JP2016119783A - Power conversion device - Google Patents

Abstract

A power converter capable of reducing loss of a switching element is provided. A power converter includes a plurality of series circuits in which a first switching element and a second switching element are connected in series, and each series circuit is connected in parallel, and one end of each series circuit is connected to the positive side. The other end is a negative side, and further includes a filter circuit having one end connected to each connection point of the first switching element and the second switching element, and the other end of the filter circuit is an AC side. The first switching element is a bipolar transistor, and a diode is connected in antiparallel between the collector and emitter of the bipolar transistor, and the second switching element is an FET, and a diode is connected between the drain and source of the FET. Connected in antiparallel. [Selection] Figure 1

Description

  The present invention relates to a power conversion device that converts power to both.

  2. Description of the Related Art In recent years, bi-directional power conversion devices that convert direct current from a battery into alternating current when the alternating current input from the outside is converted into direct current and the alternating current power is output during battery charging have attracted attention. For example, a bidirectional DC / AC inverter including a switching element is disclosed (see Patent Document 1).

JP 2007-110856 A

  However, in the apparatus of Patent Document 1, only one of IGBT (Insulated Gate Bipolar Transistor) or MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used as all switching elements. However, when an IGBT is used as a switching element, the loss in a forward biased state increases, and when a MOSFET is used as a switching element, the loss in a reverse biased state is increased. Becomes larger.

  This invention is made | formed in view of such a situation, and it aims at providing the power converter device which can reduce the loss of a switching element.

  The power conversion device according to the embodiment of the present invention includes a plurality of series circuits in which a first switching element and a second switching element are connected in series, and each series circuit is connected in parallel. One end is a positive side, the other end is a negative side, and further includes a filter circuit having one end connected to each of connection points of the first switching element and the second switching element, and the other end of the filter circuit is connected to the AC side. The first switching element is a bipolar transistor, a diode is connected in antiparallel between the collector and emitter of the bipolar transistor, and the second switching element is an FET. Yes, a diode is connected in antiparallel between the drain and source of the FET.

  According to the present invention, the loss of the switching element can be reduced.

It is explanatory drawing which shows an example of the circuit structure of the power converter device of this Embodiment. It is explanatory drawing which shows operation | movement of each switching element in the case of converting from alternating current to direct current | flow with the power converter device of this Embodiment. It is a schematic diagram which shows the mode of the electric current which flows into the bridge circuit at the time of converting from alternating current to direct current of the power converter device of this Embodiment (positive half cycle). It is a schematic diagram which shows the mode of the electric current which flows into the bridge circuit at the time of converting from alternating current to direct current of the power converter device of this Embodiment (negative half cycle). It is explanatory drawing which shows an example of the switching loss of a transistor and FET. It is a schematic diagram which shows an example of the input current waveform by the side of alternating current of the power converter device of this Embodiment. It is explanatory drawing which shows operation | movement of each switching element in the case of converting from direct current | flow to alternating current with the power converter device of this Embodiment. It is a schematic diagram which shows the mode of the electric current which flows into the bridge circuit at the time of converting from direct current | flow to alternating current of the power converter device of this Embodiment (positive half cycle). It is a schematic diagram which shows the mode of the electric current which flows into the bridge circuit at the time of converting from direct current | flow to alternating current of the power converter device of this Embodiment (negative half cycle).

[Description of Embodiment of Present Invention]
(1) A power conversion device according to an embodiment of the present invention includes a plurality of series circuits in which a first switching element and a second switching element are connected in series, and each series circuit is connected in parallel. The series circuit further includes a filter circuit in which one end is a positive side and the other end is a negative side, and one end is connected to each connection point of the first switching element and the second switching element, and the other end of the filter circuit is In the power conversion device on the AC side, the first switching element is a bipolar transistor, and a diode is connected in antiparallel between a collector and an emitter of the bipolar transistor, and the second switching element is FET, and a diode is connected in antiparallel between the drain and source of the FET.

  The power conversion device includes a plurality of series circuits in which a first switching element and a second switching element are connected in series, and each series circuit is connected in parallel, with one end of each series circuit being a positive side and the other end being The filter circuit further includes a filter circuit having one end connected to each connection point of the first switching element and the second switching element, and the other end of the filter circuit serving as the AC side. That is, a bridge circuit is constituted by the first switching element and the second switching element of each series circuit. The filter circuit includes, for example, a capacitor and a plurality of coils, and one end of each coil is connected to each connection point of the first switching element and the second switching element, and the other end of the coil is an AC side. it can. A capacitor can be connected between the other ends of the coils. The first switching element is a bipolar transistor, and a diode is connected in antiparallel between the collector and emitter of the bipolar transistor. The second switching element is an FET, and a diode is connected in antiparallel between the drain and source of the FET.

