JP2003134818A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide size and cost reduction for a component, while keeping a restraining effect of a voltage level applied to a main switch device. SOLUTION: An intermediate tap 20 is provided at a primary main winding 5 for exciting a power transmission main transformer 4. A winding 21 is run from one end of the main winding 5 to the intermediate tap 20, and a winding 22 is run from the intermediate tap 20 to the other end. An input voltage is applied to the one end of the primary main winding 5 formed of the windings 21, 22. The other end is grounded through a main switch device 6, and a capacitance 7 for voltage resonance is provided at the main switch device 6 in parallel. An active snubber circuit 18 is constituted of a capacitance 15, an auxiliary switch device 16 connected with the capacitance 15 in series, and a diode 17 connected with the auxiliary switch device 16 in parallel. The active snubber circuit 18 is connected with the winding 21 in parallel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit suitable for use in, for example, electric equipment. Specifically, it is a power supply circuit that uses voltage resonance to transmit electric power, and is provided with an active snubber circuit that can lower the withstand voltage of a switch element when the switching pulse voltage is clamped to a peak value. is there.

[0002]

2. Description of the Related Art For example, in a power supply circuit used for electric equipment, a multi-stone system in which a voltage across both ends of a switch element, which is generally called a bridge type, is clamped to an input DC voltage, a flyback converter, a forward converter, or a push converter. A method called a pull converter or the like that does not have a voltage clamp with one stone or many stones is used. Among these, the latter method has a simple control drive circuit and is widely used.

Therefore, FIG. 4 shows a circuit diagram of the principle of the voltage resonance converter which is reported to have the highest power exchange efficiency among the latter methods.

That is, in FIG. 4, the AC power source from the input power source 41 is supplied to the diode rectifying bridge 42,
The rectified voltage is taken out through the grounding smoothing capacitance 43 at the other end. The extracted smoothed voltage is applied to one end of the primary winding main winding 45 for excitation of the power transmission main transformer 44. The other end of the main winding 45 is grounded through a main switch element 46, and a voltage resonance capacitance 47 and a damper diode 48 are provided in parallel with the main switch element 46.

Further, a rectifying diode 50 and a smoothing capacitance 51 are provided between both ends of the secondary winding 49 of the main transformer 44, and an output terminal 52 for extracting an arbitrary voltage from both ends of the capacitance 51 is led out. To be done.
The voltage on the + side of the output terminal 52 is the error amplifier 53.
A drive signal is supplied to the oscillation drive circuit 54 through the control signal and controls the conduction of the main switch element 46 in accordance with the value of this voltage. As a result, the output voltage output to the output terminal 52 is stabilized.

That is, in the oscillation drive circuit 54, for example, a drive signal is formed so that the operation oscillation frequency is variable by fixing the off time Toff of the main switch element 46 so that the output voltage becomes constant. This drive signal is the main switch element 46.
The signals of the respective parts are supplied as shown in the waveform diagram of FIG. Here, in FIG. 5A, when the conduction of the main switch element 46 is controlled as shown in FIG. 5B, for example,
The current Isw flowing through the main switch element 46 and the voltage Vsw applied between both ends are shown.

As is clear from this waveform diagram, since the waveform of the voltage Vsw is a half-sine wave of a sine wave and is very smooth, the generated noise is extremely small, and the current Isw and the voltage Vsw.
Since the sw overlap is small, switching loss can be greatly suppressed. In this way, according to the circuit of FIG. 4, voltage conversion is performed using the principle of the voltage resonance type converter, and the stabilized output voltage is taken out to the output terminal 52. This circuit is reported to have the highest power exchange efficiency.

However, in this circuit, an element having a high peak voltage value applied to the main switch element 46 and a high breakdown voltage is required. That is, in FIG. 5A, the voltage peak value Vds of the pulse generated during the off period of the main switch element 46 increases with an increase in the input voltage value and the conduction time of the main switch element 46, that is, an increase in load power. To do. Then, the main switch element 46 is required to have a withstand voltage that can withstand the application of this pulse voltage.

However, such high withstand voltage main switching element 46 is a small number of MOSFETs, and is small in number and expensive. In addition, in a high breakdown voltage MOSFET, the conduction resistance is also large, so that the loss may increase. Further, even when the bipolar transistor is adopted, the conduction loss is smaller than that of the FET, but the one having a high breakdown voltage has a switching time inferior to that of a low breakdown voltage element, and cannot attain a high frequency.

