HK1234585A1 - System and device for driving a plurality of high powered led units - Google Patents

Description

System and apparatus for driving a plurality of high power LED units

The present application is a divisional application of patent application 201280017590.8 entitled "system and apparatus for driving a plurality of high power LED units" filed on day 2012, 11/2.

Technical Field

The present invention relates to a system and apparatus for driving a plurality of high power Light Emitting Diode (LED) units. The device is particularly suitable for, but not limited to, use in high power LED lamp units such as downlights, T5, T8, troffers, Hi-Bay lamps and MR 16 bulbs.

Background

The following discussion of the background of the invention is intended to facilitate an understanding of the invention. It should be appreciated, however, that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge in any jurisdiction as at the priority date of the application.

Conventional lighting systems typically have a configuration of lamp products used in a separate driving system. For example, lamp products such as downlights have their built-in power supply or ballast which converts the incoming AC power to a higher AC voltage and current required to provide power to, for example, ignite and energize gas (referred to as a CFL lamp) to light the downlight. Examples of such other light products include T5, T8, troffers, Hi-Bay lights, street lights, and floodlights.

Similarly, when Light Emitting Diodes (LEDs) are introduced in a lighting system, the configuration adopted by the LEDs is based on an arrangement similar to "one ballast (controller)" to "one lamp" of a conventional lighting system. Thus, each LED lamp unit has its own built-in LED driver or controller that converts incoming AC power to DC voltage and current to light the LED downlight. This means that each LED lamp unit present in the lighting system has an accompanying controller dedicated to that particular LED lamp unit to convert incoming AC power to DC voltage and current to light that particular LED lamp unit, i.e. a series of 10 LED down lamps in the lighting system would require correspondingly 10 LED controller circuits. These LED controllers increase the cost and overall form factor of each lamp unit.

A prior art LED lamp unit and system are shown in fig. 1 and 2, respectively. The LED lamp unit comprises an AC power supply via an AC input 4, an AC-DC LED driver 3, an LED light/lamp module 1 and a heat sink 2.

When connected, AC supply current will flow to the input of the AC-DC LED driver 3. The AC supply current is rectified via a switched mode power supply circuit in the AC-DC LED driver 3 to provide the required DC voltage and current to the LED light module 1. For continuous lighting operation, since both the AC-DC LED driver 3 and the LEDs on the LED light module 1 will generate heat, the introduction of the heat sink 2 is important to ensure that the heat generated during lighting operation is accordingly drawn out of the heat source and dissipated. The heat sink 2 must cope with heat dissipation from both the LED light module and the AC-DC LED driver. As a result, if at any time during the lighting operation, the heat sink 2 reaches its maximum heat dissipation capacity due to design limitations of the size for the standard form factor of the particular LED lighting unit, this implementation may result in a reduction in light performance and product life.

The above described arrangement has several disadvantages:

since each LED light unit requires its own built-in controller circuit 3 for lighting, both the LED and the controller circuit generate considerable heat when the LED light unit is in continuous operation. To reduce the heat, a heat sink must be provided in each LED light unit for absorbing heat from the heat source and dissipating the heat to the ambient environment in order to provide a cooled environment for the LEDs and controller to operate in. It is important that the LED and controller circuits operate in a cooled environment, as this reduces power consumption and thus improves efficiency. However, due to the standard form factor, there is a limit to the size of the heat sink in each LED light unit. Since there are two heat generating sources (i.e., the LED lamp unit and the LED controller) in each LED light unit, the heat sink 2 typically reaches its maximum heat dissipating capacity during continuous operation where considerable heat is generated. As a result, this will lead to a reduction of the light performance of the LED light unit and the product lifetime.

Manufacturing LED light units with built-in controller circuitry and heat sink 2 is generally costly as they increase the number of components required for manufacturing. Moreover, the heat sink must also be designed to handle heat dissipation from both heat sources in the presence of its size constraints due to the standard form factor. This further increases the overall cost of producing the LED light unit.

Since the AC power is converted to DC voltage and current in the LED light unit by the controller circuit 3, safety related issues have to be solved. Therefore, the LED light units must be designed such that they meet the standard safety requirements and size limitations imposed by the standard form factor.

It is therefore an object of the present invention to overcome or at least alleviate the aforementioned problems.

Disclosure of Invention

The present invention provides a system and apparatus to alleviate the above problems and provide a "one driver to multiple high power LED lamp units" solution. To accomplish this, the system and apparatus are adapted to provide at least a relative "ripple free" current of less than 5% from the specified rated current. The specified rated current is typically (but not limited to) about 350mA to 700mA per lamp unit.

In addition, references to "flowing" and "connected" refer to both electrical current and electrical connection, unless otherwise indicated.

According to a first aspect of the invention, a system for driving a plurality of high power LED units, the system comprising a single driver for providing ripple-free constant direct current to a plurality of high power LED lamp units, wherein the single driver comprises a digital controller programmable to adjust the ripple-free constant direct current at each predetermined time interval based on detection and calculation of the duration it takes to discharge energy to the LED lamp units, thereby adjusting the ripple-free constant direct current.

Preferably, the single driver operates in an isolated ac flyback configuration with the inductive element as a transformer for isolating the plurality of high power LEDs at the secondary end of the transformer.

Preferably, the digital controller is an Application Specific Integrated Circuit (ASIC); the ASIC is further operable to detect and calculate a duration of energy released by the core of the transformer to the plurality of high power LEDs to regulate and provide a ripple-free output DC current. The ASIC is preferably programmed to receive feedback as an input at each clock cycle based on the duration of energy released by the core of the transformer to determine the amount of ripple-free constant DC current for the next clock cycle. More preferably, the ASIC is programmed to provide a voltage waveform at each clock cycle to turn the electronic switch on or off.

Preferably, each of the plurality of high power LED lamp units is connected in series with other high power LED lamp units.

Preferably, the single driver is electrically connected to a dimmer circuit for adjusting the brightness of the plurality of high power LED lamp units. The dimmer circuit preferably comprises a potentiometer, an infrared interface, a motion sensor or an environmental sensor.

Preferably, the system includes a filter capacitor operable to vary its capacitance to maintain a power factor of at least 0.9 when the dimmer is adjusted.

Where the dimmer is a potentiometer, the potentiometer is operable to operate within 0 to 10V.

