WO2007116481A1

WO2007116481A1 - Power supply apparatus

Info

Publication number: WO2007116481A1
Application number: PCT/JP2006/306885
Authority: WO
Inventors: Yasuhiro Iino
Original assignee: Fujitsu Limited
Priority date: 2006-03-31
Filing date: 2006-03-31
Publication date: 2007-10-18
Also published as: JPWO2007116481A1; JP4796133B2

Abstract

A power supply apparatus comprises a primary circuit (11) connected between an input terminal (1) and a primary winding (N1) of a transformer (5), a secondary circuit (12) connected between a secondary winding (N2) of the transformer (5) and an output terminal (2), an auxiliary winding (N3) provided in the transformer (5), first voltage detecting circuits (91, 63) for detecting a first voltage having a first polarity generated in the auxiliary winding (N3) due to a first current in the primary circuit (11), second voltage detecting circuits (92, 64) for detecting a second voltage having a second polarity generated in the auxiliary winding (N3) due to a second current in the primary circuit (11), and a comparator circuit (10) for comparing the absolute values of the first and second voltages.

Description

Specification

Power supply

Technical field

TECHNICAL FIELD [0001] The present invention relates to a power supply device, and more particularly, to a large-capacity power supply device that prevents partial excitation in a transformer.

Background art

In a power supply device such as a full-bridge converter, for example, as shown in FIG. 4, by connecting a capacitor 109 in series with the primary winding N1 of the transformer 105, the DC component is cut off, and the transformer 105 bias excitation is prevented.

In the primary-side circuit of the full-bridge converter in FIG. 4, during the positive half-wave application period (period in which a pulse with a pulse width of tl in FIG. In this case, current flows along a route a indicated by a solid arrow. That is, the current flows in the order of the power source 104 (+), the input terminal 101, the semiconductor switch 133, the transformer (main transformer) 105, the capacitor 109, the semiconductor switch 132, the input terminal 101, and the power source 104 (-). On the other hand, in the negative half-wave application period (the period in which the pulse with the pulse width t2 in FIG. 3B is applied and the period before and after that), current flows along the route b indicated by the dotted arrow. . That is, the current flows in the order of the power source 104 (+), the input terminal 101, the semiconductor switch 131, the capacitor 109, the transformer 105, the semiconductor switch 134, the input terminal 101, and the power source 104 (-). Therefore, since the DC component is blocked by the capacitor 109, the partial excitation in the transformer 105 can be prevented.

[0004] It should be noted that, by using a correction amount that suppresses the DC component due to partial excitation based on the output current of the inverter, so that the DC component flowing to the AC output side of the inverter can be suppressed even if the partial excitation phenomenon occurs. It is known to control an inverter (see Patent Document 1 below).

[0005] In addition, by providing a series circuit of a primary winding of the transformer and a resonance capacitor between the midpoints of two series circuits that also have a switching element force, efficient conversion can be performed with a simple configuration. It is known (see Patent Document 2 below).

[0006] Further, an auxiliary winding that generates a magnetic field that cancels the magnetic field generated by the transformer is provided as a transformer. By providing it, a magnetic field is generated in the auxiliary winding only during the period when the primary winding current of the transformer is overcurrent, thereby canceling out the magnetic field generated by the transformer, thereby preventing the transformer's biased excitation. It is known (see Patent Document 3 below).

Patent Document 1: Japanese Patent Laid-Open No. 8-223944

Patent Document 2: JP-A-10-136653

Patent Document 3: JP-A-53-147223

Disclosure of the invention

Problems to be solved by the invention

[0007] When the present inventor examined a power supply device (full-bridge type converter) as shown in FIG. 4, it was found that there are the following problems.

