JP2012029534A - Power supply device, and illumination device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation-type power supply device that can lower an output voltage below an effective input voltage, and can reduce an input current distortion, and to provide an illumination device having the same.SOLUTION: A power supply device has: a parallel circuit consisting of a series circuit of input capacitors C1 and C2 connected between DC output ends of a diode bridge 21 that rectifies an AC power, and a series circuit of two switching elements Q1 and Q2; and a transformer T1 having a primary coil connected between a connection point between the input capacitors C1 and C2 and connection point between the switching elements Q1 and Q2, and a secondary coil having a tap. One end of an output capacitor C3 whose both ends work as output ends is connected to the tap of the secondary coil of the transformer T1, and the other end of the output capacitor C3 is connected to both ends of the secondary coil of the transformer T1 via output diodes D3 and D4 respectively. A control circuit 3 on-off drives the two switching elements Q1 and Q2 alternately.

Description

  The present invention relates to a power supply device and a lighting device including the power supply device.

  Conventionally, as shown in FIG. 14, a power supply apparatus including a diode bridge 21 that performs full-wave rectification of input AC power, and a DC-DC converter 30 that outputs the DC output of the diode bridge 21 by smoothing and converting the voltage. Is provided (for example, refer to Patent Document 1). The diode bridge 21 is connected to the AC power source 6 via the LC type low-pass filter 20.

  In the DC-DC converter 30, the series circuit of two input capacitors Ca and Cb connected between the DC output terminals of the diode bridge 21 and the anode are connected to the DC output terminal on the high voltage side of the diode bridge 21. The first diode Da, the second diode Db whose cathode is connected to the DC output terminal on the low voltage side of the diode bridge 21, and the two connected between the cathode of the first diode Da and the second diode Db A series circuit of switching elements Qa and Qb, two diodes Dc and Dd connected in parallel to each one switching element Qa and Qb and opposite to the output voltage of the diode bridge 21, and an input Two inductors L0 connected between the connection points of the capacitors Ca and Cb and the connection points of the switching elements Qa and Qb; An output capacitor C0 connected in parallel to the series circuit of the switching elements Qa and Qb and a control circuit (not shown) for alternately turning on and off the switching elements Qa and Qb are provided, and both ends of the output capacitor C0 are output terminals. Connected to a load Z.

  The operation of the DC-DC converter 30 will be described. The frequency at which the control circuit alternately turns on and off the switching elements Qa and Qb is sufficiently higher than the frequency of the AC power input to the diode bridge 21. That is, it can be considered that the DC output voltage of the diode bridge 21 does not change during the above ON / OFF cycle.

  First, the switching element Qa on the high voltage side is turned on while the switching element Qb on the low voltage side is maintained in the off state. Then, a current flows through a path of the diode bridge 21 → the first diode Da → the high voltage side switching element Qa → the inductor L0 → the low voltage side input capacitor Cb → the diode bridge 21, and during this time, energy is accumulated in the inductor L0. . Further, the input capacitor Cb on the low voltage side is charged. Since the voltage across the two input capacitors Ca and Cb is equal to the voltage between the DC output terminals of the diode bridge 21, the input capacitor Ca on the high voltage side is discharged as the input capacitor Cb on the low voltage side is charged.

  Next, the switching element Qa on the high voltage side is turned off. Then, the energy stored in the inductor L0 is regenerated, and the inductor L0 → the input capacitor Ca on the high voltage side → the first diode Da → the output capacitor C0 → the diode Dd connected in parallel to the switching element Qb on the low voltage side → the inductor The output capacitor C0 is charged by the current flowing in the L0 loop. During this time, the input capacitor Ca on the high voltage side is further discharged, and the input capacitor Cb on the low voltage side is further charged accordingly.

