JP2003018865A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device which can reduce losses and noise of switching devices and realize a high efficiency. SOLUTION: A smoothing capacitor C0 is connected with an output end of a rectifier DB via a parallel circuit comprising a diode D1 and a capacitor C1. A series circuit comprising switching devices Q1 and Q2 is connected with both the ends of the smoothing capacitor C0 via a parallel circuit comprising a diode D2 and a capacitor C2 and reverse-parallel diodes and parallel capacitors C4 and C5 of snubber circuits are connected with the respective switching devices. A load circuit 2 is connected between the connection point of the switching devices Q1 and Q2 and the one output end of the rectifier DB via a transformer T1, and an impedance element Z is connected between the connection point of the switching devices Q1 and Q2 and the connection point of the diodes D1 and D2. The capacitor C1 can be connected in parallel between the output ends of the rectifier DB. The capacitor C2 can be connected in parallel between both the ends of the series circuit comprising the switching devices Q1 and Q2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for converting a direct current voltage obtained by rectifying and smoothing an alternating current voltage into a high frequency voltage and supplying a high frequency power to a load circuit. It is used.

[0002]

2. Description of the Related Art Conventionally, a power supply device for rectifying and smoothing an AC voltage from an AC power source to convert it into a DC voltage, converting this DC voltage into a high frequency voltage by an inverter, and supplying a high frequency power to a load resonance circuit is known. Widely used.

FIG. 16 is a circuit diagram showing such a conventional power supply device. This power supply device is a full-wave rectifier DB that full-wave rectifies an AC voltage from an AC power supply AC into a DC voltage,
A first diode D1 whose anode is connected in the forward direction to the positive output terminal of this full-wave rectifier DB, and this diode D
Smoothing capacitor C0 connected between the cathode of No. 1 and the negative output terminal of the rectifier DB, and the second diode D whose anode is connected to the cathode of the diode D1 in the forward direction.
2, the cathode of this diode D2 and the full-wave rectifier DB
Of the pair of switching elements Q1 and Q2 connected in series with the negative output terminal of the control circuit 1 for controlling ON / OFF of the pair of switching elements Q1 and Q2, and the pair of switching elements Q1 and Q2. Connection point and rectifier DB
, A transformer T1 having a primary winding n1 connected to the positive output terminal and a secondary winding n2 connected to the load circuit 2, and a capacitor C1 connected in parallel with the diodes D1 and D2. , C2.

Each of the switching elements Q1 and Q2 is, for example, a MOSFET, is connected between the source and the substrate, and has a structure having a parasitic diode in which a cathode and an anode are connected to a drain and a source, respectively. Further, the control circuit 1 alternately turns on / off the switching elements Q1 and Q2 by the operation of the switching frequency sufficiently higher than the frequency of the AC power supply AC.
That is, the switching frequency is set to such an extent that the voltage of the AC power supply AC can be regarded as constant during one cycle.

The load circuit 2 is connected between a discharge lamp (fluorescent lamp) FL having a pair of filaments, one end of which is connected to both ends of the secondary winding n2, and the other end of the pair of filaments. Preheating / resonance capacitor C3
It is composed of and. Further, the transformer T1 is a leakage transformer, and a resonance circuit is formed by the leakage inductance of the transformer T1 and the capacitor C3 (Japanese Patent Application No. 11-45411).

In the above power supply device, each switching element Q is used to reduce switching noise.
Capacitor C that is a snubber circuit connected in parallel to 1, Q2
4 and C5.

A high-frequency operation waveform of the power supply device shown in FIG.
It shows in FIG. Fig. 18 shows the low-frequency operation waveform.
You Voltage V in FIG._Q1, V_Q2, V_C1, V_C2And electricity
Flow I _T1, I_Q1, I_Q2, Iin are the same as those shown in FIG.
Corresponding to the sign signal, each switching element
Q1, Q2 voltage, capacitor C1, C2 voltage, transistor
Current of the switching element Q1, Q2, and
It means the input current. Similarly, the voltage in FIG.
V_C1, V_C2, V_T1And current I_T1, Iin are also shown in FIG.
It corresponds to the signal of the same sign shown in. I_FLIs a discharge lamp
This is the FL current.

Hereinafter, the circuit operation in the steady state will be described with reference to FIG.
A brief description will be given with reference to FIGS. Time t1 in FIG.
Then, the switching element Q2 is turned on. FIG. 17
At time t1, the switching element Q2 is turned on and the switching element Q1 is turned off, and the energy accumulated in the transformer T1 causes the primary winding n1 of the transformer T1 → diode D1 → smoothing capacitor C0 →
A current flows in the path of the parasitic diode of the switching element Q2. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1.