[0010]

On the other hand, an active snubber circuit including a capacitance and a switch element is provided in parallel with the primary side main winding 45 of the main transformer 44,
A method has been implemented in which the voltage across the main switch element 46 is clamped at a prescribed voltage level and suppressed. That is, FIG.
In, the active snubber circuit 58 is composed of the capacitance 55, the sub switch element 56 connected in series to the capacitance 55, and the diode 57 connected in parallel to the sub switch element 56.

The active snubber circuit 58 is 1
The sub-switch element 56, which is provided in parallel with the secondary main winding 45, is driven by the drive circuit 59 for a desired period in a phase shifted from the drive signal of the main switch element 46 by a predetermined time. As a result, the voltage peak value Vds of the pulse generated during the off period of the main switch element 46 is clamped to a desired value, and the voltage across the main switch element 46 is suppressed to the prescribed voltage level. The waveform of each part in these operations is as shown in FIG. 7, for example.

That is, for example, the main switch element 46 is shown in FIG.
While it is driven like the C of FIG.
Are driven as shown by D in FIG. As a result, the voltage peak value V of the pulse generated during the off period of the main switch element 46
ds is clamped to the desired value. The current Isw1 flowing through the main switch element 46 and the voltage V applied across both ends
The waveform of sw1 is as shown in A of FIG. 7, and the current Isw2 flowing through the switch element 56 and the voltage V applied across both ends are shown.
The waveform of sw2 is as shown in B of FIG.

Therefore, according to this circuit, the voltage applied to the main switching element 46 is 1 with respect to the withstand voltage of 1500 V, for example.
By designing to suppress the voltage to 200V, it becomes possible to secure the withstand voltage margin of the main switch element 46. However, in this case, the auxiliary switch element 56 forming the active snubber circuit 58 also needs to have an equivalent withstand voltage, and for example, two switch elements with a withstand voltage of 1500 V are required. Further, the loss of the sub switch element 56 cannot be ignored.

This application has been made in view of such a point, and the problem to be solved is that in the conventional device, the peak value of the voltage applied to the switch element is high and the withstand voltage is high. If an element is required and an active snubber circuit is provided to suppress the applied voltage, two switch elements with relatively high breakdown voltage are required, and the loss of these switch elements should be ignored. I couldn't do it.

[0015]

Therefore, in the present invention, an intermediate tap is provided in the primary side main winding of the main transformer, and the intermediate tap is provided between the intermediate tap and the input potential line of the input DC or the zero potential line. An active snubber circuit is provided, which reduces the voltage applied to the sub switch element and the capacitance of the active snubber circuit and maintains the effect of suppressing the voltage level applied to the main switch element. In addition, it is possible to reduce the size of parts and reduce costs.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION That is, the present invention is a power supply circuit for transmitting electric power by utilizing voltage resonance, including a main switching element and a main transformer for electric power transmission used for a main switching operation for electric power transmission. A switching pulse voltage applied between both ends of the main switching element, which is composed of a sub switching element connected in parallel with the main excitation winding of the transmission main transformer and a capacitance connected in series with the sub switching element. And an active snubber circuit that clamps a peak value, and the active snubber circuit is provided between the input potential line of the input DC and the intermediate tap provided in the excitation main winding of the power transmission main transformer. .

Further, the present invention is a power supply circuit for transmitting power by utilizing voltage resonance, wherein a main switch element and a power transmission main transformer used for a main switching operation for power transmission, and a power transmission main transformer. It consists of a sub-switch element connected in parallel with the main excitation winding of the transformer and a capacitance connected in series with this sub-switch element, and the peak value of the switching pulse voltage applied across the main switch element. An active snubber circuit for clamping is provided, and the active snubber circuit is provided between the intermediate tap provided on the excitation main winding of the power transmission main transformer and the zero potential line of the input DC.

The present invention will be described below with reference to the drawings. FIGS. 1 and 2 are block diagrams showing configurations of different embodiments of a power supply circuit according to the present invention. In addition,
In these FIG. 1 and FIG. 2, common parts are denoted by the same reference numerals.

In FIGS. 1 and 2, an AC power source from an input power source 1 is supplied to a diode rectifying bridge 2, and a rectified voltage is taken out through a grounding smoothing capacitance 3 at the other end. And this capacitance 3
The input potential line to which the smoothed voltage extracted from is supplied is the primary side main winding 5 for exciting the main transformer 4 for power transmission.
Connected to one end of. The other end of the primary side main winding 5 is connected to the primary side zero potential line.

An intermediate tap 20 is provided on the primary side main winding 5 here.
Is provided, and one end (input potential line) of the primary side main winding 5 to the intermediate tap 20 is the winding 21, and the other end of the primary side main winding 5 from the intermediate tap 20 (primary side zero potential line). Up to the winding 22. The other end of the primary side main winding 5 including these windings 21 and 22 is grounded through the main switching element 6, and a voltage resonance capacitance 7 and a damper diode 8 are provided in parallel with the main switching element 6. .

