JP2007073781A - Light emitting diode drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode driving device capable of realizing high power conversion efficiency and miniaturization.
A light-emitting diode driving device includes a transformer, a diode, a light-emitting diode, a switching element, a constant current source, a regulator, a control circuit for controlling on / off of the switching element, and a second capacitor. 11 and the control circuit 10 uses the second capacitor 11 as a power source. When the light emitting diode driving device is activated, the power supply voltage Vin is adjusted by the constant current source 8 and the regulator 9 so that the power supply voltage Vcc of the control circuit 10 becomes a constant voltage, and is applied to the second capacitor 11. When the on / off control of the switching element 7 is started, the current due to the induced electromotive force generated in the secondary side coil of the transformer 4 is supplied to the second capacitor 11.
[Selection] Figure 1

Description

  The present invention relates to a light emitting diode driving device.

An example of a conventional light emitting diode driving device is disclosed in Patent Document 1.
A conventional light-emitting diode driving device disclosed in Patent Document 1 will be described with reference to the circuit diagram of FIG.

In FIG. 9, reference numeral 41 denotes a light emitting diode group, and a plurality (three in the figure) of light emitting diodes to be driven by the light emitting diode driving device are connected in series.
In addition, an inductor 42 having one end connected to an input power source (terminal) Vin whose supply voltage fluctuates over a wide range, for example, 8 VDC to 400 VDC, and the other end connected to the p-electrode side (anode side) of the light-emitting diode group 41. Are provided, the cathode is connected to the input power source (terminal) Vin, the anode is connected to the n-electrode side (cathode side) of the light-emitting diode group 41, and the back electromotive force generated in the inductor 42 is supplied to the light-emitting diode group 41. A diode 43 is provided. An output terminal Out of a control IC 51 that controls the current flowing through the light emitting diode group 41 is connected to the anode of the diode 43.

  The control IC 51 is connected to the input power source (terminal) Vin, allows a wide range of voltage fluctuations input from the input power source Vin, and adjusts the power supplied to the control IC 51, and an output terminal Out. Are connected to the switching transistor 53 for switching the current flowing through the light emitting diode group 41, the resistor 54 for feeding back the current flowing through the light emitting diode group 41, and the voltage ( A control circuit 55 is provided for controlling the pulse width to be output to the gate so that the set peak current value is obtained while feedbacking the current value flowing through the light emitting diode group 41). The control circuit 55 obtains the power supply voltage from the HV regulator 52.

  With the above configuration, by performing pulse width control for driving the switching transistor 53, the current flowing through the light emitting diode group 41 is controlled to the set peak current value, and a predetermined light emission luminance is obtained.

  An example of the control circuit 55 is shown in FIG. An oscillator 57 and a flip-flop 58 forming a pulse width adjuster, a voltage (corresponding to a target value of a peak current passed through the light emitting diode 41) set from the outside, and a sensor input voltage (light emitting diode 41) input from the resistor 54 And comparators 59, 60, etc. for determining the pulse width.

As described above, the conventional light-emitting diode driving device is composed of the control IC 51, the inductor 42, the light-emitting diode group 41, and the diode 43, and this circuit configuration realizes miniaturization and high efficiency of the light-emitting diode driving device. Yes.
US Pat. No. 6,667,583

  However, in the conventional LED driving device, the power supply voltage of the control circuit 55 inside the control IC 51 is obtained from the input power supply Vin via the HV regulator 52. Therefore, when the input power supply Vin becomes a high voltage, There was a problem that the power consumption loss was increased, which hindered further improvement in efficiency.

  Therefore, an object of the present invention is to provide a light emitting diode driving device that can realize high power conversion efficiency and can be downsized.

  In order to achieve the above-described object, a light emitting diode driving device according to claim 1 of the present invention includes a transformer in which a power supply voltage is applied to one end of a primary coil from a voltage source, and a primary coil of the transformer. One or more light emitting diodes connected to the other end, and a cathode is connected to one end of the primary coil of the transformer, an anode is connected to the light emitting diode, and the back electromotive force generated in the primary coil of the transformer A light emitting diode block composed of diodes to be supplied to the light emitting diode; a switching element having one end connected to the light emitting diode block and the other end connected to a reference potential of the voltage source; and a high potential of the switching element Connected to the side terminal, the control terminal, and the low-potential side terminal to control the on / off of the switching element. A constant current source having one end connected to a connection point between the primary coil of the transformer and the cathode of the diode, one end connected to the other end of the constant current source, and the other end to the control A regulator connected to a power supply voltage terminal of the circuit, a capacitor having one end connected to the other end of the regulator and the control circuit, and the other end connected to a reference potential of the voltage source; The secondary coil is characterized in that one end is connected to one end of the capacitor and the other end is connected to a reference potential of the voltage source.