At time t2 in FIG. 17, the transformer T1
The energy stored in the capacitor becomes zero and the smoothing capacitor C
0 serves as a DC power source, and a current flows through a path of smoothing capacitor C0 → capacitor C1 → primary winding n1 of transformer T1 → switching element Q2. And the transformer T1 2
Electric power is supplied to the discharge lamp FL from the next winding n2.

At time t3 in FIG. 17, V _C0 (voltage of smoothing capacitor C0) + V _C1 (voltage of first capacitor C1) <Vs (AC power supply voltage), and AC power supply AC → diode bridge DB → transformer T1 1 Next winding n1 →
A current flows in the path from the switching element Q2 to the diode bridge DB and takes in the input current. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1.

At time t4 in FIG. 17, the switching element Q1 is turned on, the switching element Q2 is turned off, and the energy accumulated in the transformer T1 causes
Primary winding n1 of transformer T1 → parasitic diode of switching element Q1 → capacitor C2 → smoothing capacitor C0
→ Diode bridge DB → AC power supply AC → Current flows in the path of diode bridge DB. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1.

At time t5 in FIG. 17, the transformer T1
The energy stored in 0 becomes zero, the first capacitor C1 and the second capacitor C2 serve as a DC power source, and a current flows in the path of the primary winding n1 of the capacitor C1 → capacitor C2 → switching element Q1 → transformer T1. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1.

At time t6 in FIG. 17, the charging voltage V _C2 of the second capacitor _C2 becomes zero, the first capacitor C1 becomes a DC power source, and the capacitor C1 → diode D
2 → switching element Q1 → primary winding n of transformer T1
The current flows in the path of 1. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1.

At time t7 in FIG. 17, the circuit operation becomes similar to that at time t1, and high frequency power is supplied to the load circuit 2 by the series of circuit operations. That is, when the above-mentioned main signal waveforms are observed in one cycle of the AC power supply AC, it becomes as shown in FIG.

As shown in FIG. 18, when the voltage of the AC power supply AC rises and falls sinusoidally, the voltage V _{C1 of the} capacitor C1 descends and rises sinusoidally, and at the same time, the voltage V _{C2 of the} capacitor _C2. Rises and falls similarly to the sinusoidal voltage of the AC power supply, so that the voltage V _T1 applied to the primary winding n1 of the transformer _T1 becomes a substantially constant fluctuating amplitude voltage. As a result, the crest factor of the current I _FL flowing through the load circuit 2 on the secondary side becomes small.

[0016]

However, in the power supply device of FIG. 16, capacitors C4 and C5 are connected in parallel as snubber circuits to each of the switching elements Q1 and Q2 in order to reduce the switching noise of the switching elements Q1 and Q2. ing.

In such a circuit configuration, at time t4 in FIG. 17, when the switching element Q1 is turned on and the switching element Q2 is turned off, the capacitor C5 of the snubber circuit is charged by the energy accumulated in the transformer T1. Then, the electric charge of the capacitor C4 of the snubber circuit is discharged, and the second capacitor C2 is charged. At this time, since the capacity of the second capacitor C2 is sufficiently smaller than that of the smoothing capacitor C0, the discharge current of the capacitor C4 of the snubber circuit causes the capacitor C2 to suddenly increase.
There is a problem that the voltage of No. 2 rises, ringing occurs, and the switching loss of the switching element Q2 causes a decrease in circuit efficiency and an increase in switching noise.

The present invention has been made in view of the above points, and an object of the present invention is to provide a highly efficient power supply device by reducing loss of switching elements and switching noise.

[0019]

A power supply device according to claim 1 is
In order to solve the above problems, as shown in FIG. 1, a rectifier DB that rectifies an AC voltage Vs into a DC voltage, and a first diode D1 whose one end is connected to one output terminal of the rectifier DB in the forward direction. A smoothing capacitor C0 connected between the other end of the first diode D1 and the other output terminal of the rectifier DB, and a second end connected in the forward direction with the other end of the first diode D1. A diode D2, a pair of switching elements Q1 and Q2 connected in series between the other end of the second diode D2 and the other output terminal of the rectifier DB, and the pair of switching elements Q1 and Q2.
And a snubber element constituted by at least capacitors C4 and C5 connected in parallel to each of the pair of switching elements Q1 and Q2, and a connection point of the pair of switching elements Q1 and Q2. A transformer T1 having a primary winding n1 connected between an output terminal of the rectifier DB and a secondary winding n2 connected to a load circuit 2, and the first and second diodes D1. , D2 respectively connected in parallel
And second capacitors C1 and C2, the connection point of the pair of switching elements Q1 and Q2, and the first and second diodes D.
And an impedance element Z connected between the connection point of D1 and the connection point of D2.

