TWI707607B - LED driving circuit and LED lamps using it - Google Patents

Abstract

An LED driving circuit, characterized by having: a first voltage divider circuit for providing a first sensing voltage according to an input voltage; and a detection circuit having a sensing unit and a disableable current source The sensing unit is used to detect whether the time when the first sensing voltage is lower than a first reference voltage exceeds a threshold to determine the state of the enabling signal, and if so, to make the enabling signal present an active state to enable The disableable current source, if not, makes the enable signal present a non-active state to disable the disableable current source, and the disableable current source can be adaptively enabled when it is enabled The current value of the suction current is adjusted so that the suction current is equal to a predetermined current through an LED indicator.

Description

LED driving circuit and LED lamps using it

The present invention relates to an LED drive circuit, especially an LED drive circuit that can be matched with a switch panel with indicator lights.

In the existing switch panels used to switch lighting fixtures, in order to facilitate the user to find the position of the switch panel after the light is turned off, some switch panels rely on surface phosphor to provide weak reflection, and some are embedded in the panel. LED night light, the panel is closed, the night light is off, and the panel is off, the night light is on.

Please refer to Figure 1, which shows a circuit diagram of a conventional lighting fixture. As shown in Figure 1, the conventional lighting fixture includes a switch 11, an LED 12, a full-wave rectifier unit 13 composed of four diodes (13a, 13b, 13c, 13d), a filter capacitor 14, a The detection circuit 15, a diode 16, an inductor 17, a driver 18, and an LED module 19, wherein the detection circuit 15 has a voltage divider circuit composed of a resistor 15a and a resistor 15b to provide a first control voltage V ₁ , a first inverter circuit composed of a resistor 15c and a bipolar junction transistor 15d to generate a second control voltage V ₂ that is inverted from the first control voltage V ₁ , and a resistor 15e and a double A second inverter circuit formed by the polar junction transistor 15f provides a current path for the LED 12 when the second control voltage V ₂ is high; the diode 16, the inductor 17 and the driver 18 form a driving circuit To drive the LED module 19.

When the switch 11 is closed: the LED 12 (night light) in parallel with the switch 11 does not light; the full-wave rectifier unit 13 performs full-wave rectification on the AC voltage V _AC to generate an input voltage V _IN for the driving circuit to light up LED module 19; and at this time, the first control voltage V ₁ is at a high potential, the second control voltage V ₂ is at a low potential, and the bipolar junction transistor 15f is in the off state. When the switch 11 is turned off: the LED 12 (night light) connected in parallel with the switch 11 lights up; the level of the input voltage V _IN on the filter capacitor 14 will drop significantly, causing the drive circuit to fail to light the LED module 19 ; And at this time, the first control voltage V ₁ is a low potential, the second control voltage V ₂ is a high potential, and the bipolar junction transistor 15f is in a closed state to provide a current path for the LED 12.

In addition, considering the system cost and hardware space constraints, the filter capacitor 14 generally does not select a particularly large capacitance value. However, since the commercial power generally has a considerable voltage fluctuation range, for example, 100V AC mains will vary between AC 85V and 115V. Therefore, when the switch 11 is closed and the AC mains is at a relatively low voltage, the input voltage V _IN The trough position will be relatively low, so that the first control voltage V ₁ may be less than the turn-on voltage of the bipolar junction transistor 15d and the bipolar junction transistor 15f will be turned on, thereby dividing the current of the LED module 19 and reducing it The work efficiency of the conventional lighting fixture is improved. In addition, the bipolar junction transistor 15d and the bipolar junction transistor 15f are both high-voltage components. Whether implemented as discrete components or integrated into the chip, they have the disadvantage of high cost.

In order to solve the above problems, a novel LED driving circuit is urgently needed in the art.

An object of the present invention is to provide an LED driving circuit, which can adaptively provide a current path for the LED indicator of a switch panel without affecting the driving efficiency of an LED module, so that the This LED indicator will light up when the switch is turned off.

Another object of the present invention is to provide an LED lamp, which can adaptively provide a current path for the LED indicator of a switch panel without affecting the driving efficiency of one of its internal LED modules. The LED indicator light is lit when one of the switches of the switch panel is turned off.