  With the above-described configuration, the switching element is on / off controlled by the control circuit, and the current flowing through the light emitting diode is on / off controlled, so that an induced electromotive force is generated in the secondary coil of the transformer. Current is supplied from the secondary coil to the capacitor, and power is supplied from the capacitor to the control circuit. Therefore, since the power consumed by the control circuit can be reduced, the efficiency of the light emitting diode driving device can be further increased.

  According to a second aspect of the present invention, the connection of one end of the constant current source of the first aspect is changed from the connection point between the primary coil of the transformer and the cathode of the diode to the high potential side terminal of the switching element. It is characterized by that.

  With the above configuration, the power consumed by the control circuit is reduced, and the number of external output terminals of the package is reduced when the constant current source, the regulator, the control circuit, and the switching element are built in one semiconductor package. Therefore, the light emitting diode driving device can be further reduced in size and price.

  According to a third aspect of the present invention, there is provided the LED driving device according to the first or second aspect, wherein the control circuit changes a peak current value flowing through the switching element from the outside. It has a peak current control force terminal for the purpose.

  With the above configuration, the peak current value flowing to the switching element via the peak current control force terminal can be changed from the outside, and the light emission luminance of the light emitting diode can be dimmed. The light emission luminance of the light emitting diode suitable for the brightness of the can be obtained.

  According to a fourth aspect of the present invention, there is provided the LED driving apparatus according to the third aspect, wherein the control circuit is a start / stop circuit for starting and stopping light emission from the light emitting diode. And an oscillator, and when a start signal is output from the start / stop circuit, a current flowing through the switching element is detected, and according to a set value of a peak current value input from the peak current control terminal, It has a circuit which changes the duty ratio of the pulse outputted from the oscillator and outputs it to the control terminal of the switching element.

  With the above configuration, when a start signal is output from the start / stop circuit, the current flowing through the switching element is detected, and the peak current value input from the peak current control force terminal is set according to the set value. The on-duty of the pulse output from the oscillator is changed and output to the control terminal of the switching element, and the peak current value flowing through the switching element is controlled. Therefore, the light emission brightness of the light emitting diode can be adjusted according to the set value of the peak current value input from the peak current control power terminal, so that the light emission brightness of the light emitting diode suitable for the external brightness can be obtained. It is done.

  The light-emitting diode driving device according to claim 5 is the control circuit for a light-emitting diode driving device according to any one of claims 1 to 4, wherein the switching element generates heat. An overheat protection circuit that detects and operates when an abnormal state is detected, and the control circuit stops output to the control terminal of the switching element when the overheat protection circuit operates. It is.

  By configuring as described above, protection from abnormal oscillation accompanied by heat generation of the switching element of the light emitting diode driving device is realized. Particularly, when the light emitting diode driving device is modularized, it is effective for protecting the light emitting diode from rising in temperature. is there.

  The light emitting diode driving device of the present invention has the above-described configuration, and the switching element is on / off controlled by the control circuit, and the current flowing through the light emitting diode is on / off controlled, so that it is induced in the secondary coil of the transformer. An electromotive force is generated, current is supplied from the secondary coil to the capacitor, and power is supplied from the capacitor to the control circuit, so that the power consumed in the control circuit can be reduced, and thus the light emitting diode driving device It has the effect that further high efficiency can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
FIG. 1 is a circuit diagram of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention, and FIG. 2 is an operation waveform diagram showing changes in light-emitting diode current with respect to changes in the set voltage Vsn in the light-emitting diode driving apparatus.

  As shown in FIG. 1, an AC power supply 1 is rectified by a rectifier circuit 2 to form a voltage (power supply voltage) Vin, and a first capacitor (smoothing capacitor) 3 is connected in parallel to the output side of the rectifier circuit 2. ing. The AC power source 1 and the rectifier circuit 2 constitute a voltage source.