In this configuration, since one end of the transformer T1 is a smoothing capacitor C0 via the impedance element Z, the turn-off time of the switching element Q2 and the turn-on time of the switching element Q1 become long, so that the snubber circuit is formed. The peak value of the charging current from the capacitor C4 to the capacitor C2 becomes low. As a result, when the switching element Q2 is turned off,
The source voltage can be reduced, the loss of the switching element Q2 can be reduced, and the switching noise can be reduced. The impedance element Z may be an element having a low withstand voltage such as the voltage of the smoothing capacitor C0 or the voltage across the capacitor C2.

As shown in FIG. 9, the first capacitor C1 may be connected between the output terminals of the rectifier DB (claim 2). Even with this configuration, by reducing the drain-source voltage when the switching element Q2 is turned off, the loss of the switching element Q2 can be reduced and the switching noise can be reduced. Further, the impedance element Z may be an element having a low breakdown voltage such as the voltage of the smoothing capacitor C0 or the voltage across the capacitor C2.

Further, as shown in FIG. 11, the second capacitor C2 may be connected between both ends of the pair of switching elements Q1 and Q2 (claim 3). Even with this configuration, by reducing the drain-source voltage when the switching element Q2 is turned off, the loss of the switching element Q2 can be reduced and the switching noise can be reduced. The impedance element Z may be an element having a low withstand voltage such as the voltage of the smoothing capacitor C0 or the voltage difference between the voltage across the capacitor C2 and the smoothing capacitor C0.

Further, as shown in FIG. 12, the first capacitor C1 is connected between the output terminals of the rectifier DB, and the second capacitor C2 is connected between both ends of the pair of switching elements Q1 and Q2. It may be configured (claim 4). Even with this configuration, by reducing the drain-source voltage when the switching element Q2 is turned off, the loss of the switching element Q2 can be reduced and the switching noise can be reduced. It should be noted that the impedance element Z may be an element having a low withstand voltage such as a voltage of the smoothing capacitor C0 or a voltage difference between the voltage across the capacitor C2 and the smoothing capacitor C0.

Here, the impedance element Z may be a capacitor C6 as shown in FIG. 13A, or a series circuit of a third diode D3 and a third capacitor C6 as shown in FIG. 13B. It may be configured with a second impedance element Z2 connected in parallel with the third diode D3 (claim 5). With this configuration, the peak value of the discharge current of the capacitor C6 can be reduced.

The impedance element Z is shown in FIG.
As shown in FIG. 3 (c), a third capacitor C6 and a third switching element Q3 connected in series to the third capacitor C6 may be used (claim 6). With this configuration, the capacitor C6 can be discharged at an arbitrary time, and the switching operation in the phase advance of the switching element Q2 can be avoided.

The impedance element Z is the same as that shown in FIG.
As shown in FIG. 5, a third capacitor C6 having one end connected to a connection point A of the first and second diodes D1 and D2, and a third capacitor C6
The other end of the capacitor C6 and the pair of switching elements Q
A third diode D3 connected in a forward direction to the second diode D2 between the connection point B of 1 and Q2;
A fourth diode connected between the series circuit of the pair of switching elements Q1 and Q2, the connection point C of the second diode D2 and the other end of the third capacitor C6 so as to match the third diode D3 in the forward direction. It may be configured with D4 (Claim 7). Further, as shown in FIG. 13D, a second impedance element Z2 may be connected in series with the fourth diode D4 (claim 8).

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a schematic configuration diagram of a power supply device according to a first embodiment of the present invention, and FIGS. 2 to 6 are operation explanatory diagrams of this power supply device, FIGS. 8 is a signal waveform diagram of each part of the power supply device. The first embodiment will be described below with reference to these drawings.

This power supply device has a switching element Q in the power supply circuit configuration described in the prior art shown in FIG.
Connection point B of 1, Q2 and connection point A of diodes D1, D2
An impedance element Z is provided between and.

Next, the circuit operation of the power supply device in the steady state will be described with reference to FIGS. In FIG. 7, the voltages V _Q1 , V _Q2 , V _C1 , V _C2 and the currents I _T1 , I _Q1 ,
Each of I _Q2 and I in corresponds to the signal of the same sign shown in FIG. Similarly, the voltages V _C1 , V _C2 , and V _T1 in FIG.
Each of the currents I _T1 and I in also corresponds to the signal of the same sign shown in FIG.

At time t1 in FIG. 7, when the switching element Q2 is turned on and the switching element Q1 is turned off, the energy accumulated in the transformer T1 causes the primary winding n1 of the transformer T1 →
A current flows through the path of diode D1 → smoothing capacitor C0 → switching element Q2. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1. At this time, the voltage of the smoothing capacitor C0 is applied to the impedance element Z, and the current Iz flows.

