JP2012095408A - Step-up/step-down circuit and power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a step-up/step-down circuit in which miniaturization and cost reduction are realized while loss is reduced and to provide a power converter.SOLUTION: A step-up/step-down circuit 52 includes: a winding portion 11 which includes winding L1 and one or a plurality of windings L2 and L3, which are wound to a common core, and to which input voltage is applied; a voltage control portion 12 which switches on/off voltage applied to the first winding when the input voltage is first polarity; a voltage control portion 13 which switches on/off voltage applied to the second winding when the input voltage is second polarity; and a voltage smoothing portion 14 smoothing voltage outputted from the winding portion 11 when application of the voltage to the winding L1 is switched off in a state where the input voltage is the first polarity and voltage outputted from the winding portion 11 when the application of the voltage to the winding L2 is switched off in a state where the input voltage is the second polarity and outputting the voltage to a load.

Description

  The present invention relates to a step-up / down circuit and a power conversion device, and more particularly to a step-up / down circuit and a power conversion device having a power factor improving function.

  2. Description of the Related Art Power converters for charging driving main batteries such as electric vehicles (EV) and plug-in hybrid vehicles (HV) using ordinary household AC power have been developed.

  That is, one of the features of an electric vehicle and a plug-in hybrid car is that an in-vehicle battery can be charged using an external power source such as a household outlet. In order to charge a vehicle-mounted battery using an AC outlet of 100 V AC or 200 V AC, an AC / DC converter for converting AC voltage (AC) into DC voltage (DC) for the battery is required.

  Patent Document 1 below discloses an AC / DC converter that can increase or decrease the output DC voltage by changing the duty ratio by switching. According to the AC / DC converter, after the full-wave rectification is performed on the AC input in the step-up / step-down circuit, the release of the energy accumulated in the reactor is turned on / off by the chopper control by the switching, so that the step-up or step-down is performed. Obtain a possible DC output. Further, if the waveform of the current flowing through the reactor is controlled to be similar to the waveform of the input voltage by this on / off control, the power factor at the time of power conversion of the AC / DC converter can be improved.

Japanese Patent Laid-Open No. 10-304670

  The voltage used for the power source of the electric vehicle is higher than the voltage for household use, and the power capacity required for the components is also large. In the step-up / step-down circuit used in the power conversion device such as the AC / DC converter described in Patent Document 1, the diode bridge performs full-wave rectification on the AC input, and the switch element is full-wave rectified by the diode bridge. Switches whether or not voltage is applied to the reactor.

  However, when a full-wave rectifier circuit is provided before the step-up / step-down circuit, there are two diodes in the path for supplying power from the input side, so that a reduction in efficiency due to an increase in conduction loss becomes a problem. In addition, since a large load is applied to the switching element of the buck-boost circuit, it is necessary to use a switching element having a large power capacity or to connect and use a plurality of switching elements in parallel. The cost was increased.

  Furthermore, since the power converter used for the power supply of an electric vehicle is mounted in a motor vehicle, it is strongly desired to reduce the size of the device. Such downsizing and cost reduction of the apparatus size are demands not only for in-vehicle use but also for general electric equipment.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a step-up / step-down circuit and a power conversion device that can be reduced in size and cost while reducing loss.

  The step-up / step-down circuit according to the first aspect of the present invention is a step-up / step-down circuit for stepping up or stepping down an input voltage and supplying the input voltage to a load, and includes a first winding wound around a common core and 1 Or a plurality of second windings, the winding portion to which the input voltage is applied, and the input voltage applied to the first winding when the input voltage has the first polarity. A first voltage control unit for turning on and off, a second voltage control unit for turning on and off the input voltage applied to the second winding when the input voltage has a second polarity, and the input The voltage output from the winding section when the application of the input voltage to the first winding is turned off in a state where the voltage is the first polarity, and the input voltage is the second polarity Before the application of the input voltage to the second winding is turned off The voltage output from the winding portion is smoothed, characterized in that it comprises a smoothing unit for outputting to the load.

  According to the step-up / step-down circuit according to the first aspect, the first voltage control unit turns on / off the input voltage applied to the first winding when the input voltage has the first polarity. The second voltage control unit turns on and off the input voltage applied to the second winding when the input voltage has the second polarity. The application of the input voltage turns off the application of the voltage to the first winding when the input voltage is in the first polarity and the second winding when the input voltage is in the second polarity. When the application of voltage to the line is turned off, the winding section outputs a voltage. The smoothing unit smoothes the voltage output from the winding unit. Therefore, the power factor is improved by controlling the input current waveform and the input voltage waveform to be similar by the voltage control performed by the first voltage control unit and the second voltage control unit. Meanwhile, a boosted or stepped down DC voltage can be output. Therefore, the input voltage can be boosted or stepped down without using a full-wave rectifier circuit, so that the circuit can be reduced in size and cost while reducing the loss, and has a power factor improving function. A pressure circuit can be obtained.

  The step-up / step-down circuit according to the second aspect of the present invention is the voltage step-up / down circuit according to the first aspect, in particular, the voltage output from the winding portion is a voltage induced in the second winding. It is characterized by being.

  According to the step-up / step-down circuit according to the second aspect, since the first winding and the second winding are wound around a common core, when a voltage is applied to the first winding Also, a voltage is induced in the second winding. Therefore, by outputting the voltage induced in the second winding, it is possible to output a boosted or stepped down DC voltage while improving the power factor regardless of the polarity of the input voltage.

  The step-up / step-down circuit according to a third aspect of the present invention is the step-up / step-down circuit according to the first or second aspect, and in particular, the first voltage control unit is applied to the first winding. A first switch element that turns on and off the voltage by switching, and the second voltage control unit includes a second switch element that turns on and off the input voltage applied to the second winding, The first switch element is turned off when the input voltage has the second polarity, and the second switch element is turned off when the input voltage has the first polarity. And

  According to the step-up / step-down circuit according to the third aspect, the first voltage control unit turns on / off the input voltage applied to the first winding by switching by the first switch element. The second voltage control unit turns on and off the input voltage applied to the second winding by switching by the second switch element. When the input voltage has the second polarity, the first switch element is turned off and the input voltage is not applied to the first winding. Therefore, the voltage output from the winding unit by the switching by the second switch element is reduced. Can be turned on and off. When the input voltage has the first polarity, the second switch element is turned off and the input voltage is not applied to the second winding, so that the voltage output from the winding unit is turned on / off by switching by the second switch element. be able to. Therefore, the DC voltage output from the winding section can be changed to an arbitrary level by switching performed by the first switch element and the second switch element.