Further, a rectifying diode 10 and a smoothing capacitance 11 are provided between both ends of the secondary winding 9 of the main transformer 4, and an output terminal 12 for extracting an arbitrary voltage from both ends of the capacitance 11 is led out. To be done. Then, the voltage on the + side of the output terminal 12 is supplied to the oscillation drive circuit 14 through the error amplifier 13, and a drive signal for arbitrarily controlling the conduction of the main switch element 6 is formed according to the value of this voltage. As a result, the output voltage output to the output terminal 12 is stabilized.

That is, in the oscillation drive circuit 14, for example, a drive signal is formed so that the operation oscillation frequency is variable with the off time Toff of the main switch element 6 fixed so that the output voltage becomes constant. Then, by supplying this drive signal to the main switch element 6, an alternating current flows in the primary side main winding 5 of the main transformer 4 to perform excitation, and power is transmitted to the secondary side winding 9. As a result, a voltage corresponding to the ratio of the windings 5 and 9 is formed in the secondary winding 9. Further, the drive signal is controlled so that the output voltage is stabilized.

In this circuit, the capacitance 1
5, the sub switch element 16 connected in series to the capacitance 15, and the diode 17 connected in parallel to the sub switch element 16 constitute an active snubber circuit 18. The active snubber circuit 18 is in parallel with the winding 21 between the intermediate tap 20 and the input potential line (the embodiment of FIG. 1) or in parallel with the winding 22 between the intermediate tap 20 and the zero potential line. (Embodiment of FIG. 2).

Further, the sub switch element 16 of the active snubber circuit 18 is driven by the drive circuit 19 for a desired period in a phase shifted from the drive signal of the main switch element 6 by a predetermined time. That is, FIG. 3 shows the waveform of each part. In FIG. 3, the drive signal of the main switch element 6 described above is formed as shown in C of FIG. 3, for example, whereas the drive signal of the sub switch element 16 is formed as shown in FIG.
Is formed as shown in FIG.

As a result, the waveform of the current Isw1 flowing through the main switching device 6 and the voltage Vsw1 applied across the main switching device 6 is as shown in FIG. 3A, for example, and the current Isw2 flowing through the switching device 16 and the current Vsw1 applied across the switching device 16 are applied. The waveform of the voltage Vsw2 is, for example, as shown in B of FIG. The configuration and operation of the power transmission system including the main transformer 4 and the main switch element 6 and the active snubber circuit 18 described above are described in FIG.
This is the same as the configuration and operation of the voltage resonance type converter described in the above description.

That is, in this circuit, when the main switching element 6 is in the conducting state, the main current flows from the input voltage source (one end of the smoothing capacitance 3) to the primary side main winding 5 of the main transformer 4 and the main winding. It flows through a path called the primary side zero potential line through the switch element 6. When the main switching element 6 is opened, charging of the voltage resonance capacitance 7 from the input voltage source is started via the main winding 5.
Further, this operation is repeated to form an alternating current, and the primary side main winding 5 is excited.

When the sub switch element 16 is turned on while the main switch element 6 is open, for example, as shown in FIG.
In this embodiment, the current flowing through the capacitance 15 and the sub switching element 16 is passed through the winding 22 of the main winding 5 to the primary side zero potential line. As a result, the voltage across the main switch element 6 is clamped by the time constant of the winding 22 and the capacitance 15 from the intermediate tap 20 to the zero potential line, as if a large capacitance was connected.

Alternatively, for example, in the embodiment shown in FIG. 2, when the main switching element 6 is in the open state and the sub switching element 16 is in the conducting state, the current from the input voltage source through the winding 21 of the main winding 5 is It flows through the zero potential line on the primary side through the capacitance 15 and the sub switch element 16.
As a result, the voltage across the main switch element 6 is clamped by the time constant of the winding 21 from the input potential line to the center tap 20 and the capacitance 15 as if a large capacitance was connected.

In these circuits, the voltage applied to the sub switch element 16 and the capacitance 15 of the active snubber circuit 18 is reduced according to the turn ratio of the main winding 5 divided by the center tap 20. That is, a voltage divided by the turn ratio of the main winding 5 is applied to the sub switch element 16 and the capacitance 15 of the active snubber circuit 18. As a result, the withstand voltage required for the sub switch element 16 and the like is reduced, and it is possible to reduce the size and cost of these parts.

