JP2018182995A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a suitable technology of suppressing a ripple voltage while reducing a capacity of a reactor functioning as a filter.SOLUTION: A third arm 14 is configured so that a fifth circuit 10 having a fifth switching element 2e and a fifth diode 3e connected in a reverse parallel manner, a third connection point p3, a sixth circuit 11 having a sixth switching element 2f and a sixth diode 3f connected in a reverse parallel manner, a fifth connection point p5, a seventh circuit 12 having a seventh switching element 2g and a seventh diode 3g connected in a reverse parallel manner, a fourth connection point p4 and an eighth circuit 13 having an eighth switching element 2h and an eighth diode 3h connected in a reverse parallel manner are connected in series in this order.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a power supply device.

  Conventionally, various proposals have been made regarding a power supply device having the function of an inverter. For example, Patent Document 1 describes a power supply device shown in FIG.

  The power supply device shown in FIG. 6 is interposed between the AC power supply 107 and the load 111. In this power supply device, a first series arm 103, a second series arm 104, a third series arm 105, and a capacitor 106 are connected in parallel to one another. The first series arm 103 has a circuit in which the switching element 101a and the diode 102a are connected in antiparallel and a circuit in which the switching element 101b and the diode 102b are connected in antiparallel. In the first series arm 103, these circuits are connected in series via the connection point q1. The second series arm 104 has a circuit in which the switching element 101c and the diode 102c are connected in antiparallel and a circuit in which the switching element 101d and the diode 102d are connected in antiparallel. In the second series arm 104, these circuits are connected in series via the connection point q2. The third series arm 105 has a circuit in which the switching element 101e and the diode 102e are connected in antiparallel and a circuit in which the switching element 101f and the diode 102f are connected in antiparallel. In the third series arm 105, these circuits are connected in series via the connection point q3.

  The power supply includes a series transformer 108. The series transformer 108 includes a first primary winding 108a, a second primary winding 108b, and a secondary winding 108c. The first primary winding 108a, the second primary winding 108b and the secondary winding 108c are wound at a predetermined turns ratio.

  A reactor 109a is connected between a connection point q1 of the first series arm 103 and one end of the AC power supply 107. A reactor 109 b is connected between a connection point q 3 of the third series arm 105 and the other end of the AC power supply 107. A reactor 109c is connected between a connection point q2 of the second series arm 104 and one end of the secondary winding 108c. A reactor 109d is connected between a connection point q3 of the third series arm 105 and the other end of the secondary winding 108c.

  A capacitor 110 a is connected between the pair of reactors 109 a and 109 b and the AC power supply 107. The capacitor 110 a is connected in parallel to the AC power supply 107. A capacitor 110 b is connected between the pair of reactors 109 c and 109 d and the secondary winding 108 c. The capacitor 110b is connected in parallel to the secondary winding 108c.

  The first series arm 103 is a full bridge converter dedicated arm. The second series arm 104 is a full bridge inverter dedicated arm. The third series arm 105 is a converter / inverter common arm. These three arms operate at respective modulation rates. As a result, a voltage having the same or opposite phase as the voltage of the AC power supply 107 is applied to the secondary winding 108c. Then, a voltage corresponding to the voltage of the AC power supply 107, the voltage of the secondary winding 108c, and the turns ratio of the series transformer 108 is applied to the load 111.

  Reactors 109a and 109c function as filters.

JP 2003-230281 A

  The inventor of the present invention wanted to propose a technique suitable for suppressing the ripple voltage while reducing the capacity of the reactor functioning as a filter.

The present disclosure
What is claimed is: 1. A power supply device, to which an input power source is connected at an input end and a load is connected at an output end
A first circuit in which the first switching element and the first diode are connected in antiparallel, a first connection point, and a second circuit in which the second switching element and the second diode are connected in antiparallel are connected in series in this order And the first arm
A third circuit in which the third switching element and the third diode are connected in antiparallel, a second connection point, and a fourth circuit in which the fourth switching element and the fourth diode are connected in antiparallel are connected in series in this order And the second arm
A fifth circuit in which a fifth switching element and a fifth diode are connected in antiparallel, a third connection point, a sixth circuit in which a sixth switching element and a sixth diode are connected in antiparallel, and a fifth connection point; A seventh circuit in which the seventh switching element and the seventh diode are connected in antiparallel, a fourth connection point, and an eighth circuit in which the eighth switching element and the eighth diode are connected in antiparallel are connected in series in this order And the third arm
A series transformer having a first primary winding, a second primary winding and a secondary winding;
A first reactor,
A second reactor,
A first capacitor,
A pair of capacitors connected in series via a sixth connection point,
And a pair of clamp diodes connected in series via a seventh connection point connected to the sixth connection point,
The first arm, the second arm, the third arm, the first capacitor, and the pair of capacitors are connected in parallel with one another.
The series circuit of the sixth circuit and the seventh circuit, and the pair of clamp diodes are connected in parallel between the third connection point and the fourth connection point,
In a path connecting the input end, the first primary winding, and the output end, one end of the input end, one end of the first primary winding, and the first primary The other end of the winding and one end of the output end are arranged in this order,
In the path connecting the output end, the second primary winding, and the input end, the other end of the output end, the other end of the second primary winding, and the second One end of the primary winding and the other end of the input end are arranged in this order,
In the path connecting the first connection point, the first reactor and the input end, the first connection point, one end of the first reactor, the other end of the first reactor, and the input end The ends are arranged in this order,
In a path connecting the second connection point, the second reactor, the secondary winding, and the input end, the second connection point, one end of the second reactor, and the other end of the second reactor One end of the secondary winding, the other end of the secondary winding, the fifth connection point, and the other end of the input end portion are arranged in this order,
The potential at one end of the first capacitor is defined as a first potential, the potential at the other end of the first capacitor is defined as a second potential, and a potential intermediate between the first potential and the second potential is an intermediate potential. A power supply device is provided in which, when defined, the intermediate potential appears at the sixth connection point.

  The technique according to the present disclosure is suitable for suppressing the ripple voltage while reducing the capacity of the reactor that functions as a filter.

Power supply apparatus according to the embodiment Diagram showing control block Diagram for explaining switching of switching elements Diagram for explaining switching of switching elements Diagram showing the time transition of each part voltage Configuration diagram of the power supply device of Patent Document 1

(Findings by the inventor)
In the power supply device of FIG. 6, a converter is configured by the first series arm 103 and the third series arm 105. However, the potential at the connection point q1 of the first series arm 103 can only take two levels. Further, the potential at the connection point q3 of the third series arm 105 can only take two levels.