  A bipolar transistor (hereinafter also referred to as a transistor) is a minority carrier device that uses so-called minority carriers for electrical conduction, and generally has a large switching loss in a forward biased state. On the other hand, FET (Field Effect Transistor) is a majority carrier device that does not use minority carriers for electrical conduction, and because of the presence of parasitic diodes, switching characteristics in the reverse direction are not good, and switching loss in a state biased in the reverse direction. There are many. That is, the transistor has a small switching loss when biased in the reverse direction, and the FET (Field Effect Transistor) has a small switching loss when biased in the forward direction.

  For example, when there is a state where the first switching element is used with a reverse bias and the second switching element is used with a forward bias, all of the first switching element and the second switching element are used. Compared to the case of either transistor or FET, the first switching element is a transistor (bipolar transistor) and the second switching element is an FET, reducing the overall loss (switching loss). can do.

(2) The power conversion device according to the embodiment of the present invention always turns off the first switching element of each series circuit and turns on the second switching element of each series circuit at a predetermined frequency higher than a commercial frequency. A control unit for turning off / off is provided to convert alternating current into direct current.

  The control unit always turns off the first switching element of each series circuit, turns on / off the second switching element of each series circuit at a predetermined frequency higher than the commercial frequency, and converts alternating current into series. The series circuit connected in parallel is referred to as a first series circuit and a second series circuit. The first series circuit and the second series circuit are circuits in which a transistor (first switching element) and an FET (second switching element) are connected in series, respectively.

  In one half cycle of alternating current, alternating current flows through a diode connected antiparallel to the transistors of the first series circuit, and a diode connected antiparallel to the DC side and the FETs of the second series circuit. In addition, when each FET is turned on in one half cycle of alternating current, current flows through a diode connected in antiparallel to the FET of the first series circuit and the FET of the second series circuit, and flows to the coil on the alternating current side. Electric energy is accumulated. When each FET is turned off in one half cycle of alternating current, the diode, the direct current side, and the second series circuit connected in reverse parallel to the transistor of the first series circuit by the electrical energy accumulated in the coil A current flows through a diode connected in reverse parallel to the FET. In one half cycle of alternating current, the transistor of the first series circuit becomes a reverse bias, and the FET of the first series circuit becomes a forward bias, thereby reducing the loss.

  Similarly, in the other half cycle of the alternating current, the alternating current flows through a diode connected in antiparallel to the transistor in the second series circuit, and a diode connected in antiparallel to the direct current side and the FET in the first series circuit. In addition, when each FET is turned on in the other half cycle of the alternating current, a current flows through a diode connected in reverse parallel to the FET of the second series circuit and the FET of the first series circuit, and flows to the coil on the alternating current side. Electric energy is accumulated. When each FET is turned off in the other half cycle of the alternating current, the diode, the direct current side, and the first serial circuit connected in reverse parallel to the transistor of the second series circuit by the electric energy accumulated in the coil A current flows through a diode connected in reverse parallel to the FET. In the other half cycle of the alternating current, the transistor of the second series circuit becomes the reverse bias, and the FET of the second series circuit becomes the forward bias, thereby reducing the loss.

(3) In the power converter according to the embodiment of the present invention, in one half cycle of alternating current, the first switching element of one series circuit is always turned on, and the first switching element of the other series circuit is turned on. Always turning off a switching element, further turning off the second switching element of the one series circuit, turning on / off the second switching element of the other series circuit at a predetermined frequency higher than a commercial frequency, In the other half cycle of the alternating current, the first switching element of the one series circuit is always turned off, the first switching element of the other series circuit is always turned on, and further, A controller that turns on and off the second switching element at the predetermined frequency and always turns off the second switching element of the other series circuit, and converts direct current to alternating current; That.

  The control unit always turns on the transistor of the first series circuit (one series circuit), always turns off the transistor of the second series circuit (the other series circuit) in one half cycle of the alternating current, The FET of the series circuit is always turned off, and the FET of the second series circuit is turned on / off at a predetermined frequency higher than the commercial frequency.

