to a high-resistance state. These features make Diaak well suited as a trigger switch for triacs.

The illuminance regulator 1 of FIG. 1 includes a diac D1, which is connected between the variable resistor R1 and the capacitor C1 at the first end and the second at the second end. It is connected to the gate of the triac TR1. The illuminance regulator 1 has two terminals, namely terminals T1 and T2. The illuminance regulator 1 and the load 3 (bulb) of the illuminance regulator 1 are connected in series across the AC voltage source.

As mentioned above, the triac TR1 is turned off when the current through the triac TR1 drops below its threshold. Passing zero crossing of the AC supply voltage, the RC circuit will 'see' the actual AC supply voltage and C1 will charge. Note that this charging current also flows through the incandescent bulb 3. When the voltage across C1 reaches the trigger voltage of DIA (D1), during discharge of capacitor C1, DIAC starts conduction and supplies current to the gate of TR1. As a result, the triac TR1 is triggered and turned on, at which time current begins to flow through the triac TR1 and the capacitor C2 is discharged.

For example, by adjusting the resistance of R1 by a dimmer knob or the like for operating the potentiometer, the time required to reach the diac trigger voltage across C1 can be set. Higher value resistor R1 will require longer time to reach the diac trigger voltage for C1, thus shorter conduction interval of triac TR1. It will be appreciated that by adjusting the time the current flows through the triac TR1, a voltage can be applied to the bulb 3 so that the illumination intensity of the bulb 3 can be adjusted.

Components for filtering the electromagnetic interference (EMI) generated by the switching of the triac TR1 can be added to the basic light regulator circuit described above. For example, the capacitor C2 may be included across the inductor L1 and the triac TR1 in series with the triac TR1. These additional components help to reduce EMI, while capacitor C2 across the triac may cause the dimming regulator 1 (and load 3) to trigger the triac and charge capacitor C1. It will increase the current required to flow through. This is because this current must charge both capacitors C1 and C2.

2A is a graph showing the waveform of the AC supply voltage across the terminals T1-T3 across the illuminance regulator 1, and FIGS. 2B and 2C show the variable resistor R1 presupposing the resistive load 3. Shows an approximate waveform of the resulting voltage across the load 3 (terminals T2-T3) at different dimming regulator settings. The AC supply voltage becomes zero at the zero-crossing point t0 of the half period. At this point, the triac stops conducting and the voltage across the load 3 approaches zero. The voltage across the load 3 is not exactly zero because some current will continue to flow through the series-connected dimming regulator 1 and the load 3, for example, capacitors C1 and C2) is the current to charge.

As shown in FIG. 2B, at time t1, the capacitor C1 is sufficiently charged to trigger the diaak D1, which in turn triggers the triac TR1, and the voltage across the load 3. Is increased close to the supply voltage, and the current through the load 3 also increases significantly. When the load is high enough, the triac remains on until the next zero-crossing point t0. Thus, during each half period period A, the triac is off and the capacitor C1 is charged. The charge rate of C1 and the length of time of the period A depend on the setting of the dimming regulator, ie the resistance of the variable resistor R1 as set by the dimming knob. During period B, the triac is on and the load 3 is connected across the supply voltage and the normal operating current flows through the dimming regulator and the load. As can be seen by the waveform of FIG. 2B, the average voltage during each half cycle decreases slightly, resulting in a small decrease in the current flowing through the resistive load, which is visible as a small dimming when the load is a bulb. .

In FIG. 2C, the dimming regulator setting is changed to increase the resistance of the variable resistor R1 to further diminish the light. At time t2, capacitor C1 is sufficiently charged to trigger diac D1 and triac TR1, and the triac is maintained until the next zero-crossing point t0. Thus, for a longer period (C), the triac is off and for a shorter period (D) the triac is on. Thus, the waveform in FIG. 2C has an average voltage that is greatly reduced during each half cycle, resulting in a large decrease in current flowing through the load, resulting in a large amount of illuminance control when the load is a bulb. It can be seen that the dimming regulator performs phase control by adjusting the delay after zero-crossing after the triac is turned on, also referred to as the firing angle of the triac.

The dimming regulators, such as the dimming regulator 1 of FIG. 1, provide a sufficiently high load when the triac is off to properly charge the capacitor C1 and thus diminish the load, such as an incandescent bulb, that draws enough current. If the illuminance regulators are used for this purpose, they perform an appropriate function. That is, after zero-crossing of the supply voltage, the current flowing through the load needs to be high enough to enable recharging of the capacitor C1 (and C2) in the RC circuit. If a sufficiently high current does not flow through the load 3, the triac TR1 will not be triggered at all or will only be triggered when the dimming knob is set so that the resistance of R1 is sufficiently low. A common result is that the dimming function of the dimming device 1 is not working, that is, the light cannot be dimmed.

Loads such as incandescent bulbs of sufficient power provide a current path for charging the RC circuit, which is essential for the proper functioning of the dimming device 1. However, nowadays there are low load and discontinuous applications (eg, built-in rectifiers and capacitors) that do not draw enough current for the proper functioning of the dimming regulator 1. That is, insufficient current is provided to the load for proper charging of the RC circuit after zero-crossing of the supply voltage.

A well known example of low load application is an LED light source that includes an electronic circuit that drives one or more light emitting diodes (LEDs) that require a DC current. LED circuit 13 generally includes, in addition to one or more LEDs, a rectifier and one or more smoothing capacitors, and thus may be a discontinuous load. In this description, embodiments of the present invention will be further described in combination with LED circuits. However, embodiments of the present invention provide for other low load or discontinuous load applications, namely the RC timer circuit of the light adjuster, which enables the proper functioning of the light adjuster, such as the light adjuster 1 schematically shown in FIG. It should be understood that it can also be used in combination with applications that are unable to provide the necessary charging current for it. Loads with smoothing capacitors at the rectifier front-end may be considered to be discontinuous load applications.

3 schematically shows a light regulator system 10 according to an embodiment of the invention connected to an LED circuit 13. The dimming system includes a dimming regulator 1 and a dimming regulator triggering circuit (DTC) 12 connected in series across the AC supply voltage. The LED circuit 13 is connected in series with the illuminance regulator 1 and in parallel with the DTC 12. The combination of the DTC 12 with a load, such as the LED circuit 13, may be referred to as a dimmable device.