At time t2 in FIG. 7, the energy stored in the transformer T1 becomes zero and the smoothing capacitor C0
Becomes a DC power supply, and as shown in FIG. 3, the smoothing capacitor C0 → the first capacitor C1 → the primary winding n of the transformer T1.
1 → Current flows in the path of switching element Q2. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1. At this time, the voltage of the smoothing capacitor C0 is applied to the impedance element Z, and the current Iz flows.

At time t3 in FIG. 7, V _C0 (voltage of smoothing capacitor C0) -V _C1 (voltage of first capacitor C1) <| Vs | (rectified output voltage of AC power supply voltage Vs), and is shown in FIG. As described above, a current flows in the path of the AC power supply AC, the diode bridge DB, the primary winding n1 of the transformer T1, the switching element Q2, and the diode bridge DB to take in the input current. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1. At this time, the voltage of the smoothing capacitor C0 is applied to the impedance element Z, and the current Iz flows.

At time t4 in FIG. 7, the switching element Q1 is turned on and the switching element Q2 is turned off, and the energy accumulated in the transformer T1 causes the primary winding n1 of the transformer T1 → the switching element as shown in FIG. Q1 parasitic diode → second capacitor C2 → smoothing capacitor C0 → diode bridge DB → AC power supply A
A current flows in a path of C → diode bridge DB or primary winding n1 of transformer T1 → impedance element Z1 → smoothing capacitor C0 → diode bridge DB → AC power supply AC → diode bridge DB. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1. At this time, the impedance element Z has a capacitor C
A voltage of 2 is applied and a current Iz flows.

At time t5 in FIG. 7, the energy stored in the transformer T1 becomes zero, and the first capacitor C
The first and second capacitors C2 serve as a DC power source, and as shown in FIG. 6, the first capacitor C1 → the second capacitor C2
→ Switching element Q1 → Current flows in the path of transformer T1. Then, power is supplied to the discharge lamp FL from the secondary winding n2 of the transformer T1. At this time, the voltage of the second capacitor C2 is applied to the impedance element Z, and the current I
z flows.

At time t6 in FIG. 7, the charging voltage of the second capacitor C2 becomes zero, the first capacitor C1 becomes a DC power source, and the first capacitor C1 → second diode D2 → switching element Q1 → transformer T1. An electric current flows through the path of the primary winding n1. And the transformer T1
The secondary winding n2 supplies electric power to the discharge lamp FL.

At time t7 in FIG. 7, the circuit operation becomes the same as at time t1, and the high frequency power is supplied to the load circuit 2 by the series of circuit operations. AC power supply A
Observing the main signal waveforms in one cycle of C is as shown in FIG.

During the above circuit operation, at time t4 in FIG. 7, due to a part of the energy stored in the transformer T1, the primary winding n1 of the transformer T1 → impedance element Z → smoothing capacitor C0 → diode bridge DB → AC A current flows in the path from the power supply AC to the diode bridge DB, and the turn-off time of the switching element Q2 is lengthened, so that the peak of the charging current from the capacitor C4 of the snubber circuit to the second capacitor C2 is reduced, and the second capacitor By reducing the steep voltage rise of C2,
The turn-off loss of the switching element Q2 can be reduced, and the ringing occurring between the second capacitor C2 and the capacitor C4 of the snubber circuit can also be reduced to reduce switching noise.

It should be noted that only a voltage of the smoothing capacitor C0 or a voltage of the second capacitor C2 is applied to both ends of the impedance element Z, and an impedance element having a low withstand voltage can be used.

(Second Embodiment) FIG. 9 shows a second embodiment of the present invention.
FIG. 10 is a circuit diagram of a power supply device according to the above, FIG. 10 is a signal waveform diagram of each part in the operation of the power supply device, and Vc1 and Vc2
Is the voltage of the capacitors C1 and C2, V _T1 is the voltage of the transformer T1, and I _FL is the current of the discharge lamp FL. Embodiment 1
In the second embodiment, the capacitor C1 is connected in parallel to the diode D1. However, in the second embodiment, as shown in FIG. 9, the capacitor C1 is connected between both output terminals of the rectifier DB. is there. That is, AC power supply A
Rectifier DB for rectifying AC voltage Vs from C to DC voltage
A diode D1 having an anode connected in the forward direction to the positive terminal of the rectifier DB; a smoothing capacitor C0 connected between the diode D1 and the negative output terminal of the rectifier DB; The cathode of diode D2 connected in the direction
Of the switching elements Q1 and Q2 connected in series between the cathode of No. 2 and the negative terminal of the rectifier DB, the control circuit 1 for controlling ON / OFF of these switching elements Q1 and Q2, and the connection of the switching elements Q1 and Q2. Point and rectifier D
A transformer T1 having a primary winding n1 connected to the positive terminal of B and a secondary winding n2 connected to the load circuit 2, and a capacitor C1 connected between both output terminals of the rectifier DB. And a capacitor C2 connected in parallel with the diode D2, and an impedance element Z connected between the connection point of the switching elements Q1 and Q2 and the connection point of the diodes D1 and D2. .