  That is, when the FET of the second series circuit is turned on, a current flows through the transistor, the coil, the AC side of the first series circuit, and the FET of the second series circuit. When the FET of the second series circuit is turned off, a current in the same direction is applied to the coil, so that the diode of the first series circuit, the coil, the AC side, and the diode reversely paralleled to the transistor of the second series circuit Current flows through In one half cycle of the alternating current, the transistor of the second series circuit becomes a reverse bias, and the FET of the second series circuit becomes a forward bias, thereby reducing the loss.

  The control unit always turns off the transistor of the first series circuit (one series circuit), always turns on the transistor of the second series circuit (other series circuit) in the other half cycle of the alternating current, The FET of the series circuit is turned on / off at a predetermined frequency, the FET of the second series circuit is always turned off, and direct current is converted into alternating current.

  That is, when the FET of the first series circuit is turned on, a current flows through the transistor, the coil, the AC side of the second series circuit, and the FET of the first series circuit. When the FET of the first series circuit is turned off, the current in the same direction is applied to the coil, so that the diode of the second series circuit, the coil, the AC side, and the diode that is anti-parallel to the transistor of the first series circuit Current flows through In the other half cycle of the alternating current, the transistor of the first series circuit becomes a reverse bias, and the FET of the first series circuit becomes a forward bias, so that loss can be reduced.

[Details of the embodiment of the present invention]
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is an explanatory diagram illustrating an example of a circuit configuration of the power conversion device according to the present embodiment. The power conversion device of the present embodiment includes an AC terminal 1, a DC terminal 2, a first series circuit 10, a second series circuit 20, a filter circuit 30, a control unit 40, a smoothing capacitor 50, a DC / DC A DC converter 60 and the like are provided. When the AC power is supplied by connecting a commercial power source (a commercial frequency power source such as 50 Hz or 60 Hz) to the AC side terminal 1, the power conversion device converts the AC into DC, thereby converting the DC side terminal 2. For example, the battery 3 can be charged by outputting DC power having a required voltage. Further, when DC power is supplied by connecting a DC power source such as a battery 3 to the DC-side terminal 2, AC power can be output from the AC-side terminal 1 by converting DC to AC.

  The first series circuit 10 has a configuration in which a bipolar transistor 11 as a first switching element and an FET (Field Effect Transistor) 12 as a second switching element are connected in series. For example, an IGBT (Insulated Gate Bipolar Transistor) can be used as the bipolar transistor 11. The FET 12 may be a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). In the following description, for convenience, the bipolar transistor is simply referred to as a transistor. More specifically, the emitter of the transistor 11 and the drain of the FET 12 are connected.

  The first switching element is not limited to a transistor, and may be a minority carrier device that uses minority carriers for electrical conduction. The second switching element is not limited to the FET, and may be a majority carrier device that does not use minority carriers for electrical conduction.

  Similarly, the second series circuit 20 has a configuration in which a transistor 21 as a first switching element and an FET 22 as a second switching element are connected in series. More specifically, the emitter of the transistor 21 and the drain of the FET 22 are connected.

  The first series circuit 10 and the second series circuit 20 are connected in parallel. That is, the collectors of the transistors 11 and 21 are connected to the DC-side positive circuit 4, and the sources of the FETs 12 and 22 are connected to the DC-side negative (for example, ground level) circuit 5. Thus, the transistors 11 and 21 and the FETs 12 and 22 constitute a so-called bridge circuit. A smoothing capacitor 50 is connected between the electric paths 4 and 5. Hereinafter, the first series circuit 10 and the second series circuit 20 are collectively referred to as a bridge circuit.

  Between the collectors and emitters of the transistors 11 and 21, diodes (for example, FRD: fast recovery diode) 111 and 211 are connected in antiparallel. That is, the anode of each diode is connected to the emitter of the transistor, and the cathode is connected to the collector. The diodes 111 and 211 may be incorporated in the transistors 11 and 21 or may be externally attached.

  Between the sources and drains of the FETs 12 and 22, diodes (for example, body diodes) 121 and 221 are connected in antiparallel. That is, the anode of each diode is connected to the source of the FET, and the cathode is connected to the drain. The diodes 121 and 221 may be incorporated in the FETs 12 and 22 or may be externally attached.

  The filter circuit 30 includes coils 31 and 32, a capacitor 33, and the like. One end of the coil 31 is connected to a connection point between the emitter of the transistor 11 and the drain of the FET 12, and the other end of the coil 31 is connected to one terminal 1 on the AC side. One end of the coil 32 is connected to a connection point between the emitter of the transistor 21 and the drain of the FET 22, and the other end of the coil 32 is connected to the other terminal 1 on the AC side. A capacitor 33 is connected between the other ends of the coils 31 and 32.