4 and 5 schematically show the DTC 12 in more detail. The DTC 12 includes a bipolar current source circuit 18 including a current source circuit 17 and a rectifier 19, and a voltage-level detector 15. The voltage-level detector 15 is connected to the current source circuit 17, and both the voltage-level detector 15 and the current source circuit 17 are connected to the DC terminals of the rectifier 19.

The voltage-level detector 15 is arranged to detect the absolute value of the voltage difference between the terminals T2 and T3, that is, whether the output of the rectifier 19 is below the threshold. The positive current source circuit 18 is arranged to be activated if the voltage detected by the voltage-level detector 15 remains below the threshold and otherwise to be deactivated. Thus, the positive current source circuit 18 in the DTC 12 is a voltage-dependent current source, and as a whole the DTC 12 can be considered to operate as a positive voltage-dependent current source. As described in more detail below, this DTC 12 may be designed to dissipate less than 100 kW average power. In a well-dimensioned embodiment, the DTC 12 may lose an average power of 10-50 mA. Preferably, the loss of DTC 12 is about 30 ms. With this loss, most conventional dimming regulators can operate as intended.

The voltage-level detector 15 may comprise a microprocessor. The microprocessor is then arranged to detect whether the absolute value of the input voltage of the dimming regulator triggering circuit 12 is below a threshold. If the input voltage of the dimming regulator triggering circuit 12 is below a threshold, the microprocessor may provide a signal to instruct the positive current source circuit 18 to provide a current. In some embodiments, as described in more detail with reference to FIG. 5B, the microprocessor may direct the bipolar current source circuit 18 to provide current after zero-crossing of the input voltage.

The voltage-level detector 15 may include a comparator for detecting whether the rectified input voltage is below a threshold. The comparator includes two inputs and one output as schematically shown in FIG. 5. The first input has a reference potential, i.e. a threshold? In this example, 30V? Is connected to the same potential as. The second input is arranged to receive the input voltage of the dimming regulator triggering circuit 12. If the input voltage of the dimming regulator triggering circuit 12 at the second input of the comparator is less than the threshold at the first input of the comparator, the output of the comparator provides current as discussed above with the positive current source circuit 18 discussed above. Can be done. Operational amplifiers or voltage comparators may be used to implement the comparators and will be understood by those skilled in the art.

The rectifier 19 has terminals connected to the AC-side, i.e., terminals T2 and T3, respectively, and the current-source circuit 17 and the voltage-level detector 15 in the DC-side, i.e., the anode current source circuit 18. And other components in the DTC 12, such as, and terminals connected to a reference potential. The voltage-level detector 15 and the current source circuit 17 form a single pole circuit. The rectifier 19 is arranged such that the current generated by the current source circuit 17 can be supplied to the illuminance controller as the anode current.

The DTC 12 causes the light adjuster 1 to operate as if it were loaded by a regular incandescent lamp. If the AC supply voltage is sufficiently low, i.e., below the threshold described above, the DTC 12 is activated to allow sufficient current to flow into the RC circuit of the illuminance regulator 1. If the AC supply voltage is high enough, i.e. above the threshold, the DTC 12 is deactivated to draw no significant amount of current, thus minimizing wasted power. It should be noted that as the voltage-level detector 15 is located on the DC-side of the rectifier 19, only an absolute threshold is needed. This means that if the threshold is 30V, the DTC 12 is activated in the range of -30V to + 30V.

In some embodiments of the DTC 12, when used in connection with a main power system of 230V at 50Hz, the threshold lies between 3V and 50V. In other embodiments of the DTC 12, the minimum threshold is 10V. For example, as used in the United States, when the DTC 12 is connected with a 120V main power system at 60Hz, the threshold may lie between 3V and 25V.

For example, as shown schematically in FIG. 1 with respect to the triac TR1 being triggered by the diac D1, the current provided by the DTC 12 may be triggered by the triac in the dimming regulator. Until the voltage across the load is effectively maintained at zero. As soon as the triac is switched on, the voltage at terminal T2 increases by a significant amount. As a result, the current source circuit 17 in the DTC 12 is deactivated.

Ideally, therefore, the DTC conducts current only when the voltage at T2 exceeds the threshold, otherwise the DTC behaves like an open circuit. In practice, however, any current will flow through the DTC while being deactivated. Preferably, the current provided by the current source circuit 17 in the DTC 12 upon deactivation is negligible. If the current is at least two orders of magnitude less than the maximum current that the current source circuit 17 of the DTC 12 can provide, this current can be considered negligible. For example, if the maximum current provided by the current source circuit 17 in the DTC 12 is 15 mA, the current is considered negligible if the value is kept below 100 mA.

After zero-crossing, discontinuous load That is, if a load? Is drawn alone that draws discontinuous current such that the current is zero for any portion of the voltage cycle, the DTC 12 complementarily acts according to the state of the triac in the dimming regulator. That is, if DTC is on, the triac in the illuminator is off, and vice versa. A bridge rectifier with a capacitor at the output is one example of a discontinuous load.

On the other hand, if another load other than the discontinuous load is provided, after the zero-crossing, the dimmer 12 is cut off until the input voltage of the DTC 12 exceeds the threshold described above and the DTC 12 is shut off. Both the triac and DTC 12 in 1) can be turned on at the same time. In this case, the triacs and DTC 12 in the illuminance regulator 1 do not act completely complementary. During a few milliseconds, power is lost when both DTC and Triac are on. However, this lost power is negligible. For example, for a current source circuit 17 provided to provide a threshold of 30V and a current of 20 mA, the peak power will typically not exceed 0.6 W (only during very small intervals the peak power will be Occur, the average power will not exceed 30 mA.

In general, when passing through zero-crossing, the triac is turned off (if the triac was on) while the DTC 12 remained on. When the triac is turned on, the DTC 12 is turned off. Thus, the DTC is arranged to supply current when the absolute voltage at T2 is below the threshold. This current only needs to be sufficient to recharge the capacitors in the RC circuit of the dimming regulator and is independent of the triac's holding or hypostatic current or the minimum load of the dimming regulator in question. The current through the DTC 12 may be less than the holding current of the dimmer triac when the DTC is activated (triac is off) and when the DTC is deactivated (triac is on). This provides the advantage that the DTC 12 can also be used in combination with a triac having a holding current greater than the maximum current provided by the DTC 12. Thus, even if the DTC 12 can provide a maximum current of, for example, 20 mA, a dimming regulator comprising a triac with a holding current greater than 120 mA, for example 100 mA, may be used for low load applications. It can be used to enable light control.