In order to achieve the aforementioned purpose, an LED driving circuit is proposed, which is used with a switch panel to drive an LED module. The switch panel includes a switch and an LED indicator parallel to the switch. When the switch When closed, the LED drive circuit generates an output current according to an input voltage to drive the LED module. When the switch is open, the LED drive circuit provides a current path to light up the LED indicator. It is characterized by:

A first voltage divider circuit for providing a first sensing voltage according to an input voltage; and

A detection circuit having a sensing unit and a disableable current source, the sensing unit is used to detect whether the first sensing voltage is lower than a first reference voltage for a time exceeding a threshold to determine an enabling signal If it is, then the enable signal is made to assume an active state to enable the disableable current source, if not, the enable signal is made to assume a non-active state to disable the disableable current source, In addition, when the disabled current source is enabled, the current value of the suction current can be adjusted adaptively to make the suction current equal to a predetermined current through the LED indicator.

In one embodiment, the first voltage divider circuit is a series resistance circuit.

In an embodiment, the sensing unit has:

A comparator for performing a voltage comparison operation on the first sensing voltage and the first reference voltage to generate a comparison result signal. When the first sensing voltage is greater than the first reference voltage, the comparison result signal Presents a low potential, and when the first sensing voltage is less than the first reference voltage, the comparison result signal presents a high potential;

A timing circuit for making a timing output signal present the high potential when the time during which the comparison result signal presents the high potential exceeds the threshold; and

An inversion gate is used for performing an inversion logic operation on the comparison result signal and the timing output signal to generate the enabling signal.

In one embodiment, the disableable current source has:

A JFET transistor having a gate, a drain and a source, the gate is coupled to a reference ground, and the drain is coupled to the input voltage;

A second voltage divider circuit for generating a second sensing voltage according to the voltage of the source of the JFET transistor;

An amplifier having a consistent energy control terminal, a positive input terminal, a negative input terminal and an output terminal, the enable control terminal is coupled to the enable signal, and the positive input terminal is coupled to the second sensing voltage, The negative input terminal is coupled to a second reference voltage; and

An NMOS transistor has a gate for coupling to the output terminal of the amplifier, a drain for coupling to the source of the JFET transistor, and a source for coupling to the reference ground.

In one embodiment, the input voltage is a voltage generated after an AC voltage is rectified by a full-wave rectifier unit.

In order to achieve the foregoing objective, the present invention further provides an LED lamp, which includes an LED driving circuit and an LED module, wherein the LED driving circuit is used with a switch panel to drive the LED module, and the switch panel It includes a switch and an LED indicator in parallel with the switch. When the switch is closed, the LED drive circuit generates an output current according to an input voltage to drive the LED module. When the switch is off, the LED drive circuit A current path is provided to light the LED indicator, and the LED drive circuit is characterized by:

A first voltage divider circuit for providing a first sensing voltage according to an input voltage; and

A detection circuit having a sensing unit and a disableable current source, the sensing unit is used to detect whether the first sensing voltage is lower than a first reference voltage for a time exceeding a threshold to determine an enabling signal If it is, then the enable signal is made to assume an active state to enable the disableable current source, if not, the enable signal is made to assume a non-active state to disable the disableable current source, In addition, when the disabled current source is enabled, the current value of the suction current can be adjusted adaptively to make the suction current equal to a predetermined current through the LED indicator.

In one embodiment, the first voltage divider circuit is a series resistance circuit.

In an embodiment, the sensing unit has:

A comparator for performing a voltage comparison operation on the first sensing voltage and the first reference voltage to generate a comparison result signal. When the first sensing voltage is greater than the first reference voltage, the comparison result signal Presents a low potential, and when the first sensing voltage is less than the first reference voltage, the comparison result signal presents a high potential;

A timing circuit for making a timing output signal present the high potential when the time during which the comparison result signal presents the high potential exceeds the threshold; and

An inversion gate is used for performing an inversion logic operation on the comparison result signal and the timing output signal to generate the enabling signal.

In one embodiment, the disableable current source has:

A JFET transistor having a gate, a drain and a source, the gate is coupled to a reference ground, and the drain is coupled to the input voltage;

A second voltage divider circuit for generating a second sensing voltage according to the voltage of the source of the JFET transistor;

An amplifier having a consistent energy control terminal, a positive input terminal, a negative input terminal and an output terminal, the enable control terminal is coupled to the enable signal, and the positive input terminal is coupled to the second sensing voltage, The negative input terminal is coupled to a second reference voltage; and

An NMOS transistor has a gate for coupling to the output terminal of the amplifier, a drain for coupling to the source of the JFET transistor, and a source for coupling to the reference ground.

In one embodiment, the input voltage is a voltage generated after an AC voltage is rectified by a full-wave rectifier unit.