  Next, the switching element Qb on the low voltage side is turned on while the switching element Qa on the high voltage side is maintained in the off state. Then, a current flows through a path of the diode bridge 21 → the high voltage side input capacitor Ca → the inductor L0 → the low voltage side switching element Qb → the second diode Db → the diode bridge 21, and during this time, energy is accumulated in the inductor L0. . Further, the input capacitor Ca on the high voltage side is charged, and the input capacitor Cb on the low voltage side is discharged accordingly.

  Next, the switching element Qb on the low voltage side is turned off. Then, the energy stored in the inductor L0 is regenerated, and the inductor L0 → the diode Dc connected in parallel with the switching element Qa on the high voltage side → the output capacitor C0 → the second diode Db → the input capacitor Cb on the low voltage side → the inductor The output capacitor C0 is charged by the current flowing in the L0 loop. During this time, the input capacitor Cb on the low voltage side is further discharged, and the input capacitor Ca on the high voltage side is further charged accordingly.

  Thereafter, by repeating the same operation, a voltage obtained by boosting the voltage across the series circuit of the two input capacitors Ca and Cb is output from the output terminal (that is, both terminals of the output capacitor C0).

  The load Z connected between the output terminals of the DC-DC converter 30 is an inverter circuit that turns on the discharge lamp with AC power generated by converting the output power of the DC-DC converter 30, for example.

Japanese Patent No. 2677406

  However, the DC-DC converter 30 is a non-insulated type. Since the booster circuit is used, a voltage lower than the effective value of the output voltage of the diode bridge 21 (that is, the effective value of the input voltage from the AC power source, hereinafter referred to as “effective input voltage”) is obtained separately. A step-down circuit is required.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a power supply apparatus that is of an insulating type and can reduce an output current distortion with an output voltage lower than an effective input voltage. Another object of the present invention is to provide a lighting device including the power supply device.

  A power supply apparatus according to the present invention includes a diode bridge for full-wave rectification of input AC power, and two input capacitors connected in series between either an AC input terminal or a DC output terminal of the diode bridge. Two switching elements connected in series between the DC output terminals of the diode bridge, and a primary winding connected between a connection point between the input capacitors and a connection point between the switching elements, A transformer having a secondary winding having a tap, two output diodes, each of which is one of an anode and a cathode, each of which is common to one end of the secondary winding; An output capacitor having one end connected to the other of the anode and cathode of the output diode and the other end connected to the tap of the secondary winding; Characterized in that it comprises a control circuit for on-off driving the switching elements alternately.

  In this power supply device, it is desirable to provide a snubber capacitor connected in parallel to a series circuit of the two switching elements.

  In this power supply device, the snubber capacitor has a capacitance of 1/100 or less of the capacitance of the output capacitor.

  Further, in this power supply apparatus, the control circuit changes the frequency of the on / off drive as needed so as to maintain a constant ratio between the voltage between the DC output terminals of the diode bridge and the voltage between both terminals of the snubber capacitor. Is desirable.

  In the power supply apparatus, the control circuit may maintain a constant ratio between a voltage obtained by dividing the voltage between the DC output terminals of the diode bridge and a voltage obtained by dividing the voltage across the snubber capacitor. In addition, it is desirable to change the frequency of the on / off drive as needed.

  Furthermore, in this power supply device, it is preferable that the control circuit changes the frequency of the on / off drive as needed so as to maintain the voltage across the snubber capacitor constant.

  The power supply apparatus preferably includes a DC-DC converter having input terminals connected to both ends of the output capacitor.

  Further, in this power supply device, a series circuit of a resistor and an auxiliary switching element is connected between both ends of each of the input capacitors, and the control circuit is configured so that the average values of the voltages at both ends are matched between the input capacitors. In addition, it is desirable to drive each auxiliary switching element on and off.

  In the power supply apparatus, it is desirable that one end of the primary winding and one end of the secondary winding are connected to each other via a capacitor in the transformer.

  Furthermore, in this power supply device, it is desirable that one end on the low voltage side in the series circuit of the two switching elements and one end of the output capacitor are connected to each other via a capacitor.

