JP2003319650A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter which is capable of reducing the loss of a switching element and serges, controlling an output voltage down to zero volt, enhancing efficiency, reducing noise, and controlling the output voltage over a wide range. <P>SOLUTION: In a first current resonance circuit 2, a rectangular pulse voltage is applied to a first reactor Lr0 and a first capacitor Cri0 connected in series to generate a sinusoidal voltage waveform. Simultaneously, in a second current resonance circuit 4, the sinusoidal voltage waveform generated at the first current resonance circuit 2 is applied to a second reactor Lr1 connected in series with the first reactor Lr0, the existing an inductance Lp of a primary winding N1 of a transformer T1, and a second capacitor Cri1. The amplitude of a voltage produced in the second capacitor Cri1 is varied according to a variation in frequency, and an alternating-current voltage is applied to the primary winding N1 of the transformer T1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter applicable to a half-bridge type power converter or a full-bridge type power converter.

[0002]

2. Description of the Related Art As a conventional power conversion device, a device having a principle configuration as shown in FIG. 11 is known. First, a case where a full load is applied to the power converter shown in FIG. 11 will be described.

For example, the input voltage Vin has a duty of 50.
%, An amplitude value of 30 V, and a pulse voltage of frequency 44 kHz, and the output load consumes 11 V and 30 A. In the conventional power converter, the voltage waveform at the point A is a rectangular wave with a duty of 50% and an amplitude value of 30V.

Now, with reference to the timing chart shown in FIG. 12, one cycle is divided into a to f ranges, and the operation of the power converter in each range at full load will be described.

In the range a, the input voltage Vin is in the 0V state, and the resonance reactor Lr1 and the current resonance capacitor Cri are present.
The current resonance capacitor Cri1 is charged around 15 V (1/2 × Vin) by the current resonance caused by 1. At this time, on the secondary side of the main transformer T1, the rectifying diode D
Power is supplied to the load R via o2 and the capacitor Co.

In the range b, the input voltage Vin is in the 0V state, and the resonance reactor Lr1 and the current resonance capacitor Cri are present.
Due to the current resonance caused by 1, the current resonance capacitor Cri1 is discharged mainly at 15 V (1/2 × Vin). At this time, on the secondary side of the main transformer T1, the rectifying diode D
Power is supplied to the load R via o2 and the capacitor Co.

In the range c, the input voltage Vin is in the 0V state, and the current resonance capacitor Cri1 is caused by current resonance caused by the resonance reactor Lr1, the exciting inductance Lp of the primary winding N1 of the main transformer T1, and the current resonance capacitor Cri1.
Is discharged with 15 V (1/2 × Vin) as the center. At this time, on the secondary side of the main transformer T1, electric power is supplied to the load R via the capacitor Co.

In the range d, the input voltage Vin is in the 30V state, the resonance reactor Lr1 and the current resonance capacitor C
The current resonance capacitor Cri1 due to the current resonance caused by ri1
Is discharged with 15 V (1/2 × Vin) as the center.
At this time, on the secondary side of the main transformer T1, electric power is supplied to the load R via the rectifying diode Do1 and the capacitor Co.

In the range e, the input voltage Vin is in the 30V state, the resonance reactor Lr1 and the current resonance capacitor C are present.
The current resonance capacitor Cri1 due to the current resonance caused by ri1
Is charged around 15 V (1/2 × Vin).
At this time, on the secondary side of the main transformer T1, electric power is supplied to the load R via the rectifying diode Do1 and the capacitor Co.

In the range f, the input voltage Vin is in the state of 30V, and the resonance inductor Lr1 and the exciting inductance Lp of the primary winding N1 of the main transformer T1 and the current resonance capacitor Cri1 cause current resonance to cause current resonance capacitor Cr.
ri1 is charged mainly at 15V (1/2 x Vin). At this time, on the secondary side of the main transformer T1, electric power is supplied to the load R via the capacitor Co.

Next, a case where the load R on the power conversion device shown in FIG. 13 becomes unloaded will be described. For example, the input voltage Vin has a duty of 50% and an amplitude value of 30.
The pulse voltage is V and the frequency is 100 kHz.

Compared with the case of the full load described above, the voltage VA at the point A is a rectangular wave having a duty of 50% and an amplitude value of 30 V without any change, and since the frequency becomes high, the voltage of the current resonance capacitor Cri1 is increased. The amplitude of is getting smaller.