First, all of the current (primary current) that flows through the primary winding N 1 of the transformer 105 flows through the capacitor 109. For this reason, as the capacity of the power supply device increases, the current flowing through the capacitor 109 increases. However, the capacitor 109 is limited in its withstand voltage (the allowable ripple current). Use beyond the limits of allowable ripple current and withstand voltage is also impossible in terms of safety. In addition, it is difficult to increase the withstand voltage of the capacitor 109, and such a large improvement cannot be expected so much. In particular, the allowable ripple current of capacitor 109 can hardly be increased. Therefore, the method of preventing the partial excitation of the transformer 105 by the capacitor 109 is not suitable for a large capacity power supply device. In addition, it cannot be said that the power supply as shown in Fig. 4 is suitable for a large-capacity power supply.

Second, in the primary circuit 111 of the transformer 105, for example, a capacitor 109 must be added as an element for preventing partial excitation. However, since the primary circuit 111 is the main circuit of the power supply device, it is desirable to avoid the design and maintenance viewpoints when adding elements other than the switching elements such as the capacitor 109 to the primary circuit 111. Also, depending on the power supply device, there are restrictions on the mounting space and outer shape. However, if the capacitor 109 is added, the restriction may not be met.

An object of the present invention is to provide a large-capacity power supply device that enables stable operation by preventing partial excitation in the transformer without changing the primary circuit of the transformer. The

Means for solving the problem

[0011] The power supply device of the present invention is connected between an input terminal, an output terminal, a transformer including a primary winding and a secondary winding, and the input terminal and a primary winding of the transformer. A primary circuit, a secondary circuit connected between the secondary winding of the transformer and the output terminal, an auxiliary winding provided in the transformer, and a first current in the primary circuit A first voltage detection circuit for detecting an absolute value of the first voltage having the first polarity, and the first voltage in the primary circuit. Is a voltage generated in the auxiliary winding due to a second current flowing in a reverse direction, and is an absolute value of a second voltage having a second polarity opposite to the first polarity. A second voltage detection circuit for detecting a value; and a comparison circuit for comparing the absolute values of the first and second voltages.

[0012] Preferably, according to one embodiment of the power supply device of the present invention, the power supply device further eliminates the difference between the absolute values of the first and second voltages based on the comparison result. Thus, a control unit for controlling the primary circuit is provided.

[0013] Preferably, according to one embodiment of the power supply device of the present invention, the first voltage detection circuit includes a first voltage connected between a positive side and a middle point of the auxiliary winding. The second voltage detection circuit includes a second capacitor connected between the midpoint of the auxiliary winding and the negative side.

Preferably, according to one embodiment of the power supply device of the present invention, the first voltage detection circuit is further connected between a positive side of the auxiliary winding and the first capacitor. The second voltage detection circuit further includes a second diode connected between the negative side of the auxiliary winding and the second capacitor.

[0015] Preferably, according to one embodiment of the power supply device of the present invention, the comparison circuit includes a terminal voltage appearing at a terminal connected to a positive side of the auxiliary winding of the first capacitor. And a comparator power for comparing a terminal voltage appearing at a terminal connected to the negative side of the auxiliary winding of the second capacitor.

The invention's effect

According to the power supply device of the present invention, the transformer is provided with the auxiliary winding, and the first circuit in the primary circuit The first voltage generated in the auxiliary winding due to the current is compared with the second voltage generated in the auxiliary winding due to the second current in the primary circuit. As a result, since the partial excitation generated in the transformer can be directly detected and controlled, it is possible to prevent the partial excitation of the transformer without using an allowable ripple current or a capacitor with a limited withstand voltage. In addition, it is possible to prevent partial excitation of the transformer without adding an element other than a switching element such as a capacitor in the primary circuit which is the main circuit of the power supply apparatus.

[0017] According to an embodiment of the present invention, the primary circuit is controlled based on the result of the comparison so that the difference between the absolute values of the first and second voltages is eliminated. As a result, it is possible to directly control the operation of the primary circuit so as to cancel the bias excitation generated in the transformer based on the voltage generated in the auxiliary feeder wire, thereby preventing the transformer bias excitation without using a capacitor. can do.