  In this power supply apparatus, the second switching element connected in series between the DC output terminals of the diode bridge is connected between the connection point of the input capacitor and the connection point of the switching element. A second transformer having a primary winding and a secondary winding having a tap, and one of an anode and a cathode, respectively, which is common to one end of the secondary winding of the second transformer. One end is connected to the other of the two connected second output diodes and the anode and cathode of each second output diode, and the other end is connected to the tap of the secondary winding of the second transformer. It is preferable that the control circuit alternately turns on and off the two second switching elements.

  The illumination device of the present invention includes any one of the power supply devices described above and an electrical light source that is turned on by output power of the power supply device.

  In this illuminating device, it is desirable to provide a solid light emitting element as the electrical light source.

  According to the present invention, insulation between the input and output is achieved by the transformer, and the output voltage can be made lower than the effective input voltage due to the turns ratio of the transformer. Further, when a current flows through the primary winding of the transformer, the voltage across each input capacitor changes, and accordingly, the current is continuously input from the diode bridge, thereby improving the input current distortion.

It is a circuit block diagram which shows Embodiment 1 of this invention. It is explanatory drawing which shows the time change of the electric current Id1 which flows into the 1st diode in the same as the above, the electric current Id2 which flows through the 2nd diode, and the output current Idb of a diode bridge. It is explanatory drawing which shows the time change of the direct current output voltage Vdb of a diode bridge in the same as the above, and the current It1 which flows into the primary winding of a transformer. It is a circuit block diagram which shows Embodiment 2 of this invention. It is a circuit block diagram which shows Embodiment 3 of this invention. It is a circuit block diagram which shows the example of a change same as the above. It is a circuit block diagram which shows another example of a change same as the above. It is a circuit block diagram which shows another example of a change same as the above. It is a circuit block diagram which shows another example of a change same as the above. It is a circuit block diagram which shows another example of a change same as the above. It is a circuit block diagram which shows the circuit of the primary side of another example of a change same as the above. (A) and (b) are circuit diagrams each showing a secondary side circuit in the example of FIG. 11, (a) is a secondary side circuit of the transformer, and (b) is a secondary side of the second transformer. The circuit of is shown. It is a disassembled perspective view which shows an example of the illuminating device using the same as the above. It is a circuit block diagram which shows a prior art example.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
As shown in FIG. 1, the power supply apparatus according to the present embodiment includes a diode bridge 21 that performs full-wave rectification of AC power input from the AC power supply 6 via an LC type low-pass filter 20.

  In addition, the present embodiment includes two input capacitors C1 and C2 connected in series between the DC output terminals of the diode bridge 21. Further, in the present embodiment, a first diode D1 having an anode connected to the DC output terminal on the high voltage side of the diode bridge 21 and a second diode having a cathode connected to the DC output terminal on the low voltage side of the diode bridge 21 are used. D2, two switching elements Q1 and Q2 connected in series between the cathode of the first diode D1 and the second diode D2, and the connection point between the input capacitors C1 and C2 and the connection of the switching elements Q1 and Q2 A transformer T1 having a primary winding connected to the point and a control circuit 3 for alternately turning on and off the switching elements Q1 and Q2 are provided. Each of the switching elements Q1 and Q2 is composed of, for example, a MOSFET having a parasitic diode, and is connected with the direction of the parasitic diode opposite to the direction of the DC output of the diode bridge 21.

  Furthermore, the present embodiment includes an output capacitor C3 that is charged by the power transmitted through the transformer T1 and that has both ends connected to a load such as the light-emitting diode 4 as output ends. The output capacitor C3 is made of, for example, an electrolytic capacitor. The secondary winding of the transformer T1 is provided with a tap, and one end of the output capacitor C3 is connected to the tap. Further, the present embodiment includes two output diodes D3 and D4 each having an anode connected to one end of the secondary winding of the transformer T1, and the cathodes of the output diodes D3 and D4 are the output capacitor C3 and the cathode, respectively. Connected to the end. In the output capacitor C3, the one end connected to the tap of the secondary winding of the transformer T1 becomes an output end on the low voltage side, and the other end connected to the cathodes of the output diodes D3 and D4 is on the high voltage side. Output terminal.