  The step-up / step-down circuit according to a fourth aspect of the present invention is the step-up / step-down circuit according to the third aspect, in particular, the first winding is connected to the first end of the first switch element. And a second end connected to the second end of the second switch element, the second winding is connected to the first end of the second switch element, And a second end connected to a second end of the first switch element.

  According to the step-up / down circuit according to the fourth aspect, the first switch element is connected between the first end of the first winding and the second end of the second winding. The second switch element is connected between the second end of the first winding and the first end of the second winding. Therefore, the electric circuit to which the input voltage is applied can be switched between the electric circuit to the first coil and the electric circuit to the second coil by switching the first switch element and the second switch element.

  The step-up / step-down circuit according to a fifth aspect of the present invention is the step-up / step-down circuit according to the fourth aspect, particularly the second step of the second end of the first winding and the second end of the second switch element. The input voltage is applied between the first connection node and the second connection node between the second end of the second winding and the second end of the first switch element, whereby the input voltage Current is supplied to the first winding via the first connection node when is at the first polarity, and the second connection node is when the input voltage is at the second polarity. A current is supplied to the second winding via the wire.

  According to the step-up / down circuit according to the fifth aspect, when the input voltage has the first polarity, a current is supplied to the first connection node between the second end of the first winding and the second switch element. Supplied. When the input voltage has the second polarity, a current is supplied to a second connection node between the second end of the second winding and the first switch element. Therefore, by controlling the switching of the first switch element and the second switch element, it is possible to supply current to different windings for each polarity of the input voltage, and it is easy to move up and down without the need for a full-wave rectifier circuit. A pressure circuit can be obtained.

  The step-up / down circuit according to a sixth aspect of the present invention is the step-up / down circuit according to any one of the first to fifth aspects, in particular, the first voltage control unit is configured such that the input voltage is the second voltage. A first cut-off circuit that cuts off a current supplied to the first winding via the first voltage control unit when the polarity is a polarity; the second voltage control unit includes the input voltage; And a second cutoff circuit that cuts off a current supplied to the second winding via the second voltage control unit when the first polarity is the first polarity.

  According to the step-up / down circuit according to the sixth aspect, the first cutoff circuit is supplied to the first winding via the first voltage controller when the input voltage has the second polarity. Cut off current. The second cutoff circuit cuts off the current supplied to the second winding via the second voltage control unit when the input voltage has the second polarity. Therefore, when the input voltage has the first polarity, no input voltage is applied to the second winding, and when the input voltage has the second polarity, no input voltage is applied to the first winding. Therefore, when the input voltage has the first polarity, the DC voltage output from the winding unit is changed to an arbitrary level by on / off control of the input voltage applied to the first winding by the first voltage control unit. It becomes possible to do. When the input voltage has the second polarity, the DC voltage output from the winding unit is changed to an arbitrary level by on / off control of the input voltage applied to the second winding by the second voltage control unit. It becomes possible.

  Further, since the first cutoff circuit cuts off the current flowing through the first voltage control unit when the input voltage has the second polarity, the first voltage control unit is controlled by the input voltage having the second polarity. It is possible to prevent an overcurrent from flowing through the elements included in the. In addition, when the input voltage has the first polarity, the current flowing through the second voltage control unit is interrupted, so that the element included in the second voltage control unit is overcurrentd by the input voltage having the first polarity. Can be prevented from flowing.

  The step-up / step-down circuit according to a seventh aspect of the present invention is the step-up / step-down circuit according to any one of the first to sixth aspects, particularly for turning on / off the DC voltage applied from the load to the second winding. The load current changeover switch element is further provided.

  According to the step-up / step-down circuit according to the seventh aspect, the load current changeover switch element turns on and off the DC voltage applied from the load to the second winding. Therefore, if the load is a DC voltage source such as a battery, the on / off state of the current flowing through the second winding can be controlled by controlling the load current changeover switch element. Therefore, if the voltage output from the winding unit that receives the DC power from the load is controlled by the first voltage control unit, it is possible to output DC power or AC power to the outside.

  The step-up / step-down circuit according to an eighth aspect of the present invention is the step-up / down circuit according to the seventh aspect, particularly when the load current changeover switch element is on, by the mutual induction based on the DC voltage. When the load current selector switch element is switched from on to off when the load current changeover switching element is switched from on to off, the first winding generates self-induction in the first winding. Is characterized in that an induced voltage of the second polarity is generated.

  According to the step-up / step-down circuit according to the eighth aspect, the DC voltage is applied to the second winding during the period in which the load current changeover switching element is ON, so that the first winding is coupled to the first winding by mutual induction. Inductive voltage of the polarity is generated. When the load current changeover switch element is switched from on to off, an induced voltage of the second polarity is generated by self-induction of the first winding. Therefore, it is possible to generate a voltage of the first polarity or a voltage of the second polarity in the first winding by controlling the switching of the load current changeover switch element.

  The buck-boost circuit according to a ninth aspect of the present invention is the buck-boost circuit according to the seventh or eighth aspect, in particular, the first voltage control unit includes the first end of the first winding and the A first switch element connected between a second end of the second winding and a first end of the first winding and a second end of the second winding; A first rectifier circuit connected in parallel with the first switch element; and the first switch element between a first end of the first winding and a second end of the second winding. And the induced current switching element connected in series with the first rectifier circuit, and the induced current switching between the first end of the first winding and the second end of the second winding. A second rectifier circuit connected in parallel with the switch element, and the second voltage control unit includes a second end of the first winding and a first end of the second winding. Between Characterized in that it comprises a current cutoff circuit to be continued.

  According to the step-up / step-down circuit according to the ninth aspect, these circuit configurations can prevent the current flowing due to the induced voltage generated in the first winding from being supplied to the second voltage control unit. . In addition, the first voltage control unit can turn on and off the current flowing through the first voltage control unit by controlling the first switch element and the induced current changeover switch element.

  The step-up / step-down circuit according to a tenth aspect of the present invention is the step-up / step-down circuit according to the ninth aspect, particularly when the load current switching switch element is on and the first switch element is on, and the load By switching between the state in which the current switching switch element is off and the first switch element is off, the second node of the first winding and the second voltage control unit are connected to the second voltage control unit. The induced voltage is boosted or lowered in the direction toward the connection node between the second end of the winding and the first voltage control unit.