  Further, in the power supply device of FIG. 6, an inverter is configured by the second series arm 104 and the third series arm 105. However, the potential at the connection point q2 of the second series arm 104 can only take two levels. Furthermore, the potential at the connection point q3 of the third series arm 105 can only take two levels.

  Thus, the converter constituted by the first series arm 103 and the third series arm 105 is only a two-level converter. Also, the inverter formed by the second series arm 104 and the third series arm 105 is only a two-level inverter. Therefore, these converters and inverters do not have a configuration suitable for reducing the ripple voltage.

  Reactors 109a and 109c function as input / output filters. However, as described above, the converters and inverters formed by the series arms 103, 104 and 105 do not have a configuration suitable for reducing the ripple voltage. Therefore, in order to prevent the ripple voltage from increasing due to waveform shaping by reactors 109a and 109c, it is necessary to increase the capacity of reactors 109a and 109c to some extent.

  The inventor examined a technique suitable for suppressing the ripple voltage while reducing the capacity of the reactor functioning as a filter.

That is, the first aspect of the present disclosure is
What is claimed is: 1. A power supply device, to which an input power supply is connected at an input end and a load is connected at an output end,
A first circuit in which the first switching element and the first diode are connected in antiparallel, a first connection point, and a second circuit in which the second switching element and the second diode are connected in antiparallel are connected in series in this order And the first arm
A third circuit in which the third switching element and the third diode are connected in antiparallel, a second connection point, and a fourth circuit in which the fourth switching element and the fourth diode are connected in antiparallel are connected in series in this order And the second arm
A fifth circuit in which a fifth switching element and a fifth diode are connected in antiparallel, a third connection point, a sixth circuit in which a sixth switching element and a sixth diode are connected in antiparallel, and a fifth connection point; A seventh circuit in which the seventh switching element and the seventh diode are connected in antiparallel, a fourth connection point, and an eighth circuit in which the eighth switching element and the eighth diode are connected in antiparallel are connected in series in this order And the third arm
A series transformer having a first primary winding, a second primary winding and a secondary winding;
A first reactor,
A second reactor,
A first capacitor,
A pair of capacitors connected in series via a sixth connection point,
And a pair of clamp diodes connected in series via a seventh connection point connected to the sixth connection point,
The first arm, the second arm, the third arm, the first capacitor, and the pair of capacitors are connected in parallel with one another.
The series circuit of the sixth circuit and the seventh circuit, and the pair of clamp diodes are connected in parallel between the third connection point and the fourth connection point,
In a path connecting the input end, the first primary winding, and the output end, one end of the input end, one end of the first primary winding, and the first primary The other end of the winding and one end of the output end are arranged in this order,
In the path connecting the output end, the second primary winding, and the input end, the other end of the output end, the other end of the second primary winding, and the second One end of the primary winding and the other end of the input end are arranged in this order,
In the path connecting the first connection point, the first reactor and the input end, the first connection point, one end of the first reactor, the other end of the first reactor, and the input end The ends are arranged in this order,
In a path connecting the second connection point, the second reactor, the secondary winding, and the input end, the second connection point, one end of the second reactor, and the other end of the second reactor One end of the secondary winding, the other end of the secondary winding, the fifth connection point, and the other end of the input end portion are arranged in this order,
The potential at one end of the first capacitor is defined as a first potential, the potential at the other end of the first capacitor is defined as a second potential, and a potential intermediate between the first potential and the second potential is an intermediate potential. A power supply device is provided in which, when defined, the intermediate potential appears at the sixth connection point.

  The third arm of the first aspect is a tri-leveled arm. Then, a combination of the first arm and the third arm which is tri-leveled functions as a tri-level converter. Also, the combination of the second arm and the third arm which is tri-leveled functions as a tri-level inverter. Therefore, these converters and inverters have a configuration suitable for reducing the ripple voltage. Therefore, according to the first aspect, even if a small-capacity reactor is used as the first reactor and the second reactor, it is possible to suppress the ripple voltage.

The second aspect of the present disclosure is in addition to the first aspect,
The potential that the fifth connection point can take is three of the first potential, the intermediate potential, and the second potential,
The potential of the fifth connection point may be changed stepwise.

  The potential at the fifth connection point of the second aspect is a specific example of the potential at the fifth connection point.

The third aspect of the present disclosure is in addition to the first aspect or the second aspect,
The controller includes a controller and a voltage sensor.
The voltage sensor detects a voltage of the load when the load is connected to the output end,
The controller includes the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth. A power supply apparatus is provided, which causes a detection value of the voltage sensor to follow a target value by controlling switching of a switching element.

  According to the third aspect, the voltage of the load can be made to follow the target value while monitoring the voltage of the load.

The fourth aspect of the present disclosure is in addition to any one of the first to third aspects.
In the series transformer, when the potential of the one end of the secondary winding becomes higher than the potential of the other end of the secondary winding, the potential of the one end of the first primary winding is The potential of the other end of the first primary winding is higher than the potential of the other end of the first primary winding, and the potential of the other end of the second primary winding is greater than the potential of the one end of the second primary winding Too high,
The voltage at the one end of the input end relative to the other end of the input end is defined as an input voltage, and the voltage at the one end of the secondary winding relative to the other end of the secondary winding is a secondary winding When the amplitude of the detected value is larger than the amplitude of the input voltage when defined as a voltage, the phase of the input voltage and the phase of the secondary winding voltage are in phase, and the amplitude of the detected value is the same. A power supply device is provided in which the phase of the input voltage and the phase of the secondary winding voltage are opposite to each other when the amplitude is smaller than the amplitude of the input voltage.

  The operation of the fourth aspect is one specific example of the operation of the power supply device.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

Embodiment 1
FIG. 1 is a configuration diagram of a power supply device according to the embodiment. Hereinafter, the configuration of the power supply device 1 according to the embodiment will be described with reference to FIG. 1 and the like.

