JP6712179B2 - LED power supply - Google Patents

Description

The present invention relates to an LED power supply device, and more particularly to improvement of a drive circuit in an LED power supply device provided with a switching element for ensuring insulation.

With the development of semiconductor technology in recent years, switching power supply devices have come to be used in various fields. In particular, power supply to an LED element, which was difficult to supply a stable power until a long time ago, can now be realized by using a switching power supply using recent semiconductor technology. When the switching power supply device is used as an LED power supply device, it is necessary to ensure appropriate insulation. For example, by using a semiconductor element capable of high-speed switching operation as a switch for cutting a circuit, a switching power supply device with secured insulation can be realized. In such a circuit configuration, a drive circuit for driving the switch (semiconductor element) is required, and by performing the switching operation of the switch (semiconductor element) appropriately by the drive circuit, the insulation required for the LED power supply is obtained. It is possible to secure the sex.

By the way, since the ON/OFF signal (ON/OFF voltage) from the drive circuit to the switch is always sent during the operation of the LED power supply device, the semiconductor element as the switch needs to perform an appropriate operation corresponding to the ON/OFF signal. .. That is, when a semiconductor element is used as a switch to secure the insulation of the LED power supply device, high response characteristics are required. Therefore, in Patent Document 1, by detecting the current to the load (rectifying current of the smoothing capacitor) and turning off the MOS-FET before the rectifying current becomes 0 level, the rectifying current becomes discontinuous. Techniques for eliminating defective operations are disclosed.

Japanese Patent Laid-Open No. 2005-73335

However, with the circuit configuration as disclosed in Patent Document 1, there is a possibility that defective operation of the switch (semiconductor element) can be reduced and the response characteristics can be improved, but in order to secure the insulation of the LED power supply device as described above. It is necessary to control the switch in a few microseconds, and it is actually difficult to extract all the charges accumulated in the semiconductor element. As a result, it is extremely difficult to secure sufficient insulation by the switch using the semiconductor element only by the technique of Patent Document 1. In order to use the switching power supply device as an LED power supply device, it is essential to secure the insulation as described above.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to improve a driving method by a driving circuit without changing a switch (semiconductor element) for ensuring insulation, It is an object of the present invention to provide a switching power supply device capable of achieving a high response characteristic of a switch (semiconductor element) and realizing a safe and stable power supply.

In order to solve the above problems, an LED power supply device according to the present invention is
An LED power supply device for converting AC power from a power supply into DC power, and providing a switching element to ensure insulation between the power supply and the LED element to supply power to the LED element,
The LED power supply device includes drive means for driving the switching element,
The driving unit turns on the switching element by outputting a positive voltage that is a positive voltage value, and turns off the switching element by outputting a negative voltage that is a negative voltage value,
The driving unit may alternately and repeatedly output the positive voltage and the negative voltage to turn on and off the switching element.

Further, the LED power supply device according to the present invention,
The value of the positive voltage output from the driving means is 5V to 20V,
The value of the negative voltage output from the driving means is -6V to -25V,
The driving means outputs a negative voltage having a value larger than the value of the positive voltage.

Further, the LED power supply device according to the present invention,
It is characterized in that the driving means includes a half bridge circuit.

Further, the LED power supply device according to the present invention,
A rectifier circuit that adjusts an AC voltage from a commercial power source, and a power supply that regulates the voltage rectified by the rectifier circuit to a DC voltage to supply power to the LED element and ensure insulation between the commercial power source and the LED element. What is claimed is: 1. An LED power supply device comprising: an insulation circuit; and a drive unit having the above-mentioned characteristics for transmitting an appropriate control signal to the power supply insulation circuit,
The power supply insulation circuit includes an input side switch and an output side switch, the first input side switch is arranged on the high potential side of the input side switch, and the second input side switch is arranged on the low potential side. A first output side switch is arranged on the high potential side of the output side switch and a second output side switch is arranged on the low potential side,
Further, in the power supply insulation circuit, an inductor is provided on the secondary side of the input side switch and the primary side of the output side switch, and a first charge in which one is connected to a high potential side and the other is connected to a low potential side. A second charging capacitor having a capacitor, one of which is connected to a high potential side and the other of which is connected to a low potential side on the secondary side of the output side switch;
The first input side switch and the second input side switch are simultaneously turned on and off,
The first output side switch and the second output side switch are simultaneously turned on and off,
The drive means having the above-mentioned characteristics turns on the input side switch and turns off the output switch to charge the first charging capacitor with electric power, and turns off the input side switch and turns on the output side switch. By turning on, the second charging capacitor is charged by the electromagnetic energy from the inductor and the electric power charged in the first charging capacitor, and the LED element is powered by the electric power charged in the second charging capacitor. Characterize.