Preferably, in the isolated flyback mode, the secondary of the transformer is electrically connected to a short-circuit protection circuit.

Preferably, the ASIC is coupled with an active power factor controller. More preferably, the active power factor controller comprises at least one voltage follower. In this case, the ASIC is preferably a 14-pin configuration to control the active power factor controller and regulation of the ripple-free constant DC current.

Preferably, each high power LED lamp is provided with a heat sink shaped and configured to dissipate heat from only the high power LEDs.

Preferably, the system further comprises an electronic switch, wherein the ripple-free constant DC current is achieved by means of voltage control according to the following equation:

wherein, V_OUTIs the voltage across the output; v_INIs the input voltage; t is_OFFIs the discharge time of the iron core of the isolation transformer; t is_ONIs the on time of the electronic switch; l is₁Is the inductance value, L, of the primary winding of the transformer₂Is the inductance value of the secondary winding of the transformer.

As an alternative to the isolated configuration mode, a single driver may operate in a non-isolated configuration with the inductive element operating in a continuous mode according to the following equation:

wherein, T_OFFFixed as a constant; t is_ONIs the on time of the electronic switch; t is T_ON、T_OFFAnd T_CALCOf a total of (a), wherein T_CALCIs the time after the discharge time of the sensing element to calculate the formula; i is₁Is the required reference current, I_MAXIs the peak current. In hysteretic controller configuration, I_MAXAnd I₁May be fixed, and T may be determined_ONAnd T_OFFAnd (6) timing.

According to a second aspect of the present invention, an LED driver includes:

at least one Integrated Circuit (IC), the IC programmable using a hardware description language; a first electronic switch operable to provide a first switching period to control a power factor voltage, the first switching period being programmable by the at least one IC; and a second electronic switch operable to provide a second switching period to regulate a ripple-free constant DC current flowing into the at least one LED, the second switching period being programmable by the at least one IC. Such LED drivers provide additional current control in the form of a power controller to achieve ripple-free DC current.

Preferably, the first and second electronic switches are power MOSFETs.

Preferably, the at least one IC is an ASIC.

According to a third aspect of the present invention, an LED driver includes: a device having an input port and a plurality of output ports, comprising a reverse polarity protector arranged to be electrically connected to each of the input port and the plurality of output ports; and a plurality of open circuit protection circuits, each of the plurality of open circuit protectors being operable to be connected to the output port; wherein the reverse polarity protector is operable to reject a polarity requirement if a load is connected to any output port with the wrong polarity; the open circuit protection circuit is operable to form a closed loop series connection in the absence of a load connected to the output port or a load breakdown.

Preferably, the reverse polarity protector is a diode bridge rectifier.

Preferably, each output port includes a respective open circuit protector.

Preferably, the input ports are adapted to be connected to an LED driver, and each output port is adapted to be connected to a load comprising a high power LED lamp unit.

According to a fourth aspect of the present invention, a system according to the first aspect, wherein said loads are in series connection, further comprising apparatus according to the second and third aspects of the present invention as claimed in claims 22 to 25; wherein the input ports of the apparatus of claims 22 to 25 are operable to be connected to a single driver.

According to a fifth aspect of the present invention, a dimmer circuit for use with an LED driver, the dimmer circuit comprising at least one dimming interface operable to be connected to at least one dimming controller; and a capacitive element adjustable to maintain a power factor of at least 0.9 within the dimmer circuit.

Drawings

The following invention will be described with reference to the accompanying drawings, in which:

FIG. 1 is a perspective side view of a prior art LED lamp unit having a driver and a heat sink;

FIG. 2 is a system configuration of a "one driver one lamp unit" configuration of a prior art LED lamp system;

fig. 3 is a system diagram of "one driver multiple lamp units" or "string driver" according to an embodiment of the invention;

FIG. 4 is a circuit diagram of an LED driver circuit for isolated Alternating Current (AC) applications according to an embodiment of the present invention;

FIGS. 5a and 5b are circuit diagrams of an LED driver circuit with a power factor converter driven by a 14-pin ASIC for isolated Alternating Current (AC) applications according to another embodiment of the present invention;

FIG. 6 is a table summarizing the advantages of the present invention over multiple MR 16LED lamps compared to prior art systems;

fig. 7 shows simulation results of ripple-free constant DC current based MR 16 load;

fig. 8 shows another embodiment with a circuit arrangement in which the decoupling transformer operates in continuous mode;

FIG. 9 shows current flowing through the rectifier circuit in continuous mode;

FIG. 10 shows the structure of a hysteretic controller for continuous operation of the circuit;

fig. 11 is a PCB arrangement of an intermediate connector between an LED driver and a load according to another embodiment of the invention;

figure 12 is a diagram showing a possible arrangement of a lighting system using intermediate connectors between the driver and the load;

figure 13 is a block diagram showing another possible arrangement of a lighting system using two intermediate connectors;

FIG. 14 shows a circuit diagram of an intermediate connector; and

fig. 15 shows a general block diagram of a dimmer circuit.

Other arrangements of the invention are possible and therefore the drawings should not be construed as superseding the generality of the preceding description of the invention.

Detailed Description

In the context of the present invention, references to "ripple-free" currents and near ripple-free currents refer to allowable ripple less than (<) 5% from a specified rated current.

In the context of the present invention, a high power LED lamp unit refers to any LED lamp unit requiring at least 5 watts of power.

According to an embodiment of the present invention, there is an LED driver 10 for driving a plurality of high power LED lamps 100, as shown in fig. 4. The LED driver 10 is particularly suitable for isolated Alternating Current (AC) applications and includes a primary side and a secondary side. The primary side of the LED driver 10 is decoupled from the secondary side by means of a decoupling transformer 11. The primary side includes an electronic switch 14, a bridge rectifier circuit 16, and an Integrated Circuit (IC) controller 18. Although fig. 4 shows an isolated configuration, the skilled person will understand that the circuit may be modified for use in a non-isolated configuration, wherein the decoupling transformer 11 may be replaced by other inductive elements.

To fulfill the decoupling function, the transformer 11 is an isolation transformer, which may preferably be a planar transformer. The transformer 11 is operable to operate in a continuous or discontinuous mode, although for illustration purposes fig. 4, 5a and 5b show circuitry of the transformer 11 adapted to operate in a discontinuous mode. In the continuous mode, as shown in fig. 8 or 10, some of the output capacitors may be omitted. In case the transformer 11 is a planar transformer based on printed circuit board technology, the printed circuit board may be an FR4PCB, polyimide or other thick copper foil (lead frame).