  According to the step-up / step-down circuit according to the tenth aspect, by controlling the load current switching switch element and the first switch element, the second end of the first winding, the second voltage control unit, The DC voltage in the direction from the connection node to the connection node between the second end of the second winding and the first voltage control unit can be changed to an arbitrary level.

  The step-up / step-down circuit according to an eleventh aspect of the present invention is the step-up / step-down circuit according to the ninth aspect, particularly when the load current changeover switch element is on and the induction current changeover switch element is off, and the load By switching between a state in which the current changeover switch element is off and the induction current changeover switch element is on, the first node from the connection node between the second end of the second winding and the first voltage control unit The induced voltage is boosted or lowered in the direction toward the connection node between the second end of the winding and the second voltage control unit.

  According to the step-up / step-down circuit according to the eleventh aspect, by controlling the load current changeover switch element and the induction current changeover switch element, the second end of the second winding, the first voltage control unit, The DC voltage in the direction from the connection node to the connection node between the second end of the first winding and the second voltage control unit can be changed to an arbitrary level.

  The step-up / step-down circuit according to a twelfth aspect of the present invention is the step-up / step-down circuit according to the ninth aspect, particularly when the load current switching switch element is on and the first switch element is on, and the load A first polarity voltage output operation for switching between a state where the current switch element is off and the first switch element is off; a state where the load current switch element is on and the induction current switch element is off; Switching the second polarity voltage output operation for switching between the state where the load current changeover switch element is off and the induction current changeover switch element is on, and the second end of the first winding and the second An AC voltage is output to the outside from a connection node with the voltage control unit and a connection node between the second end of the second winding and the first voltage control unit.

  According to the step-up / step-down circuit according to the twelfth aspect, by switching between the first polarity voltage output operation and the second polarity voltage output operation, the DC voltage applied from the load is converted into power and output to the outside as an AC voltage. It becomes possible to do.

  The step-up / down circuit according to a thirteenth aspect of the present invention is the step-up / down circuit according to any one of the third, fourth, fifth, ninth, tenth, eleventh, and twelfth aspects. It further comprises a surge suppression circuit that suppresses a surge generated by the switch element in the first voltage control unit and the second voltage control unit.

  According to the step-up / step-down circuit according to the thirteenth aspect, the surge suppression circuit is caused by the switching surge by suppressing the switching surge generated from the switching elements in the first voltage control unit and the second voltage control unit. It is possible to prevent circuit malfunctions and circuit element failures.

  A power converter according to a fourteenth aspect of the present invention boosts or steps down an input terminal to which an input voltage is input, an output terminal, and the input voltage input to the input terminal, and outputs the input voltage to the load. A step-up / step-down circuit that outputs the stepped-up or step-down voltage, and the step-up / down circuit includes a first winding wound around a common core and one or more second windings, A winding section to which the input voltage is applied; a first voltage control section for turning on and off the input voltage applied to the first winding when the input voltage has a first polarity; A second voltage control unit for turning on and off the input voltage applied to the second winding when the input voltage has the second polarity; and the second voltage control unit in a state where the input voltage has the first polarity. When the application of the input voltage to one winding is turned off, And a smoothing for smoothing a voltage output from the winding portion when application of the input voltage to the second winding is turned off in a state where the input voltage has a second polarity. And a portion.

  According to the power converter of the fourteenth aspect, the input voltage input from the input end is input to the step-up / down circuit. In the step-up / step-down circuit, the first voltage control unit turns on / off the input voltage applied to the first winding when the input voltage has the first polarity. The second voltage control unit turns on and off the input voltage applied to the second winding when the input voltage has the second polarity. The application of the input voltage turns off the application of the voltage to the first winding when the input voltage is in the first polarity and the second winding when the input voltage is in the second polarity. When the application of voltage to the line is turned off, the winding section outputs a voltage. The smoothing unit smoothes the voltage output from the winding unit, and the output terminal outputs the smoothed voltage as an output voltage. Therefore, if the input voltage waveform and the input voltage waveform are controlled to be similar by the on / off control of the input voltage performed by the first voltage control unit and the second voltage control unit, the power factor is improved. The input voltage can be converted into a DC voltage that has been stepped up or stepped down. Therefore, by switching the winding to which the input voltage is applied depending on the polarity of the input voltage, a full-wave rectifier circuit is not necessary, and the circuit can be reduced in size and cost while reducing loss.

  According to the present invention, it is possible to provide a step-up / down circuit and a power conversion device that can be reduced in size and cost while reducing loss.

It is a figure which shows the structure of the power converter device which concerns on 1st Embodiment. It is a figure which shows the electric circuit through which an electric current flows when an input voltage is a 1st polarity. It is the figure which showed the relationship between the electric current and voltage in a buck-boost circuit when an input voltage is the 1st polarity. It is a figure which shows the electric circuit through which an electric current flows when input voltage is the 2nd polarity. It is the figure which showed the relationship between the electric current and voltage in a buck-boost circuit when an input voltage is the 2nd polarity. It is the figure which showed the structure of the power converter device of multiple outputs. It is a figure which shows the structure of the power converter device which concerns on 2nd Embodiment. It is a figure which shows the electric circuit through which the electric current flows in 1st polarity voltage output operation | movement. It is a figure which shows the relationship between the timing of switching in a 1st polarity voltage output operation | movement, and an electric current and a voltage. It is a figure which shows the electric circuit through which the electric current in 2nd polarity voltage output operation | movement flows. It is a figure which shows the relationship between the timing of switching in a 2nd polarity voltage output operation | movement, and an electric current and a voltage. It is the figure which showed the example of the alternating voltage which a power converter device outputs to load.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a diagram illustrating a configuration of a power conversion device according to the first embodiment.

  Referring to FIG. 1, power conversion device 101 includes a noise filter 51, a step-up / down circuit 52, and a power transmission insulating circuit 53. The step-up / step-down circuit 52 includes a winding part 11, voltage control circuits 12, 13, a voltage smoothing circuit 14, a control part 15, a capacitor C4, and a diode D5. Voltage control unit 12 includes a switching element Q1, diodes D1 and D3, a capacitor C1, and a resistance element R1. Voltage control unit 13 includes a switching element Q2, diodes D2 and D4, a capacitor C2, and a resistance element R2. The voltage smoothing circuit 14 includes a capacitor C3. Winding portion 11 includes winding L1 and winding L2 having a common core. Winding portion 11 is, for example, a two-winding reactor. Switch elements Q1, Q2 are, for example, IGBTs (Insulated Gate Bipolar Transistors).