  The power supply device 1 includes a first switching element 2a, a second switching element 2b, a third switching element 2c, a fourth switching element 2d, a fifth switching element 2e, a sixth switching element 2f, a seventh switching element 2g and an eighth switching. It has the element 2h. The power supply device 1 includes a first diode 3a, a second diode 3b, a third diode 3c, a fourth diode 3d, a fifth diode 3e, a sixth diode 3f, a seventh diode 3g, an eighth diode 3h and a pair of clamp diodes 25. have. The power supply device 1 includes a first reactor 16 a and a second reactor 16 b. The power supply device 1 includes a first capacitor 20, a pair of capacitors 21, a fourth capacitor 18a, and a fifth capacitor 18b. The power supply device 1 includes a series transformer 17. The power supply device 1 includes a voltage sensor 27 and a controller 28. The power supply device 1 has an input end 31 and an output end 32.

  The input end 31 may be connected to the input power supply 15. The input power supply 15 supplies an AC voltage to the input end 31. The input power supply 15 is, for example, a commercial power supply. Output end 32 may be connected to load 26. The output end 32 supplies an alternating voltage to the load 26. In the example of FIG. 1, the input power supply 15, the load 26, and the power supply device 1 are connected by single-phase two-wire wiring.

  In the power supply device 1, a first circuit 4 in which the first switching element 2a and the first diode 3a are connected in antiparallel is configured. A second circuit 5 is configured in which the second switching element 2b and the second diode 3b are connected in antiparallel. A third circuit 7 is configured in which the third switching element 2c and the third diode 3c are connected in antiparallel. A fourth circuit 8 in which the fourth switching element 2d and the fourth diode 3d are connected in antiparallel is configured. A fifth circuit 10 in which the fifth switching element 2e and the fifth diode 3e are connected in antiparallel is configured. A sixth circuit 11 is configured in which the sixth switching element 2 f and the sixth diode 3 f are connected in antiparallel. A seventh circuit 12 is configured in which the seventh switching element 2g and the seventh diode 3g are connected in antiparallel. An eighth circuit 13 is configured in which the eighth switching element 2h and the eighth diode 3h are connected in antiparallel.

  Note that “switching element and diode are connected in reverse parallel” means switching so that the direction of the forward current of the diode and the direction of the current flowing through the switching element when the switching element is on are opposite to each other. It indicates that elements and diodes are connected in parallel.

  A first arm 6 is configured in which a first circuit 4, a first connection point p1, and a second circuit 5 are connected in series in this order. A second arm 9 is configured in which the third circuit 7, the second connection point p2, and the fourth circuit 8 are connected in series in this order. The fifth circuit 10, the third connection point p3, the sixth circuit 11, the fifth connection point p5, the seventh circuit 12, the fourth connection point p4, and the eighth circuit 13 are connected in series in this order. The third arm 14 is configured.

  The series transformer 17 has a first primary winding 17a, a second primary winding 17b and a secondary winding 17c.

  The turns ratio between the secondary winding 17c and the first primary winding 17a is m: 1. The turns ratio between the secondary winding 17c and the second primary winding 17b is m: 1. m is a value larger than 1 and is, for example, 5 to 30. The number of turns of the first primary winding 17a and the number of turns of the second primary winding 17b may be the same or different. In the present embodiment, the number of windings is the same. In the modification in which the input power supply 15, the load 26, and the power supply device 1 are connected by single-phase three-wire wiring, if the number of windings is the same, it is easy to ensure voltage balance.

  In the series transformer 17, when one end 17cx of the secondary winding 17c is at a higher potential than the other end 17cy of the secondary winding 17c, one end 17ax of the first primary winding 17a is a first one. The potential is higher than that of the other end 17ay of the winding 17a. In the series transformer 17, when one end 17cx of the secondary winding 17c is at a higher potential than the other end 17cy of the secondary winding 17c, the one end 17bx of the second primary winding 17b is the second The potential is lower than the other end 17by of the primary winding 17b.

  The pair of capacitors 21 are connected in series via the sixth connection point p6. Hereinafter, one of the pair of capacitors 21 may be referred to as a second capacitor 21 a. Also, the other of the pair of capacitors 21 may be referred to as a third capacitor 21 b.

  The pair of clamp diodes 25 are connected in series via a seventh connection point p7. Hereinafter, one of the pair of clamp diodes 25 may be referred to as a first clamp diode 25a. Also, the other of the pair of clamp diodes 25 may be referred to as a second clamp diode 25 b.

  The seventh connection point p7 is connected to the sixth connection point p6. Specifically, the seventh connection point p7 is connected to the sixth connection point p6 at the same potential.

  The first arm 6, the second arm 9, the third arm 14, the first capacitor 20, and the pair of capacitors 21 are connected in parallel to one another.

  The series circuit of the sixth circuit 11 and the seventh circuit 12 and the pair of clamp diodes 25 are connected in parallel between the third connection point p3 and the fourth connection point p4. That is, a pair of clamp diodes 25 exist on the path connecting the third connection point p3 and the fourth connection point p4. Specifically, in this path, the third connection point p3, the cathode of the first clamp diode 25a, the anode of the first clamp diode 25a, the seventh connection point p7, and the cathode of the second clamp diode 25b, The anode of the second clamp diode 25b and the fourth connection point p4 are arranged in this order.

  A path connecting the input end 31, the first primary winding 17a and the output end 32 is configured. In this path, one end 31x of the input end 31, the one end 17ax of the first primary winding 17a, the other end 17ay of the first primary winding 17a, and one end 32x of the output end 32 They are arranged in order.

  A path connecting the output end 32, the second primary winding 17b and the input end 31 is configured. In this path, the other end 32y of the output end 32, the other end 17by of the second primary winding 17b, the one end 17bx of the second primary winding 17b, and the other end 31y of the input end 31 Are arranged in this order.

  A path connecting the first connection point p1, the first reactor 16a, and the input end portion 31 is configured. In this path, the first connection point p1, one end 16ax of the first reactor 16a, the other end 16ay of the first reactor 16a, and one end 31x of the input end 31 are arranged in this order.

  A path connecting the second connection point p2, the second reactor 16b, the secondary winding 17c, and the input end portion 31 is configured. In this path, the second connection point p2, one end 16bx of the second reactor 16b, the other end 16by of the second reactor 16b, one end 17cx of the secondary winding 17c, and the other end 17cy of the secondary winding 17c The fifth connection point p5 and the other end 31y of the input end 31 are arranged in this order.

[Switching elements 2a to 2h]
Known switching elements can be used as the switching elements 2a to 2h. In the present embodiment, the switching elements 2a to 2h are MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), specifically, n-channel MOSFETs. However, the switching elements 2a to 2h may be p-channel MOSFETs. Hereinafter, switching elements 2a to 2h may be referred to as MOSFETs 2a to 2h.

