JP6838297B2 - Power converter - Google Patents

Description

The present invention relates to a power converter.

A primary winding of a first transformer to which a direct current is input, a switching element connected in series with the primary winding of the first transformer, a capacitor connected in parallel with the switching element and connected in series with each other, and a second A primary winding of a transformer, a secondary winding of the first transformer coupled to the primary winding of the first transformer, and a pair of output terminals connected to the secondary winding of the first transformer to output DC power. , The secondary windings of the pair of second transformers, which are coupled to the primary windings of the second transformer, are connected between the pair of output terminals, and are connected so that the directions of the output currents are opposite to each other. A DC-DC converter including the above is disclosed (Patent Document 1). This DC-DC converter includes a transformer, a switching element, a diode, a smoothing capacitor, and a snubber circuit, and the capacitor of the snubber circuit is connected in parallel between the drain and the source of the switching element.

Japanese Unexamined Patent Publication No. 2012-147610

However, in the prior art, there is a problem that the parasitic inductance existing in the wiring between the capacitor of the snubber circuit and the capacitor for smoothing and the oscillating current of the resonance circuit formed by the capacitor of the snubber circuit generate electromagnetic noise.

The present invention is to provide a power conversion device that suppresses electromagnetic noise.

The present invention is a pair of wires connected to a DC power supply, a switching circuit connected between the pair of wires to convert power from the DC power supply, and a switching circuit connected between the pair of wires to smooth the power from the DC power supply. The first capacitor, the second capacitor connected between the pair of wires and protecting the switching circuit, and the first coil provided between the first capacitor and the second capacitor are provided, and the pair of wires is the first capacitor. The first wiring that connects the first capacitor and the switching circuit and the second wiring that connects the second capacitor and the switching circuit are included, and the parasitic inductance existing in the first wiring is larger than the parasitic inductance existing in the second wiring. The 1-coil solves the above problem by generating an induced electromotive force by receiving a magnetic field generated by a current flowing through the first wiring.

The present invention can provide a power conversion device that suppresses electromagnetic noise.

FIG. 1 is a schematic view of a power conversion system using the power conversion device according to the first embodiment. FIG. 2 is a plan view of the power conversion device shown in FIG. FIG. 3 is a schematic view of a power conversion system using the power conversion device according to the second embodiment. FIG. 4 is a schematic view of a power conversion system using the power conversion device according to the third embodiment. FIG. 5 is a schematic view of a power conversion system using the power conversion device according to the fourth embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
FIG. 1 is a schematic view of a power conversion system 100 using the power conversion device 10 according to the first embodiment. The power conversion system 100 includes a power conversion device 10 and peripheral circuits 16 according to the present embodiment. In FIG. 1, the peripheral circuit 16 shows the circuit in the range surrounded by the alternate long and short dash line, and the power conversion device 10 shows the circuit in the range surrounded by the dotted line excluding the peripheral circuit 16.

The power conversion device 10 includes a high-voltage power supply 1, wiring 2, a switching circuit 3, a smoothing capacitor 4, a snubber capacitor 5, and a coil 6. In FIG. 1, the switching circuit 3 shows a circuit in the range surrounded by the dotted line.

The high voltage power supply 1 is a DC power supply. For example, when the power conversion system 100 is mounted on an electric vehicle, a secondary battery such as a lithium ion battery is used as the battery for the high voltage power supply 1. The high voltage power supply 1 is connected to the switching circuit 3 via the wiring 2.

The wiring 2 is a pair of wirings that are connected to the high voltage power supply 1 and supply power from the high voltage power supply 1. The wiring 2 has a wiring 2A connected to the positive electrode of the high voltage power supply 1 and a wiring 2B connected to the negative electrode of the high voltage power supply 1. A copper or aluminum plate-shaped conductor is used for the wiring 2. For example, a bus bar is used for the wiring 2.

The switching circuit 3 is connected between the wirings 2A and 2B. The switching circuit 3 has a plurality of voltage type drive elements and a plurality of rectifier elements. In FIG. 1, the plurality of voltage-type drive elements are transistors Tr1 and Tr2, and the plurality of rectifier elements are diodes D1 and D2. The transistors Tr1 and Tr2 and the diodes D1 and D2 are connected in parallel, respectively. The diodes D1 and D2 are connected to the transistors Tr1 and Tr2 in the direction in which the current flows in the direction opposite to the current direction of the transistors Tr1 and Tr2. The same transistors are used as the transistors Tr1 and Tr2, and for example, a field effect transistor (MOSFET) made of silicon (Si) is used.

In the present embodiment, the switching circuit 3 is composed of a series circuit of the transistor Tr1 and the transistor Tr2. The transistors Tr1 and Tr2 have gate, source, and drain terminals. The drain terminal of the transistor Tr1 is connected to the wiring 2A, and the source terminal of the transistor Tr2 is connected to the wiring 2B. That is, the transistor Tr1 is electrically connected to the positive electrode side of the high voltage power supply 1, and the transistor Tr2 is electrically connected to the negative electrode side of the high voltage power supply 1. The source terminal of the transistor Tr1 and the drain terminal of the transistor Tr2 are connected. The switching circuit 3 outputs a voltage from the connected point (output terminal).

The transistors Tr1 and Tr2 operate as switching elements. The switching circuit 3 converts and outputs the DC power from the high voltage power supply 1 by the switching operation of the transistor Tr1 or Tr2. The switching circuit 3 outputs the converted voltage to the output terminal. The switching operation of the transistor Tr1 or the transistor Tr2 is that the transistor Tr1 or the transistor Tr2 is turned on or off. The transistor Tr1 is controlled by the control circuit 15 via the drive circuit 12, and the transistor Tr2 is controlled by the control circuit 15 via the drive circuit 13.

In this embodiment, the switching circuit 3 operates as a single-phase inverter circuit. When the transistor Tr1 is on and the transistor Tr2 is off, the switching circuit 3 outputs the voltage of the wiring 2A. In the above-mentioned state, the wiring 2A and the output terminal of the switching circuit 3 are conducting. Further, when the transistor Tr1 is off and the transistor Tr2 is on, the switching circuit 3 outputs the voltage of the wiring 2B. In this state, the wiring 2B and the output terminal of the switching circuit 3 are conducting. For example, when the positive electrode of the high voltage power supply 1 is 10V and the negative electrode is 0V, the switching circuit 3 outputs 10V or 0V from the output terminal according to the switching operation of the transistors Tr1 and Tr2.

The smoothing capacitor 4 is connected between the wirings 2A and 2B, and is connected in parallel with the high voltage power supply 1. The smoothing capacitor 4 is provided to smooth the DC power supplied from the high voltage power supply 1. The positive electrode of the smoothing capacitor 4 is connected to the switching circuit 3 via the wiring 2A, and the negative electrode of the smoothing capacitor 4 is connected to the switching circuit 3 via the wiring 2B. The power of the high-voltage power supply 1 smoothed by the smoothing capacitor 4 is supplied to the switching circuit 3. The capacitance value of the smoothing capacitor 4 is determined according to the power that can be supplied by the high voltage power supply 1. In the present embodiment, the capacitance of the smoothing capacitor 4 is larger than the capacitance of the snubber capacitor 5.

The snubber capacitor 5 is connected between the wirings 2A and 2B. The snubber capacitor 5 is provided between the smoothing capacitor 4 and the switching circuit 3. The snubber capacitor 5 is provided to suppress a steep rising voltage or a steep falling voltage with respect to the output voltage of the switching circuit 3. The steep rising voltage or steep falling voltage generated from the switching circuit 3 will be described later. The capacitance value of the snubber capacitor 5 is determined according to the characteristics of the transistor of the switching circuit 3, the arrangement of the snubber capacitor 5 and the switching circuit 3, the distance between the snubber capacitor 5 and the switching circuit 3, and the like. In this embodiment, the capacitance of the snubber capacitor 5 is smaller than that of the smoothing capacitor 4.

The coil 6 is provided between the smoothing capacitor 4 and the snubber capacitor 5. The coil 6 is connected to the rectifier 11. In FIG. 1, the coil 6 is provided to generate an induced electromotive force by receiving a magnetic field generated by a change in the current flowing through the wiring 2A. The induced electromotive force generated in the coil 6 will be described later.

The parasitic inductance 7 is a parasitic inductance existing in the wiring 2 connecting the smoothing capacitor 4 and the snubber capacitor 5. In FIG. 1, the parasitic inductance 7 equivalently shows the parasitic inductance in consideration of the mutual inductance of the parasitic inductance existing in the wiring 2A and the parasitic inductance existing in the wiring 2B.

The peripheral circuit 16 includes a rectifier 11, a drive circuit 12, a drive circuit 13, a low-voltage power supply 14, and a control circuit 15.

The rectifier 11 is provided to allow (rectify) a current generated by the induced electromotive force generated by the coil 6 in only one direction. The commutator 11 receives the current generated by the coil 6 as an input and rectifies it to supply electric power to the drive circuit 12.

The drive circuit 12 outputs a gate signal to the transistor Tr1 of the switching circuit 3 to drive the transistor Tr1. The drive circuit 12 is electrically connected to the gate terminal of the transistor Tr1. The drive circuit 12 operates at a voltage lower than the output voltage of the high-voltage power supply 1, and operates using the power output from the rectifier 11 as a power source. As a result, the number of parts can be reduced without separately preparing a power supply for operating the drive circuit 12. A low voltage power supply for the drive circuit 12 may be provided in case the power from the rectifier 11 is small. In this case, the drive circuit 12 operates using the electric power from the rectifier 11 as an auxiliary power source.

The drive circuit 13 outputs a gate signal to the transistor Tr2 of the switching circuit 3 to drive the transistor Tr2. The drive circuit 13 is electrically connected to the gate terminal of the transistor Tr2. The drive circuit 13 operates at a voltage lower than the output voltage of the high-voltage power supply 1, and operates using the power supplied from the low-voltage power supply 14 as a power source.

The control circuit 15 controls the transistors Tr1 and Tr2 via the drive circuit 12 and the drive circuit 13. For example, the control circuit 15 generates a PWM (pulse width modulation) signal and outputs the signal as a control signal to the drive circuit 12 and the drive circuit 13. The drive circuit 12 and the drive circuit 13 turn on and off the transistors Tr1 and Tr2 at predetermined timings based on the pulse width modulation signal. As a result, the power conversion device 10 performs an operation of converting and outputting the power of the high voltage power supply 1.

Next, the role of the snubber capacitor 5 will be described. First, the operation of the switching circuit 3 will be described immediately after the transistor Tr1 is turned on or immediately after the transistor Tr2 is turned off.

As described above, when the transistor Tr1 is turned on, the drain terminal of the transistor Tr1 and the wiring 2A become conductive. The current from the wiring 2A flows into the transistor Tr1. That is, a sudden current change occurs in the output terminal of the switching circuit 3. Then, due to the self-inductance of the transistor Tr1, an electromotive force is generated in a direction that hinders the change in current, and the voltage at the output terminal rises sharply. Then, when the current change in the transistor Tr1 becomes small, that is, in the steady state, the voltage of the output terminal becomes the voltage of the wiring 2A. Further, even immediately after the transistor Tr2 is turned on, a sudden current change occurs in the output terminal of the switching circuit 3. Then, due to the self-inductance of the transistor Tr2, an electromotive force is generated in a direction that hinders the current change, and the voltage of the output terminal drops sharply. Then, when the current change in the transistor Tr2 becomes small, that is, in the steady state, the voltage of the output terminal becomes the voltage of the wiring 2B. As described above, the switching circuit 3 instantaneously outputs a spike-shaped voltage by the switching operation of the transistors Tr1 and Tr2. The spiked output voltage puts a load on the transistor or peripheral electronic components.

The snubber capacitor 5 is provided to protect the switching circuit 3. The snubber capacitor 5 emits or charges an electric charge in response to a change in current in the transistor Tr1 or Tr2. Thereby, a sudden change in current in the transistor Tr1 or Tr2 can be suppressed. Therefore, the electromotive force due to the self-inductance of the transistors Tr1 and Tr2 is suppressed. That is, the snubber capacitor 5 allows the switching circuit 3 to suppress the spike-shaped output voltage. As a result, the snubber capacitor 5 can suppress the load on the transistor or peripheral electronic components due to the spike-shaped output voltage. Further, the snubber capacitor 5 can suppress electromagnetic noise due to the spike-shaped output voltage. By providing the snubber capacitor 5 in the vicinity of the switching circuit 3, the above-mentioned suppression effect becomes remarkable.

Next, based on the role of the snubber capacitor 5 described above, the arrangement of each component constituting the power conversion device 10 will be described. FIG. 2 is a plan view of the power conversion device 10 shown in FIG. FIG. 2 shows the wiring 2, the switching circuit 3, the snubber capacitor 5, the coil 6, the rectifier 11, and the drive circuit 12 among the power conversion devices 10 of FIG.

The smoothing capacitor 4 is provided at a predetermined distance from the switching circuit 3. The smoothing capacitor 4 is connected to the switching circuit 3 via the wiring 2. FIG. 2 shows that the positive electrode of the smoothing capacitor 4 and one end of the wiring 2A are connected, and the negative electrode of the smoothing capacitor 4 and one end of the wiring 2B are connected. In order to smooth the output voltage of the high voltage power supply 1, the smoothing capacitor 4 is formed of a capacitor larger than that of the snubber capacitor 5.

The smoothing capacitor 4 is connected to one end of the wirings 2A and 2B. The other ends of the wirings 2A and 2B are located directly above the drain terminal of the transistor Tr1 and the source terminal of the transistor Tr2. The snubber capacitor 5 has terminal electrodes at the left and right ends, respectively. Both terminal electrodes are located directly above the drain terminal of the transistor Tr1 and the source terminal of the transistor Tr2. As shown in FIG. 2, one terminal electrode of the snubber capacitor 5 is connected to the other end of the wiring 2A, and the other terminal electrode of the snubber capacitor 5 is connected to the other end of the wiring 2B. For example, both terminal electrodes of the snubber capacitor 5, the other end of the wiring 2A, and the other end of the wiring 2B are bonded with a conductive adhesive such as solder. The other end of the wiring 2A is electrically connected to the drain terminal of the transistor Tr1, and the other end of the wiring 2B is electrically connected to the source terminal of the transistor Tr2. As a result, the snubber capacitor 5 can be provided in the vicinity of the switching circuit 3. By providing it in the vicinity of the switching circuit 3, the spike-shaped output voltage of the switching circuit 3 during the switching operation can be suppressed more effectively. Further, since the snubber capacitor 5 is provided in the vicinity of the switching circuit 3, the length of the wiring 2 connecting the snubber capacitor 5 and the switching circuit 3 is shorter than the length of the wiring 2 connecting the snubber capacitor 5 and the smoothing capacitor 4. ..

As described above, the snubber capacitor 5 is preferably provided in the vicinity of the switching circuit 3. Therefore, the volume of the snubber capacitor 5 is preferably small. In the present embodiment, the snubber capacitor 5 uses a capacitor having a capacity smaller than that of the smoothing capacitor 4.

The coil 6 is provided in the vicinity of the switching circuit 3. The coil 6 is provided between the wirings 2A and 2B. The induced electromotive force generated in the coil 6 is supplied to the drive circuit 12 via the rectifier 11. The drive circuit 12 is provided in the vicinity of the switching circuit 3. As a result, the induced electromotive force generated in the coil 6 can be supplied to the drive circuit 12 without a voltage drop.

Next, the parasitic inductance existing in the wiring 2 will be described. The wiring 2 has a predetermined length because the smoothing capacitor 4 and the switching circuit 3 are provided at a distance from each other. On the other hand, the snubber capacitor 5 is provided in the vicinity of the switching circuit 3. Therefore, of the wiring 2, the wiring connecting the snubber capacitor 5 and the switching circuit 3 is shorter than the wiring connecting the smoothing capacitor 4 and the switching circuit 3. In the following description, the wiring connecting the smoothing capacitor 4 and the switching circuit 3 will be referred to as a main wiring, and the wiring connecting the snubber capacitor 5 and the switching circuit 3 will be referred to as a sub wiring. The sub wiring may be a part of the main wiring.

The wiring 2 includes a main wiring and a sub wiring. Since the main wiring is longer than the sub wiring, the parasitic inductance existing in the main wiring is larger than the parasitic inductance existing in the sub wiring.

Next, the oscillating current generated during the switching operation of the switching circuit 3 will be described with reference to FIG. First, an LC resonant circuit formed by a parasitic inductance and a snubber capacitor will be described.

In the example of FIG. 1, the parasitic inductance existing in the main wiring is indicated by the parasitic inductance 7. In FIG. 1, an LC resonance circuit is formed by the parasitic inductance 7 and the snubber capacitor 5. Next, the oscillating current generated by the LC resonance circuit will be described.

When the electric charge stored in the snubber capacitor 5 changes, an oscillating current is generated. In the example of FIG. 1, the oscillating current is generated in the main wiring. For example, consider the case where electric charge is emitted from the snubber capacitor 5 in order to suppress the spike-shaped output voltage due to the switching operation of the switching circuit 3. In this case, the released charge is supplied to the switching circuit 3. To compensate for the released charge, the charge is supplied from the smoothing capacitor 4 to the snubber capacitor 5. That is, a current flows from the smoothing capacitor 4 to the snubber capacitor 5 via the parasitic inductance 7. The parasitic inductance 7 causes a change in current, and the parasitic inductance 7 generates electric power in a direction that obstructs the direction of the current from the smoothing capacitor 4 to the snubber capacitor 5, that is, a counter electromotive force. Due to the counter electromotive force, the parasitic inductance 7 causes a change in the current in the reverse direction, and the parasitic inductance 7 generates the counter electromotive force again. Resonance by the LC resonance circuit occurs due to the repeated generation of counter electromotive forces in which the directions of the currents are different.

Due to the resonance of the LC resonance circuit, alternating current is generated in the main wiring. The alternating current flows through the main wiring as an oscillating current. When the oscillating current flows through the main wiring, electromagnetic noise due to the oscillating current is emitted from the wiring 2. As described above, the switching operation of the switching circuit 3 causes a current change at the parasitic inductance 7, and the oscillating current flows through the main wiring. As a result, the power converter 10 emits electromagnetic noise.

The oscillating current is an alternating current that oscillates at a resonance frequency determined by the inductance and the capacitor that form the LC resonance circuit. In the example of FIG. 1, the resonance frequency is determined by the parasitic inductance 7 and the snubber capacitor 5. Therefore, for example, the resonance frequency can be changed by changing the shape of the wiring 2 or the capacitance value of the snubber capacitor 5. As a result, it is possible to suppress the influence on the electronic components and the like existing around the power conversion device 10.

Further, the maximum current value of the oscillating current changes according to the switching speed of the switching circuit 3. That is, if the switching speed of the transistors Tr1 and Tr2 is high, the maximum current of the oscillating current becomes large. Therefore, the maximum current value of the oscillating current generated when the switching speed is high is larger than the maximum current value of the oscillating current generated when the switching speed is slow. As a result, the amount of electromagnetic noise emitted increases as the switching speed increases.

Next, the magnetic field generated by the oscillating current will be described. When the oscillating current flows in the main wiring, a magnetic field is generated around the main wiring. Explaining with reference to FIG. 1, magnetic fields are generated inside and outside the closed circuit formed by the smoothing capacitor 4, the snubber capacitor 5, and the parasitic inductance 7. The magnetic field inside the closed circuit is stronger than the magnetic field outside the closed circuit.

Next, the induced electromotive force generated in the coil 6 will be described. As described above, the switching operation of the switching circuit 3 generates an oscillating current in the main wiring. Then, a magnetic field is generated around the main wiring due to the oscillating current. The coil 6 receives an inductive electromotive force by receiving a magnetic field generated by a current flowing through the main wiring. The generated induced electromotive force is rectified by the rectifier 11 and supplied to the drive circuit 12. This eliminates the need to provide a low voltage power supply to operate the drive circuit 12.

Further, in the present embodiment, the coil 6 is provided between the pair of main wirings. In other words, it is provided inside the closed circuit described above. As a result, the coil 6 can receive the magnetic field inside the closed circuit to generate an induced electromotive force. When the induced electromotive force is generated, a current flows through the coil 6. The coil 6 generates a magnetic field in a direction that cancels the oscillating current by the current. Therefore, the oscillating current can be attenuated, and as a result, electromagnetic noise can be suppressed.

Further, in the present embodiment, the capacitance of the smoothing capacitor 4 is larger than the capacitance of the snubber capacitor 5. Further, by arranging the switching circuit 3, the smoothing capacitor 4, and the snubber capacitor 5 as shown in FIG. 2, the parasitic inductance existing in the main wiring becomes larger than the parasitic inductance existing in the sub wiring. Therefore, the oscillating current due to the LC resonance circuit is mainly generated in the main wiring. In this embodiment, the coil 6 is provided between the main wirings. Therefore, the coil 6 can generate most of the oscillating current as an induced electromotive force. As a result, a larger induced electromotive force can be supplied to the drive circuit 12.

Further, in the present embodiment, it is preferable that the coupling coefficient of the coil 6 and the parasitic inductance 7 is high. As a result, it is possible to generate a highly efficient induced electromotive force with respect to the oscillating current.

Further, in the present embodiment, the effect of suppressing the oscillating current can be enhanced by controlling the control circuit 15. The control circuit 15 controls so as to increase the power consumption of the drive circuit 12 when an oscillating current is generated. As a result, the control circuit 15 can consume the induced electromotive force generated by the coil 6. Therefore, a current flows through the coil 6 to generate an induced electromotive force, and the current generates a magnetic field in a direction that cancels the oscillating current. As a result, the effect of suppressing the oscillating current can be enhanced.

As described above, in the present embodiment, the power conversion device 10 is a switching circuit 3 connected between the wiring 2 connected to the high-voltage power supply 1 and the pair of wirings 2 to convert the power from the high-voltage power supply 1. A smoothing capacitor 4 connected between the pair of wirings 2 to smooth the power from the high-voltage power supply 1, a snubber capacitor 5 connected between the pair of wirings 2 to protect the switching circuit 3, and a smoothing capacitor 4. It is provided with a coil 6 provided between the snubber capacitor 5 and the snubber capacitor 5. The pair of wires 2 includes a main wire that connects the smoothing capacitor 4 and the switching circuit 3, and a sub wire that connects the snubber capacitor 5 and the switching circuit 3. The parasitic inductance present in the main wiring is larger than the parasitic inductance present in the sub wiring. The coil 6 receives an electromagnetic field generated by a current flowing through the main wiring to generate an induced electromotive force. As a result, the power conversion device 10 can generate a magnetic field so as to cancel the oscillating current flowing through the main wiring. Therefore, the vibration current can be suppressed, and as a result, electromagnetic noise can be suppressed.

Further, in the present embodiment, the coil 6 receives an induced electromotive force by receiving a magnetic field generated by a parasitic inductance 7 existing in the pair of wirings 2 and a vibration current generated by the snubber capacitor 5. Thereby, the inductance value of the coil 6 can be set according to the parasitic inductance 7 and the snubber capacitor 5. Therefore, the suppression level of the vibration current by the coil 6 can be estimated in advance. Vibration current can be suppressed, and as a result, electromagnetic noise can be suppressed.

Further, in the present embodiment, the coil 6 is provided between the pair of wirings 2. As a result, an induced electromotive force can be generated by receiving a magnetic field inside the closed circuit formed by the smoothing capacitor 4, the parasitic inductance 7, and the snubber capacitor 5. That is, a larger induced electromotive force can be generated by receiving a stronger magnetic field than the outside of the closed circuit. Therefore, it is possible to generate a stronger magnetic field and a magnetic field that cancels the oscillating current as compared with the case where the coil 6 is provided outside the closed circuit. As a result, the effect of suppressing the vibration current can be enhanced, and the effect of suppressing electromagnetic noise can be enhanced.

Further, in the present embodiment, the switching circuit 3 converts the power from the high voltage power supply 1 by the switching operation, and the vibration current flows through the main wiring by the switching operation. The coil 6 receives an electromagnetic field generated by an oscillating current flowing in the main wiring to generate an induced electromotive force. That is, the maximum current value of the oscillating current or the frequency of occurrence of the oscillating current changes according to the switching speed or the number of switchings of the switching circuit 3. Therefore, the vibration current can be suppressed by controlling the switching circuit 3. As a result, electromagnetic noise can be suppressed.

Further, in the present embodiment, the effect of suppressing the oscillating current can be enhanced by controlling the control circuit 15. The control circuit 15 controls so as to increase the power consumption of the drive circuit 12 when an oscillating current is generated. As a result, the drive circuit 12 can consume the induced electromotive force generated by the coil 6. Therefore, a current flows through the coil 6 to generate an induced electromotive force, and the current generates a magnetic field in a direction that cancels the oscillating current. As a result, the effect of suppressing the oscillating current can be enhanced.

Further, in the present embodiment, the power consumption of the drive circuit 12 increases as the number of switching operations of the transistors Tr1 and Tr2 increases. Therefore, as the number of switching operations of the transistors Tr1 and Tr2 increases, the number of times the oscillating current is generated also increases, and the number of times the induced electromotive force is generated in the coil 6 also increases. As a result, the drive circuit 12 can obtain more power from the coil 6.

<< Second Embodiment >>
Next, the power conversion system 200 using the power conversion device 10 according to the second embodiment will be described. FIG. 3 is a schematic view of a power conversion system 200 using the power conversion device 10 according to the second embodiment. The present embodiment has the same configuration as the power conversion device 10 according to the first embodiment, and operates in the same manner as the first embodiment except for the operations described below. In FIG. 3, the peripheral circuit 26 shows a circuit in the range surrounded by the alternate long and short dash line.

The coil 6 is provided to generate an induced electromotive force by receiving a magnetic field generated by a current flowing through the wiring 2A. The induced electromotive force generated in the coil 6 is supplied to the drive circuit 12 via the rectifier 11. Since the current flowing through the wiring 2A is the same as that of the first embodiment, the description thereof will be omitted.

Since the peripheral circuit 26 has the same configuration as the peripheral circuit 16 according to the first embodiment except that it includes the coil 21 and the rectifier 22, the description thereof will be omitted.

The coil 21 is connected to the rectifier 22. The coil 21 is provided to generate an induced electromotive force by receiving a magnetic field generated by a current flowing through the wiring 2B. The induced electromotive force generated in the coil 21 is supplied to the drive circuit 13 via the rectifier 22. Since the current flowing through the wiring 2B is the same as that of the first embodiment, the description thereof will be omitted.

The rectifier 22 is provided to rectify the current due to the induced electromotive force generated in the coil 21. The commutator 22 receives the current generated by the coil 21 as an input and rectifies it to supply electric power to the drive circuit 13.

The drive circuit 13 operates at a voltage lower than the output voltage of the high-voltage power supply 1, and operates using the power output from the rectifier 22 as a power source. Thereby, in the present embodiment, it is not necessary to provide the low voltage power supply necessary for the operation of the drive circuit 13, and the drive circuit 13 can be operated. As a result, the cost can be suppressed.

<< Third Embodiment >>
Next, the power conversion system 300 using the power conversion device 10 according to the third embodiment will be described. FIG. 4 is a schematic view of the power conversion system 300 using the power conversion device 10 according to the third embodiment. The present embodiment has the same configuration as the power conversion device 10 according to the first embodiment, and operates in the same manner as the first embodiment except for the operations described below. In FIG. 4, the peripheral circuit 36 shows a circuit in the range surrounded by the alternate long and short dash line.

Since the peripheral circuit 36 has the same configuration as the peripheral circuit 16 according to the first embodiment except that it includes the rectifier 31, the description thereof will be omitted.

The rectifier 31 is connected to the coil 6. The rectifier 31 is provided to rectify the current due to the induced electromotive force generated in the coil 6. The commutator 31 receives the current generated by the coil 6 as an input and rectifies it to supply electric power to the drive circuit 13. The drive circuit 13 operates using the electric power output from the rectifier 31 as a power source. Thereby, in the present embodiment, it is not necessary to provide the low voltage power supply necessary for the operation of the drive circuit 13, and it is not necessary to provide the coil for the drive circuit 13, so that the drive circuit 13 can be operated. As a result, the cost can be suppressed.

<< Fourth Embodiment >>
Next, the power conversion system 400 using the power conversion device 20 according to the fourth embodiment will be described. FIG. 5 is a schematic view of a power conversion system 400 using the power conversion device 20 according to the fourth embodiment. Since the power conversion device 20 according to the fourth embodiment has the same configuration as the power conversion device 10 according to the first embodiment except that the coils 41 and 42 are provided, the description other than the coils 41 and 42 will be described. Is omitted. Further, since the peripheral circuit 26 has the same configuration as the peripheral circuit 26 according to the second embodiment, the description thereof will be omitted.

The coil 41 is provided between the high voltage power supply 1 and the smoothing capacitor 4. The coil 41 is connected to the rectifier 11. The coil 41 is provided in the wiring 2A to receive an induced electromotive force by receiving a magnetic field generated by a current flowing in the wiring connecting the positive electrode of the high voltage power supply 1 and the positive electrode of the smoothing capacitor 4.

The coil 42 is provided between the high voltage power supply 1 and the smoothing capacitor 4. The coil 42 is connected to the rectifier 22. The coil 42 is provided in the wiring 2B to receive an induced electromotive force by receiving a magnetic field generated by a current flowing in the wiring connecting the negative electrode of the high voltage power supply 1 and the negative electrode of the smoothing capacitor 4.

The induced electromotive force generated in the coils 41 and 42 will be described. First, the magnetic field due to the precharge of the smoothing capacitor 4 will be described. When the power conversion system 400 is started, the current from the high voltage power supply 1 to the smoothing capacitor 4 flows as a precharge current. That is, when the power conversion system 400 is started, the smoothing capacitor 4 is started to be precharged. For example, it is assumed that a relay element (not shown) is connected between the high voltage power supply 1 and the smoothing capacitor 4. When the power conversion system 400 is started, the relay element is switched from off to on, and precharging from the high voltage power supply 1 to the smoothing capacitor 4 is started. When the precharge is started, the precharge current is flowing through the closed circuit formed by the high voltage power supply 1 and the smoothing capacitor 4. Therefore, a magnetic field is generated on the outside and the inside of the closed circuit.

The coils 41 and 42 are provided between the wirings 2A and 2B. The magnetic field generated inside the closed circuit penetrates the coil 41 and the coil 42. The precharge current changes according to the amount of electric charge stored in the smoothing capacitor 4. That is, immediately after the relay element is turned on, the current flows from the high voltage power supply 1 to the smoothing capacitor 4, so that the precharge current increases sharply, but as the charge is accumulated in the smoothing capacitor 4, the precharge current increases. It will decrease. Therefore, the magnetic field inside the closed circuit also changes according to the amount of change in the precharge current. The coils 41 and 42 generate an induced electromotive force in response to a change in the magnetic field. The induced electromotive force generated by the coil 41 is supplied to the drive circuit 12 via the rectifier 11, and the induced electromotive force generated by the coil 42 is supplied to the drive circuit 13 via the rectifier 22. Due to the above-mentioned phenomenon, electric power can be obtained from the precharge current generated when the power conversion system 400 is started.

As described above, in the present embodiment, the power conversion device 20 further includes coils 41 and 42 provided between the high voltage power supply 1 and the smoothing capacitor 4. The coils 41 and 42 receive an induced electromotive force by receiving a magnetic field generated by a current flowing from the high voltage power supply 1 to the smoothing capacitor 4. As a result, when the power conversion system 400 is started, power can be obtained from the precharge current flowing from the high voltage power supply 1 to the smoothing capacitor 4. Therefore, the induced electromotive force can be supplied to the drive circuits 12 and 13 immediately after the power conversion system 400 is started.

Further, in the present embodiment, the coils 41 and 42 are provided between the pair of wirings 2. As a result, the coils 41 and 42 can generate an induced electromotive force by receiving a magnetic field inside the closed circuit formed by the high voltage power supply 1 and the smoothing capacitor 4. That is, a larger induced electromotive force can be generated by receiving a stronger magnetic field than the outside of the closed circuit. Therefore, a larger induced electromotive force can be generated as compared with the case where the coils 41 and 42 are provided outside the closed circuit.

In the above-described embodiment, the main wiring is formed longer than the sub wiring, but the present invention is not limited to this. For example, the cross-sectional area or shape of the main wiring may be changed so that the parasitic inductance existing in the main wiring is larger than the inductance existing in the sub wiring.

Further, in the above-described embodiment, the switching circuit 3 is composed of a series circuit in which switching elements are connected in series, that is, a single-phase inverter circuit, but is not limited to this. It may be composed of a two-phase inverter circuit in which two sets of the series circuits are connected in parallel, or a three-phase inverter circuit in which three sets of the series circuits are connected in parallel. Further, in the above-described embodiment, the voltage at the connection point between the transistor Tr1 and the transistor Tr2 is used as the output voltage of the switching circuit 3, but the present invention is not limited to this. The voltage on the drain terminal side of the transistor Tr1, that is, the voltage at the connection point between the transistor Tr1 and the positive electrode of the high voltage power supply 1 may be used as the output voltage. Further, the voltage on the source terminal side of the transistor Tr2, that is, the voltage at the connection point between the transistor Tr2 and the negative electrode of the high voltage power supply 1 may be used as the output voltage.

Further, in the above-described embodiment, the switching element constituting the switching circuit 3 is composed of a voltage type drive element, but may be composed of a current type drive element. Further, the switching element is formed of a transistor made of silicon, but the switching element is not limited to this. For example, it may be formed of a voltage-driven or current-driven transistor of a wide bandgap semiconductor such as silicon carbide (SiC) or gallium nitride (GaN). Regarding the carrier speed, SiC or GaN is faster than Si, and the switching operation of the switching circuit 3 can be operated at a high speed. Furthermore, transistors are not limited to MOSFETs. For example, it may be formed of an insulated gate bipolar transistor (IGBT) capable of passing a larger current than a MOSFET.

Further, in the above-described embodiment, the snubber capacitor 5 is provided between the smoothing capacitor 4 and the switching circuit 3, but is not limited to this. For example, the snubber capacitor 5 may be provided so that the switching circuit 3 is arranged between the smoothing capacitor 4 and the snubber capacitor 5.

Further, in the above-described embodiment, the induced electromotive force generated by the coil 6 or the coil 41 is supplied to the drive circuit 12, and the induced electromotive force generated by the coil 21 or the coil 42 is supplied to the drive circuit 13. Not limited. For example, when a battery such as a lithium ion battery is used for the high voltage power supply 1, the induced electromotive force generated in each coil may be supplied to the battery.

The high-voltage power supply 1 according to the above-described embodiment is a DC power supply, the pair of wirings 2 is a pair of wirings, the smoothing capacitor 4 is a first capacitor, the snubber capacitor 5 is a second capacitor, and the coil 6 or the coil 21 is a first. The main wiring corresponds to the first wiring, the sub wiring corresponds to the second wiring, the transistor Tr1 or Tr2 corresponds to the semiconductor switching element, and the coil 41 or the coil 42 corresponds to the second coil, respectively.

It should be noted that the embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above-described embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

1 ... High voltage power supply 2 ... Wiring 2A ... Wiring 2B ... Wiring 3 ... Switching circuit Tr1 ... Transistor Tr2 ... Transistor D1 ... Diode D2 ... Diode 4 ... Smoothing capacitor 5 ... Snubber capacitor 6 ... Coil 7 ... Parasitic inductance 10 ... Power converter 11 ... Rectifier 12 ... Drive circuit 13 ... Drive circuit 14 ... Low voltage power supply 15 ... Control circuit

Claims (11)

A pair of wires connected to a DC power supply and
A switching circuit connected between the pair of wires and converting power from the DC power supply,
A first capacitor connected between the pair of wires and smoothing the power from the DC power supply,
A second capacitor connected between the pair of wires and protecting the switching circuit,
A first coil provided between the first capacitor and the second capacitor is provided.
The pair of wirings includes a first wiring that connects the first capacitor and the switching circuit, and a second wiring that connects the second capacitor and the switching circuit.
The parasitic inductance existing in the first wiring is larger than the parasitic inductance existing in the second wiring.
The first coil receives a magnetic field generated by a current flowing through the first wiring to generate an induced electromotive force.
The electric power based on the induced electromotive force is a power conversion device that is supplied to the drive circuit as a power source for the drive circuit that drives the switching circuit. The power conversion device according to claim 1.
The first coil is a power conversion device that generates the induced electromotive force by receiving the magnetic field generated by the parasitic inductance existing in the first wiring and the oscillating current by the second capacitor. The power conversion device according to claim 1 or 2.
A power conversion device in which the capacity of the first capacitor is larger than the capacity of the second capacitor. The power conversion device according to any one of claims 1 to 3.
The second capacitor is a power conversion device provided between the first capacitor and the switching circuit. The power conversion device according to any one of claims 1 to 4.
The first coil is a power conversion device provided between the pair of wirings. The power conversion device according to any one of claims 1 to 5.
The switching circuit converts the electric power from the DC power supply by the switching operation.
A power conversion device in which the current flows through the first wiring due to the switching operation. The power conversion device according to any one of claims 1 to 6.
The first wiring is a power conversion device longer than the second wiring. The power conversion device according to any one of claims 1 to 7.
The switching circuit is a power conversion device including a semiconductor switching element. The power conversion device according to claim 8.
The switching circuit is a power conversion device having a series circuit in which the semiconductor switching elements are connected in series. The power conversion device according to any one of claims 1 to 9.
Further, a second coil provided between the DC power supply and the first capacitor is provided.
The second coil is a power conversion device that generates an induced electromotive force by receiving a magnetic field generated by a current flowing from the DC power supply to the first capacitor. The power conversion device according to claim 10.
The second coil is a power conversion device provided between the pair of wirings.

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