  As shown in FIG. 1, a transformer 4 to which the power supply voltage Vin is applied from the voltage source is provided at one end of the primary coil, and one of the transformer 4 is connected in series to the other end of the primary coil. The p electrode (anode side) of the light emitting diode group 6 composed of the above light emitting diodes is connected. The cathode is connected to one end of the primary coil of the transformer 4, the anode is connected to the n electrode (cathode side) of the light emitting diode group 6, and the back electromotive force generated in the primary coil of the transformer 4 is supplied to the light emitting diode group 6. A diode 5 is provided. The primary coil of the transformer 4, the light emitting diode group 6, and the diode 5 constitute a light emitting diode block PB.

A control block CB for controlling the current flowing through the light emitting diode group 6 is provided.
In the control block CB, the drain (one end) is connected to the connection point between the light emitting diode 6 and the diode 5 of the light emitting diode block PB via the drain terminal 13, and the source (the other end) is a reference potential (source terminal) 15. The first switching element 7 connected to the reference potential (minus output terminal of the rectifier circuit 2) via the, the high potential side terminal 17, the gate terminal (control terminal) 18 of the first switching element 7, and the low potential side One end (input side) is connected to the cathode of the primary coil of the transformer 4 and the diode 5 via the power supply terminal 21 and the control circuit 10 connected to the terminal 19 for on / off control of the first switching element 7. And a constant current source 8 to which a power supply voltage Vin (positive output terminal of the rectifier circuit 2) is applied, and one end (input side) connected to the other end (output side) of the constant current source 8. Is, the other end (output side) is provided with a regulator 9 connected to the supply voltage terminal 16 of the control circuit 10. The regulator 9 controls the power supply voltage Vcc to be a constant voltage.

  Further, the control circuit 10 has a peak current control force terminal 20 for inputting a set voltage Vsn for changing the peak current value flowing through the first switching element 7 from the outside via the setting input terminal 12 of the control block CB. ing. The set voltage Vsn is a reference voltage (set voltage) that can be arbitrarily set from the outside. By changing the set voltage Vsn, the current flowing through the first switching element 7 can be changed, and thus the light emitting diode group. 6 can be changed, and the light emission luminance of the light emitting diode group 6 can be adjusted, so that the light emission luminance of the light emitting diode group 6 suitable for the external brightness can be obtained.

  One end is connected to the other end (output side) of the regulator 9 and the control circuit 10 via the power supply voltage terminal 14 of the control block CB to which the power supply voltage Vcc is supplied, and the other end is set to the reference potential of the voltage source. The connected second capacitor 11 is provided, and the secondary coil of the transformer 4 has one end connected to one end of the second capacitor 11 and the other end connected to the reference potential of the voltage source.

The operation of the light emitting diode driving apparatus according to Embodiment 1 will be described with reference to FIG.
When the light emitting diode driving device is activated, the power supply voltage Vin formed by rectifying the AC power supply 1 by the rectifier circuit 2 is supplied to the control circuit block CB through the power supply terminal 21, the constant current source 8, and the regulator 9. The voltage is applied to the second capacitor 11 (power is supplied), the second capacitor 11 is filled, and the voltage at both ends is increased. At this time, the regulator 9 controls the power supply voltage Vcc of the control circuit 10 to be a constant voltage. The power to the control circuit 10 is supplied from the second capacitor 11.

  Subsequently, on / off control (pulse width control) of the first switching element 7 by the control circuit 10 is started in accordance with the externally set voltage Vsn. When the set voltage Vsn is high, the pulse width is long (on duty is long), and when the set voltage Vsn is low, the pulse width is short (on duty is short).

  When the first switching element 7 is in the on state, current flows through the first capacitor 3 → the primary coil of the transformer 4 → the light emitting diode group 6 → the first switching element 7, and when the first switching element 7 is in the off state, Current flows through the primary side coil → light emitting diode group 6 → diode 5 → primary side coil of the transformer 4 (current flows through the closed loop). Therefore, as shown in FIG. 2, the waveform of the current IL flowing through the light emitting diode group 6 is a current waveform that rises when the first switching element 7 is in the on state and gradually falls when the first switching element 7 is in the off state. In a state where the on / off control of the first switching element 7 is performed, the pulse current flowing through the primary coil of the transformer 4 is also the same as the pulse current waveform flowing through the light emitting diode group 6, and this pulse current causes the transformer 4 to An induced electromotive force is generated in the secondary coil, and a current due to the induced electromotive force is supplied to the second capacitor 11, filled and smoothed, and the power of the regulator 9 and the control circuit 10 is supplied via the power supply terminal 14 of the control block CB. Applied to the voltage terminal 16. As a result, power is supplied to the control circuit 10 from the second capacitor 11, and power supply from the power supply terminal 21 to the control block CB via the constant current source 8 and the regulator 9 is stopped.

