WO2022153614A1 - Multi-level inverter - Google Patents

Abstract

This multi-level inverter includes a battery, a first capacitor connected between a midpoint wire and a low potential input wire, a second capacitor connected between a high potential input wire and the midpoint wire, a charging circuit, and a control circuit. The charging circuit includes a direct current charging port, a charging positive electrode wire connecting the positive electrode of the direct current charging port and a cathode of a first midpoint-side intermediate diode, and a charging negative electrode wire connecting the negative electrode of the direct current charging port and an anode of a second midpoint-side intermediate diode. When a charger is connected to the direct current charging port, the control circuit executes boost control by repeatedly alternating a first operation of turning a first midpoint-side intermediate switching element on to charge the first capacitor by means of electric power from the charger, and a second operation of turning a second midpoint-side intermediate switching element on to charge the second capacitor by means of electric power from the charger.

Description

Multi-level inverter

(Cross-reference of related applications)
This application is a related application of Japanese Patent Application Japanese Patent Application No. 2021-004091 filed on January 14, 2021, and claims priority based on this Japanese patent application, and is described in this Japanese patent application. All the contents are incorporated herein by reference.

The techniques disclosed herein relate to multi-level inverters.

A multi-level inverter is disclosed in Japanese Patent Publication No. 2011-109801. The multi-level inverter converts the DC power input from the battery into AC power. The multi-level inverter can control the voltage of each output wiring in multiple levels. According to the multi-level inverter, the output current can be controlled more accurately.

The battery may be charged by applying a voltage to the battery with an external charger. At this time, if the supply voltage of the charger is lower than the output voltage of the battery, it is necessary to boost the supply voltage of the charger and apply the boosted voltage to the battery. In such a case, conventionally, a boost converter circuit is provided in the multi-level inverter, and the supply voltage of the charger is boosted by the boost converter circuit. In this configuration, there is a problem that the entire multi-level inverter becomes large. This specification proposes a technique for boosting the supply voltage of a charger by using an inverter circuit inside a multi-level inverter.

The multi-level inverter disclosed in the present specification includes a battery, a high potential input wiring connected to the positive side of the battery, a low potential input wiring connected to the negative side of the battery, a midpoint wiring, and the midpoint. The first capacitor connected between the wiring and the low potential input wiring, the second capacitor connected between the high potential input wiring and the midpoint wiring, the first output wiring, and the second output wiring. It has a third output wiring, a first switching circuit, a second switching circuit, a third switching circuit, a charging circuit, and a control circuit. The first switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the first output wiring. The second switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the second output wiring. The third switching circuit is connected to the high potential input wiring, the midpoint wiring, the low potential input wiring, and the third output wiring. The first switching circuit is connected between the first upper arm switching element connected between the high potential input wiring and the first output wiring, and the first output wiring and the low potential input wiring. 1 The lower arm switching element, the first midpoint side intermediate diode whose anode is connected to the midpoint wiring, the cathode is connected to the cathode of the first midpoint side intermediate diode, and the anode is the first. To the first output side intermediate diode connected to the output wiring, the first middle point side intermediate switching element connected in parallel with the first middle point side intermediate diode, and the first output side intermediate diode. On the other hand, it has a first output side intermediate switching element, which is connected in parallel. The second switching circuit is connected to a second upper arm switching element connected between the high potential input wiring and the second output wiring, and a second upper arm switching element connected between the second output wiring and the low potential input wiring. 2 The lower arm switching element, the second midpoint side intermediate diode whose cathode is connected to the midpoint wiring, the anode is connected to the anode of the second midpoint side intermediate diode, and the cathode is the second. To the second output side intermediate diode connected to the output wiring, the second middle point side intermediate switching element connected in parallel with the second middle point side intermediate diode, and the second output side intermediate diode. On the other hand, it has a second output side intermediate switching element, which is connected in parallel. The charging circuit connects the DC charging port, the positive electrode of the DC charging port, and the cathode of the first midpoint side intermediate diode, and the negative electrode of the DC charging port and the middle of the second midpoint side. It has a charging negative electrode wiring, which connects the diode to the anode. When the charger is connected to the DC charging port, the control circuit turns on the first midpoint side intermediate switching element and charges the first capacitor with the electric power of the charger. The boost control is executed by turning on the second middle point side intermediate switching element and alternately repeating the second operation of charging the second capacitor by the electric power of the charger.

In this multi-level inverter, an inverter circuit that converts DC power into AC power is configured by a first switching circuit, a second switching circuit, a third switching circuit, and the like. In the first operation, the positive electrode of the DC charging port is connected to the midpoint wiring by turning on the first midpoint side intermediate switching element. Therefore, in the first operation, the first capacitor can be charged by connecting the negative electrode of the DC charging port to the low potential input wiring. In the second operation, the negative electrode of the DC charging port is connected to the midpoint wiring by turning on the second midpoint side intermediate switching element. Therefore, the second capacitor can be charged by connecting the positive electrode of the DC charging port to the high potential input wiring. In this way, the first capacitor is charged in the first operation, and the second capacitor is charged in the second operation. The control circuit alternately repeats the first operation and the second operation in the boost control. Therefore, the first capacitor and the second capacitor are charged. When the first capacitor is charged, the potential of the midpoint wiring with respect to the low potential input wiring rises to a potential close to the supply voltage of the charger. When the second capacitor is charged, the potential of the high-potential input wiring with respect to the midpoint wiring rises to a potential close to the supply voltage of the charger. Therefore, the potential of the high-potential input wiring with respect to the low-potential input wiring rises to a potential higher than the supply voltage of the charger. Therefore, a voltage higher than the supply voltage of the charger is applied to the battery to charge the battery. As described above, in this multi-level inverter, the supply voltage of the charger can be boosted to a higher voltage by using the inverter circuit, and the boosted voltage can be applied to the battery. Therefore, the battery can be charged without providing a dedicated boost converter circuit.

The circuit diagram of the multi-level inverter of Example 1. The graph which shows the low voltage charge control of Example 1. FIG. The circuit diagram of the multi-level inverter of Example 1. The circuit diagram of the multi-level inverter of Example 1. Circuit diagram of a multi-level inverter without an input switching element. The circuit diagram of the multi-level inverter of Example 1. The circuit diagram of the multi-level inverter of the modification of Example 1. The graph which shows the low voltage charge control of Example 2. The circuit diagram of the multi-level inverter of Example 2. The circuit diagram of the multi-level inverter of Example 3. The graph which shows the low voltage charge control of Example 3. The circuit diagram of the multi-level inverter of Example 3. The circuit diagram of the multi-level inverter of Example 3. The circuit diagram of the multi-level inverter of the modification 1. The circuit diagram of the multi-level inverter of the modification 2. The circuit diagram of the multi-level inverter of the modification 3.

In the example multi-level inverter disclosed in the present specification, when either one of the charging positive wiring and the charging negative negative wiring is a specific charging wiring and the other is a non-specific charging wiring, the wiring is interposed in the specific charging wiring. It may further have the provided inductor.

According to this configuration, it is possible to prevent a surge from being input from the charging port to the first switching circuit and the second switching circuit.

In an example multi-level inverter disclosed herein, a positive electrode side diode in which the anode is connected to the charging positive electrode wiring and the cathode is connected to the high potential input wiring, and the anode is connected to the low potential input wiring. In addition, the cathode may further have a negative electrode side diode connected to the charging negative electrode wiring. The specific charging wiring may be the charging positive electrode wiring, and the anode of the positive electrode side diode may be connected to the charging positive electrode wiring on the side closer to the first midpoint side intermediate diode than the inductor. The specific charging wiring may be the charging negative electrode wiring, and the cathode of the negative electrode side diode may be connected to the charging negative electrode wiring on the side closer to the second midpoint side intermediate diode than the inductor.

In this configuration, in the first operation, the negative electrode of the charging port is connected to the low potential input wiring via the diode on the negative electrode side, so that the first capacitor can be charged appropriately. Further, in this configuration, in the second operation, the positive electrode of the charging port is connected to the high potential input wiring via the diode on the positive electrode side, so that the second capacitor can be appropriately charged.

In the example multi-level inverter disclosed in the present specification, in the first operation, the first output side intermediate switching element, the second midpoint side intermediate switching element, and the second output side intermediate switching element are turned off. You may. Further, in the second operation, the first midpoint side intermediate switching element, the first output side intermediate switching element, and the second output side intermediate switching element may be turned off.

According to this configuration, it is possible to prevent the supply voltage applied from the external charger to the charging port from being applied to the first output wiring and the second output wiring. As a result, it is possible to prevent malfunction of the device connected to each output wiring.

In the example multi-level inverter disclosed in the present specification, in the first operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm The switching element may be turned off. In the second operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element may be turned off.

According to this configuration, it is possible to more reliably prevent malfunction of the equipment connected to each output wiring.

In the example of the multi-level inverter disclosed in the present specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the pause operation. In the pause operation, the first midpoint side intermediate switching element, the first output side intermediate switching element, the second midpoint side intermediate switching element, and the second output side intermediate switching element may be turned off. ..

By executing the hibernation operation in this way, the current flowing through the inductor during the hibernation operation (that is, the current for charging the first capacitor and the second capacitor) can be reduced. Therefore, a voltage lower than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor. As a result, the voltage applied to the battery can be controlled to be lower than twice the supply voltage of the external charger.

In the example multi-level inverter disclosed in the present specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the current increasing operation. In the current increasing operation, the first midpoint side intermediate switching element and the second midpoint side intermediate switching element may be turned on.

In the current increasing operation, a current flows from the positive electrode of the charging port to the negative electrode of the charging port via the first midpoint side intermediate switching element and the second midpoint side intermediate switching element. This current passes through the inductor. The current flowing through the inductor in this way increases the current flowing through the inductor. After that, when the first operation and the second operation are performed, a voltage higher than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor by the induced electromotive force generated by the inductor. As a result, the voltage applied to the battery can be controlled to a voltage higher than twice the supply voltage of the external charger.

In the example multi-level inverter disclosed in the present specification, the second output side intermediate switching element may be turned on in the first operation. In the second operation, the first output side intermediate switching element may be turned on.

In this configuration, in the first operation, the negative electrode of the charging port is connected to the low potential input wiring via the second output side intermediate switching element, so that the first capacitor can be charged. Further, in this configuration, in the second operation, the positive electrode of the charging port is connected to the positive electrode of the battery via the first output side intermediate switching element, so that the second capacitor can be charged.

In the example multi-level inverter disclosed in the present specification, in the boost control, the control circuit may repeat the first operation, the second operation, and the current increasing operation. In the current increasing operation, the first midpoint side intermediate switching element and the second midpoint side intermediate switching element may be turned on.

In the current increasing operation, a current flows from the positive electrode of the charging port to the negative electrode of the charging port via the first midpoint side intermediate switching element and the second midpoint side intermediate switching element. This current passes through the inductor. The current flowing through the inductor in this way increases the current flowing through the inductor. After that, when the first operation and the second operation are performed, a voltage higher than the supply voltage of the external charger can be applied to the first capacitor and the second capacitor by the induced electromotive force generated by the inductor. As a result, the voltage applied to the battery can be controlled to a voltage higher than twice the supply voltage of the external charger.

The example multi-level inverter disclosed in the present specification may further have a switch connected to the specific charging wiring in series with the inductor.

The multi-level inverter or external charger may be provided with an input capacitor that connects the positive and negative electrodes of the charging port. When the multi-level inverter performs an inverter operation (that is, an operation of outputting AC power to the output wiring) while the first switching circuit and the second switching circuit are connected to the input capacitor, a part of the current is transferred to the input capacitor. It flows and the waveform of AC power collapses. On the other hand, if a switch is provided in the specific charging wiring as described above, the AC power waveform can be prevented from collapsing by keeping the switch off during the operation of the inverter.

In the example multi-level inverter disclosed in the present specification, the semiconductor switching is such that the switch is in the forward direction with respect to the semiconductor switching element interposed in the specific charging wiring and the current flowing through the specific charging wiring. A diode may be provided in series with the element in the specific charging wiring.

According to this configuration, the switch can be miniaturized.

An example multi-level inverter disclosed herein further includes an input capacitor that connects the non-specific charging wiring to the inductor and the specific charging wiring on the side closer to the DC charging port than the switch. May be good.

According to this configuration, the AC power waveform can be prevented from collapsing by turning off the switch while the inverter is operating.

The example multi-level inverter disclosed herein may further have a relay that turns the charging negative electrode wiring on and off.

According to this configuration, the charging port can be electrically separated from each switching circuit when the charging port is not in use.

In the example multi-level inverter disclosed in the present specification, the specific charging wiring may be the charging positive electrode wiring. In this case, the multi-level inverter may further have a charging diode in which the anode is connected to the charging positive electrode wiring between the inductor and the relay and the cathode is connected to the positive electrode of the battery.

According to this configuration, two levels of voltage can be received at the charging port as the supply voltage. When a low voltage is supplied as the supply voltage, the battery can be charged by boost control. Further, when a high voltage is supplied as the supply voltage, the high voltage can be applied to the positive electrode of the battery via the charging diode. This allows the battery to be charged.

In the example multi-level inverter disclosed in the present specification, the specific charging wiring may be the charging negative electrode wiring. In this case, the multi-level inverter may further have a charging diode in which the cathode is connected to the charging negative electrode wiring between the inductor and the relay and the anode is connected to the negative electrode of the battery.

According to this configuration, two levels of voltage can be received at the charging port as the supply voltage. When a low voltage is supplied as the supply voltage, the battery can be charged by boost control. Further, when a high voltage is supplied as the supply voltage, the high voltage can be applied to the negative electrode of the battery via the charging diode. This allows the battery to be charged.

FIG. 1 shows a circuit diagram of the multi-level inverter 10a of the first embodiment. The multi-level inverter 10a is mounted on the vehicle. Further, the vehicle is equipped with a traveling motor 60. The traveling motor 60 is a three-phase motor. The multi-level inverter 10a includes a battery 18. The multi-level inverter 10a converts the DC power output by the battery 18 into three-phase AC power, and supplies the three-phase AC power to the traveling motor 60. As a result, the traveling motor 60 is driven and the vehicle travels.

The multi-level inverter 10a has an inverter circuit 30 and a charging circuit 70. The inverter circuit 30 converts the DC power applied by the battery 18 into three-phase AC power. The charging circuit 70 charges the battery 18.

The inverter circuit 30 has a high potential input wiring 12, a midpoint wiring 14, a low potential input wiring 16, a first capacitor 31, and a second capacitor 32. The high potential input wiring 12 is connected to the positive electrode of the battery 18. The low potential input wiring 16 is connected to the negative electrode of the battery 18. The output voltage Vb (that is, DC voltage) of the battery 18 is applied between the high-potential input wiring 12 and the low-potential input wiring 16. The potential VH of the high-potential input wiring 12 is higher than the potential VL of the low-potential input wiring 16. The first capacitor 31 is connected between the midpoint wiring 14 and the low potential input wiring 16. The second capacitor 32 is connected between the high potential input wiring 12 and the midpoint wiring 14. Therefore, the potential VM of the midpoint wiring 14 is higher than the potential VL of the low potential input wiring 16 and lower than the potential VH of the high potential input wiring 12. In the inverter operation for supplying three-phase AC power to the traveling motor 60, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 (that is, the difference between the potential VH and the potential VL) is the output of the battery 18. Equal to voltage Vb. Further, in the inverter operation, the potential VM of the midpoint wiring 14 is about 1/2 of the potential VH. In the charging operation for charging the battery 18, a voltage higher than the output voltage Vb of the battery 18 is applied as the voltage VHL.

The inverter circuit 30 has three output wirings 50u, 50v, and 50w. The output wirings 50u, 50v, 50w are connected to the traveling motor 60. Further, the inverter circuit 30 includes a U-phase switching circuit 41, a V-phase switching circuit 42, and a W-phase switching circuit 43. The U-phase switching circuit 41 is connected to the high-potential input wiring 12, the low-potential input wiring 16, the midpoint wiring 14, and the output wiring 50u. The V-phase switching circuit 42 is connected to the high-potential input wiring 12, the low-potential input wiring 16, the midpoint wiring 14, and the output wiring 50v. The W-phase switching circuit 43 is connected to the high-potential input wiring 12, the low-potential input wiring 16, the midpoint wiring 14, and the output wiring 50w.

The U-phase switching circuit 41 has switching elements 41US, 41MMS, 41OMS, and 41LS. The switching elements 41US, 41MMS, 41OMS, and 41LS are composed of MOSFETs (metal oxide semiconductor field effect transistors). Further, the U-phase switching circuit 41 has diodes 41UD, 41MMD, 41OMD, and 41LD. The cathode of the diode 41UD is connected to the high potential input wiring 12. The anode of the diode 41UD is connected to the output wiring 50u. The switching element 41US is connected in parallel with the diode 41UD. The drain of the switching element 41US is connected to the high potential input wiring 12. The source of the switching element 41US is connected to the output wiring 50u. The cathode of the diode 41LD is connected to the output wiring 50u. The anode of the diode 41LD is connected to the low potential input wiring 16. The switching element 41LS is connected in parallel to the diode 41LD. The drain of the switching element 41LS is connected to the output wiring 50u. The source of the switching element 41LS is connected to the low potential input wiring 16. The anode of the diode 41MMD is connected to the midpoint wiring 14. The cathode of the diode 41MMD is connected to the cathode of the diode 41OMD. The anode of the diode 41OMD is connected to the output wiring 50u. The switching element 41MMS is connected in parallel to the diode 41MMD. The source of the switching element 41MMS is connected to the anode of the diode 41MMD. The drain of the switching element 41MMS is connected to the cathode of the diode 41MMD. The switching element 41OMS is connected in parallel to the diode 41OMD. The drain of the switching element 41OMS is connected to the cathode of the diode 41OMD. The source of the switching element 41OMS is connected to the anode of the diode 41OMD.

The gates of the switching elements 41US, 41MMS, 41OMS, and 41LS are connected to the control circuit 90. Therefore, the switching elements 41US, 41MMS, 41OMS, and 41LS are controlled by the control circuit 90. When the switching element 41US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50u, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50u. When the switching element 41MMS and the switching element 41OMS are turned on, the midpoint wiring 14 is electrically connected to the output wiring 50u, and the potential VM of the midpoint wiring 14 is applied to the output wiring 50u. When the switching element 41LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50u, and the potential VL of the low potential input wiring 16 is applied to the output wiring 50u. In this way, the U-phase switching circuit 41 changes the potential of the output wiring 50u between the potential VH, the potential VM, and the potential VL.

The V-phase switching circuit 42 has switching elements 42US, 42MMS, 42OMS, and 42LS. The switching elements 42US, 42MMS, 42OMS, and 42LS are composed of MOSFETs. Further, the V-phase switching circuit 42 has diodes 42UD, 42MMD, 42OMD, and 42LD. The cathode of the diode 42UD is connected to the high potential input wiring 12. The anode of the diode 42UD is connected to the output wiring 50v. The switching element 42US is connected in parallel to the diode 42UD. The drain of the switching element 42US is connected to the high potential input wiring 12. The source of the switching element 42US is connected to the output wiring 50v. The cathode of the diode 42LD is connected to the output wiring 50v. The anode of the diode 42LD is connected to the low potential input wiring 16. The switching element 42LS is connected in parallel to the diode 42LD. The drain of the switching element 42LS is connected to the output wiring 50v. The source of the switching element 42LS is connected to the low potential input wiring 16. The cathode of the diode 42MMD is connected to the midpoint wiring 14. The anode of the diode 42MMD is connected to the anode of the diode 42OMD. The cathode of the diode 42OMD is connected to the output wiring 50v. The switching element 42MMS is connected in parallel to the diode 42MMD. The source of the switching element 42MMS is connected to the anode of the diode 42MMD. The drain of the switching element 42MMS is connected to the cathode of the diode 42MMD. The switching element 42OMS is connected in parallel to the diode 42OMD. The drain of the switching element 42OMS is connected to the cathode of the diode 42OMD. The source of the switching element 42OMS is connected to the anode of the diode 42OMD.

The gates of the switching elements 42US, 42MMS, 42OMS, and 42LS are connected to the control circuit 90. Therefore, the switching elements 42US, 42MMS, 42OMS, and 42LS are controlled by the control circuit 90. When the switching element 42US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50v, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50v. When the switching element 42MMS and the switching element 42OMS are turned on, the midpoint wiring 14 is electrically connected to the output wiring 50v, and the potential VM of the midpoint wiring 14 is applied to the output wiring 50v. When the switching element 42LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50v, and the potential VL of the low potential input wiring 16 is applied to the output wiring 50v. In this way, the V-phase switching circuit 42 changes the potential of the output wiring 50v between the potential VH, the potential VM, and the potential VL.

The W-phase switching circuit 43 has switching elements 43US, 43MMS, 43OMS, and 43LS. The switching elements 43US, 43MMS, 43OMS, and 43LS are composed of MOSFETs. Further, the W-phase switching circuit 43 has diodes 43UD, 43MMD, 43OMD, and 43LD. The cathode of the diode 43UD is connected to the high potential input wiring 12. The anode of the diode 43UD is connected to the output wiring 50w. The switching element 43US is connected in parallel to the diode 43UD. The drain of the switching element 43US is connected to the high potential input wiring 12. The source of the switching element 43US is connected to the output wiring 50w. The cathode of the diode 43LD is connected to the output wiring 50w. The anode of the diode 43LD is connected to the low potential input wiring 16. The switching element 43LS is connected in parallel to the diode 43LD. The drain of the switching element 43LS is connected to the output wiring 50w. The source of the switching element 43LS is connected to the low potential input wiring 16. The cathode of the diode 43MMD is connected to the midpoint wiring 14. The anode of the diode 43MMD is connected to the anode of the diode 43OMD. The cathode of the diode 43OMD is connected to the output wiring 50w. The switching element 43MMS is connected in parallel to the diode 43MMD. The source of the switching element 43MMS is connected to the anode of the diode 43MMD. The drain of the switching element 43MMS is connected to the cathode of the diode 43MMD. The switching element 43OMS is connected in parallel to the diode 43OMD. The drain of the switching element 43OMS is connected to the cathode of the diode 43OMD. The source of the switching element 43OMS is connected to the anode of the diode 43OMD.

The gates of the switching elements 43US, 43MMS, 43OMS, and 43LS are connected to the control circuit 90. Therefore, the switching elements 43US, 43MMS, 43OMS, and 43LS are controlled by the control circuit 90. When the switching element 43US is turned on, the high potential input wiring 12 is electrically connected to the output wiring 50w, and the potential VH of the high potential input wiring 12 is applied to the output wiring 50w. When the switching element 43MMS and the switching element 43OMS are turned on, the midpoint wiring 14 is electrically connected to the output wiring 50w, and the potential VM of the midpoint wiring 14 is applied to the output wiring 50w. When the switching element 43LS is turned on, the low potential input wiring 16 is electrically connected to the output wiring 50w. Therefore, the potential VL of the low potential input wiring 16 is applied to the output wiring 50w. In this way, the W-phase switching circuit 43 changes the potential of the output wiring 50w between the potential VH, the potential VM, and the potential VL.

The diode 41UD is 41LD, 41MMD, 41OMD, 42UD, 42LD, 42MMD, 42OMD, 43UD, 43LD, 43MMD, 43OMD are parasiticly formed inside the body diode (that is, MOSFET) of the MOSFET connected in parallel. It may be a diode).

Further, even if the switching elements 41US, 41MMS, 41OMS, 41LS, 42US, 42MMS, 42OMS, 42LS, 43US, 43MMS, 43OMS, and 43LS are composed of elements other than MOSFETs (for example, IGBT (insulated gate bipolar transistor)). good. In that case, the emitter of the IGBT can be connected to the anode of the diode connected in parallel, and the collector of the IGBT can be connected to the cathode of the diode connected in parallel.

In the inverter operation, the U-phase switching circuit 41, the V-phase switching circuit 42, and the W-phase switching circuit 43 change the potentials of the output wirings 50u, 50v, and 50w between the potential VL, the potential VM, and the potential VL. As a result, three-phase AC power is generated between the output wirings 50u, 50v, and 50w, and the three-phase AC power is supplied to the traveling motor 60.

The charging circuit 70 includes a charging positive electrode wiring 22, a charging negative electrode wiring 24, a charging port 72, a relay module 74, an input capacitor 76, an inductor 77, an input switching element 78, and an input diode 79.

An external charger 92 is connected to the charging port 72. The charging port 72 has a positive electrode 72a and a negative electrode 72b. When the charger 92 is connected to the charging port 72, a voltage Vs (hereinafter referred to as a supply voltage Vs) is applied between the positive electrode 72a and the negative electrode 72b so that the positive electrode 72a has a higher potential than the negative electrode 72b by the charger 92. Will be done. A low-voltage charger 92a and a high-voltage charger 92b can be connected to the charging port 72. The low voltage charger 92a supplies a low voltage VsL (for example, 400V) as a supply voltage Vs. The high voltage charger 92b supplies a high voltage VsH (for example, 800V) as a supply voltage Vs. The low voltage VsL is lower than the output voltage Vb of the battery 18, and the high voltage VsH is higher than the output voltage Vb of the battery 18.

One end of the charging positive electrode wiring 22 is connected to the positive electrode 72a of the charging port 72. The other end of the charging positive electrode wiring 22 is connected to the cathode of the diode 41MMD, the cathode of the diode 41OMD, the drain of the switching element 41MMS, and the drain of the switching element 41OMS. One end of the charging negative electrode wiring 24 is connected to the negative electrode 72b of the charging port 72. The other end of the charging negative electrode wiring 24 is connected to the anode of the diode 42MMD, the anode of the diode 42OMD, the source of the switching element 42MMS, and the source of the switching element 42OMS.

The input capacitor 76 is connected between the charging positive electrode wiring 22 and the charging negative electrode wiring 24. The input capacitor 76 smoothes the voltage applied between the charging positive electrode wiring 22 and the charging negative electrode wiring 24.

The relay module 74 is arranged between the input capacitor 76 and the charging port 72. The relay module 74 has a relay 74a and a relay 74b. The relay 74a is interposed in the charging positive electrode wiring 22 on the side closer to the charging port 72 than the input capacitor 76. The relay 74b is interposed in the charging negative electrode wiring 24 on the side closer to the charging port 72 than the input capacitor 76. When the relays 74a and 74b are turned off, the charging port 72 is electrically cut off from the input capacitor 76, the inverter circuit 30, and the like. The relays 74a and 74b are controlled by the control circuit 90.

The inductor 77 is interposed in the charging positive electrode wiring 22 on the side closer to the inverter circuit 30 than the input capacitor 76.

The input switching element 78 is interposed in the charging positive electrode wiring 22 on the side closer to the inverter circuit 30 than the inductor 77. The input switching element 78 is an IGBT. The collector of the input switching element 78 is connected to the inductor 77. The input switching element 78 is controlled by the control circuit 90. The input diode 79 is interposed in the charging positive electrode wiring 22 on the side closer to the inverter circuit 30 than the input switching element 78. The anode of the input diode 79 is connected to the emitter of the input switching element 78. The cathode of the input diode 79 is connected to the cathode of the diode 41MMD.

The multi-level inverter 10a further has a positive electrode side diode 82 and a negative electrode side diode 84. The anode of the positive electrode side diode 82 is connected to the charging positive electrode wiring 22 between the inductor 77 and the input switching element 78. The cathode of the positive electrode side diode 82 is connected to the high potential input wiring 12. The anode of the negative electrode side diode 84 is connected to the low potential input wiring 16. The cathode of the negative electrode side diode 84 is connected to the charging negative electrode wiring 24.