  In the present embodiment, a light emitting diode 4 which is a kind of solid state light emitting device is connected as a load between both ends of the output capacitor C3. The step-down from the effective value of the output voltage of the diode bridge 21 to a voltage suitable for the light emitting diode 4 is achieved by the turn ratio of the transformer T1. As a load, for example, an organic EL (not shown) may be connected instead of the light emitting diode 4. As described above, if a light emitting diode 4 or a solid light emitting element such as an organic EL is used as an electrical light source, power consumption per luminous flux can be reduced as compared with the case where an incandescent lamp or a discharge lamp is used as an electrical light source. .

  The control circuit 3 alternately turns on and off the switching elements Q1 and Q2 at a frequency sufficiently higher than the frequency of the AC power input to the diode bridge 21. As a result, the current Id1 flowing through the first diode D1, the current Id2 flowing through the second diode D2, and the input current to the diode bridge 21 (ie, the output current from the diode bridge 21) Idb are as shown in FIG. It becomes a waveform. Of the input current to the diode bridge 21, the high frequency component is attenuated by the action of the low pass filter 20. Further, as shown in FIG. 3, the envelope of the current It1 flowing through the primary winding of the transformer T1 is referred to as a DC output (pulsating current output) voltage (hereinafter referred to as “rectified voltage”) on both the positive and negative sides. .) Vdb waveform.

  According to the above configuration, insulation between the input and output is achieved by the transformer T1, and the output voltage can be made lower than the effective input voltage by the turn ratio of the transformer T1. Furthermore, when a current flows through the primary winding of the transformer T1, the voltage across the input capacitors C1 and C2 changes, and the current is continuously input from the diode bridge DB. Is done.

(Embodiment 2)
Since the basic configuration of this embodiment is the same as that of the first embodiment, the description of the common parts is omitted.

  As shown in FIG. 4, this embodiment includes a snubber capacitor C4 connected in parallel to a series circuit of switching elements Q1 and Q2. The snubber capacitor C4 suppresses pulses generated when the switching elements Q1 and Q2 are driven on and off, and the capacitance of the snubber capacitor C4 may be 1/100 or less of the capacitance of the output capacitor C3. When a film capacitor is used as the snubber capacitor C4, the size can be reduced as compared with the case where an electrolytic capacitor is used as the snubber capacitor C4.

  The control circuit 3 also turns on and off the switching elements Q1 and Q2 so that the waveform of the voltage across the snubber capacitor C4 (hereinafter referred to as “snubber voltage”) Vsn is similar to the waveform of the rectified voltage Vdb. Change from time to time. In other words, the control circuit 3 performs feedback control so that the snubber voltage Vsn is a constant multiple of the rectified voltage Vdb.

  Specifically, the control circuit 3 includes an operational amplifier OP1, a voltage controlled oscillation circuit 31 that generates an output having a frequency corresponding to the output voltage of the operational amplifier OP1, and an output of the voltage controlled oscillation circuit 31 with an appropriate voltage with an on-duty of 50%. And a rectangular wave generation circuit 32 for shaping the rectangular wave. The output of the rectangular wave generation circuit 32 is directly input to the gate of the switching element Q2 on the low voltage side, and is input to the gate of the switching element Q1 on the high voltage side via the negative circuit 33. Thereby, the switching elements Q1 and Q2 are alternately turned on and off at the output frequency of the voltage controlled oscillation circuit 31.