  When such a light emitting diode driving apparatus according to the first embodiment of the present invention is used, power is not supplied to the control circuit 10 via the constant current source 8 and the regulator 9 in the wide input range of the AC power supply 1, but a transformer is used. Since the power is supplied to the control circuit 10 by the induced electromotive force of 4, the light emitting diode driving device capable of constant current control and capable of reducing the power consumed in the control block CB can be realized. In addition, a light emitting diode driving device can be realized with a simple configuration. Therefore, further improvement in efficiency of the light emitting diode driving device can be realized. This appears as a large difference in efficiency, particularly when the AC power supply 1 is a high voltage input. In addition, a light emitting diode driving device that can reduce the power consumed by the control block CB can be realized with a simple configuration in which the transformer 4 and the second capacitor 11 are provided.

  Further, the constant current source 8, the regulator 9, and the control circuit 10 shown in FIG. 1 are preferably integrated on the same semiconductor substrate. At that time, the power supply voltage terminal 14, the high potential side terminal 17 of the control circuit 10, the control terminal (gate terminal) 18 of the control circuit 10, the low potential side terminal 19 of the control circuit 10, and the power supply terminal 21 to the control block CB. Are integrated as external connection terminals. By incorporating it into a package having five or more terminals, the number of parts can be greatly reduced, the dimensions of the parts can be reduced, and a more compact and inexpensive power supply can be realized.

Furthermore, the first switching element 7, the constant current source 8, the regulator 9, and the control circuit 10 are preferably integrated on the same semiconductor substrate. At this time, at least four terminals of the drain terminal 13, the power supply voltage terminal 14, the reference potential (source terminal) 15, and the power supply terminal 21 to the control circuit block are integrated as external connection terminals. By incorporating it into a package having four or more terminals, the number of components can be greatly reduced, the size of the components can be reduced, and a more compact and inexpensive power supply can be realized.
[Embodiment 2]
FIG. 3 is a circuit diagram of a light emitting diode driving apparatus according to Embodiment 2 of the present invention. The second embodiment is the same as the first embodiment shown in FIG. 1 except that the first capacitor (smoothing capacitor) 3 is not provided. Only the additional points are described.

In the second embodiment, since the first capacitor 3 is not provided, the voltage rectified by the rectifier circuit 2 is supplied as it is as an input power source. For this reason, for example, when the input power supply voltage Vin is close to 0 V, the power supply voltage Vcc of the control circuit 10 is significantly reduced, so that a period during which the on / off control of the first switching element 7 by the control circuit 10 is not performed occurs. However, in the case of visible light such as the light-emitting diode group 6, flickering of the light-emitting diode group 6 cannot be recognized by human eyes as long as it is above the commercial frequency level. Therefore, it is possible to further reduce power consumption as the light emitting diode driving device. Furthermore, since there is no first capacitor 3, noise generation due to harmonics is greatly reduced, so that no noise countermeasure component is required, and further downsizing of the light emitting diode driving device is realized at the same time.
[Embodiment 3]
FIG. 4 is a circuit diagram of a light emitting diode driving apparatus according to Embodiment 3 of the present invention. Compared with the first embodiment shown in FIG. 1, the third embodiment has no power supply terminal 21 to the control block CB, and one end of the constant current source 8 is not connected to the first capacitor 3 but to the drain terminal 13. Since the configuration, basic operation, and effects are the same except for connection, only differences and additional points will be described below.

  When the power supply terminal 21 to the control block CB is eliminated, when the constant current source 8, the regulator 9, and the control circuit 10 shown in FIG. 4 are integrated on the same semiconductor substrate, the power supply voltage terminal 14, the control At least four terminals of the high potential side terminal 17 of the circuit 10, the control terminal 18 of the control circuit 10, and the low potential side terminal 19 of the control circuit 10 are integrated as external connection terminals. By incorporating it into a package having four or more terminals, the number of components can be greatly reduced, the size of the components can be reduced, and a more compact and inexpensive power supply can be realized.