In order to enable proper functioning of the DTC 12 in the lighting system, for example, when connected to an LED circuit 13 as shown in FIG. 2, the rectifier 19 can be Capacitance on the AC-side is preferably minimized. Preferably, there is no additional capacitance between the terminals T2 and T3.

Thus, the DTC 12 can be used to provide a method for triggering the dimming regulator in an alternating current circuit. This method will include detecting whether the absolute value of the input voltage of the DTC is below a threshold. Then, if the detected voltage is below the threshold, current is provided by the current source circuit, which is the current flowing through the DTC and the dimming regulator. If the detected voltage is not below the threshold, only negligible current flows through the DTC and the dimming regulator. Before detecting the value of the DTC input voltage, the input voltage can be generated by rectifying the AC voltage of the AC current circuit. Subsequently or alternatively, the input voltage can be converted to a voltage suitable for detection. As a result, the current provided by the current source circuit can be limited.

6 shows a simplified circuit diagram of an embodiment of a DTC, such as the DTC 12 shown in FIGS. 3 and 4. It should be understood that this embodiment is one example of one possible implementation of the invention. As will be appreciated by those skilled in the art, many implementations are possible. For example, instead of bipolar NPN transistors, other switches such as bipolar PNP transistors, integrated gate bipolar transistors (IGBTs) or metal oxide semiconductor field effect transistors (MOSFETs) may be used. In this embodiment, the anode current source circuit 18 again comprises a current source circuit 17 and a rectifier 19. Rectifier 19 includes a full-wave diode bridge rectifier. The current source circuit 17 includes two resistors R2 and R3, and two NPN transistors Q1 and Q2. The voltage-level detector 15 includes an NPN transistor Q3 and two resistors R4 and R5.

In this embodiment, the DC voltage source V1 is connected to the collector of the transistor Q3 of the voltage-level detector 15. Resistor R6 is selected such that when Q3 is off, the desired base current is applied to Q1. The DC voltage source V1 may be an external voltage source. It is to be understood that instead of DC voltage source V1 and resistor R6, a current source may also be used to obtain the desired base current. Resistors R4 and R5 form a voltage divider designed such that the voltage at T7 is Q3 off if the voltage at T4 is below the threshold.

In this embodiment of the current source circuit 17, the collector of Q1 is connected to the terminal of the rectifying diode bridge as indicated by T4. The base of Q1 is connected to the collector of Q2 and is also connected to the collector of Q3 in the voltage-level detector 15. If the voltage at T4 is below the threshold described above, Q3 will be off and R6 will now provide current to the base of Q1. As a result, the voltage at T6 increases so that Q1 turns on. As a result, Q1 conducts current and depending on the impedance of the current source, the voltage at T4 decreases even more, which results in a much lower voltage at T7. As a result, the switch-off time of Q3 is limited. If the current through Q1 exceeds a certain value, the base voltage of Q2 exceeds its switch-on voltage, Q2 begins to conduct, and at the same time stabilizes the potential at T6, thus controlling the collector current through Q1. . The resistors R2 and R3 have suitable characteristics? That is, it is used to design a current source having transistor Q2 start to conduct when the emitter current through transistor Q1 exceeds a certain value, for example, a nominal current in the range of 10-20 mA. Thus, the combination of transistor Q2 and resistors R2 and R3 provides a feedback circuit that effectively limits the collector current of transistor Q1. R3 sets the current to approximately 0.6 / R3, and R2 functions to protect Q2 when the triac is fired. The combination of transistors Q1 and Q2 with resistors R2 and R3 forms a stable current source circuit 17 for voltages of T4 higher than approximately 1V relative to the negative terminal of rectifier 19. If the voltage to T4 falls below approximately 1V, the collect current will decrease. To meet EMI requirements, a 220Ω resistor can be added in series to the collector of Q1 to limit the current slope at low voltage levels.

When the voltage-level detector 15 detects that the voltage at T4 is lower than the predetermined threshold, the current source circuit 17 is activated, and when the voltage at T4 again rises above the predetermined threshold. Deactivated.

To obtain a DTC 12 designed to supply 15 mA of current when the voltage at T2 is between −30 V and 30 V, typical values of the components shown in FIG. 6 are as follows: R 2 = 4.7 mA; R 3 = 27 Hz; R4 = 6.6 kW (generally constructed by placing two resistors in series with a value of 3.3 kW); R 5 = 100 Hz; R 6 = 47 Hz; Q1 = FMMT458; Q2 = BC817; Q3 = BC817; V1 = 10V. The current provided to the components provided by the DTC 12 shown in FIG. 6 and having the values described above during activation would be approximately 20 mA, but ideally during deactivation the current would be approximately 49 mA. Adding leakage current through transistor Q1 can add several kHz.

7a schematically shows a graph of the calculation of the behavior of the current through the current I _DTC , ie DTC, as a function of the voltage V _DTC , ie the voltage across the DTC. In this calculation, the DTC of FIG. 6 is used in which the conventional values described above are used for the respective components. As a result, the DTC is arranged to supply a maximum current having an absolute value of 20 mA when the voltage across the DTC is lower than the threshold of 30 V. Due to the rectifier, current can be supplied to the dimming regulator in opposite directions.

It can be noted that when V _DTC approaches zero, I _DTC becomes equal to zero and quickly rises to a design current at a specific value of V _DTC , in which case I _DTC does not exceed 20 mA. The low current close to 0 V _DTC is due to the fact that at low voltage the current source circuit 17 only supplies the current as needed, ie the dimming regulator 1 only needs a limited current to charge its timer circuit. (During the orientation on the grid, the current will be higher). The shape of the curve shown in FIG. 7A, associated with the current source circuit 17 shown schematically in FIG. 5, is the result of transistor Q1 being saturated at low voltages.

FIG. 7B schematically illustrates a graph of voltage-current behavior between terminals of the embodiment of the dimming triggering circuit of FIG. 4 that includes a microprocessor or direction sensing component. As shown in FIG. 7B, just before the passage of zero-crossing, the DTC 12 can be switched on simultaneously while the triac in the illuminator 11 is also on. As a result, power is dissipated for a short period of time, i.e. for the time required for the voltage across the DTC 12 to progress towards zero from the threshold. In an embodiment that includes a microprocessor as the voltage-level detector 15, the microprocessor may be programmed in a manner that only allows the positive current source circuit 18 to be activated after the passage of zero-crossing. As a result, the voltage-current behavior between the terminals of the DTC 12 becomes as schematically shown in FIG. 7B.