  Switch element Q1 has a gate for receiving a control signal from control unit 15, a collector connected to the first end of winding L1, and an emitter connected to the anode of diode D1. Switch element Q2 has a gate for receiving a control signal from control unit 15, a collector connected to the first end of winding L2, and an emitter connected to the anode of diode D2.

  One end of the noise filter 51 is connected to a node P1, which is a connection node between the cathode of the diode D2 and the second end of the winding L1. The cathode of the diode D5 and the other end side of the noise filter 51 are connected to a node P2, which is a connection node between the cathode of the diode D1 and the second end of the winding L2.

  The power conversion device 101 converts AC power supplied from the AC power source 201 into DC power and supplies the DC power to the load 202. The load 202 is a main power (battery) for driving such as EV and plug-in HV, for example.

  The noise filter 51 removes AC power noise received from the AC power supply 201 and outputs the noise to the step-up / down circuit 52.

  The step-up / step-down circuit 52 converts the AC power received from the noise filter 51 into DC power and outputs the DC power to the power transmission insulating circuit 53. The power transmission insulating circuit 53 transmits power while performing insulation between the step-up / step-down circuit 52 and the load 202. The step-up / down circuit 52 adjusts the level of the output DC voltage in this power conversion.

  More specifically, in the step-up / step-down circuit 52, the switch element Q1 and the switch element Q2 are in a state in which an input voltage to the step-up / step-down circuit 52 is applied to the winding L1 under the control of switching by the control unit 15. Is applied to the winding L2 and the state in which the input voltage is not applied to the winding L1 and the winding L2.

  When the input voltage from the AC power supply 201 has the first polarity, the control unit 15 performs control so that the switch element Q2 is turned off. And the control part 15 controls on-off of the input voltage applied to the coil | winding L1 by switching the switch element Q1. FIG. 2 is a diagram illustrating an electric circuit through which a current flows when the input voltage has the first polarity.

  Note that the first polarity is a polarity of a voltage at which the potential of the node P1 is higher than the potential of the node P1 and the node P2. Further, the potentials of the node P1 and the node P2 are compared, and the polarity of the voltage at which the potential of the node P2 is higher is defined as the second polarity.

  In FIG. 2, a current Iin is an input current of the step-up / step-down circuit 52. The voltage Vin is an input voltage of the step-up / step-down circuit 52. The voltage Vout is an output voltage of the step-up / down circuit 52. The current IC is a current flowing through an electric circuit including the capacitor C3 and the load 202, the diode D5, and the winding L2.

  When the switch element Q1 is turned on in a state where the input voltage has the first polarity, a current flows in the direction indicated by the arrow of the current Iin in FIG. 2 due to a potential difference due to the input voltage. That is, a current Iin flows from one end side of the noise filter 51 to the other end side of the noise filter 51 through the winding L1, the switch element Q1, and the diode D1. At this time, a magnetic flux Φ is generated in the winding L1 due to the current flowing in the winding L1.

  Since the winding L1 and the winding L2 have a common core, the magnetic flux Φ generated in the winding L1 interlinks in the winding L2 through the common core. That is, the magnetic flux Φ is a magnetic flux shared by the winding L1 and the winding L2. Magnetic energy corresponding to the magnitude of the magnetic flux Φ is accumulated in the winding L1 and the winding L2.

  When the switch element Q1 is turned off, the current Iin is cut off, so that an induced voltage is generated in the winding L2 by self-induction. At this time, the current IC flows in the direction of the arrow shown in FIG. That is, due to the magnetic energy stored in the winding L2, a current IC flows from the one end side of the capacitor C3 to the other end side of the capacitor C3 through the winding L2 in the direction of conduction of the diode D5. With this current IC, the capacitor C3 is charged and power is supplied to the load 202, and the output voltage of the step-up / down circuit 52 is smoothed.

  FIG. 3 is a diagram showing a relationship between current and voltage in the step-up / step-down circuit 52 when the input voltage has the first polarity. In FIG. 3, a period in which the switch element Q1 is on is a period Ton, and a period in which the switch element Q1 is off is a period Toff.

  Referring to FIG. 3, current Iin flows in accordance with voltage Vin that is an AC voltage when switch element Q1 is turned on. Since the current Iin flows through the winding L1, the rising delay is determined by a time constant corresponding to the inductance of the winding L1. That is, the current Iin has a waveform that follows the voltage Vin, and the current Iin has a waveform similar to the waveform of the voltage Vin by performing switching with the frequency adjusted. The switching frequency at this time is, for example, several kHz to several tens of kHz.

  The current IC flows according to the induced voltage of the winding L2 while the switch element Q1 is off. Therefore, as the induced voltage decreases, the current IC also decreases. Since the magnetic flux Φ is a magnetic flux shared by the winding L1 and the winding L2, it is not turned on / off by switching of the switch element Q1, but continuously changes according to the current Iin and the current IC. The output voltage Vout is smoothed by the capacitor 3 and output as a DC voltage.

At this time, the relationship between the effective voltage Vein of the input voltage Vin and the magnetic flux Φ is expressed by using the number of turns n1 of the winding L1.
It is expressed.

Further, the relationship between the effective voltage Veout of the input voltage Vout and the magnetic flux Φ is expressed using the number of turns n2 of the winding L2.
It is expressed.

That is, the relationship between the effective voltage Vein of the input voltage and the effective voltage Veout of the output voltage is
It becomes.

  Since the number of turns n1 and the number of turns n2 are constants determined based on the specifications of the winding L1 and the winding L2, the input / output voltage ratio Veout / Vein of the step-up / step-down circuit 52 is the ON time in switching of the switch element Q1. And the off time ratio. The voltage Veout, which is a DC voltage whose output level is set by switching of the switch element Q1, is output to the load 202 via the power transmission insulating circuit 53.

  Further, in the step-up / step-down circuit 52, when the switch element Q1 is turned off with the input voltage from the AC power supply 201 having the first polarity, the input voltage Vin is subtracted from the output voltage Vout at both ends of the voltage control unit 13. A voltage is applied. Therefore, the diode D2 blocks the current flowing from the AC power supply 201 through the voltage control unit 13 when the input voltage from the AC power supply 201 has the first polarity, so that the reverse voltage is applied to the switch element Q2. It is prevented from being applied and the switch element Q2 is protected.