Resistor R_PAnd a capacitor C_PConnected in a parallel configuration with the primary side of the transformer 11. Diode D_PConnected to a resistor R_PCapacitor C_PAnd a transformer 11. Diode D_PIs connected to the primary side of the transformer 11 in a series configuration. Diode D_PIs connected to the resistor R in a series configuration_PAnd a capacitor C_P。

Capacitor C_SConnected in parallel to the secondary side of the transformer 11 for filtering the output voltage. D_SA diode is connected to the secondary side of the transformer 11 and the capacitor C_S. Diode D_SIs connected to the secondary side of the transformer 11 in a series configuration. Diode D_SIs connected to the capacitor C in a series configuration_SIf applicable. LED load 100 is connected to capacitor C in a parallel configuration_S. Each LED load 100 may be connected in series with another LED load 100. The secondary side may optionally include a short-circuit protection circuit 44, which will be explained in detail later.

The electronic switch 14 is typically a power transistor. In this particular embodiment, the electronic switch 14 is more preferably a power MOSFET. In a MOSFET configuration, the drain of the electronic switch 14 is connected to a diode D_PAnd the primary side of the transformer 11. The gate of electronic switch 14 is connected to the output pin of IC18 and the source of electronic switch 14 is connected to ground potential.

It should be understood that the electronic switch 14 may be replaced by other functionally equivalent components.

The IC controller 18 includes an internal oscillator configured to be turned on for a specific on-period T of each clock cycle determined by the internal oscillator_ON(switching frequency) turns on the gate of the electronic switch 14. The IC controller 18 is preferably an Application Specific Integrated Circuit (ASIC) that is programmable to sense and compute the inductive element L as a primary input₁And L₂The discharge time of (1). ASIC 18 is programmable and configured to turn on with T each clock cycle based on the following inputs_ONGate of the electronic switch 14 for the on-period:

(a.) based on a sensing element L₁And L₂A reference constant K of the discharge time of (a);

(b.) for LED I_OUTThe required output DC has no ripple current;

(c.) the digitized voltage value V tapped off from the voltage divider 22 and digitized_DD(V_in) The voltage divider 22 is connected in parallel with the bridge rectifier 16;

(d.) of the core of the transformer 11 measured by the voltage divider 30 and compared to a reference voltageDischarge time value T_OFF(ii) a And

(e.) the switching period T (i.e., the switching period of the electronic switch 14 as determined by the oscillator).

Using the five inputs received, IC18 calculates the output T_ONWhich is the on-time of the electronic switch 14 expressed mathematically in equation (1).

The reference constant K is calculated based on the inductance values of the primary and secondary windings of the transformer 11 as described in equation 2.

Wherein L is₁Is the inductance value, L, of the primary winding of the transformer 11₂Is the inductance value of the secondary winding of the transformer 11. The value of reference K may be stored in a memory within IC 16. For a non-isolated Direct Current (DC) flyback configuration, a reference constant K is calculated according to the following mathematical expression:

wherein L is₃Is the inductance value of the inductive element in the flyback configuration.

Using equations (1) and (2), I is derived as follows_OUT：

IC controller 18 may further include a dimming pin coupled to variable resistor 40 for performing dimming on LED load 100. The dimming pin facilitates the flexibility of performing dimming via various dimming devices such as potentiometers, motion sensors, or infrared sensors.

The IC controller 18 described above is typically 8-pin. To fine-tune the level of control of the IC controller 18, a high resolution IC controller may be used. Except for the required ripple-free current I_OUTIn addition to fine-tuning control, an active Power Factor Controller (PFC) improves circuit performance.

In another embodiment below, a high resolution IC controller is illustrated that has the ability to fine tune the desired ripple-free current control and provide active power factor control.

Another embodiment of the invention in the form of an LED driver 500 for driving a plurality of high power LED lamp units 100 is shown in fig. 5a and 5b (primary side emphasized). The LED driver 500 comprises a first electronic switch 513; a second electronic switch 514; a bridge rectifier circuit 516 and an integrated circuit controller 518. The LED driver 500 further includes an active Power Factor Controller (PFC) circuit 520. Compared to the previous embodiments, the active Power Factor Controller (PFC) is operable to constitute an additional current controller stage for achieving an improved ripple-free constant DC current. The integrated circuit controller 518 is operable to control the switching frequency of the first electronic switch 513 and the second electronic switch 514 to achieve a desired power factor and to output a ripple-free current I_OUT。

Integrated IC controller 518 is similar to IC controller 18, including an internal oscillator, a built-in analog-to-digital converter, and the like. It also includes more pins for further control of the PFC controller. In this embodiment, IC controller 518 includes 14 pins. The overall resolution is higher (10 bits), allowing the switching frequency and I to the electronic switches 513, 514_OUTBetter adjustment and fine tuning.

The bridge rectifier 516 is operable to receive an AC input and generate a rectified voltage output. Passing the rectified voltage output through a capacitor C₄。C₄Operable to act as an input voltage filter to further rectify the incoming currentThe rectified voltage of the device circuit 516 is filtered. Capacitor C₄Connected in parallel to a resistor R₈And R₉And an inductor L₄Are connected in series.

Resistor R₈And R₉Forming an input voltage divider, R being in operation₈And R₉With the voltage in between as the input voltage (denoted as V)_inP) Tapping into the ASIC.

Inductor L₄And a resistor R₁₀And R₁₁Are connected in series. Resistor R₁₀And R₁₁Forming a PFC voltage divider for measuring via T the PFC output voltage_2PPin input, provides PFC feedback voltage to controller 518.

The first electronic switch 513 is connected in series to the inductive element L₄And connected in parallel to the PFC divider. The first electronic switch 513 provides a variable frequency to control the PFC output voltage. Both the first electronic switch 513 and the second electronic switch 514 may be N-channel power MOSFETs. The gate of the first electronic switch 513 is triggered by an ASIC (MOSOUT pin), the drain of which is connected to L₄Connected in series and the source is grounded.

In operation, the controller 518 drives the first electronic switch 513 to provide the necessary power factor voltage at the drain of the first electronic switch 513.

It should be understood that the first electronic switch 513 may be replaced by other functionally equivalent components.