In this configuration, as shown in FIG. 10, the voltage Vc1 of the capacitor C1 is equal to the voltage Vc of the smoothing capacitor C0.
_The voltage waveform is a voltage waveform clamped by _C0 and the voltage | Vs | after rectification of the input voltage Vs. Therefore, since the voltage V _T1 as shown in FIG. 10 is applied to the primary winding n1 by the voltage Vc1 and the voltage Vc2, a voltage having a substantially constant fluctuation level is applied to the transformer T1. It will be. As a result, the crest factor of the current I _FL flowing through the load circuit 2 on the secondary side becomes small.

In the second embodiment as well, as in the first embodiment, the peak of the charging current from the capacitor C4 of the snubber circuit to the second capacitor C2 is reduced by increasing the turn-off time of the switching element Q2. By reducing the steep voltage rise of the second capacitor C2, it is possible to reduce the turn-off loss of the switching element Q2, and the capacitor C4 of the snubber circuit and the second
Switching noise can also be reduced by reducing the ringing that occurs between the capacitors C2.

It is possible to use an impedance element having a low withstand voltage, to which only the voltage of the smoothing capacitor C0 or the voltage of the capacitor C2 is applied to both ends of the impedance element Z.

(Embodiment 3) FIG. 11 is a circuit diagram of a power supply device according to Embodiment 3 of the present invention. The power supply device of FIG. 11 includes a rectifier DB that rectifies the AC voltage Vs from the AC power supply AC into a DC voltage, a diode D1 whose anode is connected to the positive terminal of the rectifier DB in the forward direction, and the diode D1 and the rectifier. A smoothing capacitor C0 connected between the negative output terminals of DB, a diode D2 connected in the forward direction with the cathode of the diode D1, and a series connection between the cathode of this diode D2 and the negative terminal of the rectifier DB. Switching elements Q1 and Q2, a control circuit 1 that controls ON / OFF of these switching elements Q1 and Q2, and a primary connected between the connection point of the switching elements Q1 and Q2 and the positive terminal of the rectifier DB. Transformer T1 having a winding n1 and a secondary winding n2 connected to the load circuit 2, and the switching connected in series. Capacitor is connected across the child Q1, Q2 C2
And a capacitor C1 connected in parallel with the diode D1
And an impedance element Z connected between the connection point of the switching elements Q1 and Q2 and the connection point of the diodes D1 and D2. Also in this configuration, as in the first embodiment, by increasing the turn-off time of the switching element Q2, the peak of the charging current from the capacitor C4 of the snubber circuit to the capacitor C2 is reduced, and the steep voltage rise of the capacitor C2 is reduced. By reducing it, it is possible to reduce the turn-off loss of the switching element Q2, and the capacitor C2
Switching noise can also be reduced by reducing the ringing that occurs between the capacitor C4 and the snubber circuit capacitor C4.

A low withstand voltage impedance element can be used because only the voltage of the smoothing capacitor C0 or the voltage difference between the capacitor C2 and the smoothing capacitor C0 is applied to both ends of the impedance element Z.

(Embodiment 4) FIG. 12 is a circuit diagram of a power supply device according to Embodiment 4 of the present invention. The power supply device of FIG. 12 includes a rectifier DB that rectifies the AC voltage Vs from the AC power supply AC into a DC voltage, a diode D1 whose anode is connected to the positive terminal of the rectifier DB in the forward direction, and the diode D1 and the rectifier. A smoothing capacitor C0 connected between the negative output terminals of DB, a diode D2 connected in the forward direction with the cathode of the diode D1, and a series connection between the cathode of this diode D2 and the negative terminal of the rectifier DB. Switching elements Q1 and Q2, a control circuit 1 that controls ON / OFF of these switching elements Q1 and Q2, and a primary connected between the connection point of the switching elements Q1 and Q2 and the positive terminal of the rectifier DB. Transformer T1 having a winding n1 and a secondary winding n2 connected to the load circuit 2, and the switching connected in series. Capacitor is connected across the child Q1, Q2 C2
And a capacitor C1 connected between the output terminal of the rectifier DB
And an impedance element Z connected between the connection point of the switching elements Q1 and Q2 and the connection point of the diodes D1 and D2. Also in this configuration, as in the first embodiment, by increasing the turn-off time of the switching element Q2, the peak of the charging current from the capacitor C4 of the snubber circuit to the capacitor C2 is reduced, and the steep voltage rise of the capacitor C2 is reduced. By reducing it, it is possible to reduce the turn-off loss of the switching element Q2, and the capacitor C2
Switching noise can also be reduced by reducing the ringing that occurs between the capacitor C4 and the snubber circuit capacitor C4.