  On the other hand, when the input voltage from the AC power supply 201 has the second polarity, the control unit 15 performs control so that the switch element Q1 is turned off. And the control part 15 controls ON / OFF of the input voltage applied to the coil | winding L2 by switching switch element Q2. FIG. 4 is a diagram illustrating an electric path through which a current flows when the input voltage has the second polarity.

  In FIG. 4, a current Iin is an input current of the step-up / step-down circuit 52. The voltage Vin is an input voltage of the step-up / step-down circuit 52. The voltage Vout is an output voltage of the step-up / down circuit 52. The current IC is a current flowing through an electric circuit including the capacitor C3 and the load 202, the diode D5, and the winding L2.

  When the switch element Q2 is turned on in a state where the input voltage has the second polarity, a current flows in the direction indicated by the arrow of the current Iin in FIG. 4 due to a potential difference due to the input voltage. That is, current Iin flows from one end side of noise filter 51 to the other end side of noise filter 51 through winding L2, switching element Q2, and diode D2. In the winding L2, a magnetic flux Φ corresponding to the current Iin flowing through the winding L2 is generated, and magnetic energy is accumulated.

  When the switch element Q2 is turned off, the current Iin is cut off, so that an induction voltage is generated in the winding L2 by self-induction. At this time, the current IC flows in the direction of the arrow shown in FIG. That is, due to the magnetic energy stored in the winding L2, a current IC flows from the one end side of the capacitor C3 to the other end side of the capacitor C3 through the winding L2 in the direction of conduction of the diode D5. With this current IC, the capacitor C3 is charged and power is supplied to the load 202, and the output voltage of the step-up / down circuit 52 is smoothed.

  FIG. 5 is a diagram showing the relationship between the current and voltage in the buck-boost circuit 52 when the input voltage has the second polarity. In FIG. 5, a period in which the switch element Q2 is on is a period Ton, and a period in which the switch element Q2 is off is a period Toff.

  Referring to FIG. 5, current Iin flows according to input voltage Vin, which is an alternating voltage, when switch element Q2 is turned on. Since the current Iin flows through the winding L2, the rise delay is determined by a time constant corresponding to the inductance of the winding L2. That is, the current Iin has a waveform that follows the voltage Vin, and the current Iin has a waveform similar to the waveform of the voltage Vin by performing switching with the frequency adjusted. The switching frequency at this time is, for example, several kHz to several tens of kHz.

  The current IC flows according to the induced voltage of the winding L2 while the switch element Q2 is off. Therefore, as the induced voltage decreases, the current IC also decreases. The magnetic flux Φ generated in the winding L2 is not turned on / off by switching of the switch element Q2, but continuously changes according to the current Iin and the current IC. The output voltage Vout is smoothed by the capacitor 3 and output as a DC voltage.

At this time, the relationship between the effective voltage Vein of the input voltage Vin and the magnetic flux Φ is expressed by using the number of turns n2 of the winding L2.
It is expressed.

Further, the relationship between the effective voltage Veout of the input voltage Vout and the magnetic flux Φ is expressed using the number of turns n2 of the winding L2.
It is expressed.

That is, the relationship between the effective voltage Vein of the input voltage and the effective voltage Veout of the output voltage is
It becomes.

  Therefore, the input / output voltage ratio Veout / Vein of the step-up / step-down circuit 52 is set by the ratio between the on time and the off time in switching of the switch element Q2. The voltage Veout, which is a DC voltage whose output level is set by switching of the switch element Q2, is output to the load 202 via the power transmission insulating circuit 53.

  Further, in the step-up / step-down circuit 52, when the switch element Q2 is turned off with the input voltage from the AC power supply 201 having the second polarity, the input voltage Vin is subtracted from the output voltage Vout at both ends of the voltage control unit 12. A voltage is applied. Therefore, the diode D1 blocks the current flowing from the AC power supply 201 through the voltage control unit 12 when the input voltage from the AC power supply 201 has the second polarity, so that the reverse voltage is applied to the switch element Q1. It is prevented from being applied, and the switch element Q1 is protected.

  Regardless of the polarity of the input voltage from the AC power supply 201, the diode D3 protects the switching element Q1 from the reverse current generated by switching of the switching element Q1. The diode D4 protects the switch element Q2 from a reverse current generated by switching of the switch element Q2.

  Furthermore, regardless of the polarity of the input voltage from AC power supply 201, capacitor C1 and resistance element R1 suppress the surge current of the switching surge generated in switch element Q1. Capacitor C2 and resistance element R2 suppress the surge current of the switching surge generated in switch element Q2.

  As described above, the power converter 101 uses the control unit 15 to switch the switching element regardless of whether the input / output voltage from the AC power supply 201 is the first polarity or the second polarity by the step-up / down circuit 52. By controlling the switching between Q1 and the switch element Q2, the output DC voltage can be boosted or stepped down, and the input AC power can be converted into DC power. Therefore, the power conversion device 101 according to the embodiment of the present invention does not need to use a full-wave rectifier circuit when performing step-up / step-down of the input voltage, and therefore reduces loss compared to the case of using a full-wave rectifier circuit. It is possible.

  Note that the power input to the power conversion apparatus 101 is not limited to AC power, and DC power may be input. In this case, the operation of the AC power supply 201 described in the present embodiment is either the first polarity operation or the second polarity operation, and the output DC voltage can be boosted or stepped down. The voltage can be set to any level.

  When the step-up / step-down circuit 52 converts AC power into DC power, the waveform of the input current Iin and the waveform of the input voltage Vin are similar to each other by switching performed by the switch element Q1 and the switch element Q2. If controlled, the power factor in the power conversion can be improved.

  Further, the step-up / step-down circuit 52 does not require a full-wave rectifier circuit by switching the winding to which the input voltage is applied depending on the polarity of the input voltage. Moreover, since the winding part 11 which is a two-winding reactor has a plurality of windings wound around one core, it has a size that is not much different from that of a one-winding reactor. Therefore, the step-up / step-down circuit 52 is not enlarged even if it includes the winding portion 11.

  In addition, the step-up / step-down circuit 52 blocks the current flowing through the switch element that is not used according to the polarity of the input voltage from the AC power supply 201 by the diodes D1 and D2, and prevents the reverse voltage from being applied. Therefore, since the switch elements having a relatively small power capacity can be used for the switch elements Q1 and Q2, the step-up / down circuit 52 can be reduced in size and cost.

  Further, since the step-up / step-down circuit 52 includes a circuit that suppresses the switching surge generated in the switch elements Q1 and Q2, it is possible to prevent malfunction of the circuit due to the switching surge and failure of the switch element and the diode. .