[0018] Further, according to one embodiment of the present invention, the first voltage detection circuit includes a first capacitor, and the second voltage detection circuit includes a second capacitor force. As a result, the first and second voltages can be detected with a relatively simple configuration, and as a result, the partial excitation of the transformer can be prevented.

[0019] According to one embodiment of the present invention, the first voltage detection circuit includes a first capacitor and a first diode, and the second voltage detection circuit includes a second capacitor and a second diode. Consists of. As a result, it is possible to prevent the current from flowing backward in the first and second voltage detection circuits and accurately detect the first and second voltages. As a result, it is possible to prevent the partial excitation of the transformer. Can do.

[0020] According to one embodiment of the present invention, the first and second voltages are compared using a comparator. As a result, the first and second voltages can be detected by a circuit having a relatively simple configuration, and as a result, the partial excitation of the transformer can be prevented.

Brief Description of Drawings

FIG. 1 is a diagram showing an example of the configuration of a power supply device according to the present invention.

2 is an explanatory diagram of the operation of the power supply device of FIG.

FIG. 3 shows the waveform of the power supply device of FIG.

FIG. 4 is an explanatory diagram of a conventional power supply device. Explanation of symbols

[0022] 1 input terminal

2 Output terminal

5 lances

11 Primary circuit

12 Secondary circuit

13 Partial excitation detection circuit

14 Control unit

31-34 Semiconductor switch

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a configuration diagram of a power supply device, and shows a configuration of a power supply device according to an embodiment of the present invention. The power supply device includes an input terminal 1, an output terminal 2, a transformer 5, a primary circuit 11, a secondary circuit 12, a partial excitation detection circuit 13, and a control unit 14. The transformer 5 includes an auxiliary feeder N3 in addition to the primary feeder N1 and the secondary feeder N2. N1 also represents the power of the primary winding N1. The same applies to N2 and N3. As will be described later, the secondary winding N2 is divided into two equal parts at the midpoint between the first portion N2-1 and the second portion N2-2 of the secondary winding N2. The auxiliary shoreline N3 is also divided into two equal parts at the midpoint between the first part N3-1 and the second part N3-2 of the auxiliary shoreline N3 so as to correspond to the secondary shoreline N2.

[0024] A plurality of (that is, two) input terminals 1 are provided. A power supply 4 is connected between the input terminals 1. The power supply 4 supplies power to the power supply device, for example, a power supply having a waveform as shown in the uppermost part of FIG. The power source 4 is not limited to this, and may be other various power sources.

The primary circuit (input circuit) 11 is connected between the input terminal 1 and the primary winding N 1 of the transformer 5. The primary circuit 11 has a bridge circuit force composed of first to fourth switching elements, for example, semiconductor switches 31 to 34. The first and second semiconductor switches 31 and 32 are connected in series in this order to constitute a first series circuit. The third and fourth semiconductor switches 33 and 34 are connected in series in this order to form a second series circuit. First and second series circuits are connected in parallel and inserted between input terminals 1. Transformer 5 primary feeder N1 The other terminal is connected to the connection point (midpoint) of the first and second semiconductor switches 31 and 32 connected in series. The other terminal of the primary winding N1 of the transformer 5 is connected to a connection point (midpoint) of the third and fourth semiconductor switches 33 and 34 connected in series.

As is well known, the semiconductor switches 31 to 34 are made of, for example, semiconductor elements such as power MOSFETs, IGBTs, BJTs, SITs, thyristors, and GTOs. A predetermined control signal is supplied from the control unit 14 to each of the control electrodes (gate electrode, base electrode, etc.) of the semiconductor switches 31 to 34. Thus, the ON / OFF of the semiconductor switches 31 to 34 is basically controlled so as to correspond to the change in the amplitude of the output of the power supply 4.