Please refer to FIG. 2, which shows a circuit diagram of an embodiment of the lighting fixture of the present invention. As shown in FIG. 2, an LED lamp 100 is coupled to a switch panel 110 (including a switch 110a and an LED 110b connected in parallel with the switch 110a), wherein the LED lamp 100 includes a full-wave rectifier unit 101 and a filter capacitor 102. A voltage divider circuit 103 (consisting of a first resistor 103a and a second resistor 103b connected in series), a detection circuit 104, a driving circuit 105 (including a diode 105a, an inductor 105b and a driver 105c) and an LED module 106, wherein the detection circuit 104 has a comparator 104a, a timing circuit 104b, an inverter 104c, a third resistor 104d, a fourth resistor 104e, an amplifier 104f, and an NMOS circuit The crystal 104g and a JFET transistor 104h, wherein the comparator 104a, the timing circuit 104b and the inverter 104c constitute a sensing unit, the third resistor 104d, the fourth resistor 104e, the amplifier 104f, the NMOS transistor 104g and the JFET transistor 104h constitutes a disableable current source, and the sensing unit is used for a first sensing voltage V ₁ provided by the voltage divider circuit 103 to be lower than a first reference voltage V _{REF1 for} a time exceeding a threshold (for example But not limited to 10ms), the output of the enabling signal EN presents an active state (for example, but not limited to a high potential), and the disableable current source is adaptable when the enable signal EN presents the active state The current value of the sink current is adjusted to make the sink current equal to the drive current scheduled to pass through one of the LEDs 110b on the switch panel 110 to stably light the LED 110b.

When the switch 110a is closed: the LED 110b (night light) in parallel with the switch 110a does not light; the full-wave rectifier unit 101 performs full-wave rectification on the AC voltage V _AC to generate an input voltage V _IN for the driving circuit 105 to light the LED module Group 106; in this case, the time that the first sensing voltage V _{1 is} lower than the first reference voltage V _REF1 will not exceed the threshold, and the enabling signal EN will assume an inactive state (such as but not limited to a low potential) , And the NMOS transistor 104g is in an off state.

When the switch 110a is turned off: the LED 110b (night light) in parallel with the switch 110a lights up; the level of the input voltage V _IN on the filter capacitor 102 will drop significantly, causing the driving circuit 105 to fail to light the LED module 106; In this case, the time that the first sensing voltage V _{1 is} lower than the first reference voltage V _REF1 will exceed the threshold, and the enabling signal EN will assume the above-mentioned active state to enable the disableable current source.

Specifically, the working principle of the sensing unit is described as follows:

The comparator 104a is used to perform a voltage comparison operation on the first sensing voltage V ₁ and the first reference voltage V _REF1 to generate a comparison result signal. When the first sensing voltage V _{1 is} greater than the first reference voltage V _REF1 , The comparison result signal presents a low potential, and when the first sensing voltage V _{1 is} less than the first reference voltage V _REF1 , the comparison result signal presents a high potential;

The timing circuit 104b is used to make a timing output signal exhibit the high potential when the time for the comparison result signal to exhibit the high potential exceeds the threshold;

The inversion gate 104c is used to perform an inversion logic operation on the comparison result signal and the timing output signal to generate an enable signal EN.

The working principle of this disableable current source is explained as follows:

The third resistor 104d and the fourth resistor 104e form a voltage divider circuit to generate a second sensing voltage V ₂ according to the source voltage V _{X of the} JFET transistor 104h;

The amplifier 104f has an enabling control terminal, a positive input terminal, a negative input terminal, and an output terminal. The enable control terminal is coupled to the enable signal EN, the positive input terminal is coupled to the second sensing voltage V ₂ , and the negative The input terminal is coupled to the second reference voltage V _REF2 , and the output terminal is coupled to the NMOS transistor 104g;

The NMOS transistor 104g has a gate, a drain and a source, the gate is coupled to the output terminal of the amplifier 104f, the drain is coupled to the JFET transistor 104h, and the source is coupled to a reference ground;

The JFET transistor 104h has a gate, a drain and a source, the gate is coupled to the reference ground, the drain is coupled to the input voltage V _IN , and the source is coupled to all of the NMOS transistor 104g Described very much.

When the enable signal EN assumes the above-mentioned active state, the amplifier 104f will be enabled, thereby enabling a negative feedback circuit formed by the amplifier 104f, the NMOS transistor 104g, the third resistor 104d and the fourth resistor 104e to make The sink current of the JFET transistor 104h can be adaptively adjusted to the rated current of the LED 110b.