When the conventional power converter is in a no-load state,
When the frequency is brought close to infinity, the voltage VA at the point A does not change, and the voltage Vcir1 of the current resonance capacitor Cri1 becomes
As shown in FIG. 14, it becomes 15V (1/2 × Vin).

Therefore, the output voltage Vout is

## EQU1 ## (VA-Vcir1) * Lp * 1 / (Lr1 + Lp) * S1 / N1 (1) That is, in the above example, the minimum value is 3.75.
V, and the measured value at a frequency of 100 kHz is 3.95V.
become.

FIG. 14 is a diagram showing the relationship between the output voltage Vout output from the conventional power converter and the operating frequency f. As shown in FIG. 14, when the conventional power converter is in the no-load state, the output voltage Vout is Vin / 2 even if the operating frequency f is shifted to lower the output voltage Vout.

Next, FIG. 15 is a diagram in which the principle configuration of a conventional power converter is applied to a half-bridge power converter. The first and second switching elements Q1 and Q2 both have a dead time as a period in which they are turned off, and are alternately turned on and off with the same duty.

First and second switching elements Q1, Q2
Are alternately turned on and off, the resonance reactor L2,
Excitation inductance of the primary winding N1 of the main transformer T1,
A square wave voltage is applied to the current resonance circuit 111 configured by the current resonance capacitor C2, and a sinusoidal resonance current flows through the current resonance circuit 111.

This resonance current charges and discharges the current resonance capacitor C2, changes the voltage of the current resonance capacitor C2, and supplies power to the load 5 from the secondary windings S1, S2 side of the main transformer T1.

In such a configuration, since the resonance current changes depending on the switching frequency of the first and second switching elements Q1 and Q2, it is necessary to control the frequency in order to stabilize the output voltage Vout. At this time, if the currents flowing through the first and second switching elements Q1 and Q2 are controlled within a positive range, the currents flow through the first and second parasitic diodes D1 and D2, which are diodes for commutation, and zero current switching (ZCS) is performed. Can be realized. Further, zero voltage switching (ZVS) can be realized by charging and discharging the voltage resonance capacitor C3.

Therefore, the first and second switching elements Q
1 and Q2 can perform soft switching, and have an advantage that loss and surge of a switching element can be reduced.

[0021]

Here, FIG. 16 and FIG.
With reference to the timing chart shown in FIG. 7, the operations of the half-bridge type power converter at full load and at no load will be compared and described. Note that FIG. 16 is a timing chart showing the operation of the conventional half-bridge type power conversion device at full load. Further, FIG. 17 is a timing chart showing the operation of the conventional half-bridge type power conversion device under no load.

First, the operating waveform when the switching frequency is low at full load and the operating waveform when the switching frequency is high at no load are compared. In this case, when there is no load, the terminal voltage of the primary winding N1 of the main transformer T1 is smaller, the terminal voltage of the secondary windings S1 and S2 of the main transformer T1 is smaller, and the voltage of the current resonance capacitor C2 is smaller. The voltage is approaching ½ × the voltage of the DC power supply (15V under the present condition).

In the conventional half-bridge type power converter, the rectangular wave voltage generated by the first and second switching elements Q1 and Q2 is applied to the resonance reactor L2.
Excitation inductance of the primary winding N1 of the main transformer T1,
The voltage was applied to the current resonance circuit 111 composed of the current resonance capacitor C2.

In such a conventional configuration, the output voltage Vout at no load has a current resonance constituted by the resonance reactor L2, the exciting inductance of the primary winding N1 of the main transformer T1, and the current resonance capacitor C2. Circuit 111
In, the exciting inductance of the primary winding N1 of the main transformer T1 always appears.

For this reason, even if the switching frequency is increased, the output voltage Vout is the input voltage Vin, the resonance reactor L2, the exciting inductance Lp of the primary winding N1 of the main transformer T1, the secondary winding number N2 of the main transformer T1, From the primary winding number N1 of the main transformer T1,

[Equation 2]   Vout ≧ Vin × 1/2 × {Lp / (L1 + Lp)} × N2 / N1 (2) Could only be reduced to.

Specifically, under the present condition, the output voltage V
The output could not be less than 3.75V, and the measured value was 3.87V. Therefore, even if the switching frequency is increased under no load, the output voltage Vout cannot be reduced to 0V, and there is a problem that the output voltage Vout cannot be controlled in a wide range under no load.

Therefore, the output voltage Vout when the switching frequency is increased under no load can be reduced to 0V, and there has been a demand for wide-range control.

The present invention has been made in view of the above,
The purpose is to reduce the loss and surge of the switching element, to control the output voltage down to zero volts, and to improve the efficiency, reduce the noise, and control the output voltage in a wide range. To provide.

[0029]

The invention according to claim 1 is
In order to solve the above problems, an electric power converter that applies an AC voltage to a primary winding of a transformer, rectifies and smoothes an AC voltage induced in a secondary winding of the transformer, and supplies an output voltage output to a load. A first current resonance circuit for applying a rectangular wave pulse voltage to a first reactor and a first capacitor connected in series to generate a sine wave voltage waveform,
A second reactor connected in series with the first reactor and an exciting inductance of a primary winding of the transformer;
A sinusoidal voltage waveform generated from the first current resonance circuit is applied to the capacitor, the amplitude of the voltage generated in the second capacitor is changed according to the change in frequency, and an AC voltage is applied to the primary winding of the transformer. And a second current resonance circuit for increasing the frequency of the rectangular wave pulse voltage and decreasing the output voltage to zero.

In order to solve the above-mentioned problems, the invention according to claim 2 applies an AC voltage to a primary winding of a transformer, rectifies and smoothes an AC voltage induced in a secondary winding of the transformer, and outputs the AC voltage. A power conversion device for supplying an output voltage to a load, the switching element converting a DC voltage supplied from a DC power source into a rectangular wave pulse voltage, and a reactor connected in series with the rectangular wave pulse voltage. And a first capacitor for applying a sinusoidal voltage waveform to the first capacitor
A sinusoidal voltage waveform generated from the first current resonance circuit is applied to the current resonance circuit, the exciting inductance of the primary winding of the transformer connected in series with the reactor, and the second capacitor to change the frequency. According to the second current resonance circuit that changes the amplitude of the voltage generated in the second capacitor to apply an AC voltage to the primary winding of the transformer, and compares the output voltage with a predetermined reference voltage to determine an error voltage. An error voltage detection circuit for detecting, and an oscillation frequency is changed according to an error voltage signal output from the error voltage detection circuit,
And a control circuit for controlling ON / OFF of the switching element, the control circuit controlling an oscillation frequency so that the output voltage becomes the predetermined reference voltage.

In order to solve the above-mentioned problems, the third aspect of the present invention applies an AC voltage to the primary winding of the transformer to rectify and smooth the AC voltage induced in the secondary winding of the transformer. A power conversion device that supplies an output voltage to be output to a load, wherein a switching element that converts a DC voltage supplied from a DC power supply into a rectangular wave pulse voltage and the rectangular wave pulse voltage are connected in series. A first current resonance circuit that applies a first capacitor and a second capacitor that are connected in parallel to a reactor and a primary winding of the transformer to generate a sinusoidal voltage waveform, and the transformer that is connected in series to the reactor. Applying a sinusoidal voltage waveform generated from the first current resonance circuit to the exciting inductance of the primary winding and the second capacitor, and to the second capacitor according to the change in frequency. A second current resonance circuit that changes the amplitude of the applied voltage to apply an AC voltage to the primary winding of the transformer; and an error voltage detection circuit that compares the output voltage with a predetermined reference voltage to detect an error voltage. A control circuit that changes the oscillation frequency according to an error voltage signal output from the error voltage detection circuit and controls ON / OFF of the switching element, wherein the control circuit has the output voltage of the predetermined value. The gist is to control the oscillation frequency so that the reference voltage is obtained.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Principle) FIG. 1 is a diagram showing a principle configuration of a power converter according to the present invention. In FIG. 1, the input voltage Vin is
The pulse voltage is a rectangular wave having a duty of 50% and an amplitude value of 30V.

The input voltage Vin is connected to the first current resonance circuit 2 including a resonance reactor Lr0 and a current resonance capacitor Cri0 via an input resistor Rin. In the first current resonance circuit 2, a sinusoidal voltage waveform is generated from the connection point A between the resonance reactor Lr0 and the current resonance capacitor Cri0.

The connection point A is a resonance reactor Lr1,
Excitation inductance L of the primary winding N1 of the main transformer T1
p is connected to the second current resonance circuit 4 including the current resonance capacitor Cri1.

The main transformer T1 has a primary winding N1 and secondary windings S1 and S2, and a rectifying / smoothing circuit 6 is connected to the secondary windings S1 and S2. This rectifying / smoothing circuit 6 has 2
The output voltage Vout rectified and smoothed by the diodes Do1, Do2 and the capacitor Co is connected to one end of the secondary windings S1, S2 via the diodes Do1, Do2, respectively.
Is output to.

Next, with reference to the timing chart shown in FIG. 2, a case where the load on the power conversion device becomes the full load will be described. For example, assume that the input voltage Vin is a pulse voltage having a duty of 50%, an amplitude value of 30 V, and a frequency of 44 kHz, and 11 V and 30 A are consumed in the output load R.

In the power converter of the present invention, the input voltage Vin
After the resonance reactor Lr0 and the current resonance capacitor C
Since the first current resonance circuit 2 consisting of ri0 is connected,
As shown in FIG. 2, the voltage waveform at the point A has a sine wave shape centered at 15 V (1/2 × Vin), which is about 1/2 of the input voltage Vin.

Next, with reference to the timing chart shown in FIG. 3, a case where the load R on the power conversion device becomes unloaded will be described. For example, the input voltage Vin is a pulse voltage having a duty of 50%, an amplitude value of 30 V, and a frequency of 100 kHz.

Compared with the case of the full load described above, the amplitude of the voltage VA at the point A becomes smaller and the amplitude of the voltage of the current resonance capacitor Cri1 becomes smaller because the frequency becomes higher.

When the power converter of the present invention is in a no-load state, when the frequency is brought close to infinity, the voltage VA at the point A
Is 15V (1/2 × V), which is about 1/2 of the input voltage Vin.
in). Further, the voltage of the current resonance capacitor Cri1 is about 1/2 of the input voltage Vin, which is 15 V (1/2 ×).
Vin).

Therefore, the output voltage Vout is the voltage V at the point A.
A, from the voltage Vcri1 of the current resonance capacitor Cri1,

## EQU3 ## Vout = (VA-Vcri1) .times.Lp / (Lr1 + Lp) .times.S1 / N1 (3) That is, in the above example, the output voltage Vout
Has a minimum value of 0V and an actual measurement value of 0.25V at a frequency of 100 kHz.

FIG. 4 is a diagram showing the relationship between the output voltage Vout output from the power converter of the present invention and the operating frequency f. As shown in FIG. 4, when the power converter of the present invention is in a no-load state, the operating frequency f shifts to a high region to lower the output voltage Vout, and the output voltage Vout converges to 0V.

As described above, in the conventional power converter, since the voltage waveform at the point A is a rectangular wave, the resonance reactor Lr1, the exciting inductance Lp of the primary winding N1 of the main transformer T1 and the current resonance capacitor Cri1. A rectangular wave voltage is applied to the current resonance circuit 101 consisting of
The output voltage Vout is 0V even if the switching frequency is increased.
Could not be lowered to.

On the other hand, in the power converter of the present invention, the resonance reactor Lr0 and the current resonance capacitor Cri.
By connecting the first current resonance circuit 2 consisting of 0 to the front stage of the first current resonance circuit 4, the voltage waveform at the point A is generated in a sine wave shape. Therefore, the sine wave voltage should be applied to the second current resonance circuit 4. As a result, the output voltage Vout can be lowered to 0V as the switching frequency rises.

As described above, in the first current resonance circuit 2, the reactor Lr0 in which the rectangular wave pulse voltage is connected in series is used.
And a first capacitor Cri0 to generate a sinusoidal voltage waveform. At the same time, in the second current resonance circuit 4, the reactor Lr1 connected in series to the reactor Lr0 and the primary winding N1 of the main transformer T1 are excited. A sinusoidal voltage waveform generated from the first current resonance circuit 2 is applied to the inductance Lp and the second capacitor Cri1, and the second voltage is changed according to the change in frequency.
By changing the amplitude of the voltage generated in the capacitor Cri1 and applying the AC voltage to the primary winding N1 of the main transformer T1,
The AC voltage induced in the secondary windings S1 and S2 of the main transformer T1 can be rectified and smoothed to supply the output voltage Vout to the load R, and the output voltage Vout can be increased according to the increase in the frequency of the rectangular wave pulse voltage. Vout can drop to zero.

(First Embodiment) FIG. 5 is a diagram in which the power converter according to the first embodiment of the present invention is applied to a half-bridge type power converter. Between the one end and the other end of the DC power supply 1, the first and second switching elements Q1,
Q2 is connected in series. Specifically, the + terminal of the DC power supply 1 is connected to the drain of the first switching element Q1, the source of the first switching element Q1 and the drain of the second switching element Q2 are connected, and further the source of the second switching element Q2. Is connected to the-terminal of the DC power supply 1.

Also, the first and second switching elements Q
Diodes D1 and D2 are connected in antiparallel to 1 and Q2. The main transformer T1 has a primary winding N1 and secondary windings S1 and S2, and a rectifying and smoothing circuit 3 is connected to the secondary windings S1 and S2.

This rectifying / smoothing circuit 3 has secondary windings S1 and S.
2 is connected to the anodes of the diodes D3 and D4, respectively, and the cathodes of the diodes D3 and D4 are commonly connected to one end of the inductance L1. Further, the other end of the inductance L1 is connected to one end of the capacitor C1 and the load 5 Is connected to one end and the input terminal of the comparator CP1. The other end of the capacitor C1 and the other end of the load 5 are connected to a center tap to which the secondary windings S1 and S2 are commonly connected.

The source of the first switching element Q1 and the second
At the connection point B with the drain of the switching element Q2, the first current resonance circuit 15 including the resonance reactor L2 and the current resonance capacitor C4, and the resonance reactors L2 and 1 are connected.
The exciting inductance of the next winding N1 and the second current resonance circuit 17 including the current resonance capacitor C2 are connected in parallel.

The source of the first switching element Q1 and the second
At the connection point B with the drain of the switching element Q2, a voltage resonance capacitor C3 is connected in parallel with the second switching element Q2. The comparator CP1 compares the output voltage Vout output from the rectifying / smoothing circuit 3 to the load 5 with the reference voltage Vref1 and outputs an error voltage signal according to the magnitude relationship between the two to the control circuit 7.

The control circuit 7 changes the oscillation frequency according to the error voltage signal output from the comparator CP1,
Control signals H and L for alternately turning on and off the first and second switching elements Q1 and Q2 with a dead time are output to the drive circuits 9 and 11, respectively.

The drive circuits 9 and 11 are, for example, pulse transformers, and the control signals H and L output from the control circuit 7 are used.
To drive signals VKH and VKL respectively, and
It outputs between the gate and source of the switching elements Q1 and Q2, respectively.

Next, with reference to the timing charts shown in FIGS. 6 and 7, the operation of the half-bridge type power converter at full load and at no load will be compared and explained. Note that FIG.
[Fig. 6] is a timing chart showing an operation of the half-bridge type power converter at full load. For example, the input voltage Vin has a duty of 50%, an amplitude value of 30 V, and a frequency of 3.
With a pulse voltage of 5 kHz, with an output load of 11 V,
It is assumed that 30A is consumed. Further, FIG. 7 is a timing chart showing the operation of the half-bridge type power converter when there is no load. For example, input voltage Vin
Has a duty of 50%, an amplitude value of 30 V, and a frequency of 200 k
The pulse voltage is Hz.

First, the control signals H and L output from the control circuit 7 are input to the drive circuits 9 and 11 and converted into drive signals VKH and VKL, respectively, and the gates of the first and second switching elements Q1 and Q2 are Output between sources.
The first and second switching elements Q1 and Q2 have a dead time in which they are both turned off according to the drive signals VKH and VKL output from the drive circuits 9 and 11, and are alternately turned on and off with the same duty.

First and second switching elements Q1, Q2
Are alternately turned on and off, the resonance reactor L2,
A square wave voltage is applied to the first current resonance circuit 15 formed by the current resonance capacitor C4, and a sinusoidal resonance current flows through the first current resonance circuit 15. At the same time, a sinusoidal resonance current flows in the second current resonance circuit 17 configured by the resonance reactor L2, the excitation inductance of the primary winding N1 of the main transformer T1, and the current resonance capacitor C2.

The voltage of the current resonance capacitor C2 is changed by this resonance current, and the primary winding N1 of the main transformer T1 is changed.
An AC voltage VN1 is applied to the load 5, and power is supplied to the load 5 from the secondary windings S1 and S2 of the main transformer T1.

Since this resonance current changes depending on the switching frequency of the first and second switching elements Q1 and Q2, the control circuit 7 stabilizes the output voltage Vout.
The frequency is controlled by.

Then, the first and second switching elements Q
If the currents flowing through the first and second transistors Q1 and Q2 are controlled in the positive range, the first and second parasitic diodes D1 and D that are commutation diodes are used.
A current flows through 2 and zero current switching (ZCS) can be realized. At the same time, zero voltage switching (ZVS) can be realized by charging and discharging the voltage resonance capacitor C3.
Therefore, the first and second switching elements Q1 and Q2 perform soft switching, and the loss and surge of the first and second switching elements Q1 and Q2 can be reduced.

Next, as shown in FIG. 7, when the load 5 is unloaded, the exciting inductance of the primary winding N1 of the main transformer T1 is always present. However, by increasing the switching frequency, the voltage value of the current resonance capacitor C2 becomes half of the input voltage Vin, and at the same time, the voltage value of the current resonance capacitor C4 changes to the input voltage Vin.
1/2, so that the voltage value applied to the primary winding N1 of the main transformer T1 becomes 0V.

As a result, the secondary winding S of the main transformer T1
The voltage value induced in 1, S2 becomes 0V. Therefore, the output voltage Vout can be controlled to 0V, and the output voltage Vout can be controlled to 0V under any load condition.

Further, the DC voltage supplied from the DC power supply 1 is converted into a rectangular wave pulse voltage by the switching elements Q1 and Q2, and in the first current resonance circuit 15, the rectangular wave pulse voltage is connected in series. A voltage waveform having a sinusoidal waveform is generated by applying it to the reactor L2 and the first capacitor C4, and in the second current resonance circuit 17, the exciting inductance of the primary winding N1 of the main transformer T1 connected in series with the reactor L2 and the 2 The first current resonance circuit 1 is connected to the capacitor C2.
5 is applied, the amplitude of the voltage generated in the second capacitor C2 is changed according to the change in frequency, and an AC voltage is applied to the primary winding N2 of the main transformer T1. The AC voltage induced in the secondary windings S1 and S2 of the transformer T1 is rectified and smoothed to supply the output voltage Vout to the load. Then, the comparator CP1 compares the output voltage Vout with the reference voltage Vref1 to detect an error voltage,
The oscillation frequency of the control circuit 7 is changed in accordance with the error voltage signal output from the comparator CP1 so that the switching element is turned on / off, and the control circuit 7 oscillates the output voltage Vout to the reference voltage Vref1. By controlling the frequency, it is possible to realize high efficiency of the device, low noise, and control of a wide range of output voltage.

(Second Embodiment) FIG. 8 is a diagram in which the power converter according to the second embodiment of the present invention is applied to a half-bridge type power converter. A feature of the present embodiment is that in the half-bridge type power converter shown in FIG. 5, a current resonance capacitor C5 is connected in parallel to the primary winding N1 of the main transformer T1 as shown in FIG. is there.

Next, with reference to the timing charts shown in FIGS. 9 and 10, the operation of the half-bridge type power converter at full load and at no load will be described in comparison. Note that FIG. 9 is a timing chart showing the operation of the half-bridge type power converter at full load. For example, the input voltage Vin is a pulse voltage having a duty of 50%, an amplitude value of 30 V, and a frequency of 43 kHz, and is 11 at the output load.
It is assumed that V and 30A are consumed. Furthermore, FIG.
[Fig. 6] is a timing chart showing an operation under no load with respect to the half-bridge type power converter. For example, the input voltage Vin has a duty of 50%, an amplitude value of 30V, and a frequency of 2
The pulse voltage is 00 kHz.

First, the control signals H and L output from the control circuit 7 are input to the drive circuits 9 and 11, respectively, and converted into drive signals VKH and VKL, and the gates of the first and second switching elements Q1 and Q2 are Output between sources.

First and second switching elements Q1, Q2
Are drive signals VKH and V output from the drive circuits 9 and 11.
There is a dead time that turns off according to KL, and turns on and off alternately with the same duty.

First and second switching elements Q1, Q2
Are alternately turned on and off, the resonance reactor L2,
Current resonance capacitor C5, current resonance capacitor C2
A square wave voltage is applied to the first current resonance circuit 21 configured by, and a sinusoidal resonance current flows in the first current resonance circuit 21. At the same time, a sinusoidal resonance current flows in the second current resonance circuit 17 configured by the resonance reactor L2, the excitation inductance of the primary winding N1 of the main transformer T1, and the current resonance capacitor C2.

The voltage of the current resonance capacitor C2 is changed by this resonance current, and the primary winding N1 of the main transformer T1 is changed.
An AC voltage VN1 is applied to the load 5, and power is supplied to the load 5 from the secondary windings S1 and S2 of the main transformer T1.

Since this resonance current changes according to the switching frequency of the first and second switching elements Q1 and Q2, the control circuit 7 stabilizes the output voltage Vout.
The frequency is controlled by.

Then, the first and second switching elements Q
If the currents flowing through the first and second transistors Q1 and Q2 are controlled in the positive range, the first and second parasitic diodes D1 and D that are commutation diodes are used.
A current flows through 2 and zero current switching (ZCS) can be realized. At the same time, zero voltage switching (ZVS) can be realized by charging and discharging the voltage resonance capacitor C3.
Therefore, the first and second switching elements Q1 and Q2 perform soft switching, and the loss and surge of the first and second switching elements Q1 and Q2 can be reduced.

Next, as shown in FIG. 10, when the load 5 is unloaded, the exciting inductance of the primary winding N1 of the main transformer T1 always appears. However, by increasing the switching frequency, the voltage value of the series capacitor constituted by the current resonance capacitor C2 and the current resonance capacitor C5 becomes about 1/2 of the input voltage Vin.
Then, the voltage value applied to the primary winding N1 of the main transformer T1 becomes 0V.

As a result, the secondary winding S of the main transformer T1
The voltage value induced in 1, S2 becomes 0V. Therefore, the output voltage Vout can be controlled to 0V, and the output voltage Vout can be controlled to 0V under any load condition.

Further, the DC voltage supplied from the DC power supply 1 is converted into a rectangular wave pulse voltage by the switching elements Q1 and Q2, and in the first current resonance circuit 21, the rectangular wave pulse voltage is connected in series to the reactor. L2 and the primary winding N1 of the main transformer T1 are connected in parallel to the first capacitor C5 and the second capacitor C2 to generate a sinusoidal voltage waveform, and in the second current resonance circuit 17, the reactor L2 is connected in series. Primary winding N1 of main transformer T1 connected to
Of the main transformer T1 by applying a sinusoidal voltage waveform generated from the first current resonance circuit 21 to the exciting inductance of the second capacitor C2 and changing the amplitude of the voltage generated in the second capacitor C2 according to the change of the frequency. By applying an AC voltage to the primary winding N1, the secondary windings S1 and S of the main transformer T1 are
Output voltage Vout by rectifying and smoothing the AC voltage induced in 2
Supply to the load. Then, the comparator CP1 compares the output voltage Vout with the reference voltage Vref1 to detect the error voltage, and changes the oscillation frequency of the control circuit 7 according to the error voltage signal output from the comparator CP1 to control the ON / OFF of the switching element. By controlling the oscillation frequency so that the output voltage Vout becomes the reference voltage Vref1 by the control circuit 7, it is possible to realize high efficiency of the device, low noise, and control of a wide range of output voltage. it can.

[0073]

According to the present invention, since the amplitude of the voltage generated in the second capacitor is changed according to the change in frequency and the AC voltage is applied to the primary winding of the transformer, the output voltage is controlled to zero volt. Moreover, since a sinusoidal voltage is applied to the current resonance circuit of the composite resonance type converter in which the current resonance type converter and the partial voltage resonance circuit are combined,
The loss and the surge of the switching element can be reduced, and therefore, the efficiency of the converter, the noise reduction, and the control of the output voltage in a wide range can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of a power conversion device according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the power conversion device of the present invention.

FIG. 3 is a timing chart for explaining the operation of the power conversion device of the present invention when there is no load.

FIG. 4 is a diagram showing the relationship between the output voltage Vout and the operating frequency f when no load is output from the power converter of the present invention.

FIG. 5 is a diagram in which the power conversion device according to the first embodiment of the present invention is applied to a half-bridge type power conversion device.

FIG. 6 is a timing chart showing the operation of the half-bridge power converter shown in FIG. 5 at full load.

7 is a timing chart showing the operation of the half-bridge power converter shown in FIG. 5 when there is no load.

FIG. 8 is a diagram in which the power conversion device according to the second embodiment of the present invention is applied to a half-bridge type power conversion device.

9 is a timing chart showing the operation of the half-bridge power converter shown in FIG. 8 at full load.

10 is a timing chart showing the operation of the half-bridge power converter shown in FIG. 8 when there is no load.

FIG. 11 is a diagram showing a principle configuration of a conventional power conversion device.

FIG. 12 is a timing chart for explaining the operation of the conventional power converter at full load.

FIG. 13 is a timing chart for explaining the operation of the conventional power converter when there is no load.

FIG. 14 is a diagram showing the relationship between the output voltage Vout and the operating frequency f when no load is output from the conventional power converter.

FIG. 15 is a diagram in which the principle configuration of a conventional power conversion device is applied to a half-bridge type power conversion device.

FIG. 16 is a timing chart showing the operation of a conventional half-bridge type power converter at full load.

FIG. 17 is a timing chart showing the operation of the conventional half-bridge type power conversion device under no load.

[Explanation of symbols]

1 DC power supply 2 First current resonance circuit 3 Rectification smoothing circuit 4 Second current resonance circuit 5 load 6 Rectification smoothing circuit 7 control circuit 9,11 Drive circuit 15 First current resonance circuit 17 Second current resonance circuit 21 First Current Resonance Circuit Co capacitor C1 capacitor CP1 comparator C2, C4, C6 Current resonance capacitor C3 voltage resonance capacitor Cri0 current resonance capacitor Cri1 Current resonance capacitor D1, D2, D3, D4, Do1, Do2 diode Rin input resistance L1 inductance L2 Resonance reactor Lr0 Resonance reactor Lr1 Resonance reactor Lp Main transformer primary winding excitation inductance N1 primary winding Q1, Q2 First and second switching elements S1, S2 secondary winding T1 main transformer

Claims (3)

[Claims] 1. A power converter in which an AC voltage is applied to a primary winding of a transformer, an AC voltage induced in a secondary winding of the transformer is rectified and smoothed, and an output voltage that is output is supplied to a load. And a first current resonance circuit that applies a rectangular wave pulse voltage to a first reactor and a first capacitor that are connected in series to generate a sinusoidal voltage waveform, and that is connected in series to the first reactor. The second inductor and the exciting inductance of the primary winding of the transformer and the second
A sinusoidal voltage waveform generated from the first current resonance circuit is applied to the capacitor, the amplitude of the voltage generated in the second capacitor is changed according to the change in frequency, and an AC voltage is applied to the primary winding of the transformer. And a second current resonance circuit for reducing the output voltage to zero by increasing the frequency of the rectangular wave pulse voltage. 2. A power converter in which an alternating voltage is applied to a primary winding of a transformer, an alternating voltage induced in a secondary winding of the transformer is rectified and smoothed, and an output voltage output is supplied to a load. A switching element for converting a DC voltage supplied from a DC power supply into a rectangular wave pulse voltage, and a sinusoidal voltage waveform by applying the rectangular wave pulse voltage to a reactor and a first capacitor connected in series. Generating a first current resonance circuit, an exciting inductance of a primary winding of the transformer connected in series with the reactor, and a first capacitor in a second capacitor.
A second current for applying a sinusoidal voltage waveform generated from a current resonance circuit, changing the amplitude of the voltage generated in the second capacitor according to a change in frequency, and applying an AC voltage to the primary winding of the transformer. A resonance circuit; an error voltage detection circuit that compares the output voltage with a predetermined reference voltage to detect an error voltage; an oscillation frequency that changes according to an error voltage signal output from the error voltage detection circuit; A control circuit that controls ON / OFF of an element, wherein the control circuit controls an oscillation frequency so that the output voltage becomes the predetermined reference voltage. 3. A power converter for applying an AC voltage to a primary winding of a transformer to rectify and smooth an AC voltage induced in a secondary winding of the transformer and supply an output voltage to a load. And a switching element for converting a DC voltage supplied from a DC power supply into a rectangular wave pulse voltage, a reactor in which the rectangular wave pulse voltage is connected in series, and a primary winding of the transformer connected in parallel. A first current resonance circuit for applying a sinusoidal voltage waveform to the first and second capacitors, an exciting inductance of the primary winding of the transformer connected in series with the reactor, and the second capacitor First
A second current for applying a sinusoidal voltage waveform generated from a current resonance circuit, changing the amplitude of the voltage generated in the second capacitor according to a change in frequency, and applying an AC voltage to the primary winding of the transformer. A resonance circuit; an error voltage detection circuit that compares the output voltage with a predetermined reference voltage to detect an error voltage; an oscillation frequency that changes according to an error voltage signal output from the error voltage detection circuit; A control circuit that controls ON / OFF of an element, wherein the control circuit controls an oscillation frequency so that the output voltage becomes the predetermined reference voltage.