The secondary circuit (output circuit) 12 is connected between the secondary winding N 2 of the transformer 5 and the output terminal 2. A plurality of (that is, two) output terminals 2 are provided. A DC voltage, which is the output of this power supply device, is output between the output terminals 2. The secondary circuit 12 includes diodes 61 and 62, an inductance 7, and a capacitor 8. As is well known, the diodes 61 and 62 may be composed of MOSFET, IGBT, SIT or the like instead of the diode. The output voltage of the transformer 5 is output to one of the output terminals 2 via the diodes 61 and 62 connected to both terminals of the secondary winding N 2 of the transformer 5. The other of output terminals 2 is connected to the midpoint of secondary winding N2 of transformer 5. That is, the secondary winding N2 of the transformer 5 is divided into two by the midpoint so that the power ratio of the first part N2-1 and the second part N2-2 is equal. The inductance 7 and the capacitor ₈ constitute a smoothing circuit, and this smoothing circuit is inserted between the output terminals 2. Thereby, the output voltage of the transformer 5 is rectified and smoothed.

The partial excitation detection circuit 13 includes a first voltage detection circuit, a second voltage detection circuit, and a comparison circuit 10. The auxiliary winding N3 of the transformer 5 can be considered to constitute a part of the partial excitation detection circuit 13. Further, it can be considered that the partial excitation detection circuit 13 is provided in the secondary circuit 12.

[0029] The first voltage detection circuit is a voltage generated in the auxiliary winding N3 due to the first current in the primary circuit 11, and is the absolute value of the first voltage having the first polarity. To detect. The first current is the current of route a (indicated by the dotted line in Fig. 2 described later), and is the current during the positive half-wave period. The first voltage detection circuit includes a first capacitor 91 and a first diode 63. The first diode 63 is a diode for preventing reverse current flow. It is. Therefore, the first voltage detection circuit only needs to include at least the first capacitor 91. The first capacitor 91 is connected between the positive terminal of the auxiliary feeder N3 and the midpoint. The first diode 63 is connected between the positive terminal of the auxiliary conductor N3 and the first capacitor 91. The midpoint of the auxiliary feeder N3 is connected to the ground potential.

[0030] The second voltage detection circuit is a voltage generated in the auxiliary winding N3 due to the second current in the primary circuit 11, and has a second polarity opposite to the first polarity. Detect the absolute value of the second voltage. The second current is the current of route b (indicated by the alternate long and short dash line in FIG. 2), and is the current during the negative half-wave period. The second voltage detection circuit is also powered by the second capacitor 92 and the second diode 64. The second diode 64 is a diode for preventing reverse current flow (return). Therefore, the second voltage detection circuit may include at least the second capacitor 92. The second capacitor 92 is connected between the midpoint of the auxiliary feeder N3 and the negative terminal. The second diode 64 is connected between the negative terminal of the auxiliary feeder N3 and the second capacitor 92.

The comparison circuit 10 includes a comparator 10, for example, and compares the absolute values of the first and second voltages to obtain the difference. That is, the output of the first capacitor 91 that is the first voltage detection circuit is input to one input terminal of the comparator 10. The output of the second capacitor 92, which is the second voltage detection circuit, is input to the other input terminal of the comparator 10. As a result, the comparison circuit 10 is connected to the terminal voltage appearing at the terminal connected to the positive side of the auxiliary feeder N3 of the first capacitor 91 and to the negative side of the auxiliary feeder N3 of the second capacitor 92. The terminal voltage appearing at the terminal is compared to find the difference. The output of the comparison circuit 10 is input (feedback) to the control unit 14.

[0032] As is well known, the control unit 14 supplies predetermined control signals to the control electrodes of the semiconductor switches 31 to 34 constituting the primary circuit 11, and controls the ONZOFF thereof. In other words, during one positive half-wave period, the semiconductor switches 32 and 33 are turned on (ON), and at the same time, the semiconductor switches 31 and 34 are turned off (OFF). Next, in the negative half-wave period, the semiconductor switches 31 and 34 are turned on (ON), and at the same time, the semiconductor switches 32 and 33 are turned off (OFF). Further, as will be described later, the control unit 14 controls the primary circuit 11 based on the result of comparison in the comparison circuit 10 (the obtained difference, the same applies hereinafter). 1 Next circuit 11 is feedback controlled.