  In the present embodiment, in the first arm 6, the first switching element 2a and the second switching element 2b are connected in series via the first connection point p1. Specifically, the drain of the first MOSFET 2a, the source of the first MOSFET 2a, the first connection point p1, the drain of the second MOSFET 2b, and the source of the second MOSFET 2b are arranged in this order.

  In the present embodiment, in the second arm 9, the third switching element 2c and the fourth switching element 2d are connected in series via the second connection point p2. Specifically, the drain of the third MOSFET 2c, the source of the third MOSFET 2c, the second connection point p2, the drain of the fourth MOSFET 2d, and the source of the fourth MOSFET 2d are arranged in this order.

  In the present embodiment, in the third arm 14, the fifth switching element 2e, the sixth switching element 2f, the seventh switching element 2g, and the eighth switching element 2h are connected in series in this order. A third connection point p3 exists between the fifth switching element 2e and the sixth switching element 2f. A fifth connection point p5 is present between the sixth switching element 2f and the seventh switching element 2g. A fourth connection point p4 exists between the seventh switching element 2g and the eighth switching element 2h. Specifically, the drain of the fifth MOSFET 2e, the source of the fifth MOSFET 2e, the third connection point p3, the drain of the sixth MOSFET 2f, the source of the sixth MOSFET 2f, the fifth connection point p5, the drain of the seventh MOSFET 2g, the source of the seventh MOSFET 2g, the fourth connection The point p4, the drain of the eighth MOSFET 2h and the source of the eighth MOSFET 2h are arranged in this order.

[Diodes 3a to 3h]
The diodes 3a to 3h are freewheeling diodes. Well-known diodes can be used as the diodes 3a to 3h.

  In the present embodiment, in the first arm 6, the first diode 3a and the second diode 3b are connected in series via the first connection point p1. Specifically, the cathode of the first diode 3a, the anode of the first diode 3a, the first connection point p1, the cathode of the second diode 3b, and the anode of the second diode 3b are arranged in this order.

  In the present embodiment, in the second arm 9, the third diode 3c and the fourth diode 3d are connected in series via the second connection point p2. Specifically, the cathode of the third diode 3c, the anode of the third diode 3c, the second connection point p2, the cathode of the fourth diode 3d, and the anode of the fourth diode 3d are arranged in this order.

  In the present embodiment, in the third arm 14, the fifth diode 3e, the sixth diode 3f, the seventh diode 3g, and the eighth diode 3h are connected in series in this order. A third connection point p3 exists between the fifth diode 3e and the sixth diode 3f. A fifth connection point p5 is present between the sixth diode 3f and the seventh diode 3g. A fourth connection point p4 exists between the seventh diode 3g and the eighth diode 3h. Specifically, the cathode of the fifth diode 3e, the anode of the fifth diode 3e, the third connection point p3, the cathode of the sixth diode 3f, the anode of the sixth diode 3f, the fifth connection point p5, and the seventh diode 3g The cathode, the anode of the seventh diode 3g, the fourth connection point p4, the cathode of the eighth diode 3h, and the anode of the eighth diode 3h are arranged in this order.

[Capacitors 20, 21a and 21b]
Well-known capacitors can be used as the capacitors 20, 21a and 21b. In the present embodiment, the capacitance of the second capacitor 21 a and the capacitance of the third capacitor 21 b are the same.

[Clamp diodes 25a and 25b]
Well-known diodes can be used as the clamp diodes 25a and 25b.

  Clamp diodes 25a and 25b clamp the potentials of connection points p3 and p4 to a potential that follows the potentials of connection points p6 and p7.

[Capacitors 18a and 18b and Reactors 16a and 16b]
The fourth capacitor 18a and the first reactor 16a constitute a low pass filter (LC filter). The low pass filter reduces the ripple voltage on the side of the input power supply 15 in the power supply device 1. The fifth capacitor 18 b and the second reactor 16 b constitute a low pass filter (LC filter). The low pass filter reduces the ripple voltage on the secondary winding 17 c side of the power supply device 1.

[Control Definition and Control Overview]
The control performed in the present embodiment will be described below. In the following description, the voltage of the input power supply 15 may be referred to as an input voltage Vin. The input voltage Vin has a positive value when the potential at one end 31x of the input end 31 is higher than that at the other end 31y. The current flowing from the input power supply 15 to one end 31x of the input end 31 may be referred to as a current Iin.

  The voltage across the terminals of the first capacitor 20 may be referred to as a voltage Vdc1. Specifically, the voltage Vdc1 is a difference obtained by subtracting the potential of the other end 20y from the potential of the one end 20x of the first capacitor 20. The voltage between terminals of the second capacitor 21a may be referred to as a voltage Vdc2. Specifically, the voltage Vdc2 is a difference obtained by subtracting the potential of the other end 21ay from the potential of the one end 21ax of the second capacitor 21a. The voltage between terminals of the third capacitor 21b may be referred to as a voltage Vdc3. Specifically, the voltage Vdc3 is a difference obtained by subtracting the potential of the other end 21by from the potential of the one end 21bx of the third capacitor 21b. In the example of FIG. 1, one end 20x of the first capacitor 20, one end 21ax of the second capacitor 21a, and one end 21bx of the third capacitor 21b are positive-side ends. The other end 20y of the first capacitor 20, the other end 21ay of the second capacitor 21a, and the other end 21by of the third capacitor 21b are negative ends. Further, in the present embodiment, Vdc2 is half of Vdc1, and Vdc3 is also half of Vdc1. That is, Vdc2 = Vdc3 = 1/2 · Vdc1. For this reason, in the present embodiment, the potential of one end 20x of the first capacitor 20 is defined as a first potential, and the potential of the other end 20y of the first capacitor 20 is defined as a second potential. When an intermediate potential is defined as an intermediate potential, it can be said that the intermediate potential appears at the sixth connection point p6 (and the seventh connection point p7). Here, the “potential between the first potential and the second potential” indicates an average value of the first potential and the second potential. That is, the intermediate potential indicates the same average value.

  The supply voltage to the load 26 may be described as Vout. Vout takes a positive value when one end 32x side of the output end portion 32 has a higher potential than the other end 32y side. The current flowing from one end 32x of the output end 32 to the load 26 may be referred to as a current Iout.