In FIG. 7B, it can be easily seen that I _DTC undergoes some kind of hysteresis. That is, the value of I of the _DTC in the _DTC specific V depends on the previous values of the V _DTC. Portions of the graph that show that I _DTC is independent of past values of V _DTC are shown schematically in gray lines. Portions of the graph that schematically show that I _DTC depends on past values of V _DTC are shown schematically in black lines. The arrows indicate the direction of change of V _DTC .

Set point  Filter circuit

The lighting system as shown in FIG. 3 is generally arranged such that the LED driver circuit in the load 13 includes a current controller for supplying DC current to the LEDs, the light intensity of the DC current and thus the LEDs of the supply voltage. Is independent. The current controller controls the LED current within the limits of the system so that any change in the supply voltage will not produce any change in the LED current. LED current is controlled in accordance with the setpoint, and different current levels result from different setpoint values. In some embodiments of the invention, the average rectified voltage measured using the voltage-level detector 15 of the DTC 12 may be used as a set point for the driver circuit. The setpoint filter circuit can be used to further optimize the dimming of the load. This optimization can illuminate the load over a range different from the dimming set, so that the entire range of adjusted setpoints occurs over the entire range of the dimming set (ie, dimming set point value). For example, the circuit may vary the driver circuit setpoint value by generating an adjusted setpoint value over a range of 0-100% corresponding to a 30-80% dimmer knob setting.

Optimization may also take the form of more sensitive dimming in the low light-intensity regions, i. May take a less sensitive form of dimming. The lighting system includes an LED light source, but the setpoint filter circuit can use it to bring the selected light intensity (ie, selected by the dimmer knob setting) closer to the sensed intensity. Conventional incandescent lamps use electrical power to heat the tungsten filaments so that the tungsten filaments emit light, and typically convert about 10% of the electrical energy consumed into visible light. Incandescent lamps exhibit a progressive response curve and the light generation from the bulb is approximately proportional to the effective voltage for the third power (cubic response). Note that the RMS voltage has a nonlinear relationship to the effective voltage when it is phase-controlled voltage waveforms.

The human eye generally perceives light intensity according to a logarithmic curve. Thus, when the load current is varied linearly by adjusting the dimming regulator, the tertiary response of the incandescent light is rather well matched to the logarithmic response of the human eye, so that the dimming of the light is perceived as relatively linear and smooth. However, LEDs exhibit a nearly linear response rather than a tertiary response, where the luminous intensity is almost proportional to the current flowing through the LED. Thus, if the load current varies linearly, the perceived change in light intensity does not have an intuitive relationship with the knob position of the dimming regulator.

The setpoint filter circuit can be used to adjust the setpoint used by the driver circuit so as to generate a setpoint with a progressive response approaching an exponential change when the light adjuster setting is changed. 8 shows a circuit diagram of an embodiment of a setpoint filter circuit for generating an approximation of an exponential change in the case of a setpoint. The circuit includes a low-pass filter LPF comprising resistors R10-R13 and capacitor C10. The input 20 to the LPF can be taken, for example, from the output of the rectifier of the DTC 12 shown in FIG. 6, or from another point that adequately provides the rectified voltage across the load.

This LPF circuit serves as a barrier between the low voltage circuits of the LED driver and the high voltage input, and obtains a substantially ripple-free set point for the LED current controller, and a point between 0 and 90 degrees. It serves a dual purpose to function as a low pass filter to eliminate flicker of light sources during unstable dimmer performance due to spurious triac firing that may occur at the whistle. Preferably a secondary LPF is used to measure the rectified supply voltage and determine its average voltage, although a primary filter can also be used or a third or higher order filter can be used. These filters also provide sufficient supply, such as a hiccup mode (the driver circuit starts at a (too) low input voltage, switches off again due to lack of supply current, and switches on again when the DC capacitor is recharged). Repeat until this is possible) to provide some time to keep the filtered terminal voltage below the hysteresis threshold.

When the dimming regulator is set to diminish the load, the triac should be off until after the associated phase delay according to the dimming regulator setting, for example, for period C of FIG. 2C.

If the triac is fired between 90 and 170 degrees during a half cycle, the triac firings are generally stable and predictable. However, when the triac is fired to charge the DC-link capacitors (capacitors on the DC side of the rectifiers of the driver circuit) in a very short time, no more current flows thereafter. Next, the triac will turn off because the current drops below the triac holding current (generally only a few hundred microseconds after triggering). Without current flow, the voltage across the driver circuit will follow the supply voltage (eg, the voltage at T2 will follow the voltage at T1).

At triac firing angles between 0 and 90 degrees a double (or multiple) firing of the triac may occur and some firings may be skipped. The double firing illuminates a current that is too small to maintain a load current exceeding the triac's holding current for the triac to turn off again after firing, but sufficient to recharge the capacitor C1 and cause retriggering of the triac. This can occur when the dimmer is connected to a resistive load large enough to be drawn through the regulator circuit. Skipped firings can occur because the triac can only be switched on when the DC-link voltage is lower than the current value of the supply voltage. If the trigger pulse arrives early (close to zero-crossing) the triac will be triggered but will not be fired because the input rectifier does not allow negative current. Appropriate values of the components of the LPF in this embodiment are as follows: 10 ms for R10 and R11, 3.9 ms for R12 and R13, and 22 ms for C10. The LPF is designed as a second-order filter to filter out spurious switching of the dimmer triac.

The output from the LPF is provided to the integrated operational amplifier U10, and the output 22 of U10 is an intermediate setpoint value representing the approximate setting of the dimming knob. It is used to drive the gate of transistor Q10 with a threshold voltage of about 2V and handles the progressive function. The source terminal of Q10 is connected to a voltage divider comprising resistors R18, R19, and R20, and the drain terminal is connected to a reference voltage Vref derived from the standard integrated voltage reference U11. The resulting signal 24 at the source terminal of Q10 can then be used as an input to the current controller of the LED driver circuit.