Please refer to Figure 3, which shows a working waveform diagram of one of the lighting fixtures in Figure 2. As shown in FIG. 3, when the first sensing voltage V _{1 is} lower than the first reference voltage V _{REF1 for} a time that does not exceed the threshold T _S (10 ms), the enable signal EN will assume the inactive state (low potential ) - denotes a switch 110a is closed; the time when the first sensing voltage V ₁ is lower than the first reference voltage V _REF1 exceeds a threshold value T _S (10 ms), the enable signal EN will exhibit active state (the high potential) -Represents that the switch 110a is off.

In addition, since the input voltage V _IN rectified by the full-wave rectification unit 101 is a high voltage, the JFET transistor 104h must use a high-voltage component.

In addition, the JFET transistor 104h is functionally equivalent to a resistor. Since the rated current of the night light of different types of switch panels is different, the drive circuit of the night light cannot be set to a fixed current. According to the above design, when the enable signal EN signal presents the stated action state, if the rated current of the LED 110b is greater than the absorption current of the disableable current source, the source voltage V _{X of} the JFET transistor 104h will increase High, causing the second sensing voltage V _{2 to} increase to increase the absorption current of the disableable current source; conversely, if the rated current of the LED 110b is less than the absorption current of the disableable current source, the JFET transistor 104h The source voltage V _{X of} V will drop, causing the second sensing voltage V _{2 to} drop to reduce the absorption current of the disable current source, and finally a dynamic balance is achieved.

In addition, the JFET transistor 104h can also provide a power path for the detection circuit 104 to generate internal power, the first reference voltage V _REF1 and the second reference voltage V _REF2 .

According to the above description, the present invention can provide the following advantages:

1. LED lamps have high efficiency.

Even though the rectified input voltage of the detection circuit of the present invention has a relatively low trough, if the input voltage time is lower than a reference voltage for a time period that does not exceed a threshold value (about 10mS), it will be considered that the switch panel is not turned off, so The drive circuit of the night light will be activated, so excess power consumption will not be lost.

2. It is easy to integrate into the chip, and the system cost is low.

The detection circuit of the present invention only uses a high-voltage element JFET transistor 104h that is easy to integrate into the driver chip, which not only saves hardware space, but also reduces the application cost of the system. In addition, the JFET transistor 104h can also be used as the startup resistor of the driver chip, so no additional startup resistor is needed, which simplifies the system design.

The disclosure of the present invention is one of the preferred embodiments, and any partial changes or modifications that are derived from the technical ideas of the present invention and are easily inferred by those skilled in the art will not depart from the scope of the patent right of the present invention.

In summary, regardless of the purpose, means and effect of this case, it is shown that it is very different from the conventional technology, and its first invention is suitable for practicality, and it does meet the patent requirements of the invention. I implore the examiner to investigate and grant the patent as soon as possible Society is for the best prayer.

11: switch 12: LED 13: Full-wave rectifier unit 13a, 13b, 13c, 13d: diode 14: filter capacitor 15: Detection circuit 15a, 15b, 15c, 15e: resistance 15d, 15f: bipolar junction transistor 16: Diode 17: Inductance 18: drive 19: LED module 100: LED lamps 101: Full-wave rectifier unit 102: filter capacitor 103: Voltage divider circuit 103a: first resistor 103b: second resistor 104: detection circuit 104a: Comparator 104b: Timing circuit 104c: reverse and gate 104d: third resistor 104e: fourth resistor 104f: amplifier 104g: NMOS transistor 104h: JFET transistor 105: drive circuit 105a: Diode 105b: Inductance 105c: drive 106: LED module 110: switch panel 110a: switch 110b: LED

Figure 1 shows a circuit diagram of a conventional lighting fixture. Fig. 2 is a circuit diagram of an embodiment of the lighting fixture of the present invention. Fig. 3 shows a working waveform diagram of the lighting fixture of Fig. 2;

100: LED lamps

101: Full-wave rectifier unit

102: filter capacitor

103: Voltage divider circuit

103a: first resistor

103b: second resistor

104: detection circuit

104a: Comparator

104b: Timing circuit

104c: reverse and gate

104d: third resistor

104e: fourth resistor

104f: amplifier

104g: NMOS transistor

104h: JFET transistor

105: drive circuit

105a: Diode

105b: Inductance

105c: drive

106: LED module

110: switch panel

110a: switch

110b: LED

Claims (10)

An LED driving circuit is used with a switch panel to drive an LED module. The switch panel includes a switch and an LED indicator light connected in parallel with the switch. When the switch is closed, the LED driving circuit depends on an input The voltage generates an output current to drive the LED module. When the switch is turned off, the LED drive circuit provides a current path to light up the LED indicator. The LED drive circuit is characterized by: a first voltage divider Circuit for providing a first sensing voltage according to the input voltage; and a detection circuit having a sensing unit and a disableable current source, the sensing unit is used for detecting that the first sensing voltage is low Whether the time at a first reference voltage exceeds a threshold to determine the state of the enable signal, if yes, make the enable signal present an active state to enable the current source that can be disabled, if not, enable the enable signal The signal presents an inactive state to disable the disableable current source, and when the disableable current source is enabled, the current value of its sink current can be adjusted adaptively so that the sink current passes through the LED One of the indicator lights has the same predetermined current. According to the LED driving circuit described in item 1 of the scope of patent application, the first voltage divider circuit is a series resistor circuit. According to the LED driving circuit described in claim 1, wherein the sensing unit has: a comparator for performing a voltage comparison operation on the first sensing voltage and the first reference voltage to generate a comparison A result signal. When the first sensing voltage is greater than the first reference voltage, the comparison result signal presents a low level, and when the first sensing voltage is less than the first reference voltage, the comparison result signal presents a high level ; A timing circuit for making a timing output signal present the high potential when the time for the comparison result signal to present the high potential exceeds the threshold; and a flip and gate for the comparison result signal and the timing The output signal performs an inverse and logical operation to generate the enable signal. The LED driving circuit described in the first item of the scope of patent application, wherein the disableable current source has: a JFET transistor with a gate, a drain and a source, and the gate is coupled to a reference Ground, the drain is coupled to the input voltage; a second voltage divider circuit for generating a second sensing voltage according to the voltage of the source of the JFET transistor; an amplifier having a uniform energy control terminal, A positive input terminal, a negative input terminal and an output terminal, the enable control terminal is coupled to the enable signal, the positive input terminal is coupled to the second sensing voltage, the negative input terminal is coupled to a second Reference voltage; and an NMOS transistor having a gate to couple to the output terminal of the amplifier, a drain to couple to the source of the JFET transistor, and a source to couple to the reference ground . The LED driving circuit described in the first item of the scope of patent application, wherein the input voltage is a voltage generated by an AC voltage rectified by a full-wave rectifier unit. An LED lamp includes an LED drive circuit and an LED module, wherein the LED drive circuit is used with a switch panel to drive the LED module. The switch panel includes a switch and an LED in parallel with the switch Indicator light. When the switch is closed, the LED drive circuit generates an output current according to an input voltage to drive the LED module. When the switch is open, the LED drive circuit provides a current path to light up the LED indicator. , The LED driving circuit is characterized by having: a first voltage divider circuit for providing a first sensing voltage according to the input voltage; and a detection circuit having a sensing unit and a disable current source The sensing unit is used to detect whether the time when the first sensing voltage is lower than a first reference voltage exceeds a threshold to determine the state of the enabling signal, and if so, to make the enabling signal present an active state to enable The disableable current source, if not, makes the enable signal present a non-active state to disable the disableable current source, and the disableable current source can be adaptively enabled when it is enabled The current value of the suction current is adjusted to make the suction current equal to a predetermined current through the LED indicator. According to the LED lamp described in item 6 of the scope of patent application, the first voltage divider circuit is a series resistor circuit. The LED lamp as described in item 6 of the scope of patent application, wherein the sensing unit has: a comparator for performing a voltage comparison operation on the first sensing voltage and the first reference voltage to generate a comparison result Signal, when the first sensing voltage is greater than the first reference voltage, the comparison result signal presents a low potential, and when the first sensing voltage is less than the first reference voltage, the comparison result signal presents a high potential; A timing circuit for making a timing output signal exhibit the high potential when the time for the comparison result signal to exhibit the high potential exceeds the threshold; and a flip-flop for the comparison result signal and the timing output The signal undergoes an inverse and logical operation to generate the enabling signal. The LED lamp described in item 6 of the scope of patent application, wherein the disableable current source has: a JFET transistor with a gate, a drain and a source, and the gate is coupled to a reference ground , The drain is coupled to the input voltage; a second voltage divider circuit for generating a second sensing voltage according to the voltage of the source of the JFET transistor; an amplifier with a consistent energy control terminal, a A positive input terminal, a negative input terminal, and an output terminal, the enable control terminal is coupled to the enable signal, the positive input terminal is coupled to the second sensing voltage, and the negative input terminal is coupled to a second reference Voltage; and an NMOS transistor having a gate to couple to the output terminal of the amplifier, a drain to couple to the source of the JFET transistor, and a source to couple to the reference ground. For the LED lamp described in item 6 of the scope of patent application, the input voltage is a voltage generated by an AC voltage rectified by a full-wave rectifier unit.

Images