  The voltage at the first connection point p1 with respect to the other end 20y of the first capacitor 20 may be referred to as a voltage Vc. The voltage at the fifth connection point based on the other end 20y of the first capacitor 20 may be referred to as a voltage Vn. The voltage at the second connection point with reference to the other end 20y of the first capacitor 20 may be referred to as Vinv.

  The current flowing from the other end 16ay to the one end 16ax may be referred to as a current ILin. The current flowing from the one end 16bx to the other end 16by of the second reactor 16b may be referred to as ILout.

  In the following, it is assumed that the inductances of the first reactor 16a and the second reactor 16b are both L for simplification of the description. In the present embodiment, the circuit equation of Equation 1 holds.

  By the way, the voltage of the commercial power supply is obliged to fall within a predetermined management range. Specifically, the voltage of the commercial power supply is obliged to be within the range of 202V ± 20V for 200V system and within 101V ± 6V for 100V system. In the distribution line, the voltage of the distribution line decreases as it travels from the sending side to the terminal side due to the impedance of the distribution line and the current flow. In order to set the voltage at the terminal side to the lower limit of the control range or more, the voltage on the sending side is generally set to a higher value within the control range. In addition to the voltage distribution between the delivery side and the end side, the momentary fluctuation of the energizing current due to load fluctuation is combined, and the voltage of the commercial power supply usually changes depending on the place and time. It is. For this reason, the voltage of the commercial power supply does not always have the expected value. This means that when a commercial power supply is used as the input power supply 15, the input voltage Vin does not always take the expected value. Specifically, when the input power supply 15 is a 200V commercial power supply, the input voltage Vin is not necessarily 200V in a strict sense, and may be slightly deviated from 200V depending on the place and the time zone. The same applies to the case where the input power supply 15 is a 100 V commercial power supply. If the supply voltage Vout to the load 26 is not adjusted, this deviation may cause the supply voltage Vout to deviate from an expected value. For example, when the supply voltage Vout becomes larger than expected due to the input voltage Vin being larger than expected, power consumption such as standby power in the load 26 becomes large. The deviation of the input voltage Vin can occur also when the input power supply 15 is a power supply other than a commercial power supply.

  The power supply device 1 according to the present embodiment can alleviate or eliminate the above-mentioned problem derived from the deviation of the input voltage Vin. Specifically, the power supply device 1 detects the supply voltage Vout using the voltage sensor 27. Then, when the detected value of the supply voltage Vout is larger than the target value, the power supply device 1 performs control to reduce the supply voltage Vout. More specifically, in this case, the power supply device 1 sets the phase of the voltage at one end 17cx with respect to the other end 17cy of the secondary winding 17c to be in phase with the phase of the input voltage Vin. As a result, the supply voltage Vout becomes lower than the input voltage Vin, and the supply voltage Vout can be brought close to the target value. Specifically, the supply voltage Vout can be matched to the target value. By operating the power supply device 1 in this manner, unnecessary increase in power consumption can be avoided. That is, the power supply device 1 can function as a power saving device.

  However, when the detection value of the supply voltage Vout by the voltage sensor 27 is smaller than the target value, the power supply device 1 can also perform control to increase the supply voltage Vout. Specifically, in this case, the power supply device 1 can make the phase of the voltage of the one end 17cx with respect to the other end 17cy of the secondary winding 17c opposite to the phase of the input voltage Vin. As a result, the supply voltage Vout becomes higher than the input voltage Vin, and the supply voltage Vout can be brought close to the target value. Specifically, the supply voltage Vout can be matched to the target value.

  In the present embodiment, the target value of the supply voltage Vout is the same as the value (200 V or 100 V in the above example) assumed as the input voltage Vin. However, the target value of the supply voltage Vout may be different from the assumed value of the input voltage Vin depending on the input voltage specification on the load side and the like. For example, when the input power supply 15 is a 200 V commercial power supply, the target value of the supply voltage Vout may be 200 V, higher than 200 V, or lower than 200 V. The same applies to the case where the input power supply 15 is a 100 V commercial power supply.

[Controller 28]
In the present embodiment, the controller 28 cooperates with the voltage sensor 27 to perform the above-mentioned control to bring the supply voltage Vout closer to the target value (specifically, to match). Specifically, the voltage sensor 27 detects the voltage of the load 26 when the load 26 is connected to the output end 32. The controller 28 includes a first switching element 2a, a second switching element 2b, a third switching element 2c, a fourth switching element 2d, a fifth switching element 2e, a sixth switching element 2f, a seventh switching element 2g and an eighth switching. By controlling the switching of the element 2h, the detection value of the voltage sensor 27 is made to follow the target value.

  Specifically, the controller 28 controls the switching elements 2a to 2h based on pulse width modulation. Hereinafter, switching of the switching elements 2a to 2h will be described.

  First, control of the switching elements 2a, 2b and 2e to 2h present in the first arm 6 and the third arm 14 will be described. The controller 28 determines the on / off timing of the switching elements 2a, 2b and 2e to 2h by comparing the carrier wave and the modulation factor. The controller 28 has elements for determining the modulation factor. Specifically, as shown in FIG. 2, the controller 28 includes a subtraction unit 41, a proportional integral control unit (PI control unit) 42, a subtraction unit 43, and a proportional integral control unit (PI control unit) 44; A division unit 45 and a modulation factor setting unit 46 are provided. In the present specification, the modulation rate is used in the same meaning as the modulation wave.

  The operation of each element shown in FIG. 2 will be described below. In addition, although the combination of the 1st arm 6 and the 3rd arm 14 can function as a bidirectional | two-way converter, below, the case where this combination functions as a regenerative converter is demonstrated. That is, the case where control to make the supply voltage Vout lower than the input voltage Vin is performed will be described. By the following control, the inter-terminal voltage Vdc1 of the first capacitor 20 becomes substantially constant, and the power is regenerated to the input power supply 15.

  The subtracting unit 41 calculates the difference (difference voltage) between the voltage Vdc1 and the target voltage value Vdc_ref. The voltage Vdc1 is detected by a voltage sensor (not shown). The way of providing the target voltage value Vdc_ref is not particularly limited. The target voltage value Vdc_ref is given to the controller 28 from the outside of the controller 28 in one example.

  The PI control unit 42 calculates a command current ILin_ref which brings the differential voltage close to zero (specifically, converges to zero) by proportional integral control. The command current ILin_ref is a command value (target value) of the current ILin.

  The subtracting unit 43 calculates a difference (difference current) obtained by subtracting the current ILin from the command current ILin_ref. The current ILin is detected by a current sensor (not shown).