As the dimming regulator setting is changed to diminish the load, a lower average voltage across the load results in a lower reference voltage (Vref). When the output of U10 is low, transistor Q10 is turned off and the value of adjusted setpoint signal 24 is determined by the output of voltage divider R18 / R19 / R20 and U10. When the output of U10 rises high enough to turn on transistor Q10, the adjusted setpoint signal 24 is determined by the resistors R19 and R20 and the output of U10. In this example, the gate-source threshold voltage of Q10 is utilized to realize a slow adjusting range of between 10 and 40 kV (approximately between 70 V and 130 V average input), with a faster interval of 40 to 305 kV after this range. (Approximately between 130V and 175V) or from any other required maximum value. Appropriate values for the recent embodiment of the circuit of FIG. 8 are as follows: R14 = 278 kPa; R 15 = 680 Hz; R 16 = 470 Hz; R17 = 39 Hz; R18 = 270 Hz; R 19 = 33 Hz; R20 = 1.72 Hz; C11 = 100 Hz; C12 = 100 Hz; C13 = 10 Hz; C14 = 100 ms. For U10, Tecas Instruments' LM358ADR dual operational amplifier can be used; for Q10, Fairchild Semiconductor's 2N7002 N-channel enhancement mode field effect transistor can be used; for U11, an adjustable precision shunt from Zetex Semiconductor or Texas Instruments Regulators may be used.

The output 24 of the setpoint filter can be used as a reference for the LED current controller to approximate smooth dimming for the user. Since the human eye has a logarithmic sense of luminance, "low-gear" and "high-gear" setpoint shapers are implemented. As shown in the example of FIG. 9A, the setpoint filter circuit generates an adjusted setpoint change with two slopes. In the example shown in FIG. 9A, the actual illuminance controller setting SP1 is plotted on the horizontal axis, and the adjusted setpoint SP2 output by the setpoint filter is plotted on the vertical axis. As shown in the figure, over the first portion of the range of illuminance control settings (0-20% in this example), the adjusted setpoint remains at a very low value 34 until the breakpoint, Rising at a slow rate 31 over two portions (20-50% in this example), rising at a fast rate 32 over the third portion of the range (50-80% in this example), It remains at a high value 35 (in this example, 100% unregulated value) over 4 portions (80-100% in this example). Thus, the setpoint filter generates a tuned illuminator setpoint with a "two-gear" progressive response, which approximates the exponential response. This progressive behavior of the adjusted setpoint produces a corresponding progressive response of the light intensity from the LED light source as the dimming controller setting increases linearly, making it aware of a smoother change in luminance due to the logarithmic response of the human eye. do.

This progressive response greatly reduces the sensitivity to dimmer firing angle changes (ie, changes in triac turn-on delay after zero-crossing) at low light settings. Light regulator firing angle changes occur as a result of changes in the AC supply voltage, for example. These changes can cause visible flicker of the dimmed light source, especially at low dimming settings. The adjusted setpoint generated by the setpoint filter circuit shown in FIG. 9A has a flat portion 34 and a small slope 31 at low dimming settings, changing the sensitivity of the lighting system to these variations. Reduce, reduce or eliminate flicker.

The dual-slope adjusted setpoint curve shown in FIG. 9A is an approximation of the ideal exponential response as shown in FIG. 9B. An adjustment setpoint curve with three, four or more slopes can be implemented to approximate a more exponential curve, using techniques known to those skilled in the art. In addition, the microprocessor can also be used to generate a adjusted setpoint that follows the ideal exponential response.

The adjustment setpoint generated by the setpoint filter circuit is used as a setpoint input to the current controller to drive the LEDs. 10 shows a simplified circuit of the secondary side transformer T10 of the LED driver circuit. As described above, the setpoint filter circuit of FIG. 8 generates the setpoint voltage 24 regulated across R20 in a piece-wise linear manner as a function of the output of the integrated amplifier U12. The adjusted setpoint 24 is input to the operational amplifier U12 via a resistor R21, where the integrated circuit is in equilibrium when the voltage across the secondary shunt resistor R24 is equal to the voltage across R20. . The shunt resistor R24 is connected in series with the series-connected LEDs LED1-4. Amplifier U12 coupled with R20-R24 and C15 forms current controller circuit 27.

The output of U12 provides a feedback signal to shunt regulator U11 and optical combiner U13 via resistor R22 and voltage dividers R25 and R26. Optical coupler U13 provides a feedback signal to the fly-back controller on the primary side of T10. This part of the circuit forms the voltage controller circuit 26. The output of U12 can be considered the reference value for the voltage controller around U11. If the current through R24 is too low, the voltage feedback from U12 will result in a higher voltage-control set point. This reduces the current through the optical combiner U13 to signal the fly-back controller to increase its power flow so that a commanded voltage reference is obtained and the required LED current is realized. If the current through R24 is too high, the feedback signal causes a lower voltage set point. The flyback controller will reduce power flow to the secondary side, thus reducing the LED current.

Appropriate values for the embodiment of the circuit of FIG. 10 are as follows: R20 = 1.72 Hz; R21 = 4.7 kPa; R22 = 8.2 Hz; R 23 = 2.7 Hz; R24 = 39 Hz; R25 = 12 Hz; R26 = 2.49 Hz; R 27 = 2.7 Hz; C15 = 1 ms; C16 = 3 Hz. For U12, Texas Instruments' LM358ADR dual operational amplifier can be used, and for U13, NEC's PS2801C-1 optocoupler can be used. For the PWM controller, Texas Instruments' UCC28600 configured to operate in constant-output-voltage-control mode can be used.

Time base Set point  Control

The above-described lighting system can be considered as a system in which both a power signal for driving the LEDs and an information signal for setting the intensity of the LEDs are implemented in the same signal, and an average voltage is applied across the load. Such an arrangement generally depends on the voltage across the load, which depends on the knob-setting of the dimming regulator. When this is not the case, in particular due to the operation of the illuminance controller with low load or discontinuous load, the illuminance control of the load does not always coincide with the setting of the illuminance controller.

As mentioned above, the lighting system described herein may operate at loads below the holding current of the dimming regulator triac. The DTC described above will draw enough current to ensure the trigger of the triac. Once triggered, the DTC will deactivate and draw just enough negligible current. The current flowing through the dimming regulator will drop below the holding current of the dimming regulator triac, in the case of a small load and in the case of a rectifier plus DC-link capacitor load. If the load / driver circuit has an active power-factor corrected front-end, the load behaves more like a resistor and potentially causes repeated recharge and re-ignition of the dimming circuit as shown in FIG. 11B. can do.

11A shows, as described above, when the dimming regulator setting causes firing of the triac at time t1 after the zero-crossing point t0 of each half cycle, and through the dimming regulator triac. When the combined current drawn by the load and DTC immediately after flash-charging the capacitor (s) is zero, the voltage across the load (e.g., across the terminals T2-T3 of the circuit of FIG. 3) The waveform is shown.