A low withstand voltage impedance element can be used because only a voltage of the smoothing capacitor C0 or a voltage difference between the capacitor C2 and the smoothing capacitor C0 is applied to both ends of the impedance element Z.

(Embodiment 5) In the main circuit configuration of Embodiment 1 shown in FIG. 1, as an impedance element Z connected between a connection point B of switching elements Q1 and Q2 and a connection point A of diodes D1 and D2. , The capacitor C6 shown in FIG. 13 (a) is connected.

The circuit operation of this embodiment is substantially the same as that of the first embodiment. At time t4 in FIG. 7, a part of the energy stored in the transformer T1 includes a capacitor C6 as an impedance element Z → smoothing capacitor C0 → diode bridge DB → AC power supply AC → diode bridge DB.
The capacitor C6 is charged with a voltage equivalent to V _C2 (voltage of the capacitor C2) via the capacitor C6 and the voltage increase of the capacitor C2 of the snubber circuit and the capacitor C2 due to the resonance current due to the inductance component of the transformer T1 is reduced, thereby performing switching. The drain-source voltage of the element Q1 can be reduced, and the turn-on loss of the switching element Q1 can be reduced.

At time t7, the regenerative current (solid line in FIG. 14), which is a resonant current flowing through the switching element Q2 at the moment when the switching element Q2 is turned on, and the current flowing through the capacitor C6 as a power source (broken line in FIG. 14). The combined current flows through the switching element Q2. At this time, the resonance current flowing through the switching element Q2> the current flowing through the capacitor C6 as a power source enables zero current switching of the switching element Q2 and reduces the switching loss of the switching element Q2.

(Embodiment 6) In the present embodiment, in the main circuit configuration of Embodiment 1 shown in FIG. 1, it is connected between a connection point B of switching elements Q1 and Q2 and a connection point A of diodes D1 and D2. As the impedance element Z to be used, as shown in FIG. 13B, the one in which the capacitor C6 and the cathode side of the diode D3 are connected in series and the impedance element Z2 is connected in parallel with the diode D3 is used. In the present embodiment, in the explanation of the circuit operation of the fifth embodiment, at time t4 in FIG. 7, a part of the energy stored in the transformer T1 is charged in the capacitor C6, and at time t7.
In addition, it is characterized in that discharging is performed while reducing the peak value of the discharge current of the capacitor C6 via the impedance element Z2. As a result, the condition that the resonance current flowing through the switching element Q2> the current flowing through the capacitor C6 as a power source is reduced, and the switching loss of the switching element Q2 can be reduced.

(Embodiment 7) In the present embodiment, in the main circuit configuration of Embodiment 1 shown in FIG. 1, it is connected between a connection point B of switching elements Q1 and Q2 and a connection point A of diodes D1 and D2. As the impedance element Z to be used, as shown in FIG. 13C, a capacitor C6 and a switching element Q3 connected in series are used. The switching element Q3 is composed of a MOSFET and incorporates a reverse diode. In the present embodiment, in the circuit operation description of the first embodiment, at time t4 in FIG. 7, a part of the energy stored in the transformer T1 is charged in the capacitor C6 through the reverse diode of the switching element Q3, and the capacitor C6 is charged. It is possible to arbitrarily set the timing of discharging the charged electric charge of the device by the gate signal of the switching element Q3. As the discharge timing, the switching element Q3 is turned on after a sufficient time has elapsed after the switching element Q2 was turned on. By this circuit operation, the switching loss of the switching element Q2 can be reduced.

(Embodiment 8) In the present embodiment, in the same circuit configuration as that of Embodiment 7, the switching element Q3 is turned on before the switching element Q1 is turned off as the timing for discharging the electric charge of the capacitor C6. And This circuit operation can reduce the possibility of a phase-advancing switching operation when the switching element Q2 is turned on.

(Embodiment 9) In the present embodiment, in the main circuit configuration of Embodiment 1 shown in FIG. 1, a connection point B between the switching elements Q1 and Q2 and a connection point A between the diodes D1 and D2 is connected. As the impedance element Z, the capacitor C6 and the cathode side of the diode D3 are connected in series as shown in FIG. 15, and the connection point of the diode D3 and the capacitor C6, the capacitor C2, and the switching element Q1.
The diode D4 is connected between the connection points of. In the present embodiment, in the circuit operation description of the first embodiment, at time t4 in FIG. 7, part of the energy stored in the transformer T1 is charged in the capacitor C6 via the diode D3, but the diode D4 is provided. Therefore, the voltage of the capacitor C6 is clamped to the voltage of the capacitor C2. Also in this embodiment, by reducing the voltage rise of the capacitor C2, the drain-source voltage of the switching element Q1 can be reduced and the turn-on loss of the switching element can be reduced.