FIG. 2 is an explanatory diagram of the operation of the power supply device of FIG. In FIG. 2, the control unit 14 and the reference numerals 11 to 13 are not shown.

First, the operation of the positive half-wave in the power supply device of FIG. In this case, as described above, the semiconductor switches 32 and 33 are turned on by the control signal from the control unit 14. As a result, a route indicated by a dotted line a in FIG. 2 is formed, and a current flows through this route.

That is, the current (first current) is supplied from the power supply 4 (+) to the input terminal 1, the semiconductor switch 33, the primary wire Nl of the transformer 5, the semiconductor switch 32, the input terminal 1, and the power supply 4 ( 1) (first positive line N1 positive loop). As a result, the power supply voltage Vin is applied to the primary winding N1 of the transformer 5. At the same time, a voltage corresponding to the winding direction is induced in the auxiliary winding N3 (N3-1), current flows (positive loop of the auxiliary winding N3), and the capacitor 91 is connected via the diode 63. Charge.

Next, the operation of the negative half wave in the power supply device of FIG.

In this case, as described above, the semiconductor switches 31 and 34 are turned on (ON) by the control signal from the control unit 14. As a result, a route indicated by a one-dot chain line b in FIG. 2 is formed, and a current flows through this route.

[0037] That is, the current (second current) is supplied from the power source 4 (+) to the input terminal 1, the semiconductor switch 31, the primary wire Nl of the transformer 5, the semiconductor switch 34, the input terminal 1, the power source 4 ( Flow in the order of (1) (negative loop of primary winding N1). As a result, the power supply voltage Vin is applied to the primary winding N1 of the transformer 5 in the opposite direction to the case of the positive loop. At the same time, a corresponding voltage is induced in the auxiliary winding N3 (N3-2) in the direction opposite to the winding direction, and a current flows (negative loop of the auxiliary winding N3) through the diode 64. To charge the capacitor 92.

[0038] As described above, the partial excitation detection circuit 13 detects the first and second voltages generated in the auxiliary winding N3 provided in the transformer 5. Thereby, the bias excitation detection circuit 13 detects the voltage of the primary winding N1 (and consequently the secondary winding N2) of the transformer 5. That is, the partial excitation generated in the transformer 5 is detected.

[0039] The first voltage is present at the terminal connected to the positive side of the auxiliary feeder N3 of the first capacitor 91. Detected by a first capacitor 91 which is a first voltage detection circuit. The first voltage is a voltage generated by the voltage Vin applied to the transformer 5 when a current flows in the first circuit 11 in the first direction (route a in FIG. 2). Equivalent to the voltage generated on the positive side of line N1. The value of the first voltage is a value proportional to the pulse width of the current in the primary circuit 11. That is, the voltage Vin applied to the transformer 5 causes a current to flow along the route (master side route) represented by the dotted line similar to the route a in the auxiliary feeder N3, and the first capacitor 91 is charged. The first capacitor 91 is charged to the value of the first voltage.

[0040] The second voltage is a voltage that appears at the terminal connected to the negative side of the auxiliary feeder N3 of the second capacitor 92, and is detected by the second capacitor 92 that is the second voltage detection circuit. The The second voltage is a voltage generated by the voltage Vin applied to the transformer 5 when a current flows in the second direction (route b in FIG. 2) in the primary circuit 11. Equivalent to the voltage generated on the negative side of line N1. The value of the second voltage is a value proportional to the pulse width of the current in the primary circuit 11. In other words, the voltage Vin applied to the transformer 5 causes a current to flow in the route (slave side route) represented by the alternate long and short dash line similar to the route b in the auxiliary feeder N3, and the second capacitor 92 is charged. . The second capacitor 92 is charged to the value of the second voltage.