  The control unit 40 controls switching of the transistors 11 and 21 and the FETs 12 and 22. Specifically, the output terminal of the control unit 40 is connected to the bases of the transistors 11 and 21 and the gates of the FETs 12 and 22, respectively. The control unit 40 outputs the base signal and the gate signal from the output terminal.

  The DC / DC converter 60 has a function of stepping up and down a direct current voltage.

  Transistors 11 and 21 are minority carrier devices that use so-called minority carriers for electrical conduction, and generally have a large switching loss in a forward biased state, no parasitic diode, and a reverse biased state. Switching loss at is low. On the other hand, the FETs 12 and 22 are majority carrier devices (unipolar devices) that do not use minority carriers for electrical conduction, and the switching characteristics in the reverse direction are not good due to the presence of parasitic diodes. Loss is large and switching loss is small when forward biased.

  For example, when the transistors 11 and 21 are used with a reverse bias and the FETs 12 and 22 are used with a forward bias, all of the four switching elements constituting the bridge circuit are either transistors or FETs. On the other hand, the loss (switching loss) as a whole can be reduced as compared with the case of the configuration.

  Next, operation | movement of the power converter device of this Embodiment is demonstrated. FIG. 2 is an explanatory diagram showing the operation of each switching element when converting from AC to DC by the power conversion device of the present embodiment. In FIG. 2, an AC positive half cycle indicates a period during which a positive half cycle voltage is applied to the AC side terminal 1, and an AC negative half cycle indicates a negative half cycle at the AC side terminal 1. The period during which the voltage is applied is shown.

  First, the operation in the positive half cycle of AC will be described. In the positive half cycle of the alternating current, the transistors 11 and 21 are controlled so as to be always turned off, and the FETs 12 and 22 are controlled so as to be repeatedly turned on / off at a predetermined frequency. The predetermined frequency is a frequency higher than a commercial frequency (for example, 50 Hz, 60 Hz, etc.), and can be, for example, about several kHz to several tens of kHz.

  FIG. 3 is a schematic diagram showing a state of a current flowing in the bridge circuit in the case of converting from alternating current to direct current (positive half cycle) in the power conversion device of the present embodiment. As described above with reference to FIG. 2, in the positive half cycle of alternating current, the transistors 11 and 21 are controlled to be always off, and the FETs 12 and 22 are controlled to be repeatedly turned on / off at a predetermined frequency.

  In the positive (one) half cycle of the alternating current, the alternating current is connected in antiparallel to the coil 31, the diode 111 connected in antiparallel to the transistor 11 in the first series circuit, and the FET 22 in the direct current side, second series circuit. The diode 221 and the coil 32 flow.

  Further, when the FETs 12 and 22 are turned on in the positive half cycle of the alternating current, the coil 31, the FET 12 of the first series circuit, and the FET 22 of the second series circuit are anti-parallel as indicated by the arrows shown in FIG. A current flows through the diode 221 and the coil 32 connected to each other, and electric energy is accumulated in the coils 31 and 32 on the AC side.

  When the FETs 12 and 22 are turned off in the positive half cycle of the alternating current, the coil 31 and the first series circuit are generated by the electric energy accumulated in the coils 31 and 32 as shown by the broken lines in FIG. A current flows through the diode 111 connected in antiparallel to the transistor 11 of FIG. 5, the diode 221 connected in antiparallel to the FET 22 of the direct current side, second series circuit, and the coil 32.

  In the positive half cycle of the alternating current, the transistor 11 of the first series circuit becomes a reverse bias, and the loss of the transistor 11 can be reduced. The FET 12 of the first series circuit becomes a forward bias, and the loss of the FET 12 is reduced. It is possible to reduce the loss, and the power conversion apparatus as a whole can reduce the loss.

  Next, the operation | movement in the negative half cycle of alternating current is demonstrated. As shown in FIG. 2, in the negative half cycle of the alternating current, as in the positive half cycle, the transistors 11 and 21 are controlled to be always turned off, and the FETs 12 and 22 are repeatedly turned on / off at a predetermined frequency. To be controlled.