Power diode D₃And an inductive element L₄Are connected in series. Which allows the forward pass of the rectified PFC current; this is regulated by a first electronic switch 513.

C₅Is a capacitive filter for filtering the PFC output voltage.

Inductive element L₄It may be a standard inductor as shown in fig. 5a, or a transformer as shown in fig. 5 b. For L₄Is the case of a transformer comprising L_4pPrimary inductance and L_4sA secondary inductance. As shown in FIG. 5b, L_4pFrom pin 1 to pin 6; l is_4sPin 1 of the slave IC controller 518 is connected to pin 7.

The following equation (4) is applied to the transformer variant to control the output voltage of the PFC:

V_PFC,OUTis the output voltage of the PFC, L_4pIs the primary inductor value, L, of the PFC transformer_4sIs the value of the secondary inductor of the PFC transformer, V_inIs the input voltage, T_Q2onIs the on-time, T, of the first electronic switch 513_Q2offIs the discharge time of the PFC transformer. Controlling T via MOSOUT pin of controller 518_Q2on，V_inAnd T_Q2offIs a feedback value for ensuring and verifying V_PFC,OUTCorrectly tracking the required output voltage V_OUT。

Equation (4) is called a voltage follower, where V_PFC,OUTFollowing V_OUT(ii) a In the sense after solving the equation, if V_PFC,OUTLess than expected (within allowable deviation), T is increased_Q2onOtherwise, T is decreased_Q2on。

Based on the total number of LED units and the required current I to be supplied to the LED units_OUTTo determine V_OUT。

For the second electronic switch 514, for adjusting and calculating I_OUTIs the same as that explained in equations (1) to (3).

As described above, the secondary side of the LED driver 10, 500 may further include the voltage protection circuit 44. Referring to fig. 4, although not explicitly shown in fig. 5a and 5b, for a voltage protection circuit that may be included in the secondary side of the LED driver 500, the voltage protection circuit 44 includes a zener diode 46, a Silicon Controlled Rectifier (SCR)48, and a resistor 50. When a short circuit is detected, the zener diode 46 will conduct, thereby enabling the SCR 48 and reducing the output voltage of the LED 100.

In the context of operation of driving a string of LED light units, the LED driver 10, 500 is illustrated in the following example:

to operate the circuit, the variable resistor is adjusted to be V_R(LED driver 10) or V_inPGenerating a voltage value N (for the LED driver 500), wherein the value N is the on-time period T of the electronic switch 14, 514 corresponding to the generation of the maximum approximately ripple-free constant current to drive the plurality of LED lamp units 100_ONAnd (4) adjusting. Adjusting the decrement or increment of the value of N will be based on feedback and directly result in T_ONT, based on a variable resistor V_RChange I accordingly_OUTTo dim or brighten the LED lamp unit 100.

For the optimization of equations (1) to (3), the equations of the circuit may be expressed in alternative forms

A＝V_IN*T_ON*T_OFF(5)

B＝1/K*I_OUT*(T_ON+T_OFF+T_CALC) (6)

Wherein, T_CALCThe time used for calculating the formula after the discharge time of the inductive element, and the switching time period of the electronic switch is T_ON、T_OFFAnd T_CALCThe sum of (a);

in I_OUTThe values of a and B are compared in each adjustment cycle.

If A is greater than B, i.e. A>B, then T_ONIs adjusted to T_ON-N for the next time period T.

If A is less than B, i.e. A<B, then T_ONIs adjusted to T_ON+N。

In the case where A is equal to B, T is not updated_ON，T_ONRemain unchanged.

According to the number of lamp units 100 and the required current I_OUTThe user performs design optimization by changing several key components as follows:

inductor L of transformer 11₁And L₂；

Switching frequency, drain-source voltage V of the electronic switch 14, 514_DSAnd a drain current I_D；

Capacitor C_SAnd a diode D_SThe value of (c). Care must be taken to ensure that capacitor C_SThe voltage across should be higher than the voltage of the LED load 100.

Forward current I of diode_FAnd repeating peak reverse voltage V_RRMIs to select a suitable diode D_SThe parameters considered.

Once the above components are adjusted to the load specification, the IC controller 18, 518 detects and calculates the duration of energy released to the load via the core of the transformer 11 (or the inductive element for the non-isolated flyback configuration) to the LED load 100 to adjust the constant output current. Thus, the controller 18, 518 can operate over a wide range of load voltages and constant currents for the high power LED lamp 100.

The embodiment provides a constant DC current to a plurality of high power LED lamp units 100 that is approximately ripple free. Said configuration of a driver for a plurality of lamps is referred to by the applicant as "tandem configuration".

As an optional feature, the IC controller 18, 518 may further comprise a Multipoint Control Unit (MCU) to enable communication with an intelligent control module such as power line, Digital Addressable Lighting Interface (DALI), wireless protocol for the overall lighting control system.

The embodiment is based on the concept of a single LED driver 10, 500 to drive a plurality of high power LED lamp units 100, each provided with a heat sink shaped and configured to dissipate heat from only the high power LEDs and a single driver configured to provide an approximately ripple-free constant DC current to the plurality of high power LED lamp units, in comparison to the prior art MR 16 system where one LED driver 3 is required for each LED lamp unit 4. This standard ASIC driver design solution is driven at constant current and provides a wide range of flexibility to drive a series of any number of LEDs within the overall lighting system, the advantages of which are summarized in fig. 6.

FIG. 7 shows I measured from a high power LED load 100_OUTThe range of ripple-free constant DC current is shown.

The above embodiments shown in fig. 4, 5a and 5b are illustrated as current controllers (i.e. using I)_OUT) IC controller implementation of (a); and a transformer 11, 511 operating in discontinuous mode. Due to the flexibility of programming the ASIC based controller 18, 518, four different combinations and/or modes may be implemented as follows:

A. voltage control instead of current control;

B. using primary inductor current feedback rather than T-based_OFFOf (2) a feedback (or monitoring) discontinuity

A mode;

C. using primary inductor current feedback rather than T-based_OFFOf (2) a continuous mode of feedback (or monitoring)

Formula (I); and

D. continuous mode for hysteretic controller.

A. Voltage control instead of current control

For using voltage control instead of current control, equation (3) can be rewritten as:

wherein, V_OUTIs the output voltage. Wherein L is₁Is equal to L₂The equation is modified to:

B. using primary inductor current feedback rather than T-based _OFF In discontinuous mode of feedback (or monitoring)

For substitution based on T_OFFBy means of a discontinuous mode of feedback (or monitoring) of the primary inductor current, the peak current I can be adjusted_MAXInput voltage V_INThe relationship with the sensing element L is mathematically expressed as:

in the case where the inductive element L is a single inductor used in a non-isolated configuration for example,

substituting equation (6) into equation (3) yields:

the inductive element L is a transformer, L₁And L₂In the case of representing the primary and secondary inductances separately,

to apply equation (7) or (8), the circuits shown in fig. 4, 5a and 5b can be modified so that the primary current can be read by the ASIC controller through a resistor from the source of the electronic switch 14, 514 to ground, or using a current transformer in series with the electronic switch 14, 514, or a filtered inductor if in the case of a forward configuration.