The control unit 14 controls the primary circuit 11 based on the comparison result in the comparison circuit 10 so that the difference between the absolute values of the first and second voltages is eliminated. In other words, the control unit 14 switches the semiconductor circuit 32 and 33 in the primary circuit 11 to the ON / OFF time (ON time in the positive half-wave, in FIG. 3A). (Pulse width tl) and the ON time in the switching of semiconductor switches 31 and 34 (ON time in the negative half-wave, pulse width t2 in Fig. 3 (A)) is longer than the value at that time. Control to make it shorter or shorter.

[0042] For example, when the first voltage is larger than the second voltage, the conduction time (ON time) tl of the semiconductor switches 32 and 33 is, for example, shorter than the conduction time at that time by a predetermined time. It is. The range of shortening is determined empirically (the same applies hereinafter). Or, the conduction time t2 force of the semiconductor switches 31 and 34, for example, longer than the current conduction time by a predetermined time. The On the other hand, when the second voltage is larger than the first voltage, the conduction time t2 of the semiconductor switches 31 and 34 is shortened by a predetermined time, for example, from the conduction time at that time. Or, the conduction time tl force of the semiconductor switches 32 and 33 is made longer by a predetermined time than the conduction time at that time, for example. By sequentially performing this control, tl = t2 is finally obtained. Thereby, partial excitation in the transformer 5 can be prevented.

FIG. 3 shows a waveform of the power supply device of FIG. In particular, Fig. 3 (A) shows the waveform when the power supply unit of Fig. 1 is normal, and Fig. 3 (B) shows the waveform when the power supply unit of Fig. 1 is abnormal.

In FIG. 3A, the bias excitation of the transformer 5 is prevented by the bias excitation detection circuit 13 (and the control unit 4). As a result, in the input waveform from the power source 4, the pulse width tl on the positive side (positive half-wave application period) and the pulse width t2 on the negative side (negative half-wave application period) are equal. As a result, the current I in the primary circuit 11 is a normal wave corresponding to the input waveform.

T1-N1

The current I that flows in the auxiliary feeder N3-1 and the current I that flows in the auxiliary feeder N3-2

T1N3-1 T1 also has a normal waveform. As a result, the first voltage V generated in the capacitor 91 and the capacitor

N3-2 C1

The second voltage V generated in the sensor 92 is equal, and the difference is “0”. In this case, control

C2

The unit 14 maintains the pulse width tl and the pulse width t2 as they are. Therefore, this waveform indicates that the partial excitation detection of the transformer 5 can be prevented by the partial excitation detection circuit 13.

[0045] On the other hand, in FIG. 3B, for some reason, the input waveform from the power source 4 is equal to the pulse width tl on the positive side and the pulse width t2 on the negative side. Disappear. That is, tl> t2. As a result, the first voltage generated in the capacitor 91

C1

It becomes larger than the voltage V of 2. That is, V> V. In this state, the transformer 5

C2 CI C2

It will be saturated by excitation and will eventually be destroyed by overcurrent. The same applies to tl <t2.

Note that the waveform in FIG. 3B is almost the same as that in the case where the capacitor 109 is omitted in the power supply device in FIG. In other words, in a power supply device that performs large-capacity power conversion, the capacitor 109 cannot be applied (connected) due to restrictions on the withstand voltage of the capacitor 109 and the allowable ripple current. For this reason, the transformer 105 is saturated by the bias excitation, and is eventually destroyed by the overcurrent, and the bias excitation of the transformer 105 cannot be prevented.

Therefore, in the present invention, the comparison circuit 10 generates the first voltage V generated in the capacitor 91 and Compare the second voltage V generated in the capacitor 92 with the difference V = V

C2 CS C1

-V> 0 (or V = V -V> 0) so that the differential V force is "0" ("0"

C2 CS C2 ci cs

The primary circuit 11 is controlled. As a result, again, as shown in FIG. 3A, in the input waveform from the power supply 4, the pulse width tl on the positive side and the pulse width t2 on the negative side are equal. Therefore, this waveform indicates that the bias excitation of the transformer 5 is prevented by the bias excitation detection circuit 13 of the present invention.