According to the present invention, in an LED power supply device provided with a switching element for ensuring insulation between the power supply side and the load side (LED element side), a positive voltage is output when the switching element is on, and a positive voltage is output when it is off. By providing a driving means for outputting a negative voltage, and alternately outputting a positive voltage and a negative voltage from the driving means, it becomes possible to enhance the responsiveness of the switching element, while ensuring good insulation, and An LED power supply device capable of stable power supply can be realized.
Further, the driving means outputs the negative voltage value in the off operation which is larger than the positive voltage value in the on operation and outputs the result, thereby further improving the responsiveness of the switching element. ..

FIG. 1 shows a simplified schematic principle diagram of an LED power supply device according to the present invention. The schematic block diagram of the LED power supply device which concerns on embodiment of this invention is shown. An example of a semiconductor element used for each switch included in the LED power supply device according to the embodiment of the present invention will be shown. 6 shows a time chart of a basic operation of a drive circuit included in the LED power supply device according to the embodiment of the present invention. 7 shows a time chart of drive voltages from a drive circuit included in the LED power supply device according to the embodiment of the present invention. 7 shows a time chart of another drive voltage from the drive circuit included in the LED power supply device according to the embodiment of the present invention. FIG. 3 shows a schematic principle diagram of a drive circuit in the LED power supply device according to the present invention. Specific examples of element configurations that can be used in the drive circuit in the LED power supply device according to the present invention will be shown.

Hereinafter, the LED power supply device of the present invention will be described with reference to the drawings, but the invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

First, the insulation using the switching element in the LED power supply device according to the embodiment of the present invention will be described with reference to a simplified principle diagram. FIG. 1 is a simplified schematic principle diagram of an LED power supply device according to an embodiment of the present invention. The LED power supply device 110 shown in the figure supplies a proper voltage while maintaining insulation between the power supply 112 that supplies a DC voltage (and a DC current) and the power supply 112 side and the load side (LED element 122 side). Power supply insulation circuit 116 of FIG. In addition, the power supply insulation circuit 116 includes an input side switch S10, a freewheeling diode D1, a first coil L1, a first charging capacitor C1, an output side switch S20, and a second coil for suppressing a peak value of current. L2 and a second charging capacitor C2 for supplying stable DC power to the LED element 122 are provided.

In the present embodiment, in order to obtain a switching power supply device that ensures insulation, the power supply insulation circuit 116 includes an input side switch S10 and an output side switch S20, and the input side switch S10 and the output side switch S20. Are controlled so that there is no period in which they are on at the same time. The input side switch S10 is composed of a high input side switch S11 arranged on the high potential side and a low input side switch S12 arranged on the low potential side, and the output side switch S20 is arranged on the high potential side. It comprises a high output side switch S21 and a low output side switch S22 arranged on the low potential side. Basically, the high input side switch S11 and the low input side switch S12 are simultaneously turned on and off, and the high output side switch S21 and the low output side switch S22 are simultaneously turned on and off.

When the power supply 112 is turned on, a DC voltage from the power supply 112 reaches the input side switch S10 included in the power supply insulation circuit 116. At this time, the input-side switch S10 (input-side high-voltage switch S11, input-side low-voltage S12) is turned on by a drive signal from a drive circuit (not shown), and the DC power from the power supply 112 is changed to the power supply 112. →High input side switch S11 →First coil L1 →First charging capacitor C1 →Low input side switch S12 →Power supply 112 to charge the first charging capacitor C1. At this time, the output side switch S20 (the output side high voltage switch S21 and the output side low voltage switch S22) is turned off by the drive signal from the drive circuit. Therefore, the power supply 112 on the input side and the second charging capacitor C2 and the LED element 122 on the output side are insulated from each other. Next, the input side switch S10 (high input side switch S11, low input side S12) is turned off, and the output side switch S20 (high output side switch S21, low output side S22) is turned on. Then, the current as the magnetic field energy stored in the first coil L1 is the first coil L1→high output side switch S21→second coil L2→second charging capacitor C2→low output side switch S22→diode D1→first It flows with one coil L1 to charge the second charging capacitor C2. In addition, the charge stored in the first charging capacitor C1 is changed to the first charging capacitor C1→high output side switch S21→second coil L2→second charging capacitor C2→low output side switch S22→first charging capacitor C1. By flowing, the second charging capacitor C2 is charged, and the LED element 122 is turned on by the electric power charged in the second charging capacitor C2. In this way, the energy from both the first coil L1 and the first charging capacitor C1 is stored in the second charging capacitor C2, so that the LED power supply device 110 capable of supplying a large amount of DC power can be realized. is there.