  The power conversion apparatus 101 according to the first embodiment of the present invention may further employ a configuration as shown in FIG. FIG. 6 is a diagram illustrating a configuration of the power converter 101 having a plurality of outputs.

  Referring to FIG. 6, power conversion device 101 includes noise filter 51, step-up / step-down circuit 52, and power transmission insulating circuits 53 and 54. The step-up / step-down circuit 52 includes a winding unit 11, voltage control circuits 12, 13, voltage smoothing circuits 14, 16, a control unit 15, a capacitor C4, and diodes D5, D6. The voltage control unit 12 includes a switch element Q1 and a diode D1. Voltage control unit 13 includes a switching element Q2 and a diode D2. The voltage smoothing circuit 14 includes a capacitor C3. The voltage smoothing circuit 16 includes a capacitor C4. Winding portion 11 includes winding L1, winding L2, and winding L3 having a common core.

  The power conversion device 101 performs the same operation as that of the power conversion device 101 shown in FIG. 1, converts AC power supplied from the AC power source 201 into DC power, and supplies the DC power to the load 202 and the load 203. At this time, the output voltage to the load 202 and the output voltage to the load 203 can be set to different levels by using different windings for the winding L2 and the winding L3.

<Second Embodiment>
In the power conversion device used for the power source of electric vehicles, not only power conversion for charging the in-vehicle battery, but also electric devices can be used by outputting AC voltage using the in-vehicle battery as a power source. There is a growing need for power conversion to charge another battery by outputting. Therefore, in the power conversion device according to the present invention, AC or DC is output to the outside using a battery as a power source.

  FIG. 7 is a diagram illustrating a configuration of a power conversion device according to the second embodiment.

  Referring to FIG. 7, power conversion device 101 includes a noise filter 51, a step-up / down circuit 52, and a power transmission insulating circuit 53. The step-up / step-down circuit 52 includes a winding unit 11, voltage control circuits 12, 13, a voltage smoothing circuit 14, a control unit 15, a capacitor C4, a diode D5, and a switch element Q4. Voltage control unit 12 includes switch elements Q1, Q3 and diodes D1, D3. Voltage control unit 13 includes a switching element Q2 and diodes D2 and D4. The voltage smoothing circuit 14 includes a capacitor C3. Winding portion 11 includes winding L1 and winding L2 having a common core. Winding portion 11 is, for example, a two-winding reactor. Switch elements Q1-Q4 are, for example, IGBTs (Insulated Gate Bipolar Transistors).

  Switch element Q1 has a gate for receiving a control signal from control unit 15, a collector connected to the first end of winding L1, and an emitter connected to the emitter of switch element Q3. Diode D3 has a cathode connected to the first end of winding L1 and an anode connected to the emitter of switch element Q3, and is connected in parallel to switch element Q1.

  Switch element Q2 has a gate for receiving a control signal from control unit 15, a collector connected to the first end of winding L2, and an emitter connected to the anode of diode D2. The diode D4 has a cathode connected to the first end of the winding L2 and an anode connected to the anode of the diode D2, and is connected in parallel with the switch element Q2.

  Switch element Q3 has a gate for receiving a control signal from control unit 15, a collector connected to the second end of winding L2, and an emitter connected to the emitter of switch element Q1. Diode D1 has a cathode connected to the second end of winding L2 and an anode connected to the emitter of switch element Q1, and is connected in parallel to switch element Q3.

  Diode D2 has an anode connected to the emitter of switching element Q2 and diode D4, and a cathode connected to node P1, which is a connection node between the second end of winding L1 and one end of the noise filter.

  Switch element Q4 is connected to node P2, which is a connection node between the emitter connected to the first end of capacitor C3 and one end of power transmission insulating circuit 53, the cathode of diode D1, and the second end of winding L2. And a connected collector. Diode D5 has an anode connected to the first end of capacitor C3 and one end of power transmission insulating circuit 53, and a cathode connected to node P2, and is connected in parallel to switch element Q4.

  One end of the noise filter 51 is connected to the node P1. The other end side of the noise filter 51 is connected to the node P2. The other end side of the capacitor C3 and the other end side of the power transmission insulating circuit 53 are connected to a connection node between the first end of the winding L2 and the collector of the switch element Q2.

  The power conversion device 101 converts AC power supplied from the AC power source 201 into DC power and supplies the DC power to the load 202. The load 202 is a main power (battery) for driving such as EV and plug-in HV, for example.

  The noise filter 51 removes AC power noise received from the AC power supply 201 and outputs the noise to the step-up / down circuit 52.

  The power transmission insulating circuit 53 performs power transmission between the step-up / down circuit 52 and the load 202 while performing insulation between the step-up / down circuit 52 and the load 202.

  The step-up / step-down circuit 52 turns off the switch elements Q3, Q4 to convert the AC power input from the AC power source 201 into DC power by converting the load 202 into the same manner as the step-up / step-down circuit 52 of the first embodiment. Output to.

  In addition, when a DC voltage is input from the load 202, the power conversion device 101 performs a first polarity voltage output operation and a second polarity voltage output operation for boosting or stepping down the DC voltage input from the load 202. FIG. 8 is a diagram illustrating an electric path through which a current flows in the first polarity voltage output operation. In the first polarity voltage output operation, the power conversion device 101 supplies the first polarity DC voltage to the load 204 by boosting or stepping down the DC power supplied from the load 202 such as a battery by the step-up / down circuit 52. To do.

  In FIG. 8, a current Iin2 is a current supplied from the load 202 and flowing through the winding L2. The voltage Vin2 is a voltage applied to the step-up / step-down circuit 52 by the load 202. The current Iout2 is an output current of the buck-boost circuit 52. The voltage Vout2 is an output voltage of the buck-boost circuit 52.

  More specifically, in the step-up / step-down circuit 52, the control unit 15 performs switching control so that the switch element Q1 and the switch element Q4 are turned on. During the period when the switch element Q4 is on, the current Iin2 flows through the winding L2 due to the DC voltage input from the load 202. At this time, in the winding L1 having a common core with the winding L2, an induced voltage in the direction from the node P1 to the node P2 is generated by mutual induction. Since the switch element Q1 is on, the current Iout2 flows. That is, at this time, the winding part 11 functions as a transformer, and the voltage Vout2 is output to the load 204.