As can be seen from the above, the partial excitation detection circuit 13 can prevent the partial excitation of the transformer 5. As a result, it is possible to realize a large-capacity power supply device (that performs large-capacity power conversion) in which the partial excitation of the transformer 5 is prevented.

As described above, the present invention has been described according to the embodiment. The present invention can be variously modified within the scope of the gist thereof.

[0050] For example, the present invention is not limited to the full-bridge converter shown in FIG. 1, but can be applied to various switching converters such as a push-pull converter, and a DC component is cut off using a capacitor. Industrial applicability that can be applied to various types of power supplies

[0051] As described above, according to the present invention, in the power supply device, it is possible to prevent partial excitation of the transformer without using a capacitor that is limited in allowable ripple current or withstand voltage. Therefore, since no capacitor is used, even if a large current flows through the primary winding of the transformer, it is possible to prevent partial excitation of the transformer. As a result, it is possible to realize a power supply device that performs large-capacity power conversion while preventing partial excitation of the transformer. In addition, it is possible to prevent the partial excitation of the transformer without adding elements other than the switching element in the primary circuit which is the main circuit of the power supply device. Therefore, the design and maintenance of the power supply device can be facilitated, and the mounting space and the external shape of the power supply device can be dealt with.

Claims

The scope of the claims

[1] Input terminal,

An output terminal;

A transformer with primary and secondary windings,

A primary circuit connected between the input terminal and a primary winding of the transformer; a secondary circuit connected between a secondary winding of the transformer and the output terminal; and provided in the transformer An auxiliary auxiliary line,

A first voltage detection circuit for detecting an absolute value of a first voltage having a first polarity, which is a voltage generated in the auxiliary winding due to a first current in the primary circuit; A voltage generated in the auxiliary winding due to a second current flowing in a direction opposite to the first current in the primary circuit, and having a second polarity opposite to the first polarity. A second voltage detection circuit for detecting an absolute value of the second voltage,

A comparison circuit for comparing absolute values of the first and second voltages.

A power supply device characterized by that.

[2] The power supply device according to claim 1,

A controller that controls the primary circuit based on a result of the comparison so that a difference between absolute values of the first and second voltages is eliminated;

A power supply device characterized by that.

[3] In the power supply device according to claim 2,

The primary circuit is a bridge circuit composed of semiconductor switches,

The control unit controls switching of the semiconductor switch based on a result of the comparison so that a difference between absolute values of the first and second voltages is eliminated.

A power supply device characterized by that.

[4] In the power supply device according to claim 3,

The primary circuit includes a first series circuit in which the first and second semiconductor switches are connected in series in this order, and a second series circuit in which the third and fourth semiconductor switches are connected in series in this order. The power of the bridge circuit connected in parallel,

The control unit determines the absolute values of the first and second voltages based on the comparison result. Control the switching of the first and fourth semiconductor switches and the switching of the second and third semiconductor switches so that there is no difference.

A power supply device characterized by that.

[5] In the power supply device according to claim 1,

The first voltage detection circuit comprises a first capacitor connected between a positive side and a middle point of the auxiliary winding;

The second voltage detection circuit comprises a second capacitor connected between the midpoint of the auxiliary feeder and the negative side

A power supply device characterized by that.

[6] In the power supply device according to claim 5,

The first voltage detection circuit further comprises a first diode connected between a positive side of the auxiliary winding and the first capacitor;

The second voltage detection circuit further includes a second diode connected between the negative side of the auxiliary winding and the second capacitor.

A power supply device characterized by that.

[7] In the power supply device according to claim 5,

The comparison circuit appears at a terminal voltage appearing at a terminal connected to the positive side of the auxiliary lead of the first capacitor and at a terminal connected to the negative side of the auxiliary lead of the second capacitor. Comparing with terminal voltage

A power supply device characterized by that.