As described above, when the input side switch S10 is turned on, the output side switch S20 is turned off, and conversely, when the output side switch S20 is turned on, the input side switch S10 is turned off. Since this is repeated, the power source 112 and the LED element 122 are always kept in an insulated state.

Next, the LED power supply device according to the embodiment of the present invention will be described. FIG. 2 shows a schematic diagram of the LED power supply device according to the embodiment of the present invention. Here, the LED power supply device in the present specification is a switching power supply device for performing stable power supply to the LED element. The LED power supply device 10 shown in the figure has a power supply 12 for supplying a commercial AC voltage, a rectifying/smoothing circuit 14 for rectifying the AC voltage, and electric power from the rectifying/smoothing circuit 14 to adjust the power to the LED element 22. A power supply insulation circuit 16 for supplying DC power, a drive circuit 18 for driving the power supply insulation circuit 16, and a detection circuit 20 for detecting a current flowing through the LED element 22 and sending it to the drive circuit 18 as a detection signal. I have it.

First, the rectifying/smoothing circuit 14 will be described.
The rectifying/smoothing circuit 14 includes a filter circuit 24, a diode bridge circuit DB, a smoothing capacitor Ca, a power factor correction circuit 26, and an electrolytic capacitor Cb. When an AC commercial voltage (AC 100 V, AC 200 V, etc.) is applied by the power supply 12, the commercial voltage reaches the diode bridge circuit DB via the filter circuit 24. The diode bridge circuit DB is composed of a diode element or the like, but may be composed of another semiconductor element as long as it can perform the same function. The full-wave rectified voltage (also called pulsating voltage) by the diode bridge circuit DB is smoothed to a rough DC voltage by the smoothing capacitor Ca. Then, the smoothed voltage reaches the power factor correction circuit 26. The power factor correction circuit 26 generates a boosted voltage by charging the electrolytic capacitor Cb after flowing a current through the inductor by turning the switching element on and off. In this way, the voltage that has been boosted and has the power factor improved reaches the power supply insulation circuit 16.

Next, the power supply insulation circuit 16 will be described. The power supply insulation circuit 16 basically operates on the principle described in FIG. The power supply insulation circuit 16 includes an input side switch S10, a free wheeling diode D1, a first coil L1, a first charging capacitor C1 and an output side switch S20, and a second coil L2 for suppressing a peak value of current. The second capacitor C2 for supplying stable DC power to the LED element 22. The input side switch S10 includes a high input side switch S11 arranged on the high potential side and a low input side switch S12 arranged on the low potential side, and the output side switch S20 is arranged on the high potential side. An output side switch S21 and a low output side switch S22 arranged on the low potential side are provided. Any of these four switches may be used as long as high-speed switching is possible, but semiconductor devices such as MOSFETs and IGBTs are preferable. Further, for example, as shown in FIG. 3, it is preferable to connect the diodes in series in the forward direction as a countermeasure against an additional diode between the parasitic diode of the MOSFET and the CE of the IGBT.

When the voltage from the rectifying/smoothing circuit 14 reaches the input side switch S10, the drive circuit 18 turns on the input side switch S10 (drive signal ds1) and turns off the output side switch S20 (drive signal ds2). At this time, the power from the rectifying/smoothing circuit 14 flows to the high input side switch S11→coil L1→first charging capacitor C1→low input side switch S12→rectifying/smoothing circuit 14 (electrolytic capacitor Cb) to perform the first charging. Charge the capacitor C1. At this time, the output side switch S20 (the high output side switch S21 and the low output side switch S22) is in the state of being turned off by the drive signal ds2 from the drive circuit 18 as described above. Therefore, the power supply 12 on the input side (and the rectifying/smoothing circuit 14) and the LED element 22 on the output side (and the second charging capacitor C2) are in an insulated state. Next, the drive circuit 18 turns off the input side switch S10 (high input side switch S11 and low input side S12) and turns on the output side switch S20 (high output side switch S21 and low output side S22). Then, the current as the magnetic field energy stored in the first coil L1 is the first coil L1→high output side switch S21→second coil L2→second charging capacitor C2→low output side switch S22→diode D1→first It flows with one coil L1 to charge the second charging capacitor C2. In addition, the electric charge stored in the first charging capacitor C1 flows through the first charging capacitor C1→high output side switch S21→second coil L2→second charging capacitor C2→low output side switch S22→first charging capacitor C1. As a result, the second charging capacitor C2 is charged, and the LED element 22 is turned on by the DC power charged in the second charging capacitor C2.