  In the control circuit 3, the operational amplifier OP1 constitutes an integration circuit by connecting the inverting input terminal and the output terminal via the capacitor Cfb. Further, in the operational amplifier OP1, the voltage obtained by dividing the rectified voltage Vdb by the resistors Ra and Rb is input to the non-inverting input terminal via the resistor Re, and the snubber voltage Vsn is divided by the resistors Rc and Rd to the inverting input terminal. The pressed voltage is input via the resistor Rf.

  That is, the control circuit 3 lowers the on / off frequency (hereinafter referred to as “operation frequency”) of the switching elements Q1 and Q2 as the snubber voltage Vsn is lower than the rectified voltage Vdb.

  According to the experiment of the present inventor, the waveform of the snubber voltage Vsn is similar to the waveform of the rectified voltage Vdb by the above control, and the voltage across the output capacitor C3 is maintained substantially constant.

  Here, when the control circuit 3 detects the voltage across the output capacitor C3 and performs feedback control so as to keep it constant, in order to ensure insulation between the primary side and the secondary side of the transformer T1. For example, it is necessary to insert a component such as a photocoupler between the control circuit 3 and the output capacitor C3. On the other hand, in the present embodiment, since the voltage across the output capacitor C3 is not detected, a component such as a photocoupler is unnecessary.

  Instead of changing the operating frequency as described above or in addition to changing the operating frequency as described above, the control circuit 3 changes the duration of the ON state of one switching element Q1 and the other switching element. The feedback control described above may be realized by changing the ratio of the on-time duration of Q2. Since such a control circuit 3 can be realized by a well-known technique, detailed illustration and description thereof are omitted.

(Embodiment 3)
Since the basic configuration of this embodiment is the same as that of the second embodiment, the description of the common parts is omitted.

  In the present embodiment, a snubber capacitor C4 having a relatively high capacitance, such as an electrolytic capacitor, is used. The capacitance of the snubber capacitor C4 is the same as that of the output capacitor C3, for example.

  The control circuit 3 performs feedback control so as to maintain the snubber voltage Vsn at a constant voltage.

  Specifically, as shown in FIG. 5, in the operational amplifier OP1 of the control circuit 3, a predetermined reference voltage Vref is input to the non-inverting input terminal. In addition, a resistor Rg is inserted between the other end of the capacitor Cfb whose one end is connected to the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP1, and the voltage obtained by dividing the snubber voltage Vsn is the resistance Rf. Through the capacitor Cfb and the resistor Rg.

  That is, as the snubber voltage Vsn is lower than the target voltage obtained by dividing the reference voltage Vref by the voltage dividing ratio, the control circuit 3 turns on / off frequencies of the switching elements Q1 and Q2 (hereinafter referred to as “operation frequency”). Called).

  According to the experiment of the present inventor, the snubber voltage Vsn and the voltage across the output capacitor C3 are maintained substantially constant by the above control.

  Also in this embodiment, since the voltage across the output capacitor C3 is not detected as in the second embodiment, a part such as a photocoupler is unnecessary.

  Instead of changing the operating frequency as described above or in addition to changing the operating frequency as described above, the control circuit 3 changes the duration of the ON state of one switching element Q1 and the other switching element. The feedback control described above may be realized by changing the ratio of the on-time duration of Q2. Since such a control circuit 3 can be realized by a well-known technique, detailed illustration and description thereof are omitted.

  In each of the first to third embodiments, a DC-DC converter 5 may be connected to the subsequent stage of the output capacitor C3 as shown in FIG. The DC-DC converter 5 of FIG. 6 is a circuit in which a capacitor between output terminals is omitted in a known buck converter. That is, the DC-DC converter 5 of FIG. 6 includes a switching element Q7 having one end connected to one end on the high voltage side of the output capacitor C3, a cathode connected to the other end of the switching element Q7, and an output capacitor C3. A diode D7 having an anode connected to one end on the low voltage side, an inductor L1 connected as a series circuit with the light emitting diode 4 between both ends of the diode D7, and a drive circuit for periodically turning on and off the switching element Q7 51. The drive circuit 51 receives, for example, a dimming signal, which is an electric signal for instructing optical output, from the outside. The higher the optical output instructed by the dimming signal is, the higher the on-duty of the switching element Q7 is increased. Increase the light output. The dimming signal may be a rectangular wave (so-called PWM signal) whose on-duty is increased as the indicated optical output is higher, or an analog voltage signal whose voltage value is increased as the indicated optical output is higher. May be. The power supply of the drive circuit 51 is generated by voltage dividing resistors R11 and R12 that divide the voltage across the output capacitor C3, and a Zener diode ZD connected in parallel to the low voltage side voltage dividing resistor R12. Since the drive circuit 51 as described above can be realized by a well-known technique, detailed illustration and description thereof will be omitted. As the DC-DC converter 5, other known circuits may be used instead of the above circuits.