C. Using primary inductor current feedback rather than T-based _OFF In a continuous mode of feedback (or monitoring)

For substitution based on T_OFFBy means of a continuous mode of feedback (or monitoring) of the primary inductor current, it is understood that the current to the LED flowing through the rectifier diode string is the same as the current over the LED.

The waveform of the current in the continuous mode is shown in fig. 9. For a given on-time T_ONIf T is_OFFFixed, then the current across the diode can be calculated as:

wherein T ═ T_ON+T_OFF+T_CALC；T_CALCIs the discharge timing of the transformer or inductor element.

All of the above information can be obtained from the primary inductive element L. Specifically, the circuit arrangement shown in fig. 8 includes:

i. a resistor in series with the electronic switch;

a current transformer optically connected in series with the electron switch; and

a filter inductor.

The circuit arrangement shown in fig. 8 comprises a first transformer 811 for isolating the load. The filter inductor 820 is used in the same manner as the inductor in the hysteretic controller.

Controlling the output current I by means of feedback from a resistor 822 connected to the source of the electronic switch_OUT。

Resistor 822 is used for protection purposes and not for control purposes. The reset circuit 812, which includes an inductor 823 and a diode 824, is used in a forward configuration to allow the transformer core to fully discharge the residual energy. This serves to avoid saturation of the core after a certain operating time.

D. Continuous mode for hysteretic controller

The structure of the hysteretic controller is shown in fig. 10. To achieve this, T may be determined according to equation (9)_ONAnd T_OFFTiming to fix I_MAXAnd I₁The value of (c). However, the current I_OUTWould be the area under the figure.

It should be understood that the continuous mode described above is particularly suitable only for non-isolated flyback and feed-forward configurations. However, it reduces the minimum number of components required and can provide ripple-free current without the need for a load capacitor. Thereby, cost savings can be realized.

In the described embodiment, the dimmer 40 may be used as a module for SSL lighting dimming control, for saving energy, to replace a conventional triac dimmer. The dimmer 40 is arranged and operable to use energy only when light is required; otherwise, the light is automatically dimmed to reduce intensity or turned off completely (both to save power compared to when the light is fully on).

As shown in fig. 4, 5a and 5b, the IC controller is connected to the dimmer 40 for better dimming performance and energy saving, e.g., to maintain the power factor at greater than or equal to 0.9 at a low dimming level, less than 10% of the total light output, for energy saving purposes. Although the dimmer 40 is shown in fig. 4, 5a and 5b, the skilled person will readily appreciate that the dimmer 40 is readily incorporated into the circuits shown in the isolated/non-isolated configuration as well as in the continuous or discontinuous mode.

To elaborate further explanation regarding the operation of the dimmer 40 with reference to fig. 15 in order to meet the above objectives of energy conservation and maintaining a high power factor, fig. 15 constitutes another embodiment comprising a dimmer circuit for use with an LED driver, the dimmer circuit comprising at least a dimming interface operable to connect to at least one dimming controller; and a capacitive element adjustable to maintain a power factor of at least 0.9 within the dimmer circuit.

As shown in fig. 15, dimmer 40 may comprise various devices capable of interfacing with dimming interface 1670, including IC controller 18, 518 pins for lighting dimming control.

When the power is turned on, current flows to the rectifier 1516, which in turn turns on the switching power supply 1600 including the ASIC controllers 18, 518. Providing an isolated or non-isolated supply of ripple-free constant DC output current 1610. The switching power supply 1600 may be isolated or non-isolated, and depending on the configuration, the inductive element 1511 may be an isolation transformer. The output of the inductive element 1511 provides an isolated or non-isolated ripple-free constant DC output current 1610 to the LED load 1700 to turn on the light. By default, the LED load 1700 consumes 100% of the energy to turn the light on unless the power is turned off.

Dimmer 40 may be a 0-10V dimmer 1708. When the dimmer is set to 10V, the DC output current 1610 sets the light output to 100%. When the dimmer is set to 5V, the DC output current 1610 sets the light output to 50% of the total light. At 0V, no light is provided.

An Infrared (IR) remote control 1711 may also be used for remote lighting control. This configuration requires the dimming interface to have a suitable IR receiver so that when the IR transmitter sends a signal, the IR receiver will decode the signal and accordingly generate a PWM duty cycle from the range 0-100% for dimming control. When the duty cycle is set to 100%, the DC output current 1610 will then set the light output to 100%, and when the IR emitters transmit 50% duty cycle, the DC output current 1610 will transmit 50% of the total light output. If the IR emitter transmits a 0% duty cycle PWM signal, no light is provided.

Another type of dimmer may be embodied as a motion sensor 1712. When no motion is detected by the motion sensor 1712, the DC output current 1610 changes the output current from 100% to 20% for dimming purposes, or even turns off the output current. This means that energy is only used when motion is detected by the motion sensor 1712.

Another option is to use an environmental sensor 1714 to detect environmental conditions, such as when dawn comes, DC output current 1610 will turn off the output current and turn off light 1700. When the environment sensor 1714 detects that the environment has become dusk, the DC output current 1610 turns the output current on to 100%.

It should be understood that any other device designed with a PWM output duty cycle from 0-100% may be connected to the dimmer interface for LED lighting dimming control. A dimmer interface is a circuit comprising one or more microcontroller devices for detecting dimming signals from various dimmers (IR remote, motion, ambient … …, etc.) and converting the input dimming signals to analog voltages to an ASIC controller for dimming control. It may also be included in the ASIC controller mentioned in the other embodiments. In an implementation aspect, the "dimmer interface" may be a small module board mounted on the power supply PCB or integrated in the power supply circuit PCB.