Fig. 11B shows that the light regulator has a small resistive load? An example of a voltage waveform at the same dimming regulator setting when connected to? Is too small to maintain a load current exceeding the holding current of the triac. Small resistive loads of this type can be provided in a driver circuit having an active power factor correcting front end that drives a direct current circuit at low power.

At time t1, the triac is triggered and the voltage rises rapidly. However, the current flowing through the triac is not sufficient to keep the triac in conduction, the triac is turned off again and the voltage across the load drops due to the resistive nature of the load. As the voltage across the dimming regulator increases, the RC circuit in the dimming regulator is recharged, reactivating and triggering the dimming regulator triac without DTC. As shown in FIG. 11B, multiple triggering of the triac results in each half cycle. This multiple triggering of the triac may be connected to a resistive load at low power, such as an active power factor correction circuit boost converter with discontinuous switching that the triac-based dimming driver drives the DC link or directly drives the LEDs. Is caused when.

As can be seen by comparing the average voltage during each half cycle of FIGS. 11A and 11B, this multiple triggering results in a very unstable voltage and a lower average voltage across the load. If this voltage is used to derive the setpoint to control the intensity of the LEDs, this will result in an oscillating setpoint. If the average (or RMS) voltage is used to set the intensity of the LED light source in this situation, it will result in incorrect dimming with an unstable light-output.

The solution to this problem is to use time information to adjust the LED light source intensity rather than voltage level information. The time delay from the zero-crossing point to the first triggering of the triac following zero-crossing can be used to derive the LED light source intensity control value (also referred to as the firing angle or phase control value). This time delay value varies with the charging time of the RC controller of the dimming regulator, which depends on the setting of the dimming knob and is not affected by multiple triac firings that may occur later in the half cycle.

The microprocessor can be used to derive the LED intensity setpoint value from the time delay value. One way to implement this is to measure the occurrence time of the rising and falling edges of the current through the DTC, or to measure the voltage associated with these rising and falling edges. The rising and falling edges of these currents are shown, for example, in FIG. 7B, corresponding to the moment when the triac is turned off at zero-crossing and the DTC is active (rising edge), the triac is triggered and the DTC is deactivated ( Falling edge) corresponds to the moment. The time between two rising edges represents the cycle time between zero-crossings of the supply voltage, and the time between the rising edge and the falling edge represents the time delay between zero-crossing and the first triac firing time. From these measurements, the triac firing angle can simply be calculated. This can be conveniently done in the embodiments shown in FIGS. 3 and 6 by measuring the rising and falling edges of the voltage at T6 at the base of transistor Q1 of current source circuit 17 of DTC 12. Can be. In the above-described embodiment, this voltage will be about 0.5V when DTC is activated and Q3 is on, and about 1.5V when DTC is inactive and Q3 is off.

The time between associated rising / falling edges can be measured using a clock that starts when the edge is detected and stops when the next associated edge is detected. To determine the triac off duty-cycle, the time between the rising edge of the DTC current and the next falling edge of the DTC current can be determined and distributed by the time between the two rising edges. The triac on duty cycle is then (1-off-duty cycle). A progressive function can be used to derive the current set point for the LEDs, which can be the saturation index. As can be appreciated by one skilled in the art, such clock and progressive functions can be implemented using a microprocessor or microcontroller.

This solution also allows the system to be designed for application in dimmable circuits, for example, from 90 V to 240 V AC supply voltage, for use in universal supply input, countries using different AC voltages. . Since the intensity control value of the light source depends on the time delay value rather than the voltage value, the value of the input voltage and the resulting average load voltage will not change as a function of the AC supply voltage. This allows a single design to be used throughout the world, thereby reducing manufacturing costs due to larger economic scales.

Hysteresis  And minimum current

Dimmers without an "off" switch behave like a series capacitor when set to the minimum (eg, light source off) position. AC current will flow through this "capacitor" and charge the DC side of the rectifier in the LED driver circuit. This may be sufficient to start up the controller chip in the LED driver circuit after a short time period. This can cause the LEDs to flash briefly, discharging the DC link. The under-voltage will then be detected, the controller will switch off and the period will start over. To prevent this unwanted flash operation, the current control circuit can provide some positive feedback to create hysteresis. In this way, the current controller will receive zero setpoint until the average input voltage exceeds a certain limit. The current set point is then switched to a low value (eg, about 30 mA). By returning the illuminator knob to a lower setting, the LED current can then be reduced (eg, to about 10 mA). Thus, in this low dimming setting the LED can be turned on or off, depending on the previous dimming setting.

In order to avoid changes in illumination intensity due to interaction of the dimming circuit in close proximity to no-load (ie low dimming settings), a minimum current through the LED is also desirable. In close proximity to no load, the voltage on the DC side of the rectifier in the LED driver circuit increases due to the LC filter inside the light regulator (e.g., inductor L1 and capacitor C2 included in the light regulator circuit of FIG. 1). Tend to. This increase raises the measured average load voltage, which causes the LED current to rise. This increase in current will cause the DC voltage to be lower, and the LED current will decrease again. The result is an oscillation of the LED current. This problem can be avoided by keeping the LED current at or above a minimum, generally at least 5 mA. If the firing angle of the illuminator regulator triac approaches 180 degrees, the circuit will stop and go into hiccup mode. However, no hysteresis will result in light, which is similar to that of incandescent bulbs.

As shown in FIG. 12, hysteresis and minimum current can be implemented in the embodiment shown in FIG. 10 by adding resistors R30 and R31 and capacitor 17. R30 and R23 generate positive feedback near amplifier U12. When the LED is controlled, the output of U12 is about 2.5V, and when the LED is off, the output of U12 is about 8V. Thus, about 10 Hz hysteresis will appear at node 24. The minimum current is determined by this hysteresis and the resistor across Q10 (not shown) which raises the reference 24 from ground. If the LED is off and the reference 24 rises, U12 will toggle as soon as the-input of U12 exceeds the + input. After toggling, the + input will drop by about 10 ms, thus increasing the setpoint by about 10 ms / R24 = 30 ms. Appropriate values are as follows: R 30 = 1.2 Hz; R31 = 4.7 Hz; And C17 = 10 Hz.

Overvoltage and Undervoltage  protect

The secondary circuit of the LED driver is preferably designed to function as a current source only between certain limits, for example between 8.3V and 17.3V output voltages, and to use voltage control outside this range. If the current setpoint for the LED is zero, the driver circuit must still be functional. To allow this, the driver circuit output is then voltage controlled to avoid under-voltage-lockout of the flyback controller chip. In addition, for voltages above the current control threshold, the driver circuit also controls voltage to avoid overvoltage in the circuit (especially power transistors on the primary side of the driver circuit) in the event of unconnected or open-circuit failure of the LEDs. Move to mode. Current control limits can be set by resistor values and utilize a voltage reference chip to achieve very low tolerance. The built-in overvoltage protection provided in certain flyback controller chips is preferably not used due to its too high tolerances.