Drive Circuit Here, the basic operation of the drive circuit 18 will be described. FIG. 4 shows a time chart of on/off of each switch (input side switch S10 and output side switch S20) which receives the drive signal from the drive circuit 18. The control signal ds1 shown in FIG. 2 represents a drive signal for the input side switch S10 (S11 and S12), and the drive signal ds2 represents a drive signal (drive voltage) for the output side switch S20 (S21 and S22). At point a in FIG. 4, the input switch S10 (S11 and S12) is turned on by sending the drive signal ds1, and the output switch S20 (S21 and S22) is turned off by the drive signal ds2. That is, during this period (point a), the first charging capacitor C1 is being charged. At point b in FIG. 4, the drive circuit 18 sends the drive signal ds1 to turn off the input side switch S10, and sends the drive signal ds2 to turn on the output side switch S20. That is, during this period (point b), the second charging capacitor C2 is charged, and the LED element 22 is turned on by the electric power charged in the second charging capacitor C2. Here, in FIG. 4, a rest period T is provided between the points a and b. That is, in the actual driving operation of the LED power supply device 10, reliable insulation is realized by providing a pause period T in which both switches (four switches) of the input side switch S10 and the output side switch S20 stop operating. -ing

However, in reality, even if the drive control as shown in FIG. 4 described above is performed, if the semiconductor element used as each switch is, for example, an FET, a feedback capacitance between the gate and the drain, or an IGBT. For example, due to the feedback capacitance between the gate and collector, the effect of the voltage applied to the drain or collector causes a phenomenon in which the charge accumulated in the insulated gate is hard to disappear during the off operation (generally the Miller effect and Call). Further, the recent FETs or IGBTs are composed of an assembly of a large number of minute FETs or IGBTs, and the electric charges accumulated in the gates of all the minute elements do not disappear at the same time, and there are variations due to some time delay. Exists. Further, variations in the time delay also occur depending on the type of conductive material inside the semiconductor element, the thickness of the wiring, and the like.

Therefore, the drive circuit 18 in the LED power supply device 10 of the present embodiment realizes prompt extraction of the electric charge accumulated in the gate by applying a negative voltage (negative voltage) to the gate during the OFF operation. . Specifically, as shown in FIG. 5, during the ON operation, the positive voltage +V is applied similarly to the ON voltage shown in FIG. By applying a negative voltage −V as shown in FIG. 5 instead of 0 V as shown in FIG. 4 during the OFF operation, it becomes possible to quickly extract the charge of the gate, and the response characteristic of each switch is Can be improved. The voltage at this time is preferably about ±5 V to ±25 V for both the positive voltage and the negative voltage, and more preferably ±10 V to ±15 V. Further, as shown in FIG. 6, by increasing the voltage value of the negative voltage during the off operation to be larger than the positive voltage during the on operation, the charge can be extracted faster, so that the response characteristic can be further improved. .. For example, when the value of the positive voltage +V during the ON operation is +5V, the value of the negative voltage -V during the OFF operation may be changed from -6V to -25V. Further, similarly to the time chart shown in FIG. 4, a pause period T may be provided between the ds1 on operation (ds2 off operation) and the ds2 on operation (ds1 off operation). In this case, a negative voltage is applied to both ds1 and ds2 during the idle period T.

In this way, by outputting the drive signal of the negative voltage from the drive circuit 18 at the time of the off operation, it becomes possible to improve the response characteristics, and it is possible to secure good insulation.

Next, switching between the positive voltage and the negative voltage of the drive circuit 18 will be described. FIG. 7 shows a schematic principle diagram of a drive circuit in the LED power supply device according to the present invention. As shown in the figure, a positive voltage (ON operation of each switch) and a negative voltage (OFF operation of each switch) are realized by switching the Hi switch and the Lo switch. Specifically, when it is desired to turn on S10 (or S20) shown in FIG. 2, a positive voltage of +V can be output to S10 (or S20) by using a Hi switch. When it is desired to turn off S10 (or S20), the negative voltage of -V can be output to S10 (or S20) by switching to the Lo switch. Further, since it is necessary to send separate drive signals to the drive signals ds1 and ds2 in FIG. 2, two circuits shown in FIG. 7 are actually required inside the drive circuit 18. Then, FIG. 8 shows a specific circuit example for realizing the switching circuit. FIG. 8A is a specific circuit diagram in which an FET is used as a positive voltage/negative voltage switching circuit, and FIG. 8B is a specific circuit diagram in which a bipolar transistor is used as a positive voltage/negative voltage switching circuit. It is a circuit diagram. Further, the switching circuit is not limited to the circuit shown in FIG. 8, and any circuit may be used as long as the drive control shown in the time chart of FIG. 5 or 6 can be realized.