Furthermore, the first switching element 7, the constant current source 8, the regulator 9, and the control circuit 10 are preferably integrated on the same semiconductor substrate. At that time, at least three terminals of the drain terminal 13, the power supply voltage terminal 14, and the reference potential (source terminal) 15 are integrated as external connection terminals. By incorporating it into a package having three or more terminals, the number of parts can be greatly reduced, the dimensions of the parts can be reduced, and a more compact and inexpensive power supply can be realized.
[Embodiment 4]
FIG. 5 is a circuit diagram of a light-emitting diode driving apparatus according to Embodiment 4 of the present invention. In the fourth embodiment, the first switching element 7 is connected to the connection point between the light emitting diode group 6 of the light emitting diode block PB and the primary coil of the transformer 4 as compared with the third embodiment shown in FIG. Except for the above, the configuration and effects are the same. In the fourth embodiment, when the first switching element 7 is in the OFF state, current flows through the primary coil of the transformer 4 → the light emitting diode group 6 → the diode 5 → the primary coil of the transformer 4 (current flows through the closed loop).

In the fourth embodiment, one end of the constant current source 8 is connected to the drain terminal 13 of the control block CB (the high potential side terminal of the first switching element 7). It is also possible to change the connection to the connection point between the coil and the cathode of the diode 5 and connect to the voltage source.
"Circuit example of the control circuit 10"
6 to 8 show circuit examples of the control circuit 10 used in the light emitting diode driving devices in the first to fourth embodiments.

  The control circuit 10 shown in FIG. 6 includes a start / stop circuit 22 for starting / stopping the on / off control of the first switching element 7, a pulse oscillator 23 for outputting the MAXDUTY signal and the CLOCK signal in synchronization, and a peak current control. A blanking pulse is output when the drain current detection circuit 24 that detects the drain current by comparing the set voltage Vsn input through the power terminal 20 and the voltage of the high potential terminal 17 and the output of the AND circuit 28 described later is on. An ON-circuit blanking pulse generator 29, an AND circuit 25 that takes the logical product of the detection output signal of the drain current detection circuit 24 and the output signal of the ON-time blanking pulse generator 29, and an output signal of the AND circuit 25 An OR circuit 26 (oscillator 2) that takes a logical sum with a NOT (NOT) signal of the MAXDUTY signal of the pulse oscillator 23 Only the MAXDUTY signal input from the inverter), a flip-flop 27 that is set by the CLOCK signal of the pulse oscillator 23 and reset by the output signal of the OR circuit 26, the MAXDUTY signal of the pulse oscillator 23, and the output signal of the flip-flop 27 It comprises an AND circuit 28 that takes the logical product of the output signals (start signal) of the start / stop circuit 22.

  With this configuration, the on / off control of the first switching element 7 is started when the start signal is output from the start / stop circuit 22, and is set in the drain current detection circuit 24 for the first switching element 7. PWM control is executed to change the duty ratio of the pulse output from the oscillator 23 while feeding back the drain current detected by comparing the voltage Vsn with the voltage at the high potential terminal 17. The maximum on-duty is defined by the MAXDUTY signal of the oscillator 23. Further, the set voltage Vsn of the drain current detection circuit 24 can be arbitrarily set from the outside, that is, the detection peak current value flowing through the first switching element 7 can be changed, so that the current flowing through the light emitting diode can be changed. (Light control function)

  The control circuit 10 shown in FIG. 7 newly provides an overheat protection circuit 30 that operates by detecting that the first switching element 7 is in an abnormal state having heat generation, and operates the operation signal of the overheat protection circuit 30 as an AND circuit. When the overheat protection circuit 30 is operated by inputting to 28, the output to the control terminal 18 of the first switching element 7 is stopped, except that the control circuit 10 shown in FIG. The overheat protection circuit 30 protects the drive device from an abnormal state or the like in which the first switching element 7 generates heat, particularly when the whole or part of the light-emitting diode drive device is modularized. Protection from abnormal oscillation accompanied by heat generation of the first switching element 7 of the device is realized, which is effective for temperature rise protection of the light emitting diode.

  The control circuit 10 shown in FIG. 8 is the same as the control circuit shown in FIG. 6 except that a new series circuit of a second switching element 31 and a resistor 32 connected in parallel with the first switching element 7 is provided. This shows another detection method related to the detection of the drain current detection circuit 24, and the detection is performed by the voltage across the resistor 32. Here, the current flowing through the first switching element 7 and the current flowing through the second switching element 31 are preferably configured to have a certain ratio.

  The light emitting diode driving device according to the present invention can be used for all devices and equipment using light emitting diodes, and is particularly useful as LED lighting equipment.