  The PI control unit 44 calculates an inter-line voltage command value Vm_ref which brings the differential current close to zero (specifically, converges to zero) by proportional integral control. The line voltage command value Vm_ref is a command value (target value) of the line voltage between the first arm 6 and the third arm 14. The line voltage between the first arm 6 and the third arm 14 is a difference obtained by subtracting the voltage Vn of the fifth connection point p5 from the voltage Vc of the first connection point p1.

  The dividing unit 45 calculates the modulation factor m_ref of the first arm 6 and the third arm 14 by dividing the line voltage command value Vm_ref by the detected value of the voltage Vdc1. The modulation factor m_ref is a signal synchronized with the phase of the input power supply 15.

  The modulation factor setting unit 46 sets the modulation factor of the first arm 6 and the third arm 14 in the current control cycle to m_ref.

  The controller 28 repeats the above control using the elements shown in FIG. 2 at predetermined intervals. Thus, the modulation factor m_ref is sequentially set. That is, the modulation rate m_ref is successively updated. The set modulation factor m_ref is given to a comparator (not shown).

  The comparison unit controls the switching elements 2a, 2b and 2e to 2h by comparing the modulation factor m_ref set as described above with the carrier wave.

  Specifically, as shown in FIG. 3, the comparison unit controls the first switching element 2 a and the second switching element 2 b by comparing the first carrier with the modulation factor m_ref. The first carrier extends in both positive and negative directions from the zero point, and is a wave having a desired amplitude larger than that of the modulation wave m_ref. The zero point corresponds to the straight line extending left and right in FIG. During a period in which the modulation wave is higher than the first carrier wave, the first switching element 2a is turned on and the second switching element 2b is turned off. While the modulation wave is lower than the first carrier wave, the first switching element 2a is turned off and the second switching element 2b is turned on. That is, the second switching element 2b is turned on complementarily to the first switching element 2a. In FIG. 3, the stage described as “2a” indicates the on / off timing of the first switching element 2a. The stage described as "2b" represents the on / off timing of the second switching element 2b.

  The comparison unit controls the fifth switching element 2e and the seventh switching element 2g by comparing the second carrier wave with the modulation factor m_ref, as shown in FIG. The second carrier is a wave that extends from the zero point only in the negative direction. The zero point corresponds to the straight line extending left and right in FIG. During a period in which the modulation wave is higher than the second carrier wave, the fifth switching element 2e is turned off and the seventh switching element 2g is turned on. During a period in which the modulation wave is lower than the second carrier wave, the fifth switching element 2e is turned on and the seventh switching element 2g is turned off. That is, the seventh switching element 2g is turned on complementarily to the fifth switching element 2e. In FIG. 4, the stage described as “2e” indicates the on / off timing of the fifth switching element 2e. The stage described as "2g" represents the on / off timing of the seventh switching element 2g.

  The comparison unit controls the sixth switching element 2f and the eighth switching element 2h by comparing the third carrier wave with the modulation factor m_ref as shown in FIG. The third carrier is a wave which has the same amplitude as the second carrier, is in phase synchronization with the second carrier, and extends only in the positive direction from the zero point. During a period in which the modulation wave is higher than the third carrier wave, the sixth switching element 2 f is turned off and the eighth switching element 2 h is turned on. The sixth switching element 2 f is turned on and the eighth switching element 2 h is turned off in a period in which the modulation wave is lower than the third carrier wave. That is, the eighth switching element 2h is turned on complementarily to the sixth switching element 2f. In FIG. 4, the stage described as “2 f” indicates the on / off timing of the sixth switching element 2 f. The stage described as "2h" represents the on / off timing of the eighth switching element 2h.

  By switching of the switching elements 2e to 2h shown in FIG. 4, the voltage Vn can take three levels of 0, 1/2 · Vdc1 and Vdc1. That is, the third arm 14 functions as an arm having three levels.

  Next, control of the switching elements 2c and 2d in the second arm 9 will be described.

  The controller 28 has a control block for controlling switching of the switching element of the second arm 9. In this control block, first, the voltage sensor 27 detects the supply voltage Vout to the load 26. Thereby, a detected value of the supply voltage Vout is obtained. Next, this detected value is used to calculate the effective value Vout_rms of the supply voltage Vout. A difference voltage is obtained by subtracting the calculated effective value from the voltage effective value command value Vout_ref_rms. The voltage effective value command value Vout_ref_rms is a command value (target value) of the voltage effective value Vout_rms. The obtained differential voltage is multiplied by a gain derived from the turns ratio of the series transformer 17 and further multiplied by sinwt. Thereby, a command value (target value) of a target voltage of the secondary winding 17c, that is, a voltage difference between the voltage Vinv at the second connection point p2 and the voltage Vn at the fifth connection point p5 is obtained. The above gain is m / 2. Further, sinwt is a synchronization signal calculated from the voltage phase of the input power supply 15. sin is a sine function. w is the angular velocity of the voltage of the input power supply 15; t is time. The voltage phase of the input power supply 15 can be detected by a sensor (not shown).

  As understood from the above description, the difference between the voltage Vc of the first connection point p1 and the voltage Vn of the fifth connection point p5 is the command value (the target value based on the modulation factor m_ref described with reference to FIG. Control of switching of the switching elements 2a, 2b and 2e to 2h of the first arm 6 and the third arm 14 is performed so as to be. Along with this control, the control of the switching of the switching elements 2c and 2d of the second arm 9 is made to match the difference between the voltage Vinv at the second connection point p2 and the voltage Vn at the fifth connection point p5. To be done. Thus, the voltage Vinv at the second connection point p2 is controlled together with the voltage Vc at the first connection point p1 and the voltage Vn at the fifth connection point p5. Since the amplitudes of the voltages Vc, Vn and Vinv depend on the duty of each arm, they can be variably controlled individually.

  In this manner, the difference between the voltage Vinv at the second connection point p2 and the voltage Vn at the fifth connection point p5 is controlled. That is, the line voltage between the second arm 9 and the third arm 14 is controlled. By this control, the voltage of the secondary winding 17c is controlled to a desired voltage. In the present embodiment, the phase of the voltage at one end 17cx with respect to the other end 17cy of the secondary winding 17c is in phase with the phase of the input voltage Vin. The phase of the voltage at one end 17ax with respect to the other end 17ay of the first primary winding 17a is in phase with the phase of the input voltage Vin, and the voltage at one end 17bx with respect to the other end 17by of the second primary winding 17b The phase is opposite to the phase of the input voltage Vin.