(Embodiment 10) In this embodiment, FIG.
In the circuit configuration of the ninth embodiment shown in FIG. 13, the impedance element Z2 is connected between the cathode side of the diode D4 and the cathode side of the diode D2, as shown in FIG. 13 (d). Also in the present embodiment, by reducing the peak of the current flowing from the capacitor C6 to the capacitor C2, it is possible to reduce the sudden voltage increase of the capacitor C2 and reduce the switching loss of the switching element Q2.

[0055]

As described above, according to the first aspect of the invention, a rectifier for rectifying an AC voltage into a DC voltage, and a first end whose forward direction is connected to one output terminal of the rectifier
A diode, a smoothing capacitor connected between the other end of the first diode and the other output terminal of the rectifier, and a second diode having one end connected in the forward direction to the other end of the first diode, A pair of switching elements connected in series between the other end of the second diode and the other output terminal of the rectifier, a diode connected in anti-parallel with each of the pair of switching elements, and a pair of switching elements And a snubber element that is connected in parallel to each of the above-described capacitors and a primary winding that is connected between a connection point of the pair of switching elements and one output terminal of the rectifier, and a load circuit. A transformer having a secondary winding connected thereto, first and second capacitors respectively connected in parallel with the first and second diodes, and Since the circuit configuration has an impedance element connected between the connection point of the switching element and the connection point of the first and second diodes, and one end of the transformer is connected to the smoothing capacitor through the impedance element, As the turn-off and turn-on times of the switching element become longer, the peak value of the charging current from the capacitor of the snubber circuit to the second capacitor becomes lower. As a result, the drain-source voltage when the switching element is turned off can be reduced, the loss of the switching element can be reduced, and the switching noise can be reduced. Further, the impedance element may be an element having a low breakdown voltage of about the voltage of the smoothing capacitor or the voltage across the second capacitor.

In addition, as in the invention described in claim 2, the first capacitor is connected between the output terminals of the rectifier, and in the invention described in claim 3, the second capacitor is connected to the pair. A configuration in which the switching element is connected between both ends of the switching element, or, as in the invention according to claim 4,
A capacitor is connected between the output terminals of the rectifier, and the second
The same effect can be obtained in a configuration in which a capacitor is connected between both ends of the above-mentioned pair of switching elements.

Further, as in the invention described in claim 5, in the circuit configuration according to claims 1 to 4, the impedance element is connected in parallel to the series circuit of the third diode and the third capacitor and the third diode. By using a second impedance element composed of the second impedance element, the peak value of the discharge current of the third capacitor can be reduced.

Further, as in the invention described in claim 6, in the circuit configuration according to claims 1 to 4, as the impedance element, a third capacitor and a third switching element connected in series to the third capacitor are provided. By using the one configured by and, it is possible to discharge the third capacitor at an arbitrary time, and it is possible to avoid the switching operation in the phase advance of the switching element.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a first operation explanatory diagram of the power supply device according to the first embodiment of the present invention.

FIG. 3 is a second operation explanatory diagram of the power supply device according to the first embodiment of the present invention.

FIG. 4 is a third operation explanatory diagram of the power supply device according to the first embodiment of the present invention.

FIG. 5 is a fourth operation explanatory diagram of the power supply device according to the first embodiment of the present invention.

FIG. 6 is a fifth operation explanatory diagram of the power supply device according to the first embodiment of the present invention.

FIG. 7 is a high frequency operation waveform diagram of the power supply device according to the first embodiment of the present invention.

FIG. 8 is a low-frequency operation waveform diagram of the power supply device according to the first embodiment of the present invention.

FIG. 9 is a circuit diagram of a power supply device according to a second embodiment of the present invention.

FIG. 10 is a low-frequency operation waveform diagram of the power supply device according to the second embodiment of the present invention.

FIG. 11 is a circuit diagram of a power supply device according to a third embodiment of the present invention.

FIG. 12 is a circuit diagram of a power supply device according to a fourth embodiment of the present invention.

FIG. 13 is a circuit diagram of a main part of a power supply device according to Embodiments 5, 6, 7 and 9 of the present invention.

FIG. 14 is an operation explanatory diagram of the power supply device according to the fifth embodiment of the present invention.

FIG. 15 is a circuit diagram of a power supply device according to an eighth embodiment of the present invention.

FIG. 16 is a circuit diagram of a conventional power supply device.

FIG. 17 is a high-frequency operation waveform diagram of a conventional power supply device.

FIG. 18 is a low-frequency operation waveform diagram of the conventional power supply device.

[Explanation of symbols]

1 control circuit 2 load circuit DB full wave rectifier Q1 switching element Q2 switching element T1 transformer D1 diode D2 diode C1 capacitor C2 capacitor

Continued front page    F term (reference) 3K072 AA02 AC02 AC11 BA04 BB01                       BC02 CA14 CB05 DB03 DC07                       DD04 FA05 FA06 GA03 GB12                       GC04 HB06                 5H007 AA01 AA02 BB03 CA02 CB23                       CB25 CC32 FA13 HA02

Claims (8)

[Claims] 1. A rectifier that rectifies an AC voltage into a DC voltage, a first diode whose one end is connected to one output terminal of the rectifier in the forward direction, and the other end of the first diode and the other of the rectifier. A smoothing capacitor connected between the output terminal and the second terminal, a second diode whose one end is connected in the forward direction to the other end of the first diode, the other end of the second diode and the other output terminal of the rectifier A pair of switching elements connected in series between, a diode antiparallel connected to each of the pair of switching elements, and a snubber element configured by at least a capacitor connected in parallel to each of the pair of switching elements; A load circuit is connected with a primary winding connected between a connection point of the pair of switching elements and one output terminal of the rectifier. A transformer having a secondary winding, first and second capacitors respectively connected in parallel with the first and second diodes, a connection point of the pair of switching elements and a connection point of the first and second diodes A power supply device, comprising: an impedance element connected in between. 2. A rectifier that rectifies an AC voltage into a DC voltage, a first diode whose one end is connected to one output terminal of the rectifier in a forward direction, and the other end of the first diode and the other of the rectifier. A smoothing capacitor connected between the output terminal and the second terminal, a second diode whose one end is connected in the forward direction to the other end of the first diode, the other end of the second diode and the other output terminal of the rectifier A pair of switching elements connected in series between, a diode antiparallel connected to each of the pair of switching elements, and a snubber element configured by at least a capacitor connected in parallel to each of the pair of switching elements; A load circuit is connected with a primary winding connected between a connection point of the pair of switching elements and one output terminal of the rectifier. A transformer having a secondary winding; a first capacitor connected between output terminals of the rectifier; a second capacitor connected in parallel with the second diode; a connection point of the pair of switching elements; A power supply device, comprising: an impedance element connected to a connection point of the second diode. 3. A rectifier that rectifies an AC voltage into a DC voltage, a first diode whose one end is connected to one output terminal of the rectifier in a forward direction, and the other end of the first diode and the other of the rectifier. A smoothing capacitor connected between the output terminal and the second terminal, a second diode whose one end is connected in the forward direction to the other end of the first diode, the other end of the second diode and the other output terminal of the rectifier A pair of switching elements connected in series between, a diode antiparallel connected to each of the pair of switching elements, and a snubber element configured by at least a capacitor connected in parallel to each of the pair of switching elements; A load circuit is connected with a primary winding connected between a connection point of the pair of switching elements and one output terminal of the rectifier. A transformer having a secondary winding, a first capacitor connected in parallel with the first diode, a second capacitor connected across the series circuit of the pair of switching elements, and a connection of the pair of switching elements. A power supply device comprising: an impedance element connected between the point and a connection point of the first and second diodes. 4. A rectifier for rectifying an AC voltage into a DC voltage, a first diode whose one end is connected to one output terminal of the rectifier in a forward direction, and the other end of the first diode and the other of the rectifier. A smoothing capacitor connected between the output terminal and the second terminal, a second diode whose one end is connected in the forward direction to the other end of the first diode, the other end of the second diode and the other output terminal of the rectifier A pair of switching elements connected in series between, a diode antiparallel connected to each of the pair of switching elements, and a snubber element configured by at least a capacitor connected in parallel to each of the pair of switching elements; A load circuit is connected with a primary winding connected between a connection point of the pair of switching elements and one output terminal of the rectifier. A transformer having a secondary winding; a first capacitor connected between the output terminals of the rectifier; a second capacitor connected between both ends of a series circuit of the pair of switching elements; A power supply device comprising: an impedance element connected between the connection point and the connection points of the first and second diodes. 5. The impedance element includes a third diode whose forward direction matches a second diode, and the third diode.
The power supply device according to claim 1, comprising a third capacitor connected in series with the diode and a second impedance element connected in parallel with the third diode. 6. The impedance element according to claim 1, wherein the impedance element includes a third capacitor and a third switching element connected in series to the third capacitor. Power supply. 7. The impedance element includes a third capacitor whose one end is connected to a connection point of the first and second diodes, and a third capacitor between the other end of the third capacitor and the connection point of the pair of switching elements. A third diode connected so as to match the forward direction of the second diode, a third diode and a forward direction between the series circuit of the pair of switching elements, the connection point of the second diode, and the other end of the third capacitor. 5. The power supply device according to claim 1, further comprising: a fourth diode connected so as to match with each other. 8. The power supply device according to claim 7, further comprising a second impedance element connected in series with the fourth diode.