It is a circuit diagram of the light emitting diode drive device in Embodiment 1 of this invention. It is a characteristic view which shows operation | movement of the light emitting diode drive device. It is a circuit diagram of the light emitting diode drive device in Embodiment 2 of this invention. It is a circuit diagram of the light emitting diode drive device in Embodiment 3 of this invention. It is a circuit diagram of the light emitting diode drive device in Embodiment 4 of this invention. It is a circuit diagram which shows an example of the control circuit used in Embodiment 1-4 of this invention. It is a circuit diagram which shows an example of the control circuit used in Embodiment 1-4 of this invention. It is a circuit diagram which shows an example of the control circuit used in Embodiment 1-4 of this invention. It is a circuit diagram of the conventional light emitting diode drive device. It is a circuit diagram of the control circuit used with the conventional light emitting diode drive device.

Explanation of symbols

CB control block PB light emitting diode block 1 AC power supply 2 rectifier circuit 3 smoothing capacitor 4 transformer 5 diode 6 light emitting diode (or a plurality of light emitting diode groups connected in series)
7 First switching element 8 Constant current source 9 Regulator 10 Control circuit 11 Capacitor 12 Control block setting input terminal 13 Control block drain terminal 14 Control block power supply voltage terminal 15 Control block source terminal (reference potential)
16 Control circuit power supply voltage terminal 17 Control circuit high potential side terminal 18 Control circuit control terminal 19 Control circuit low potential side terminal 20 Control circuit peak current control terminal 21 Control block power supply terminal 22 Start / stop circuit 23 Oscillator 24 Drain current detection circuit 25 AND circuit 26 OR circuit (1 input terminal: with inverter)
27 RS flip-flop 28 AND circuit 29 Blanking pulse generator when ON 30 Overheat protection circuit 31 Second switching element 32 Resistance

Claims (5)

A transformer in which a power supply voltage is applied to one end of the primary side coil from a voltage source, one or more light emitting diodes connected to the other end of the primary side coil of the transformer, and a cathode at one end of the primary side coil of the transformer A light emitting diode block composed of a diode connected to the light emitting diode, the anode being connected to the light emitting diode, and supplying a back electromotive force generated in the primary coil of the transformer to the light emitting diode;
A switching element having one end connected to the light emitting diode block and the other end connected to a reference potential of the voltage source;
A control circuit connected to the high-potential side terminal, the control terminal, and the low-potential side terminal of the switching element to control on / off of the switching element;
A constant current source having one end connected to a connection point between a primary coil of the transformer and a cathode of the diode;
One end is connected to the other end of the constant current source, and the other end is connected to the power supply voltage terminal of the control circuit;
One end is connected to the other end of the regulator and the control circuit, the other end includes a capacitor connected to a reference potential of the voltage source,
The secondary coil of the transformer has one end connected to one end of the capacitor and the other end connected to a reference potential of the voltage source. A transformer in which a power supply voltage is applied to one end of the primary side coil from a voltage source, one or more light emitting diodes connected to the other end of the primary side coil of the transformer, and a cathode at one end of the primary side coil of the transformer A light emitting diode block composed of a diode connected to the light emitting diode, the anode being connected to the light emitting diode, and supplying a back electromotive force generated in the primary coil of the transformer to the light emitting diode;
A switching element having one end connected to the light emitting diode block and the other end connected to a reference potential of the voltage source;
A control circuit connected to the high-potential side terminal, the control terminal, and the low-potential side terminal of the switching element to control on / off of the switching element;
A constant current source having one end connected to the high potential side terminal of the switching element;
One end is connected to the other end of the constant current source, and the other end is connected to the power supply voltage terminal of the control circuit;
One end is connected to the other end of the regulator and the control circuit, the other end includes a capacitor connected to a reference potential of the voltage source,
The secondary coil of the transformer has one end connected to one end of the capacitor and the other end connected to a reference potential of the voltage source. The light emitting diode driving device according to claim 1, wherein the control circuit has a peak current control force terminal for changing a peak current value flowing in the switching element from the outside. The control circuit includes a start / stop circuit for starting and stopping light emission from the light emitting diode, and an oscillator,
When a start signal is output from the start / stop circuit, a current flowing through the switching element is detected and output from the oscillator according to a set value of a peak current value input from the peak current control terminal 4. The light emitting diode driving device according to claim 3, further comprising a circuit that changes a duty ratio of the pulse and outputs the pulse to a control terminal of the switching element. The control circuit includes an overheat protection circuit that detects that the switching element is in an abnormal state having heat generation and operates.
5. The light emitting diode driving device according to claim 1, wherein the control circuit stops output to the control terminal of the switching element when the overheat protection circuit operates. 6.

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