As described above, in the LED power supply device according to the present invention, in the LED power supply device provided with the switching element for ensuring the insulation between the power supply side and the load side (LED element side), the positive voltage is applied when the switching element is on. It is possible to improve the responsiveness of the switching element by providing a drive circuit that outputs a negative voltage during the off operation, and alternately output a positive voltage and a negative voltage from the drive circuit, which results in good insulation. It is possible to realize an LED power supply device capable of ensuring stable power supply while ensuring the above. Further, the drive circuit outputs the negative voltage value at the time of the off operation larger than the positive voltage value at the time of the on operation, and thereby the response of the switching element can be further enhanced. ..
Further, the LED power supply device of the above embodiment has switches using semiconductor elements on both the high potential side and the low potential side, but for example, only one side (either one of the high potential side or the low potential side) The effect of the present invention can be realized even in other circuit configurations in which the insulation between the input side and the output side can be ensured by providing a switch in (4) or inserting a switch in another place to perform a switching operation.

10 110 LED power supply device 12 112 Power supply 14 Rectification smoothing circuit 16 116 Power supply insulation circuit 18 Drive circuit 20 Current detection circuit 22 122 LED element 24 Filter circuit 26 Power factor improvement circuit S10 Input side switch S11 High input side switch S12 Low input side Switch S20 Output side switch S21 High output side switch S22 Low output side switch DB Diode bridge circuit D1 Return diode L1 First coil L2 Second coil Ca Smoothing capacitor Cb Electrolytic capacitor C1 First charging capacitor C2 Second charging capacitor R1 Current Detection resistor OP Isolation amplifier

Claims (3)

A rectifier circuit that adjusts an AC voltage from a commercial power source, and a power supply that regulates the voltage rectified by the rectifier circuit to a DC voltage to supply power to the LED element and ensure insulation between the commercial power source and the LED element. An LED power supply device comprising: an insulating circuit; and driving means for sending an appropriate control signal to the power supply insulating circuit ,
The power supply insulation circuit includes an input side switch and an output side switch, the first input side switch is arranged on the high potential side of the input side switch, and the second input side switch is arranged on the low potential side. A first output side switch is arranged on the high potential side of the output side switch and a second output side switch is arranged on the low potential side,
Further, in the power supply insulation circuit, an inductor is provided on the secondary side of the input side switch and the primary side of the output side switch, and a first charge in which one is connected to a high potential side and the other is connected to a low potential side. A second charging capacitor having a capacitor, one of which is connected to a high potential side and the other of which is connected to a low potential side on the secondary side of the output side switch;
The first input side switch and the second input side switch are simultaneously turned on and off,
The first output side switch and the second output side switch are simultaneously turned on and off,
The drive means turns on the input side switch and turns off the output side switch to charge the first charging capacitor with electric power, and then turns off both the input side switch and the output side switch. And then turning on the output side switch and turning on the output side switch to charge the second charging capacitor with the electromagnetic energy from the inductor and the electric power charged in the first charging capacitor. 2 The LED element is powered by the power charged in the charging capacitor,
The drive means turns on the input side switch and the output side switch by outputting a positive voltage that is a positive voltage value, and outputs the negative voltage that is a negative voltage value by outputting the input side switch and the output side switch. Switch off,
The driving means turns on and off the input side switch and the output side switch by alternately and repeatedly outputting the positive voltage and the negative voltage,
Further, the driving means outputs a negative voltage to both the input side switch and the output side switch during the idle period, the LED power supply device. The LED power supply device according to claim 1, wherein
The value of the positive voltage output from the driving means is 5V to 20V,
The value of the negative voltage output from the driving means is -6V to -25V,
The LED power supply device, wherein the driving means outputs a negative voltage having a value larger than the positive voltage value. It is an LED power supply device in any one of Claim 1 to 2, Comprising:
An LED power supply device, wherein the driving means includes a half bridge circuit.

Images