  By the way, if the average values of the voltages at both ends of the input capacitors C1 and C2 are different from each other, the life of one of the input capacitors C1 and C2 may be shortened. Therefore, the configuration of FIG. 7 may be employed in each of the first to third embodiments. That is, a series circuit of switching elements (hereinafter referred to as “auxiliary switching elements”) Q3 and Q4 and resistors Rb1 and Rb2 are arranged in parallel with the input capacitors C1 and C2, respectively. Furthermore, the control circuit 3 appropriately turns on the auxiliary switching elements Q3 and Q4 that are normally maintained in the off state so that the average values of the voltages across the input capacitors C1 and C2 coincide with each other. Since the control circuit 3 as described above can be realized by a well-known technique, detailed illustration and description thereof will be omitted.

  Furthermore, in each of the first to third embodiments, instead of connecting the series circuit of the input capacitors C1 and C2 between the DC output terminals of the diode bridge 21, the series circuit of the input capacitors C1 and C2 is a diode as shown in FIG. You may connect between the alternating current input terminals of the bridge 21. In this case, since the backflow of the current through the parasitic diodes of the switching elements Q1 and Q2 is blocked by the diode bridge 21, the first diode D1 and the second diode D2 can be omitted. In this case, the diode bridge 21 is composed of a fast rectifying element (FRD).

  In each of the first to third embodiments, as shown in FIGS. 9 and 10, in the transformer T1, between one end of the primary winding and one end of the secondary winding, or between the two switching elements Q1 and Q2 In the series circuit, one end (that is, ground) on the low voltage side and one end of the output capacitor C3 may be connected to each other via the capacitor Cs. If this configuration is adopted, noise flows through the capacitor Cs, so that the noise intensity as a whole can be suppressed.

  Furthermore, Embodiments 1 to 3 can be replaced with appropriate equivalent circuits. For example, instead of using one transformer T1 having a tap in the secondary winding, as shown in FIG. 10, two transformers T3 and T3 in which the primary windings and the secondary windings are connected in series with each other, respectively. T4 may be used. In this case, instead of the tap of the secondary winding of the transformer T1, the secondary windings of the two transformers T3 and T4 are connected to one end on the low voltage side in the output capacitor C3. If the said structure is employ | adopted, about each transformer T3, T4, a structure can be simplified rather than the transformer T1 which has a tap.

  In each of the first to third embodiments, as shown in FIG. 11, two circuits for transmission and output may be provided. The example of FIG. 11 will be specifically described. A series circuit including two second switching elements Q5 and Q6 is connected in parallel to the series circuit of the switching elements Q1 and Q2. In addition, the example of FIG. 11 includes a second transformer T2 in which a primary winding is connected between a connection point of the second switching elements Q5 and Q6 and a connection point of the input capacitors C1 and C2. Furthermore, as shown in FIG. 12, the secondary winding of the second transformer T2 is provided with a tap, and one end of a second output capacitor C5 made of, for example, an electrolytic capacitor is connected to the tap. The other end of the second output capacitor C5 is connected to both ends of the secondary winding of the second transformer T2 via one second output diode D5 and D6, respectively. A load such as a separate light emitting diode 4a can be connected between both ends of the second output capacitor C5 serving as the second output terminal.