  FIG. 9 is a diagram illustrating a relationship between switching timing, current, and voltage in the first polarity voltage output operation. In FIG. 9, a period Ton is a period in which the switch element Q4 is on and the switch element Q1 is on. The period Toff is a period in which the switch element Q4 is off and the switch element Q1 is off. Further, when the first polarity voltage output operation is performed, the switch elements Q2 and Q3 are off.

At this time, the relationship between the effective voltage Vein2 of the input voltage Vin2 and the effective voltage Veout2 of the output voltage Vout2 during the period when the switch element Q4 is on is expressed by using the number of turns n1 of the winding L1 and the number of turns n2 of the winding L2. When,
It is expressed.

  In addition, during the period in which the switch element Q1 and the switch element Q4 are off, the current path is interrupted, so that the current Iin2 and the current Iout2 do not flow. Therefore, the effective voltage Veout2 of the output voltage Vout2 is controlled by switching between the period Ton when the switch element Q1 is on and the switch element Q4 is on and the period Toff when the switch element Q1 is off and the switch element Q4 is off. Is stepped up or down. The switching frequency in this chopper control is, for example, several kHz to several tens kHz. In this way, the step-up / step-down circuit 52 performs the first polarity voltage output operation.

  FIG. 10 is a diagram illustrating an electric path through which a current flows in the second polarity voltage output operation. In the second polarity voltage output operation, the power conversion device 101 boosts or steps down the DC power supplied from the load 202 such as a battery by the step-up / down circuit 52 and supplies the DC power to the load 204 as a second polarity voltage. To do.

  In FIG. 10, a current Iin2 is a current supplied from the load 202 and flowing through the winding L2. The voltage Vin2 is a voltage applied to the step-up / step-down circuit 52 by the load 202. The current Iout2 is an output current of the buck-boost circuit 52. The voltage Vout2 is an output voltage of the buck-boost circuit 52.

  More specifically, in the step-up / step-down circuit 52, the control unit 15 controls the switch element Q4 and the switch element Q3 so that the switch element Q4 is on and the switch element Q3 is off. During the period when the switch element Q4 is on, the current Iin2 flows through the winding L2 due to the DC voltage input from the load 202. At this time, the magnetic flux Φ resulting from the current Iin2 is generated in the winding L2. This magnetic flux Φ is linked in the winding L1 through a common core.

  Next, the control unit 15 controls the switch element Q4 and the switch element Q3 so that the switch element Q4 is turned off and the switch element Q3 is turned on. When the switching of the state of the switch element is performed, the current Iin2 flowing through the winding L2 is cut off, so that the winding L1 is generated in the common core of the winding L2 and the winding L1 by self-induction. An induced voltage is generated in a direction to maintain the magnetic flux Φ. At this time, since the switch element Q3 is on, the current Iout2 flows due to the induced voltage generated in the winding L1, and power is supplied to the load 204.

  FIG. 11 is a diagram illustrating a relationship between switching timing, current, and voltage in the second polarity voltage output operation. The period Ton is a period in which the switch element Q4 is off and the switch element Q3 is on. The period Toff is a period in which the switch element Q4 is on and the switch element Q3 is off. Further, when the second polarity output operation is performed, the switch elements Q1 and Q2 are off.

  Referring to FIG. 11, current Iin2 flows in accordance with the DC voltage applied from load 202 when switch element Q4 is turned on. Since the current Iin2 flows through the winding L2, the rise delay is determined by a time constant corresponding to the inductance of the winding L2.

  The current Iout2 flows according to the induced voltage of the winding L2 while the switch element Q3 is on. Therefore, the current Iout2 also decreases as the induced voltage decreases. The magnetic flux Φ generated in the winding L2 is not turned on / off by switching of the switch element Q3, but continuously changes according to the current Iin2 and the current Iout2.

At this time, the relationship between the effective voltage Vein2 of the input voltage Vin2 and the magnetic flux Φ is expressed by using the number of turns n2 of the winding L2 and the period Toff in which the switch element Q4 is on and the switch element Q3 is off.
It is expressed.

Further, the relationship between the effective voltage Veout2 of the input voltage Vout2 and the magnetic flux Φ is expressed using the number of turns n1 of the winding L1 and the period Ton in which the switch element Q4 is off and the switch element Q3 is on.
It is expressed.

Since the winding L1 and the winding L2 have a common core, the relationship between the effective voltage Vein2 of the input voltage and the effective voltage Veout2 of the output voltage is
It becomes.

  Since the number of turns n1 and the number of turns n2 are constants determined based on the specifications of the winding L1 and the winding L2, the input / output voltage ratio Veout2 / Vein2 from the load 202 to the load 204 is the switching element Q4 and the switching element. It can be set by the ratio of the on-time and off-time in switching with Q3. The switching frequency at this time is, for example, several kHz to several tens of kHz.

  Therefore, when the DC voltage is applied from the load 202, the step-up / step-down circuit 52 can increase or decrease the output DC voltage by changing the duty ratio by switch control by the control unit 15, and the output voltage can be set to an arbitrary level. Can be set to

  In this manner, the step-up / step-down circuit 52 can step up or step down the DC voltage applied from the load 202 and output it to the load 204 by performing the first polarity voltage output operation or the second polarity voltage output operation. . In addition, since the direction of the voltage output to the load 204 is opposite between the first polarity voltage output operation and the second polarity voltage output operation, the first polarity voltage output operation and the second polarity voltage output operation are switched. Thus, the step-up / step-down circuit 52 outputs an AC voltage to the load 204.

  FIG. 12 is a diagram illustrating an example of an AC voltage output from the power conversion apparatus 101 to the load 204. However, Vout2 in FIG. 12 displays the voltage of the first polarity as positive and the voltage of the second polarity as negative. The step-up / step-down circuit 52 controls the switching of the switching elements Q1 to Q4 by the control unit 15, so that, for example, a voltage obtained by boosting or stepping down the first polarity so as to be similar to a sine wave and the first voltage Outputs voltage that has been boosted or lowered in polarity. Since switching of the switch elements Q1 to Q4 is performed at a frequency of, for example, several kHz to several tens of kHz, the switching of the switch element is sufficiently short compared with the frequency of the commercial power supply. Therefore, the voltage output from the step-up / down circuit 52 can be used as an AC voltage in the external load 204.

  As described above, the power conversion device 101 can convert the AC power supplied from the AC power source 201 into DC power and supply the DC power to the load 202. Further, the DC voltage applied from the load 202 by the step-up / step-down circuit 52 can be boosted or lowered to be converted into a first polarity DC voltage, a second polarity DC voltage, or an AC voltage. Become.