  FIG. 4 is a schematic diagram showing a state of a current flowing through the bridge circuit when converting from alternating current to direct current (negative half cycle) in the power conversion device of the present embodiment. In the negative (other) half cycle of the alternating current, the alternating current is connected in reverse parallel to the coil 32, the diode 211 connected in antiparallel to the transistor 21 in the second series circuit, and the FET 12 in the direct current side, first series circuit. The diode 121 and the coil 31 flow.

  Further, when the FETs 12 and 22 are turned on in the negative half cycle of the alternating current, the coil 32, the FET 22 of the second series circuit, and the FET 12 of the first series circuit are antiparallel as indicated by the arrows shown in FIG. A current flows through the diode 121 and the coil 31 connected to each other, and electric energy is accumulated in the coils 31 and 32 on the AC side.

  When the FETs 12 and 22 are turned off in the negative half cycle of the alternating current, the coil 32 and the second series circuit are caused by the electric energy accumulated in the coils 31 and 32 as shown by the broken lines in FIG. Current flows in the diode 211 connected in antiparallel to the transistor 21, the DC side, the diode 121 connected in antiparallel to the FET 12 of the first series circuit, and the coil 31.

  In the negative half cycle of the alternating current, the transistor 21 of the second series circuit becomes a reverse bias, and the loss of the transistor 21 can be reduced. The FET 22 of the second series circuit becomes a forward bias, and the loss of the FET 22 is reduced. It is possible to reduce the loss, and the power conversion apparatus as a whole can reduce the loss.

  FIG. 5 is an explanatory diagram showing an example of switching loss of a transistor and an FET. In the example of FIG. 5, when the input voltage is 400 V, the output voltage is 280 V, the output power is 6.6 kW, and the operating frequency is 75 kHz, the transistor and FET are forward biased and reverse biased. An example of the switching loss is shown. The numerical values of the switching losses of the transistors and FETs are not limited to the example of FIG. 5, but when other numerical values are used as parameters, the switching loss tends to be the same as the example of FIG. Have.

  As can be seen from FIG. 5, the FET has a large switching loss when biased in the reverse direction and a small switching loss when biased in the forward direction. In addition, the transistor has a large switching loss in a forward biased state and a small switching loss in a reverse biased state. Thus, transistors are used for switching elements that are biased in the reverse direction, and FETs are used for switching elements that are biased in the forward direction, so that all elements are transistors or all elements are FETs. As a whole, loss can be reduced.

  FIG. 6 is a schematic diagram illustrating an example of an input current waveform on the AC side of the power conversion device according to the present embodiment. As shown in FIGS. 3 and 4, the FETs 12 and 22 are repeatedly turned on / off at a predetermined frequency, so that the current flowing through the coils 31 and 32 repeatedly increases and decreases at the predetermined frequency. In FIG. 6, the waveform indicated by reference character Il indicates the current flowing through the coils 31, 32, that is, the AC side input current. The average value of the input current Il is approximately the same as the phase of the waveform of the input voltage applied between the terminals 1 on the AC side, as indicated by reference numeral Ia. Thereby, a power factor can be made high. In FIG. 6, the waveform indicated by the symbol Ip represents the peak value of the input current Il. FIG. 6 schematically shows the current waveform, which is different from the actual current waveform.

  Next, the case of converting from direct current to alternating current will be described. FIG. 7 is an explanatory diagram showing the operation of each switching element when converting from direct current to alternating current by the power conversion device of the present embodiment. In FIG. 7, an AC positive half cycle indicates a period in which a positive half cycle voltage is output from the AC side terminal 1, and an AC negative half cycle indicates a negative half cycle from the AC side terminal 1. Indicates a period during which the voltage is output.

  First, the operation in the positive half cycle of AC will be described. In the positive (one) half cycle of the alternating current, the transistor 11 is always turned on, the transistor 21 is always turned off, the FET 12 is always turned off, and the FET 22 is turned on / off repeatedly at a predetermined frequency. . The predetermined frequency is a frequency higher than a commercial frequency (for example, 50 Hz, 60 Hz, etc.), and can be, for example, about several kHz to several tens of kHz.

  FIG. 8 is a schematic diagram showing a state of a current flowing through the bridge circuit in the case of converting from direct current to alternating current (positive half cycle) in the power conversion device of the present embodiment. As described above in FIG. 7, in the positive half cycle of alternating current, the transistor 11 is controlled to be always on, the transistor 21 is always turned off, the FET 12 is always turned off, and the FET 22 is repeatedly turned on / off at a predetermined frequency. To be controlled.