Thus, the present invention has been described with reference to the specific embodiments described above. Elements and components of one embodiment may be used with other embodiments. Although the above-described embodiments include a DTC, this can be omitted. Moreover, it will be apparent that various functions of the setpoint filter circuit or driver circuit described above in the context of various embodiments may be omitted in these embodiments or included in other embodiments.

It will be appreciated that the embodiments described above allow for various modifications and alternative forms well known to those skilled in the art. For example, instead of using a DTC with a full-wave rectifier, such as a diode rectifier bridge, two DTCs with a half-wave rectifier can be used. In the latter case, one DTC will be used for one direction of AC current and the other DTC will be used in the opposite direction. The described circuits can be designed using bipolar transistors or MOSFETS or other types of switching elements. The terms “base”, “collector” and “emitter”, and “gate”, “drain”, and “source” refer to connections to bipolar transistors or FETs as well as similar connections to other types of transistors. Should be interpreted broadly. Moreover, embodiments of the invention have been described with respect to lighting systems. However, the present invention may also relate to circuits for other types of applications.

Claims (50)

An illumination system operating using a dimmer circuit 1 comprising a triac TR1 connected to a load,
The load comprises a driver circuit for supplying current to a light source comprising one or more LEDs LED1-4, the current being determined at least in part by an adjusted setpoint value,
The system includes a setpoint filter circuit 20 for obtaining a light adjuster setpoint value 21 and for generating an adjusted setpoint value 24 that is at least partially determined by the setting of the light adjuster circuit 1. More,
The sensitivity of the adjusted setpoint value to changes in the illuminator setpoint value is low at the lower of the illuminator setpoint values,
Lighting system. The method of claim 1,
The setpoint filter circuit increases the adjusted setpoint at a lower rate 31 at lower values of the dimming set point value and at a higher rate 32 at higher values of the dimming set point value. Configured to
Lighting system. The method of claim 2,
A change in the adjusted setpoint value in response to changes in the illuminance controller setpoint value is close to an exponential response 36,
Lighting system. The method according to any one of claims 1 to 3,
Wherein the setpoint filter circuit generates a full range of the adjusted setpoint values over a full range of the dimming set point values;
Lighting system. The method according to any one of claims 1 to 4,
The setpoint filter circuit generates an adjusted setpoint value having a minimum value 34 greater than zero,
Lighting system. 6. The method according to any one of claims 1 to 5,
The setpoint filter circuit has a first substantially constant value 34 during the dimming set point value of the first range, and increases at a low rate 31 during the dimming set point value of the second range, Increase at a high rate 32 during the illuminator setpoint value in the 3 range and generate the adjusted setpoint having a second substantially constant value 35 during the illuminator setpoint value in the fourth range. felled,
Lighting system. 7. The method according to any one of claims 1 to 6,
The setpoint filter circuit 20 comprises a second or higher order low pass filter 22 for filtering the received dimming set point value 21.
Lighting system. The method according to any one of claims 1 to 7,
The setpoint filter circuit 20 includes a differential amplifier U10 for generating an intermediate setpoint value 23, the differential amplifier U10 for generating a regulated setpoint value 24. Q10) to control,
Lighting system. The method according to any one of claims 1 to 8,
The driver circuit comprises a voltage control circuit 26 and a current control circuit 27, wherein the voltage control circuit controls the voltage at the output of the driver circuit according to a voltage set point, and the current control circuit is a current. Changing the voltage set point in accordance with a set point,
Lighting system. The method of claim 9,
The current control circuit operates within a predetermined range and the voltage set point is maintained at a threshold value when the current control circuit is at the boundary of its operating range.
Lighting system. 11. The method according to any one of claims 1 to 10,
The setpoint filter circuit obtains the illuminance regulator setpoint value from the voltage at the output terminal T2 of the illuminance regulator circuit 1,
Lighting system. 10. The method according to any one of claims 1 to 9,
The setpoint filter circuit derives the illuminance regulator setpoint value from the firing angle of the illuminance regulator triac TR1,
Lighting system. The method of claim 12,
The setpoint filter circuit derives the dimmer setpoint value from a time delay between zero crossing of a supply voltage and a first triggering of the triac after the zero crossing point.
Lighting system. The method according to claim 12 or 13,
It further comprises a light regulator triggering circuit 12 for triggering the light regulator triac TR1,
The dimmer setpoint value is determined at least in part by the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges. felled,
Lighting system. 15. The method of claim 14,
The dimmer setpoint value is determined at least in part by a time delay between the rising and falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges.
Lighting system. The method according to any one of claims 1 to 15,
When the dimming regulator triac TR1 is on, the current through the dimming regulator circuit 1 is less than the holding current of the dimming regulator triac,
Lighting system. 17. The method according to any one of claims 1 to 16,
It further comprises a light regulator triggering circuit 12 for triggering the light regulator triac TR1,
The dimming regulator triggering circuit includes a voltage-level detector 15 for detecting whether an input voltage of the dimming regulator triggering circuit is less than a threshold value, and a current if the voltage detected by the voltage-level detector is less than the threshold value. Comprising a bipolar current source circuit 17 which provides
Lighting system. The method of claim 17,
The maximum current through the dimming regulator triggering circuit 12 is less than the holding current of the dimming regulator triac TR1,
Lighting system. The method according to claim 17 or 18,
When the dimming regulator triac TR1 is on, the current through the dimming regulator triggering circuit 12 is less than the holding current of the triac,
Lighting system. 20. The method according to any one of claims 17 to 19,
When the dimming regulator triac TR1 is off, the current through the dimming regulator triggering circuit 12 is less than the holding current of the triac,
Lighting system. 21. The method according to any one of claims 17 to 20,
The dimming regulator triggering circuit dissipates less than 100 kW average power during operation,
Lighting system. Use in a lighting system comprising a triac dimming circuit (1), a light source comprising one or more LEDs, and a driver circuit for supplying current to the one or more LEDs (LED1-4) Setpoint filter circuit 20 for
The current is determined at least in part by an adjusted setpoint value,
An input circuit for obtaining an illuminance adjuster setpoint value (21) determined at least in part by the setting of said illuminance adjuster circuit (1); And