The capacitor 1630 is a component that affects the power factor. When the dimming circuit is activated, the switching power supply 1600 will automatically charge 1630 capacitors to maintain the power factor ≧ 0.9, so that the power factor is always maintained ≧ 0.9 no matter how low the dimming level becomes.

Dimmer designs according to various embodiments enable users to dim their LED lighting units down to 1-2% of the original drive current without any flickering phenomena.

According to another embodiment of the invention, a device 1100 is provided for use with any of the LED drivers 10, 500 described in the previous embodiments. As shown in fig. 11, the device 1100 is an intermediate connector between the LED driver 10, 500 and the LED load 100. The intermediate connector is hereinafter referred to as "junction box".

Fig. 11 shows a PCBA design of a junction box 1100. Junction box 1100 includes an input connector 1120 and a plurality of output connectors 1140 arranged to implement the following:

a. the high-power LED lamp load 100 is easy to install;

b. the method is beneficial to a plurality of LED lamps 100 connected in series, and the problem of complete open circuit of the system under the condition that the high-power LED lamp 100 is damaged is solved;

c. errors common during installation, particularly errors associated with electrical polarity reversal, are reduced or eliminated altogether.

With regard to point (b.) above, the series connection of the LED lighting units 100 ensures that each lamp unit 100 will be driven at exactly the same current, and therefore each LED lighting unit 100 will produce the same brightness. For lighting systems where uniform brightness is important, a series connection is advantageous over a parallel connection.

To accomplish this, the junction box includes a reverse polarity protector 1160 and an open circuit protector 1180. The reverse polarity protector is preferably a rectifier 1160.

As shown in fig. 11, there are 9 output connectors 1140. The input connector 1120 is arranged to connect with a driver output connector and the junction box output connector 1140 is arranged to connect with an LED load 100, the LED load 100 comprising an SSL driver-less lighting unit ribbon end cable.

The input connector 1120 is typically a connectorized connector for coupling with the output connector of the LED driver 10, 500, which is typically a cable drop-in. The output connector 1140 is typically a cable lead-in such that an electrical connector of the LED lamp 100, such as a tapeless SSL cable, can be inserted therein to create a closed electrical loop.

Fig. 12 shows a lamp system comprising a single LED driver 10, 500, a single junction box 1100 and an SSL driver-less light unit/load 100.

The LED drivers 10, 500 with the cable plug-in connector 1100 are connected to the input connector 1120 and the SSL driver-less lighting unit with the tape tip cable is plugged into the output connector 1140 in order to create a fully networked lighting system for lighting purposes once energized.

Fig. 13 shows another possible arrangement with two junction boxes 1100, where the entire system includes a single string driver 10, 500, a dual junction box 110 and an SSL driver-less lighting unit 100.

The required driver output voltage, predetermined by qualified personnel, will determine the total number of SSL driver-less lighting units 100 or the number of junction boxes that should be used for the entire lighting network, in order to drive all SSL driver-less lighting units with a ripple-free constant current of the required design.

As a simplified example, if the driver 10, 500 is designed to have a maximum output voltage rating of 170V DC, and there is only a single junction box in the lighting system, then each SSL driver-less lighting unit forward voltage is limited to 18.8 VDC/cell (170VDC divided by 9 cells). If two junction boxes 1100 are used, the SSL driver-less lighting unit forward voltage is limited to 10VDC per cell (170VDC divided by 17 cells).

Fig. 14 shows a circuit diagram between the input and output connectors, and the arrangement of the rectifier 1160 and the open circuit protection circuit 1180. The bridge rectifier 1160 acts as reverse polarity protection so that there are no polarity issues between the drive 10, 500 and the junction box 1100 during installation. A reverse polarity protector in the form of a bridge rectifier 1160 protects the drivers 10, 500 and junction box 1100 from damage if the lamp unit 100 is connected in reverse polarity by an installer mistake. Open circuit protection circuit 1180 preferably includes a zener diode 1220, a Silicon Controlled Rectifier (SCR)1240, and a resistor 1260 at each output port 1140.

Additional rectifiers may be added to the lighting unit 100. This solves the following problems:

although the rectifier 1160 provides reverse polarity protection between the drivers 10, 500 and the junction box 1100, the particular lighting load 100 must be connected in the correct polarity for the particular lighting unit to function properly. To overcome this problem, the lighting unit must also have a rectifier to provide reverse polarity protection.

When any open circuit occurs at any output connector 1140 and/or when the voltage exceeds the specified reverse breakdown voltage of the zener diode 1220, causing the zener diode 1220 to operate in a reverse bias mode, a Silicon Controlled Rectifier (SCR)1240 will be triggered at the gate terminal to enable current to flow through the Silicon Controlled Rectifier (SCR)1240, thereby maintaining a closed loop for the overall lighting system so that other connected lighting units 100 in the network continue to operate as normal. The resistor 1260 acts as a current limiter for the zener diode 1220 to prevent excessive current from flowing through the zener diode 1220. Another resistor 1280 may be connected in parallel with the open protection circuit and in parallel with the output connector 1140.

As an alternative or in addition to the open circuit protector 1180, it should be appreciated that the resistor 1280 may be configured to function as a cross/shunt resistor for placement of a particular output connector 1140 to which that particular output connector 1140 is not connected to its load 100 in order to maintain a closed loop of the overall lighting system. In the event that a particular output connector 1140 is permanently assumed to be not connected to any load, then the open circuit protectors connected to those output connectors may be removed.

Thus, the junction box 1100 is designed and implemented with a string driver to overcome the above-described disadvantages caused by a series connection.