  In addition, when converting the AC voltage applied from the external AC power source to the DC voltage, the power conversion device 101 switches the winding for applying the input voltage according to the polarity of the input voltage, so that a full-wave rectifier circuit is not necessary. Therefore, it is possible to reduce the size and cost of the circuit while reducing the loss.

  In the second embodiment of the present invention, as shown in the first embodiment, the switching surge in each switch element is suppressed by connecting a capacitor and a resistor element in parallel with the switch elements Q1 to Q4. May be performed.

  In the first embodiment and the second embodiment of the present invention, the case where the winding portion 11 is a two-winding reactor is illustrated. However, in the present invention, the winding portion 11 may be a transformer or the like. A plurality of windings having a common core may be included.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 11 Winding part 12, 13 Voltage control part 14, 16 Voltage smoothing part 15 Control part 51 Noise filter 52 Buck-boost circuit 53, 54 Insulation circuit for power transmission 101 Power converter 201 AC power supply 202, 203, 204 Load

Claims (14)

A step-up / step-down circuit for boosting or stepping down an input voltage and supplying it to a load,
A winding portion including a first winding and one or more second windings wound around a common core, to which the input voltage is applied;
A first voltage controller that turns on and off the input voltage applied to the first winding when the input voltage has a first polarity;
A second voltage controller that turns on and off the input voltage applied to the second winding when the input voltage has a second polarity;
The voltage output from the winding unit when the application of the input voltage to the first winding is turned off in the state where the input voltage is the first polarity, and the input voltage is the second voltage A smoothing unit that smoothes the voltage output from the winding unit when the application of the input voltage to the second winding is turned off in a state of the polarity of and outputs to the load
A step-up / step-down circuit.   The step-up / step-down circuit according to claim 1, wherein the voltage output from the winding unit is a voltage induced in the second winding. The first voltage control unit includes a first switch element that turns on and off the input voltage applied to the first winding by switching,
The second voltage control unit includes a second switch element that turns on and off the input voltage applied to the second winding by switching,
The first switch element is turned off when the input voltage is the second polarity;
The step-up / step-down circuit according to claim 1 or 2, wherein the second switch element is turned off when the input voltage has the first polarity. The first winding has a first end connected to a first end of the first switch element and a second end connected to a second end of the second switch element;
The second winding has a first end connected to a first end of the second switch element and a second end connected to a second end of the first switch element. The step-up / step-down circuit described in 1.   A first connection node between a second end of the first winding and a second end of the second switch element; and a second end of the second winding and a second of the first switch element. When the input voltage is applied between the second connection node and the end, the first winding is connected to the first winding via the first connection node when the input voltage has the first polarity. The step-up / step-down circuit according to claim 4, wherein a current is supplied and current is supplied to the second winding via the second connection node when the input voltage has the second polarity. A first voltage control unit configured to cut off a current supplied to the first winding via the first voltage control unit when the input voltage has the second polarity; Including a breaker circuit,
A second voltage control unit configured to cut off a current supplied to the second winding via the second voltage control unit when the input voltage has the first polarity; The step-up / step-down circuit according to any one of claims 1 to 5, including a cutoff circuit.   The step-up / step-down circuit according to claim 1, further comprising a load current changeover switch element that turns on and off a DC voltage applied from the load to the second winding. During the period in which the load current changeover switch element is on, an induced voltage of the first polarity is generated in the first winding by mutual induction based on the DC voltage,
The induced voltage having the second polarity is generated in the first winding by self-induction of the first winding when the load current changeover switching element is switched from on to off. The step-up / step-down circuit described. The first voltage controller is
A first switch element connected between a first end of the first winding and a second end of the second winding;
A first rectifier circuit connected in parallel with the first switch element between a first end of the first winding and a second end of the second winding;
Inductive current switching element connected in series with the first switch element and the first rectifier circuit between the first end of the first winding and the second end of the second winding When,
A second rectifier circuit connected in parallel with the induced current changeover switch element between a first end of the first winding and a second end of the second winding;
Including
The said 2nd voltage control part contains the electric current interruption circuit connected between the 2nd end of the said 1st coil | winding, and the 1st end of the said 2nd coil | winding. Buck-boost circuit.   By switching between a state in which the load current changeover switch element is on and the first switch element is on and a state in which the load current changeover switch element is off and the first switch element is off, the first The induced voltage in a direction from a connection node between the second end of one winding and the second voltage control unit to a connection node between the second end of the second winding and the first voltage control unit The step-up / step-down circuit according to claim 9, wherein the step-up / step-down circuit performs step-up or step-down.   By switching between the state where the load current changeover switch element is on and the induction current changeover switch element is off and the state where the load current changeover switch element is off and the induction current changeover switch element is on, the first The induced voltage in the direction from the connection node between the second end of the second winding and the first voltage control unit to the connection node between the second end of the first winding and the second voltage control unit The step-up / step-down circuit according to claim 9, wherein the step-up / step-down circuit performs step-up or step-down.   First polarity voltage output for switching between a state in which the load current changeover switch element is on and the first switch element is on and a state in which the load current changeover switch element is off and the first switch element is off A second switching operation between a state in which the load current changeover switch element is on and the induction current changeover switch element is off, and a state in which the load current changeover switch element is off and the induction current changeover switch element is on. By switching the polarity voltage output operation, a connection node between the second end of the first winding and the second voltage control unit, and the second end of the second winding and the first voltage control. The step-up / step-down circuit according to claim 9, wherein an AC voltage is output to the outside from a connection node with the unit.   The step-up / step-down circuit further includes a surge suppression circuit that suppresses a surge generated by the switch element in the first voltage control unit and the second voltage control unit. The step-up / step-down circuit according to claim 1. An input terminal to which an input voltage is input;
An output end;
A step-up / step-down circuit for stepping up or stepping down the input voltage input to the input end and outputting the boosted or stepped down voltage from the output end to a load;
With
The step-up / down circuit is
A winding portion including a first winding and one or more second windings wound around a common core, to which the input voltage is applied;
A first voltage controller that turns on and off the input voltage applied to the first winding when the input voltage has a first polarity;
A second voltage controller that turns on and off the input voltage applied to the second winding when the input voltage has a second polarity;
The voltage output from the winding unit when the application of the input voltage to the first winding is turned off in the state where the input voltage has the first polarity, and the input voltage has the second polarity A smoothing unit for smoothing a voltage output from the winding unit when application of the input voltage to the second winding is turned off in a state of
A power conversion device including: