JP6694408B2 - LED power supply device and LED lighting device - Google Patents

Description

  The present invention relates to an LED power supply device for supplying power to an LED load, and an LED lighting device using the power supply device.

  As a power supply device for an LED lighting device using an LED (light emitting diode), in order to stabilize the output current, a control system that is not affected by input fluctuations and load fluctuations, as in Patent Document 1, etc. Are known.

  One of them is a feedback control type power supply device. The power supply of this feedback control system is basically controlled by high frequency switching, and has a filter section 101, a switching section 102, an output section including an LED load 103, a control section 104, etc., as shown in the basic configuration of FIG. The current of the LED load 103 is detected by the detection unit 105, and the frequency of the switching unit 102 is controlled by the control unit 104 so that the current of the LED load 103 becomes constant. 4, reference numeral 106 is a commercial power source, 107 is a rectifying unit, 108 is a smoothing capacitor, and 109 is a diode.

  However, this feedback control type LED power supply device has drawbacks that noise is likely to occur, the number of parts is large, the price is high, and the shape is large.

  Further, as another type of LED power supply device, there is one using a hysteresis control system (including a critical mode control system). As shown in the basic configuration of FIG. 5, this power supply device has a filter section 111, a switching section 112, an output section including an LED load 113, a control section 114, and the like. The control section 114 outputs a constant voltage to the switching section 112. Repeated on and off so that.

  This hysteresis control type LED power supply device does not require current detection of the LED load and the configuration of the control unit 114 is simplified as compared with the feedback control type power supply device, but the switching unit 112 still exists. Therefore, there is a drawback that noise is easily generated and the number of parts is large.

  Still another type of LED power supply device is a serial control type power supply device. As shown in the basic configuration of FIG. 6, this power supply device has an output section including an LED load 121, a constant current element 122 for keeping the current of the LED load 121 constant, and a control for controlling the constant current element 122. The unit 123 is provided.

  This series control type power supply device has a significantly simplified structure as compared with the feedback control system and the hysteresis control system, but the efficiency is poor due to the large loss in the constant current element 122, and heat dissipation measures are required. Therefore, there is a drawback that the price is high and the shape is large.

JP, 2011-165920, A

  As described above, the conventional LED power supply device has drawbacks that it is likely to generate noise, has a large number of parts, is expensive, and has a large shape. Moreover, a device having no noise and a simple configuration is inefficient. There was a problem that the heat dissipation measures were necessary and the shape became large.

  The present invention has been made in view of such a technical background, and an object of the present invention is to provide an LED power supply device and an LED lighting device that have a simple configuration but can be downsized and are inexpensive.

The above problem can be solved by the following means.
(1) A rectifier circuit that rectifies an input from a commercial power source, an LED load, a power supply unit that supplies the LED load with power of only a portion of the output of the rectifier circuit that is equal to or lower than a predetermined potential, and the rectifier circuit. A smoothing capacitor for smoothing the output, a switching element connected in series with the smoothing capacitor, a constant current circuit connected in series with the LED load, a voltage on the current input side of the constant current circuit, and a current output side. A voltage detector that detects a voltage difference between the LED load and the constant current circuit that are connected in series, and the predetermined potential is the voltage detector. When the difference between the voltages of the constant current circuit detected by the switch rises to a first reference value, the switching element is turned off, and when the difference decreases to a second reference value, the switch is turned off. LED power supply, characterized in that it is set by turning on the grayed elements.
(2) The LED power supply device according to item 1, wherein the predetermined potential is set to be 1 V to 50 V higher than the forward voltage of the LED load.
(3) An LED lighting device equipped with the LED power supply device according to item 1 or 2.

According to the invention described in the above paragraph (1), a rectifier circuit that rectifies an input from a commercial power source, an LED load, and a power supply that supplies only the power of a portion of the output of the rectifier circuit that is equal to or lower than a predetermined potential to the LED load. Since the high frequency switching section is unnecessary, there is no problem of noise and the configuration is simple. Moreover, since the electric power supplied to the LED load is the electric power of only the portion of the output of the rectifier circuit which is equal to or lower than the predetermined potential, the loss can be reduced and the efficiency is high, and no heat dissipation measures are required, so that the cost can be reduced and the size can be reduced. Can be planned.
Further, the predetermined potential is turned off when the difference between the voltages of the constant current circuit detected by the voltage detection unit rises to the first reference value and turns off when the difference decreases to the second reference value. Since it is set by turning on the switching element , the predetermined potential can be set stably.

  According to the invention described in the above paragraph (2), the predetermined potential is set to 1 V to 50 V higher than the forward voltage of the LED load, so that the loss is minimized and the stable operation of the LED load is guaranteed. can do.

According to the invention described in the preceding paragraph ( 3 ), the LED lighting device can exhibit the effects exhibited by the LED power supply device described in the preceding paragraph (1) or ( 2) .

It is a circuit diagram of an LED lighting device according to an embodiment of the present invention. (A) is a waveform diagram of the output of the rectifier circuit, (B) is a waveform diagram of the voltage Vc across the smoothing capacitor, (C) is a waveform diagram of the output V2 of the voltage detection unit, and (D) is control from the first control unit. It is a wave form diagram of signal V3. It is a waveform diagram which expands and shows the mode of time T2-T5 of FIG. 2 (B). It is a circuit diagram which shows the basic composition of the conventional LED power supply device. It is a circuit diagram which shows the basic composition of the other conventional LED power supply device. It is a circuit diagram which shows the basic composition of further another conventional LED power supply device.

  An embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration of an LED lighting device 1 including an LED power supply device according to an embodiment of the present invention. The LED lighting device 1 includes a rectifying circuit 11, a smoothing capacitor 12, a switching element 13, a first control unit 14 that controls the switching element 13, an LED load 15, a constant current circuit 16, and a voltage detection unit 17. And so on.

  The rectifier circuit 11 is a circuit that full-wave rectifies the AC input from the commercial AC power supply 2. A power switch 3 is provided between the commercial AC power supply 2 and the rectifier circuit 11.

  The smoothing circuit 12 plays a role of smoothing the input voltage after full-wave rectification by the rectifying circuit 11, one end of which is connected to the positive terminal of the rectifying circuit 11 and the other end of which is connected to the switching element 13.

  The switching element 13 is, for example, a transistor or a first FET (field effect transistor) as in this embodiment. In the following description, the switching element is also called the first FET. The drain of the first FET 13 is connected to the negative terminal of the smoothing capacitor 12, and the source is connected to the negative terminal of the rectifier circuit 11. As will be described later, the first FET 13 controls the voltage across the smoothing capacitor 12 by switching on or off based on a control signal from the first controller 14 connected to the gate.

  The LED load 15 is composed of one LED or a plurality of LEDs connected in series, the anode side is connected to the positive terminal of the smoothing capacitor 12, and the cathode side is connected to the constant current circuit 16.

  The constant current circuit 16 is a circuit for keeping the current flowing through the LED load 15 at a constant value, and includes a second FET 161 that is a constant current element and a second controller 162 that controls the second FET 161. The second FET 161 has a drain connected to the cathode side of the LED load 15 and a source connected to the drain of the first FET 13. Instead of the second FET 161, another constant current element such as a transistor may be used.

  The second controller 162 inputs a drive signal to the gate of the second FET 161, operates the second FET in the active region, and controls the current flowing through the LED load 15 to be constant.

  The voltage detection unit 17 detects the voltage Vds between the drain and source of the second FET 161 which is the voltage obtained by removing the forward voltage Vf of the LED load 15 from the voltage across the smoothing capacitor 12, and performs the first control based on the detection result. The unit 14 is controlled, and in this embodiment, it is configured by a comparator that outputs H-level and L-level signals according to the drain-source voltage Vds of the second FET 161.

  Next, the operation of the LED lighting device 1 shown in FIG. 1 will be described with reference to the waveform charts shown in FIGS.

  FIG. 2A is a diagram showing an output waveform of the rectifier circuit 11, in which the input voltage V0 from the commercial AC power source 2 is full-wave rectified. In this embodiment, the electric charge of the smoothing capacitor 12 charged by the output voltage V0 of the rectifier circuit 11 is discharged through the series circuit of the LED load 15 and the second FET 161 of the constant current circuit 16, in other words, The smoothing capacitor 12 functions as a power supply source for the series circuit of the LED load 15 and the second FET 161, so that the LED load 15 is driven to light. Then, in this embodiment, as shown in FIG. 7A, the power of only the portion of the output of the rectifier circuit 11 which is smaller than the peak value Vp and equal to or lower than the predetermined potential V1 is supplied to the series circuit of the LED load 15 and the second FET 161. Is set to supply.

  2B is a waveform diagram of the voltage Vc across the smoothing capacitor, FIG. 2C is a waveform diagram of the output V2 of the voltage detection unit 17, and FIG. 2D is an output of the first control unit 14. 5 is a waveform diagram of a control signal V3 for the first FET 13 that is

  The output V2 of the voltage detection unit 17 becomes L level when the drain-source voltage Vds of the second FET 161 rises to reach the reference voltage V4, and the drain-source voltage Vds decreases, as shown in FIG. Then, a pulse signal that maintains the L level until reaching the reference voltage V5, becomes the H level when reaching the reference voltage V5, and outputs the pulse signal that maintains the H level until reaching the reference voltage V4 next time. Then, at the timing when the output voltage V0 of the rectifying circuit 11 increases and reaches a predetermined potential V1, the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4, and the output voltage V0 of the rectifying circuit 11 changes. The reference voltages V4 and V5 are set so that the drain-source voltage Vds of the second FET 161 reaches the reference voltage V5 at the timing when it decreases from the peak Vp and reaches the predetermined potential V1.

  Therefore, in this embodiment, the predetermined potential V1 is set by the drain-source voltage Vds of the second FET 161. As a result, the predetermined potential V1 can be set stably. With this setting, while the output voltage V0 of the rectifier circuit 11 exceeds the predetermined potential V1, the output V2 of the voltage detection unit 17 is at the L level, and when the output voltage V0 is equal to or lower than the predetermined potential V1, it is at the H level. Becomes

  The output voltage of the rectifier circuit 11 when the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4 and the output voltage of the rectifier circuit 11 when the drain-source voltage Vds of the second FET 161 drops to the reference voltage V5. Although the reference voltages V4 and V5 are set so that the output voltages are both approximately V0, the output voltage of the rectifier circuit 11 when the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4, and the second FET 161. The output voltage of the rectifier circuit 11 may be different when the drain-source voltage Vds of the above is reduced to the reference voltage V5.

  The control signal V3 output from the first control unit 14 is at the L level when the output V2 of the voltage detection unit 17 is at the L level and is at the H level when it is at the H level, as shown in FIG. The first control unit 14 outputs the control signal V3 to the gate of the first FET 13. Based on the control signal V3 from the first controller 14, the first FET 13 switches on and off. Specifically, when the control signal V3 is at the H level, the first FET 13 is turned on, and when the control signal V3 is at the L level, the first FET 13 is turned off. Therefore, the first FET 13 is turned off while the output voltage V0 of the rectifier circuit 11 exceeds the predetermined potential V1, and the first FET 13 is turned on while the output voltage V0 is equal to or lower than the predetermined potential V1.

  After the power switch 3 is turned on, the output voltage V0 of the rectifier circuit 11 rises, the voltage across the smoothing capacitor 12 rises, the charge stored in the smoothing capacitor 12 is supplied to the LED load 15, and the LED load 15 is driven to light up. The drain-source voltage Vds of the second FET 161 increases. As shown in FIG. 2, when the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4 at time T1, the output V2 of the voltage detection unit 17 becomes L level, and the control signal V3 from the first control unit 14 also becomes L level. It becomes a level. At this time, the value of the output voltage V0 of the rectifier circuit 11 is substantially equal to V1.

  When the control signal V3 from the first controller 14 becomes L level, the first FET 13 which is a switching element is turned off, and the charging of the smoothing capacitor 12 from the rectifier circuit 11 is stopped. On the other hand, since the charging charge of the smoothing capacitor 12 is continuously supplied to the LED load 15, the voltage Vc across the smoothing capacitor 12 gradually decreases as shown in FIG. 2 (B).

  At time T2 when the voltage Vc across the smoothing capacitor 12 approaches the forward voltage Vf of the LED load 15, when the drain-source voltage Vds of the second FET 161 drops to the reference voltage V5, the voltage detection unit 17 becomes H level, and The control signal V3 from the control unit 14 also becomes H level. At this time, the value of the output voltage V0 of the rectifier circuit 11 is substantially equal to V1.

  When the control signal V3 from the first control unit 14 changes to the H level, the first FET 13 is turned on, and a closed circuit that returns from the rectifying circuit 11 to the smoothing capacitor 12 and the first FET 13 to the rectifying circuit 11 is formed. 12 is charged by the output voltage V0 of the rectifier circuit 11. Assuming that the output voltage Vc of the smoothing capacitor 12 becomes equal to the output voltage of the rectifier circuit 11 at time T3, the output voltage V0 of the rectifier circuit 11 is in the lowering region at this time, and the drain-source voltage Vds of the second FET 161 is Since the voltage has not risen to the reference voltage V4, the output V2 of the voltage detector 17 remains at H level, and the control signal V3 from the first controller 14 also remains at H level.

  After the lapse of time T3, the voltage Vc across the smoothing capacitor 12 gradually decreases due to the decrease of the output voltage V0 of the rectifier circuit 11 and the power supply to the LED load 15, but the next half wave of the output voltage V0 of the rectifier circuit 11 is generated. From the time T4 after the start of T.sub.2, the output voltage V.sub.0 of the rectifier circuit 11 gradually rises, and the drain-source voltage Vds of the second FET 161 also rises.

  When the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4 at time T5, the voltage detection unit 17 becomes L level, the control signal from the first control unit 14 also becomes L level, and the first FET 13 is turned off. .. Then, charging of the smoothing capacitor 12 by the output voltage V0 of the rectifying circuit 11 is stopped, and the voltage Vc across the smoothing capacitor 12 gradually decreases after the time T5. During this time, a constant current flows through the LED load 15 by the constant current circuit 16, and the lighting control of the LED load 15 is stably performed.

  After that, the state from time T1 to time T5 is repeated.

  As understood from the above description, from time T1 when the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4 to time T2 when the drain-source voltage Vds of the second FET 161 decreases to the reference voltage V5. , The first FET 13 is off, and the smoothing capacitor 12 is not charged by the output voltage V0 of the rectifier circuit 11.

  Further, as described above, the timing when the output voltage V0 of the rectifier circuit 11 reaches the predetermined potential V1 and the timing when the drain-source voltage Vds of the second FET 161 reaches the reference voltage V4 are substantially the same, and the rectifier circuit The reference voltages V4 and V5 are set so that the timing at which the output voltage V0 of 11 drops to the predetermined potential V1 and the timing at which the drain-source voltage Vds of the second FET 161 drops to the reference voltage V5 are almost the same. ing. Therefore, the first FET 13 is turned off when the output voltage V0 of the rectifier circuit 11 almost reaches the predetermined potential V1, and the first FET 13 is turned on when the output voltage V0 of the rectifier circuit 11 is substantially reduced to the predetermined potential V1. The voltage Vc across the smoothing capacitor 12 does not exceed V1. That is, a portion of the output voltage V0 of the rectifier circuit 11 that exceeds the predetermined potential V1 is not used for supplying power to the LED load 15, and the power of only the portion of the output voltage V0 of the rectifier circuit 11 that is equal to or lower than the predetermined potential V1 is supplied. , LED load 15 will be supplied.

  FIG. 3 is a waveform diagram showing an enlarged view of times T2 to T5 in FIG. In FIG. 3, the difference between the voltage Vc across the smoothing capacitor 12 and the forward voltage Vf of the LED load 15 is the drain-source voltage Vds of the second FET 161 detected by the voltage detection unit 17. Then, the hatched region of the drain-source voltage Vds is the power loss by the second FET 161.

  As described above, since the voltage Vc across the smoothing capacitor 12 does not exceed the predetermined potential V1, the power loss can be reduced as compared with the case where the entire power output from the rectifier circuit 11 is supplied to the LED load 15. Will get better. Moreover, in this embodiment, the minimum value of the voltage Vc of the smoothing capacitor 12 is a value obtained by adding the forward voltage Vf of the LED load 15 and the reference voltage V5 and does not fall below the forward voltage Vf. Stable lighting operation can be realized without lighting flickering due to insufficient current.

  Here, in order to more effectively exert the effect of reducing power loss, the value of the predetermined potential V1 is preferably set to be 1 V to 50 V higher than the forward voltage Vf of the LED load. If it is less than 1V, sufficient power cannot be supplied to the LED load when the commercial power supply voltage changes unintentionally, and lighting flicker may occur. If it exceeds 50V, the power loss reduction effect may be poor. There is.

  The reference voltage V5 may be zero or may be zero or more. Further, the voltage detection unit 17 does not directly detect the drain-source voltage Vds of the second FET 161 obtained by removing the forward voltage Vf of the LED load 15 from the potential of the smoothing capacitor 12, but corresponds to the drain-source voltage Vds. The voltage may be detected.

1 LED lighting device 2 AC power supply 11 Rectifier circuit 12 Smoothing capacitor 13 Switching element (first FET)
14 1st control part 15 LED load 16 Stabilization circuit 161 2nd FET
162 Second control unit 17 Voltage detection unit

Claims (3)

A rectifier circuit that rectifies the input from the commercial power supply,
LED load,
A power supply unit for supplying to the LED load only the power of a portion of the output of the rectifier circuit that is equal to or lower than a predetermined potential;
A smoothing capacitor for smoothing the output of the rectifier circuit,
A switching element connected in series with the smoothing capacitor,
A constant current circuit connected in series with the LED load,
A voltage detection unit that detects the difference between the voltage on the current input side and the voltage on the current output side of the constant current circuit;
Equipped with
The smoothing capacitor constitutes the power supply unit for the LED load and the constant current circuit connected in series,
The predetermined potential turns off the switching element when the voltage difference of the constant current circuit detected by the voltage detection unit rises to the first reference value, and turns off when the difference decreases to the second reference value. An LED power supply device, which is set by turning on the switching element .   The LED power supply device according to claim 1, wherein the predetermined potential is set to be 1 V to 50 V higher than the forward voltage of the LED load. LED lighting device provided with an LED power supply device according to claim 1 or 2.

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