Example of an operating specification

The recommended operating specifications for the LED driver 10, 8-pin (low resolution) configuration are listed below:

operating voltage: 100 to 120VAC in the United states; european 220 to 240VAC

Operating frequency: 50/60 Hz (Hz)

AC current: 0.2 amperes (a) in the united states; european 0.1A

Inrush current: the US maximum allowable is 4A; european maximum allowable 12A

Leakage current: less than (<)0.7 milliamp

Efficiency (full load): greater than (greater than) 83%

Power factor (full load): greater than (>)0.98

Output specifications (8-pin configuration) based on 120VAC (us)/230 VAC (european) input, rated load, and 25 degrees celsius ambient temperature are listed as follows:

an output channel: 1

Output voltage range: 12 to 36VDC

Output current: 600 or 700mA

Current tolerance: plus or minus 5 percent

Current adjustment range: is not adjustable

Rated power: 21.6W_MAX(at 600mA) and 25.2W_MAX(at 700mA)

The recommended operating input specifications for the LED driver 10, 500, 14 pin configuration are listed as follows:

operating voltage: 100 to 120VAC in the United states; european 220 to 240VAC

Operating frequency: 50/60 Hz (Hz)

AC current: 1.3 amperes (a) in the united states; european 0.6A

Inrush current: the U.S. maximum allowable is 7A; european maximum allowable of 30A

Leakage current: less than (<)0.7 milliamp

Efficiency (full load): greater than (>) 86%

Power factor (full load): greater than (>)0.96

The output specifications for the LED driver 10, 500, 14 pin configuration with two output channels based on 120VAC (us)/230 VAC (european) input, rated load, and 25 degrees celsius ambient temperature are listed as follows:

an output channel: 2

Output voltage range: 35 to 85VDC (single channel) for a total of 70 to 170VDC

Output current: 600 or 700mA

Current tolerance: plus or minus 5 percent

Current adjustment range: is not adjustable

Rated power: 102W_MAX(at 600mA) and 119W_MAX(at 700mA)

The LED driver 10, 500 is particularly suitable for LED downlights, troffer LED lighting and MR 16, especially in the 0 to 40 degree celsius temperature range.

In addition, the following advantages are also apparent:

a. safer method for LED lighting unit

Since the LED driver 10, 500 is an isolated DC configuration, working only with DC driven LED lighting units, there are no safety related issues associated with AC current for the LED lighting unit 100, the LED lighting unit 100 is on the secondary side and isolated from the power line mains. Since the LED driver 10, 500 is isolated from the LED lighting unit 100, there is also no size limitation in design, and since in a built-in configuration, the LED driver 10, 500 can be designed according to safety requirements.

b. High electrical efficiency

The LED driver 10, 500, referred to as a "string driver", operates in a cooler environment because it is isolated from the LED load unit 100 and is not affected by the heat dissipated by the LED unit 100 during continuous operation. This reduces heat loss on the LED driver 10, 500 and therefore consumes less power during operation, improving efficiency. Compared to the prior art, where each LED lamp comprises its own driver directly connected to the AC mains, the power efficiency is significantly improved compared to AC driver lighting units in a complete lighting system, since the total power loss only applies to a specific single driver, whereas AC driven lighting units may have a higher total power loss due to losses on each lighting unit.

c. High efficiency (lumen/tile)

As an associated advantage, the tandem configuration provides a cooler working environment, which results in lower optical losses of the LED devices, so the higher luminous flux presented by the LED devices ultimately improves the efficiency (lumens/watt) of the overall lighting system.

d. Long service life

The LED driver 10, 500 using ASIC control does not need to use short-life components such as aluminum electrolytic capacitors, which extends the service life of the LED driver 10, 500. As for the LED lamp unit 100, being cooler and operating at approximately ripple-free constant current significantly improves the performance and reliability of the LED device and slows down the overall performance degradation process on the LED device 100, ultimately extending the life of the entire LED lighting unit.

e. Wide range of application options

The flexible design for the single LED driver 10, 500 is applicable to any type of DC driven LED lighting unit, theoretically capable of driving an unlimited number of LEDs in the overall lighting system, with minor fine-tuning of certain components as described earlier.

f. Cost-effective solution

The string driver configuration is a cost-effective solution because a single LED driver 10, 500 is capable of driving a series of DC-driven LED lighting units, whereas prior art configurations require one driver for each LED lighting unit. Furthermore, the solution also provides more competitive manufacturing costs as well as design component costs, especially for heat sinks.

g. Easy to maintain

Since the single LED driver 10, 500 is isolated from the LED lighting unit 100, if any failure occurs within the lighting system due to a failed LED driver 10, 500, the user only needs to replace the failed LED driver without having to disassemble the entire LED lighting (built-in concept). Such a maintenance procedure is simple and can be done in a relatively short period of time.

h. Miniaturization in form factor

The heat sink for the luminaire would be smaller in size where the heat sink is only designed to dissipate the heat generated by the LED lighting unit 100, generating no heat from the AC-DC LED driver because of the isolation between them. Furthermore, since the overall system requires less component count and thus uses less material than the integrated concept, individual drivers can be designed in this optimal size and instead of bulky form-factor conventional transformers, the introduction of planar transformers will further enhance the slim appearance of the driver solution.

More clearly, the LED driver 10, 500 requires less component count and fewer component copies than prior art systems where each LED lamp unit requires its own AC to DC driver. Thereby reducing the driver solution form factor. In addition to this, the manufacturing process is simplified, so that the yield and the yield are improved.

More significantly, the heat sink form factor of each LED lighting unit 100 is reduced in the string configuration, as each heat sink only needs to handle the heat dissipated by the LED lighting units 100. This is because the LED driver 10, 500 is isolated from the LED lighting unit 100. This may be beneficial for component cost because less material is used. Moreover, the overall design cycle is further shortened, since the LED lighting unit 100 and the LED driver 10, 500 design activities can be carried out simultaneously, which results in an improved time to market for the product.

The junction box 1100 further provides the following additional advantages to the string driver concept:

a. error-free installation

The junction box 1100 is designed in a "mis-operation proof" concept to provide a non-error installation experience to the end user. Polarity is a concern during installation to ensure that the entire lighting system operates as intended. By providing an interface with the drivers 10, 500 and SSL driver-less lighting unit 100 via the bridge rectifier at each junction box, accidental reverse polarity connections are eliminated during installation. Regardless of the polarity considerations, the lighting units 100 within the lighting system will function properly as long as there is continuity between the driver 10, 500 and the SSL driver-less lighting unit 100. Furthermore, there is a splice and plug-in connector design on the interface between the driver output and the junction box input, which would completely eliminate the possibility of connecting the driver output to any junction box output connector.

b. Easy to install

The junction box 1100 includes a connector design for connection purposes with the drivers 10, 500 and the driver-less SSL lighting unit 100. The user will thus find it easy to connect or plug the tape end cable into the correct or dedicated connector. In addition, due to the simplicity of installation, less time is spent on installation and system setup, resulting in lower costs.

c. Safer installation

Since only a DC power supply is present on the junction box 1100, a safe environment is created for installation.

d. Flexibility of installation

Since the string driver concept has no wire length constraints during installation, users can flexibly arrange the SSL driver-less lighting unit according to their preferred design and/or needs. Users can easily extend the wires of the SSL driver-less lighting unit 100 to their desired length in order to meet applications with specific wire specifications, such as the american cable gauge (AWG) 16-24, to obtain a perfect match to the junction box input/output connectors 1120, 1140. Moreover, the junction box is also designed to support dual (or possibly a greater number of junction box connections), which provides additional flexibility in installation.

e. Easy to maintain

The particular design features of the junction box as described in the embodiments enable the user/installer to easily identify the faulty unit and perform the necessary maintenance as they would normally experience even if the string drives were operating in a series connection.

f. Reliable connection

Since the described input/output connectors 1120, 1140 connected within the lighting system are either wire-in or latched, a good connection is given compared to the conventional screw-fastening methods widely used in the market.