  The various power supply devices can be used for an illumination device 7 as shown in FIG. 13, for example. 13 includes a case 70 that stores and holds each circuit component of the power supply device, and a fixture body 71 that holds the case 70 stored as indicated by an arrow A1 and holds the light emitting diodes 4 and 4a. And have. Since the illumination device 7 as described above can be realized by a known technique, detailed illustration and description thereof will be omitted.

3 Control circuit 4, 4a Light emitting diode (electric light source, solid state light emitting device)
5 DC-DC converter 7 Lighting device 21 Diode bridge C1, C2 Input capacitor C3 Output capacitor C4 Snubber capacitor C5 Second output capacitor D3, D4 Output diode Q1, Q2 Switching element Q3, Q4 Auxiliary switching element Q5, Q6 Second switching element Rb1, Rb2 resistance T1, T3, T4 transformer T2 second transformer

Claims (13)

A diode bridge for full-wave rectification of the input AC power;
Two input capacitors connected in series with each other between an AC input terminal and a DC output terminal of the diode bridge;
Two switching elements connected in series between the DC output terminals of the diode bridge;
A transformer having a primary winding and a secondary winding having a tap connected between a connection point between the input capacitors and a connection point between the switching elements;
Two output diodes, each of which is one of an anode and a cathode, and one common to each other is connected to one end of the secondary winding;
An output capacitor having one end connected to the other of the anode and cathode of each output diode and the other end connected to the tap of the secondary winding;
And a control circuit for alternately turning on and off the two switching elements.   The power supply device according to claim 1, further comprising a snubber capacitor connected in parallel to a series circuit of the two switching elements.   The power supply apparatus according to claim 2, wherein the capacitance of the snubber capacitor is 1/100 or less of the capacitance of the output capacitor.   3. The control circuit according to claim 2, wherein the control circuit changes the frequency of the on / off drive as needed so as to maintain a constant ratio between a voltage between DC output terminals of the diode bridge and a voltage between both terminals of the snubber capacitor. Or the power supply device of Claim 3.   The control circuit is configured to maintain a constant ratio between a voltage obtained by dividing the voltage between the DC output terminals of the diode bridge and a voltage obtained by dividing the voltage across the snubber capacitor. The power supply device according to claim 4, wherein the power supply device is changed as needed.   3. The power supply device according to claim 2, wherein the control circuit changes the frequency of the on / off drive as needed so as to maintain a constant voltage across the snubber capacitor.   The power supply apparatus according to claim 1, further comprising a DC-DC converter having input terminals connected to both ends of the output capacitor. A series circuit of a resistor and an auxiliary switching element is connected between both ends of each of the input capacitors,
8. The power supply according to claim 1, wherein the control circuit drives each of the auxiliary switching elements on and off so that an average value of both-end voltages between the input capacitors coincides with each other. apparatus.   9. The power supply device according to claim 1, wherein one end of the primary winding and one end of the secondary winding are connected to each other via a capacitor in the transformer.   The one end on the low voltage side in the series circuit of the two switching elements and one end of the output capacitor are connected to each other via a capacitor. Power supply. Two second switching elements connected in series between the DC output terminals of the diode bridge;
A second transformer having a primary winding and a secondary winding having a tap connected between a connection point of the input capacitor and a connection point of the switching element;
Two second output diodes, each of which is one of an anode and a cathode, each of which is common to one end of the secondary winding of the second transformer;
A second output capacitor having one end connected to the other of the anode and cathode of each second output diode and the other end connected to a tap of the secondary winding of the second transformer;
The power supply device according to claim 1, wherein the control circuit alternately turns on and off the two second switching elements.   An illumination device comprising: the power supply device according to any one of claims 1 to 11; and an electric light source that is turned on by output power of the power supply device.   The lighting device according to claim 12, further comprising a solid light emitting element as the electrical light source.

Images