Adjusting circuit for generating an adjusted setpoint value (24)? The sensitivity of the adjusted setpoint value to changes in the illuminator setpoint value is low at the lower of the illuminator setpoint values?
/ RTI >
Setpoint filter circuit. The method of claim 22,
The adjusted setpoint increases at a lower rate 31 at lower values of the dimming set point value and at a higher rate 32 at higher values of the dimming set point value.
Setpoint filter circuit. 24. The method according to claim 22 or 23,
A change in the adjusted setpoint value in response to changes in the illuminance controller setpoint value is close to an exponential response 36,
Setpoint filter circuit. The method according to any one of claims 22 to 24,
The adjustment circuit generates a full range of the adjusted setpoint values over a full range of the dimming set point values;
Setpoint filter circuit. The method according to any one of claims 22 to 25,
The adjustment circuit generates an adjusted setpoint value having a minimum value 34 greater than zero,
Setpoint filter circuit. 27. The method according to any one of claims 22 to 26,
The input circuit comprises a second or higher order low pass filter 22 for filtering the received dimming set point value 21.
Setpoint filter circuit. The method according to any one of claims 22 to 27,
The regulation circuit includes a differential amplifier U10 for generating an intermediate setpoint value 23, the differential amplifier U10 for controlling transistor Q10 to generate the adjusted setpoint value 24. ,
Setpoint filter circuit. The method according to any one of claims 22 to 28,
The dimming set point value is derived from the voltage at the output terminal T2 of the dimming regulator circuit 1,
Setpoint filter circuit. The method according to any one of claims 22 to 28,
The dimming set point value is derived from the firing angle of the dimming regulator triac (TR1),
Setpoint filter circuit. 31. The method of claim 30,
The dimmer setpoint value is derived from a time delay between zero crossing of the supply voltage and the first triggering of the triac after the zero crossing point.
Setpoint filter circuit. An illumination system operating using a dimming circuit 1 comprising a triac TR1,
The system comprises a light source comprising one or more LEDs, and a driver for supplying current to the dimming trigger triggering circuit 12 and one or more LEDs LED1-4 for triggering the dimming regulator triac. Includes a load that includes a circuit,
Wherein the current supplied by the driver circuit is determined at least in part by a dimming set point value, wherein the dimming set point value is derived at least partially from the firing angle of the dimming regulator triac;
Lighting system. 33. The method of claim 32,
The driver circuit derives the dimmer setpoint value from a time delay between zero crossing of a supply voltage and a first triggering of the triac after the zero crossing point,
Lighting system. 34. The method of claim 32 or 33,
The dimmer setpoint value is determined at least in part by the time of occurrence of one or more rising and / or falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges. felled,
Lighting system. 35. The method of claim 34,
The dimmer setpoint value is determined at least in part by a time delay between the rising and falling edges of the current flowing through the dimming regulator triggering circuit, or by the voltage associated with the rising and falling edges.
Lighting system. The method according to any one of claims 32 to 35,
The driver circuit includes a voltage control circuit 26 and a current control circuit 27,
The voltage control circuit controls a voltage at an output of the driver circuit according to a voltage set point, and the current control circuit changes the voltage set point according to a current set point,
Lighting system. The method of claim 36,
The current control circuit operates within a predetermined range and the voltage set point is maintained at a threshold value when the current control circuit is at the boundary of its operating range.
Lighting system. The method according to any one of claims 32 to 37,
When the dimming regulator triac TR1 is on, the current through the dimming regulator circuit 1 is less than the holding current of the dimming regulator triac,
Lighting system. The method according to any one of claims 32 to 38,
The dimming regulator triggering circuit includes a voltage-level detector 15 for detecting whether an input voltage of the dimming regulator triggering circuit is less than a threshold value, and if the voltage detected by the voltage-level detector is less than the threshold value. Comprising a positive current source circuit 17 which provides current or is deactivated,
Lighting system. The method according to any one of claims 32 to 39,
The maximum current through the dimming regulator triggering circuit 12 is less than the holding current of the dimming regulator triac TR1,
Lighting system. The method according to any one of claims 32 to 40,
The current through the dimmer triggering circuit 12 is less than the holding current of the triac when the dimmer triac TR1 is on,
Lighting system. The method according to any one of claims 32 to 41,
The current through the dimmer triggering circuit 12 is less than the holding current of the triac when the dimmer triac TR1 is off,
Lighting system. 43. The method of any of claims 32-42,
The dimming trigger triggering circuit dissipates less than 100 kW average power during operation,
Lighting system. The method according to any one of claims 32 to 43,
A setpoint filter circuit 20 for generating an adjusted setpoint value 24 from the illuminance adjuster setpoint value 21,
The sensitivity of the adjusted setpoint value to changes in the illuminator setpoint value is low at the lower of the illuminator setpoint values,
Lighting system. 45. The method of claim 44,
The setpoint filter circuit increases the adjusted setpoint at a lower rate 31 at lower values of the dimming set point value and at a higher rate 32 at higher values of the dimming set point value. Configured to
Lighting system. 46. The method of claim 44 or 45,
A change in the adjusted setpoint value in response to changes in the illuminance controller setpoint value is close to an exponential response 36,
Lighting system. 47. The method of any of claims 44-46,
Wherein the setpoint filter circuit generates a full range of the adjusted setpoint values over a full range of the dimming set point values;
Lighting system. 48. The compound of any of claims 44 to 47,
The setpoint filter circuit generates an adjusted setpoint value having a minimum value 34 greater than zero,
Lighting system. 49. The method of any of claims 44-48,
The setpoint filter circuit has a first substantially constant value 34 during the dimming set point value of the first range, and increases at a low rate 31 during the dimming set point value of the second range, Increase at a high rate 32 during the illuminator setpoint value in the three ranges and generate the adjusted setpoint value having a second substantially constant value 35 during the illuminator setpoint value in the fourth range. Composed,
Lighting system. An illumination system operating using a dimming circuit 1 comprising a triac TR1,
The system comprises a light source comprising one or more LEDs, and a driver for supplying current to the dimming trigger triggering circuit 12 and one or more LEDs LED1-4 for triggering the dimming regulator triac. Includes a load that includes a circuit,
The driver circuit includes a power factor correction circuit, wherein the current supplied by the driver circuit is determined at least in part by a dimming set point value, wherein the dimming set point value is determined from the firing angle of the dimming regulator triac. At least partially derived,
Lighting system.

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