It will be understood that the above embodiments are provided by way of example of the invention only, and that further modifications and improvements thereto as would be apparent to persons skilled in the relevant art are deemed to fall within the broad scope and ambit of the invention as described. Moreover, while single embodiments of the invention are illustrated, it is intended that the invention also cover various combinations of the described embodiments.

Claims (27)

1. A system for driving a plurality of high power LED units, the system comprising a single driver for providing ripple-free constant direct current to a plurality of high power LED lamp units,

wherein the single driver comprises a digital controller programmable to adjust the ripple-free constant direct current at each predetermined time interval based on detection and calculation of a duration taken to release energy to the LED lamp unit, thereby adjusting the ripple-free constant direct current.

2. The system of claim 1, wherein the single driver operates in an isolated ac flyback configuration having an inductive element that is a transformer for isolating the plurality of high power LEDs at the secondary end of the transformer.

3. The system of claim 2, wherein the digital controller is an Application Specific Integrated Circuit (ASIC); the ASIC is further operable to detect and calculate the duration of the energy release to the plurality of high power LEDs by the core of the transformer to regulate and provide the ripple-free output DC current.

4. The system of claim 3, wherein the ASIC is programmed to receive feedback as an input at each clock cycle based on the duration of the energy released by the core of the transformer to determine an amount of ripple-free constant DC current for a next clock cycle.

5. The system of claim 4, wherein the ASIC is programmed to provide a voltage waveform at each clock cycle to turn an electronic switch on or off.

6. The system of claim 1, wherein each of the plurality of high power LED lamp units is connected in series with other high power LED lamp units.

7. The system of claim 1, wherein the single driver is electrically connected to a dimmer circuit for adjusting the brightness of the plurality of high power LED lamp units.

8. The system of claim 7, wherein the dimmer circuit comprises a potentiometer, an infrared interface, a motion sensor, or an environmental sensor.

9. The system of claim 7, wherein the system comprises a capacitor operable to change its capacitance to maintain a power factor of at least 0.9 when adjusting the dimmer.

10. The system of claim 8, wherein the potentiometer is operable to operate within a voltage of 0 to 10V.

11. The system of claim 2, wherein the secondary side of the transformer is electrically connected to a short circuit protection circuit.

12. The system of claim 3, wherein the ASIC is coupled with an active power factor controller.

13. The system of claim 12, wherein the active power factor controller comprises at least one voltage follower.

14. The system of claim 3, wherein the ASIC is in a 14-pin configuration.

15. The system of claim 1, wherein each high power LED lamp is provided with a heat sink shaped and configured to dissipate heat from only the high power LEDs.

16. The system of claim 3, wherein the system further comprises an electronic switch, wherein the ripple-free constant DC current is achieved by means of voltage control according to the following equation:

wherein, V_OUTIs the voltage across the output; v_INIs the input voltage; t is_OFFIs the discharge time of the iron core of the isolation transformer; t is_ONIs the on-time of the electronic switch; l is₁Is the inductance value of the primary winding of said transformer, and L₂Is the inductance value of the secondary winding of the transformer.

17. The system of claim 1, wherein the single driver operates in a non-isolated configuration having an inductive element operating in a continuous mode according to the following equation:

wherein, T_OFFFixed as a constant; t is_ONIs the on-time of the electronic switch; t is T_ON、T_OFFAnd T_CALCOf a total of (a), wherein T_CALCIs the time after the discharge time of the inductive element to calculate the formula; i is₁Is the required reference current, and I_MAXIs the peak current.

18. The system of claim 17, wherein for a hysteretic controller configuration, I_MAXAnd I₁May be fixed, and T may be determined_ONAnd T_OFFAnd (6) timing.

19. An LED driver, comprising:

at least one Integrated Circuit (IC), the IC programmable using a hardware description language;

a first electronic switch operable to provide a first switching period to control a power factor voltage, the first switching period being programmable by the at least one IC; and

a second electronic switch operable to provide a second switching period to regulate a ripple-free constant DC current flowing into the at least one LED, the second switching period being programmable by the at least one IC.

20. The LED driver of claim 19, wherein said first and second electronic switches are power MOSFETs.

21. The LED driver of claim 19, wherein said at least one IC is an ASIC.

22. An apparatus having an input port and a plurality of output ports, the apparatus comprising:

a reverse polarity protector arranged to be electrically connected to the input port and each of the plurality of output ports; and

a plurality of open circuit protection circuits, each of the plurality of open circuit protectors operable to be connected to an output port;

wherein the reverse polarity protector is operable to reject a polarity requirement if a load is connected to any of the output ports with the wrong polarity; and the open circuit protection circuit is operable to form a closed loop series connection in the event that no load is connected to the output port or the load breaks down.

23. The apparatus of claim 22, wherein the reverse polarity protector is a diode bridge rectifier.

24. The apparatus of claim 22, wherein each output port includes a respective open circuit protector.

25. The apparatus of claim 22, wherein the input ports are adapted for connection with an LED driver and each of the output ports is adapted for connection with a load comprising a high power LED lamp unit.

26. A system according to claim 6, further comprising a device according to claims 22 to 25; wherein the input port of the apparatus of claims 22 to 25 is operable to connect to the single driver.

27. A dimmer circuit for use with an LED driver, the dimmer circuit comprising at least one dimming interface operable to connect to at least one dimming controller; and a capacitive element adjustable to maintain a power factor of at least 0.9 within the dimmer circuit.