  By setting the voltage phase in the series transformer 17 as described above, the supply voltage Vout decreases and approaches the target value. The current flows in the second reactor 16b from the other end 16by toward the one end 16bx. Specifically, as understood from the lower equation of Equation 1, the current ILout has a magnitude of 1 / m times the current Iout. That is, a current of that magnitude flows from the other end 16by toward the one end 16bx of the second reactor 16b. As described above, according to the present embodiment, the power supply is performed in the case where the supply voltage Vout is higher than the input voltage Vin by the simple control of the control of the line voltage between the second arm 9 and the third arm 14. It is possible to cause the device 1 to perform a regenerative operation, flow a regenerative current, and reduce the supply voltage Vout. Further, when the supply voltage Vout is lower than the input voltage Vin, the power supply device 1 is caused to perform the powering operation by reversing the positive and negative of the voltage between the lines, thereby causing the powering current to flow and raise the supply voltage Vout. You can also.

  In short, in the series transformer 17 according to the present embodiment, when the potential at one end 17cx of the secondary winding 17c becomes higher than the potential at the other end 17cy of the secondary winding 17c, the first primary winding The potential of one end 17ax of 17a is higher than the potential of the other end 17ay of the first primary winding 17a, and the potential of the other end 17by of the second primary winding 17b is the second primary winding It becomes higher than the potential of one end 17bx of 17b. The voltage at one end 31x of the input end 31 to the other end 31y of the input end 31 is defined as the input voltage Vin, and the voltage at one end 17cx of the secondary winding 17c to the other end 17cy of the secondary winding 17c is secondary When the line voltage is defined and the amplitude of the detected value is larger than the amplitude of the input voltage Vin, the phase of the input voltage Vin and the phase of the secondary winding voltage are in phase, and the amplitude of the detected value is the input voltage Vin. Of the input voltage Vin and the phase of the secondary winding voltage may be opposite to each other.

  The command value (target value) of Vinv can also be calculated based on Equation 1. Specifically, in the middle equation of Equation 1, Vin and ILout can be detected by a sensor not shown. m is known. Since the switching pattern of the switching element of the third arm 14 is determined based on the modulation factor m_ref, the midpoint voltage Vn of the third arm 14 is also known. Therefore, the command voltage of Vinv can be calculated by substituting the command voltage Vout_ref which is the command value (target value) into Vout of Expression 1.

  By controlling the switching of the switching elements 2 a to 2 h by the controller 28, the voltage of each part of the power supply device 1 makes time transition as shown in FIG. 5. Specifically, the first stage in FIG. 5 shows the time transition of the voltage Vc at the first connection point p1. The second stage shows the time transition of the voltage Vn at the fifth connection point p5. The third stage shows the line voltage between the first arm 6 and the third arm 14, that is, the difference between the voltage Vc and the voltage Vn. The fourth stage shows the voltage Vinv at the second connection point p2. The fifth stage shows the line voltage between the second arm 9 and the third arm 14, that is, the difference between the voltage Vinv and the voltage Vn.

  As shown in FIG. 5, the voltage Vn at the fifth connection point p5 is multileveled. Specifically, the voltage Vn can take three voltages in three steps of the voltage Vdc, and the voltage Vn is determined based on the switching pattern of the switching elements 2e to 2h. More specifically, as shown in FIG. 5, the voltage Vn can take three voltages: zero voltage, Vdc / 2 and Vdc. In the present embodiment, the potential of one end 20x of the first capacitor 20 is defined as a first potential, and the potential of the other end 20y of the first capacitor 20 is defined as a second potential, and the intermediate between the first and second potentials. If the potential of the fifth connection point p5 is defined as an intermediate potential, there are three potentials that the fifth connection point p5 can take: the first potential, the intermediate potential, and the second potential, and the potential at the fifth connection point p5 changes stepwise. It can be said.

  On the other hand, the voltage Vc at the first connection point p1 can have two voltages, zero and Vdc. The voltages that can be taken by the voltage Vinv at the second connection point p2 are also two, zero and Vdc. Therefore, as shown in FIG. 5, the line voltage between the first arm 6 and the third arm 14 which is a difference obtained by subtracting the voltage Vn from the voltage Vc can take three levels. Further, the line voltage between the second arm 9 and the third arm 14 which is a difference obtained by subtracting the voltage Vn from the voltage Vinv can also have three levels.

  As described above, the power supply device 1 described in the present embodiment includes the first arm 6, the second arm 9, and the third arm 14 which is divided into three levels. The combination of the first arm 6 and the third arm 14 provides the power supply 1 with the function of a single-phase three-level bidirectional converter. At the time of regeneration, the combination of the second arm 9 and the third arm 14 converts AC regenerative power in the series transformer 17 into DC power supplied to the first capacitor 20. Then, the combination of the first arm 6 and the third arm 14 causes power regeneration from the first capacitor 20 to the input power supply 15. Also, while such power regeneration is performed, the voltage of the secondary winding 17c of the series transformer 17 is controlled. Through voltage control of the secondary winding 17c, the voltage of the primary windings 17a and 17b is controlled, and the supply voltage Vout to the load 26 is controlled.

  In addition, since the third arm 14 is tri-leveled, the inter-line voltage on the input power supply 15 side, that is, the inter-line voltage between the first arm 6 and the third arm 14 is tri-leveled. Further, the line voltage on the series transformer 17 side, that is, the line voltage between the second arm 9 and the third arm 14 is also tri-leveled. The tri-leveling of the voltage between both lines on the input power source 15 side and the series transformer 17 side reduces the ripple voltage derived from the carrier component corresponding to the switching frequency on both the input power source 15 side and the load 26 side. That is, noise is reduced. For this reason, small capacity reactors can be used as the reactors 16a and 16b. Also, small-capacitance capacitors can be used as the capacitors 18a and 18b. That is, a waveform shaping filter can be configured on each of the input power supply 15 side and the secondary winding 17 c side of the series transformer 17 by the small capacity reactor and capacitor.

  A reactor may be provided between the fifth connection point p5 and the other end 31y of the input end portion 31. Similarly, a reactor may be provided between the fifth connection point p5 and the other end 17cy of the secondary winding 17c of the series transformer 17. In this way, the common mode voltage can be reduced.