  As shown in FIG. 8, when the FET 22 of the second series circuit is turned on in the positive half cycle of the alternating current, as shown by the arrows shown by the solid line in FIG. Current flows through the coil 32 and the FET 22 of the second series circuit.

  Then, when the FET 22 of the second series circuit is turned off in the positive half cycle of the alternating current, as shown by the arrow shown by the broken line in FIG. A current flows through the diode 211 that is anti-parallel to the transistor 11 of the first series circuit, the coil 31, the AC side, the coil 32, and the transistor 21 of the second series circuit. In the positive (one) half cycle of the alternating current, the transistor 21 of the second series circuit becomes a reverse bias, and the loss of the transistor 21 can be reduced, and the FET 22 of the second series circuit becomes a forward bias, The loss of the FET 22 can be reduced, and the loss can be reduced as a whole power conversion device.

  Next, the operation | movement in the negative (other side) half cycle of alternating current is demonstrated. As shown in FIG. 7, in the negative half cycle of the alternating current, the transistor 11 is always turned off, the transistor 21 is always turned on, the FET 12 is repeatedly turned on / off at a predetermined frequency, and the FET 22 is always turned off. It is controlled to become.

  FIG. 9 is a schematic diagram showing a state of a current flowing through the bridge circuit in the case of converting from direct current to alternating current (negative half cycle) in the power conversion device of the present embodiment. As shown in FIG. 9, when the FET 12 of the second series circuit is turned on in the negative half cycle of the alternating current, as shown by the arrows shown by the solid line in FIG. Current flows through the coil 31 and the FET 12 of the first series circuit.

  Then, when the FET 12 of the first series circuit is turned off in the negative half cycle of the alternating current, as shown by the arrow shown by the broken line in FIG. A current flows through the diode 111 in antiparallel to the transistor 21 of the two series circuit, the coil 32, the AC side, the coil 31, and the transistor 11 of the first series circuit. In the negative (other) half cycle of the alternating current, the transistor 11 of the first series circuit becomes a reverse bias, and the loss of the transistor 11 can be reduced, and the FET 12 of the first series circuit becomes a forward bias, The loss of the FET 12 can be reduced, and the loss can be reduced as a whole power conversion device.

  As described above, if all the switching elements used in the bridge circuit are bipolar transistors such as IGBTs, the loss during switching increases even in the forward direction. Further, if all the switching elements used in the bridge circuit are unipolar devices such as MOSFETs, the loss at the time of switching in the reverse direction increases, and an excessive surge occurs. However, according to the present embodiment, a bipolar transistor is used as a switching element in which a reverse switching operation is performed, and an FET is used as a switching element in which a forward switching operation is performed. Loss of the switching element can be reduced.

  The embodiments and examples disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

DESCRIPTION OF SYMBOLS 1 AC side terminal 2 DC side terminal 3 Battery 4, 5 Electric circuit 10 1st series circuit 20 2nd series circuit 11, 21 Transistor (1st switching element)
12, 22 FET (second switching element)
111, 121, 211, 221 Diode 30 Filter circuit 31, 32 Coil 33, 50 Capacitor 40 Control unit 60 DC / DC converter

Claims (3)

A plurality of series circuits in which the first switching element and the second switching element are connected in series, each series circuit is connected in parallel, one end of each series circuit is the positive side, the other end is the negative side, A power conversion device further comprising a filter circuit having one end connected to each connection point of the first switching element and the second switching element, the other end of the filter circuit being an AC side;
The first switching element is a bipolar transistor, and a diode is connected in antiparallel between a collector and an emitter of the bipolar transistor,
The power switching device, wherein the second switching element is an FET, and a diode is connected in antiparallel between a drain and a source of the FET. A controller that always turns off the first switching element of each series circuit and turns on / off the second switching element of each series circuit at a predetermined frequency higher than a commercial frequency;
The power conversion device according to claim 1, wherein AC is converted into DC. In one half cycle of alternating current, the first switching element of one series circuit is always turned on, the first switching element of another series circuit is always turned off, and the first switching element of the one series circuit is further turned off. 2 is always turned off, and the second switching element of the other series circuit is turned on / off at a predetermined frequency higher than the commercial frequency,
In the other half cycle of the alternating current, the first switching element of the one series circuit is always turned off, the first switching element of the other series circuit is always turned on, and further, A controller that turns on / off the second switching element at the predetermined frequency and always turns off the second switching element of the other series circuit;
The power conversion device according to claim 1, wherein direct current is converted into alternating current.

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