In these circuits, in order to make the value of the voltage Vsw1 applied across the main switch element 6 equal to that of the active snubber circuit 58 shown in FIG. 6, the inductance of the main winding 45 is set to a value. L1 and the capacitance of the capacitance 55 are values C1, and the winding 22 in FIG.
Alternatively, the inductance of the winding 21 in FIG.
1 ', and the capacitance of the capacitance 15 is set to a value C1' so that the time constants f and f'are equal to each other.

That is, these time constants f and f'are expressed by f = 1/2 × π√ (L1 × C1) or f '= 1/2 × π√ (L1' × C1 '), respectively. Value L1 'and value C so that they are equal
1'is selected.

Therefore, in these embodiments, an intermediate tap is provided on the primary side main winding of the main transformer, and an active snubber circuit is provided between this intermediate tap and the input potential line of the input DC or the zero potential line. As a result, the voltage applied to the sub-switch element and capacitance of the active snubber circuit is reduced, and the effect of suppressing the voltage level applied to the main switch element is maintained, while reducing the size of parts and cost. Can be planned.

As a result, in the conventional device, a high peak voltage value applied to the switch element and a high breakdown voltage element are required. In contrast to this, when an active snubber circuit is provided to suppress the applied voltage, However, according to the present invention, these problems can be easily solved. However, according to the present invention, two relatively high breakdown voltage switch elements are required and the loss of these switch elements cannot be ignored. It is possible.

The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention.

[0035]

According to the invention of claim 1, therefore, an intermediate tap is provided on the primary side main winding of the main transformer, and an active snubber circuit is provided between this intermediate tap and the input potential line of the input DC. As a result, the voltage applied to the sub-switch element and capacitance of the active snubber circuit is reduced, and the effect of suppressing the voltage level applied to the main switch element is maintained, while reducing the size of parts and cost. It can be achieved.

According to the invention of claim 2, an intermediate tap is provided on the primary side main winding of the main transformer, and an active snubber circuit is provided between this intermediate tap and the zero potential line of the input DC. As a result, the voltage applied to the sub-switch element and the capacitance of the active snubber circuit is reduced, and the effect of suppressing the voltage level applied to the main switch element is maintained, while reducing the size of components and cost. Is something that can be done.

As a result, in the conventional device, an element having a high voltage peak value applied to the switch element and a high withstand voltage is required. In contrast to this, when an active snubber circuit is provided to suppress the applied voltage. However, according to the present invention, these problems can be easily solved. However, according to the present invention, two relatively high breakdown voltage switch elements are required and the loss of these switch elements cannot be ignored. It is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a power supply circuit to which the present invention is applied.

FIG. 2 is a configuration diagram of an embodiment of a power supply circuit to which the present invention is applied.

FIG. 3 is a waveform diagram for the explanation.

FIG. 4 is a configuration diagram of a conventional power supply circuit.

FIG. 5 is a waveform chart for the explanation.

FIG. 6 is a configuration diagram of a power supply circuit using a conventional active snubber circuit.

FIG. 7 is a waveform diagram for the explanation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input power supply, 2 ... Diode rectification bridge, 3 ... Capacitance for smoothing, 4 ... Main transformer for power transmission, 5 ...
Primary side main winding, 6 ... Main switch element, 7 ... Voltage resonance capacitance, 8 ... Damper diode, 9 ... Secondary side winding, 10 ... Rectifying diode, 11 ... Smoothing capacitance, 12 ... Output Terminal, 13 ... Error amplifier, 14 ...
Oscillation drive circuit, 15 ... Capacitance, 16 ... Sub switch element, 17 ... Diode, 18 ... Active snubber circuit, 19 ... Drive circuit, 20 ... Intermediate tap, 21, 22 ...
Winding

Claims (2)

[Claims] 1. A power supply circuit for transmitting power using voltage resonance, comprising: a main switching element used for a main switching operation for power transmission; a power transmission main transformer; and an excitation of the power transmission main transformer. It comprises a sub-switch element connected in parallel to the main winding and a capacitance connected in series to this sub-switch element, and clamps the switching pulse voltage applied across the main switching element to a peak value. An active snubber circuit, wherein the active snubber circuit is provided between an input direct current input potential line and an intermediate tap provided on an excitation main winding of the power transmission main transformer. 2. A power supply circuit for transmitting power using voltage resonance, comprising: a main switching element used for main switching operation for power transmission, a main transformer for power transmission, and excitation of the main transformer for power transmission. It comprises a sub-switch element connected in parallel to the main winding and a capacitance connected in series to this sub-switch element, and clamps the switching pulse voltage applied across the main switching element to a peak value. An active snubber circuit, wherein the active snubber circuit is provided between an intermediate tap provided on an exciting main winding of the power transmission main transformer and a zero potential line of an input DC.