  Further, in the present embodiment, the third leveled third arm 14 is shared by the single-phase three-level converter and the three-level inverter (if this sharing is not performed, the number of arms required for the converter and the inverter) Becomes 2 × 2 = 4, and the number of required switching elements also increases). This makes it possible to reduce the ripple voltage of the carrier component corresponding to the switching frequency on both the input power supply 15 side and the load 26 side while suppressing the number of switching elements required for AC-AC conversion.

  In the present embodiment, switching elements 2a to 2h are MOSFETs. However, other elements such as IGBTs (Insulated Gate Bipolar Transistors) can also be used as the switching elements 2a to 2h.

  The switching elements 2a to 2h may use a compound semiconductor such as SiC or GaN material. Such switching elements 2a to 2h are suitable for increasing the switching frequency. By increasing the switching frequency, it is possible to reduce the ripple voltage derived from the carrier component corresponding to the switching frequency on both the input power supply 15 side and the load 26 side. Therefore, the capacitances of reactors 16a and 16b and capacitors 18a and 18b can be reduced. In addition, the conduction loss can be reduced by increasing the switching frequency. In addition, when the switching frequency is increased, the switching time is shortened, so that the switching loss can be reduced. Due to the reduction of the conduction loss and the switching loss, even when the cooling fins are attached to the power supply device 1, the cooling fins can be miniaturized.

  As described above, the controller 28 includes a control block for controlling switching of the switching elements of the first arm 6 and the third arm 14, and a control block for controlling switching of the switching elements of the second arm 9. ,have. In order to increase the voltage utilization, these control blocks in the controller 28 may be provided with means for superimposing a common mode voltage on each phase.

  The power supply apparatus according to the above embodiment is an AC-AC power supply apparatus in which the number of switching elements used is small and ripples are small at both input and output, and is useful as a distributed power supply, various power supply apparatuses, and the like.

1 power supply devices 2a, 2b, 2c, 2d, 2f, 2g, 2h, 101a, 101b, 101c, 101e, 101f switching elements 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 102a, 102b, 102c, 102d, 102e, 102f Diodes 4, 5, 7, 8, 10, 11, 12, 13 Circuits 6, 9, 14, 103, 104, 105 Arms 15, 107 Power Supplies 16a, 16b, 109a, 109b, 109c, 109d Reactors 17, 108 Series transformers 17a, 17b, 108a, 108b Primary windings 17c, 108c Secondary windings 18a, 18b, 20, 21, 21a, 21b, 106, 110a, 110b Capacitors 25, 25a, 25b Clamp diode 26, 111 Load 27 Voltage sensor 31 input Part 32 output end 28 controller 41, 43 subtraction unit 42, 44 PI controller 45 dividing unit 46 modulation factor setting unit p1, p2, p3, p4, p5, p6, p7, q1, q2, q3 connection point

Claims (4)

What is claimed is: 1. A power supply device, to which an input power source is connected at an input end and a load is connected at an output end
A first circuit in which the first switching element and the first diode are connected in antiparallel, a first connection point, and a second circuit in which the second switching element and the second diode are connected in antiparallel are connected in series in this order And the first arm
A third circuit in which the third switching element and the third diode are connected in antiparallel, a second connection point, and a fourth circuit in which the fourth switching element and the fourth diode are connected in antiparallel are connected in series in this order And the second arm
A fifth circuit in which a fifth switching element and a fifth diode are connected in antiparallel, a third connection point, a sixth circuit in which a sixth switching element and a sixth diode are connected in antiparallel, and a fifth connection point; A seventh circuit in which the seventh switching element and the seventh diode are connected in antiparallel, a fourth connection point, and an eighth circuit in which the eighth switching element and the eighth diode are connected in antiparallel are connected in series in this order And the third arm
A series transformer having a first primary winding, a second primary winding and a secondary winding;
A first reactor,
A second reactor,
A first capacitor,
A pair of capacitors connected in series via a sixth connection point,
And a pair of clamp diodes connected in series via a seventh connection point connected to the sixth connection point,
The first arm, the second arm, the third arm, the first capacitor, and the pair of capacitors are connected in parallel with one another.
The series circuit of the sixth circuit and the seventh circuit, and the pair of clamp diodes are connected in parallel between the third connection point and the fourth connection point,
In a path connecting the input end, the first primary winding, and the output end, one end of the input end, one end of the first primary winding, and the first primary The other end of the winding and one end of the output end are arranged in this order,
In the path connecting the output end, the second primary winding, and the input end, the other end of the output end, the other end of the second primary winding, and the second One end of the primary winding and the other end of the input end are arranged in this order,
In the path connecting the first connection point, the first reactor and the input end, the first connection point, one end of the first reactor, the other end of the first reactor, and the input end The ends are arranged in this order,
In a path connecting the second connection point, the second reactor, the secondary winding, and the input end, the second connection point, one end of the second reactor, and the other end of the second reactor One end of the secondary winding, the other end of the secondary winding, the fifth connection point, and the other end of the input end portion are arranged in this order,
The potential at one end of the first capacitor is defined as a first potential, the potential at the other end of the first capacitor is defined as a second potential, and a potential intermediate between the first potential and the second potential is an intermediate potential. The power supply device as defined, wherein the intermediate potential appears at the sixth connection point. The potential that the fifth connection point can take is three of the first potential, the intermediate potential, and the second potential,
The power supply device according to claim 1, wherein the potential of the fifth connection point changes stepwise. The controller includes a controller and a voltage sensor.
The voltage sensor detects a voltage of the load when the load is connected to the output end,
The controller includes the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth. The power supply device according to claim 1, wherein the detection value of the voltage sensor is made to follow a target value by controlling switching of a switching element. In the series transformer, when the potential of the one end of the secondary winding becomes higher than the potential of the other end of the secondary winding, the potential of the one end of the first primary winding is The potential of the other end of the first primary winding is higher than the potential of the other end of the first primary winding, and the potential of the other end of the second primary winding is greater than the potential of the one end of the second primary winding Too high,
The voltage at the one end of the input end relative to the other end of the input end is defined as an input voltage, and the voltage at the one end of the secondary winding relative to the other end of the secondary winding is a secondary winding When the amplitude of the detection value is larger than the amplitude of the input voltage when defined as a voltage, the phase of the input voltage and the phase of the secondary winding voltage are in phase.
The phase of the said input voltage and the phase of the said secondary winding voltage become reverse phase, when the amplitude of the said detected value is smaller than the amplitude of the said input voltage. Power supply.

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