The multi-level inverter 10a can carry out charge control. The charge control is performed when the inverter operation is not performed. When the vehicle is stopped, the relays 74a and 74b are off, and the input switching element 78 is off. When an external charger 92 is connected to the charging port 72 in the stopped state of the vehicle, the control circuit 90 detects the supply voltage Vs by a voltmeter (not shown). The control circuit 90 executes low voltage charge control when the supply voltage Vs is low voltage VsL, and executes high voltage charge control when the supply voltage Vs is high voltage VsH.

(Low voltage charge control)
When the control circuit 90 detects that the supply voltage Vs is the low voltage VsL, the control circuit 90 controls the relays 74a and 74b to turn on, and controls the input switching element 78 to turn on. As a result, the supply voltage Vs (that is, low voltage VsL) is applied between the charging positive electrode wiring 22 and the charging negative electrode wiring 24.

In the low voltage charge control, the control circuit 90 keeps the switching elements 41US, 41OMS, 41LS, 42US, 42OMS, 42LS, 43US, 43MMS, 43OMS, 43LS in the off state. Further, as shown in FIG. 2, the control circuit 90 alternately turns on the switching element 41 MMS and the switching element 42 MMS. More specifically, the control circuit 90 includes an on-period Ton1 in which the switching element 41MMS is on and the switching element 42MMS is off, an off-period Toff1 in which both the switching elements 41MMS and 42MMS are off, and the switching element 42MMS. The switching elements 41MMS and 42MMS are controlled so that the on-period Ton2 in which the switching element 41MMS is on and the switching element 41MMS is off and the off-period Toff2 in which both the switching elements 41MMS and 42MMS are off repeat in this order.

In the on period Ton1, when the switching element 41MMS is turned on, a current flows as shown by the arrow 100 in FIG. That is, the current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41MMS, the first capacitor 31, and the negative electrode side diode 84. The current flowing in this way charges the first capacitor 31. The current IL indicates the current flowing through the inductor 77. In the on period Ton1, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows (that is, the arrow 100). The induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 2, the current IL gradually increases during the on-period Ton1.

In the off period Toff1, both the switching element 41MMS and the switching element 42MMS are off, so a current flows as shown by the arrow 102 in FIG. That is, in the off period Toff1, the induced electromotive force of the inductor 77 is generated in the same direction as the direction in which the current IL flows (that is, the arrow 102). Therefore, the potential of the anode of the positive electrode side diode 82 becomes higher than the potential of the cathode of the positive electrode side diode 82 (that is, the potential of the high potential input wiring 12). Therefore, as shown by the arrow 102, a current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the positive electrode side diode 82, the battery 18, and the negative electrode side diode 84. In the off period Toff1, the induced electromotive force of the inductor 77 decreases with the passage of time. Therefore, as shown in FIG. 2, the current IL decreases during the off period Toff1.

In the on period Ton2, when the switching element 42MMS is turned on, a current flows as shown by the arrow 104 in FIG. That is, the current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the positive electrode side diode 82, the second capacitor 32, and the switching element 42MMS. The second capacitor 32 is charged by the current flowing in this way. In the on-period Ton2, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows (that is, the arrow 104). The induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 2, the current IL gradually increases during the on-period Ton2.

In the off period Toff2, both the switching element 41MMS and the switching element 42MMS are off, so that a current flows as shown by the arrow 102 in FIG. 3 as in the off period Toff1. Therefore, as shown in FIG. 2, the current IL decreases during the off period Toff2.

As described above, in the low voltage charge control, the first capacitor 31 and the second capacitor 32 are alternately charged by alternately repeating the on-period Ton1 and the on-period Ton2. The voltage VHL between the high-potential input wiring 12 and the low-potential input wiring 16 is the sum of the voltage VC1 between both ends of the first capacitor 31 and the voltage VC2 between both ends of the second capacitor 32. By charging the first capacitor 31, the voltage VC1 between both ends of the first capacitor 31 rises to a maximum low voltage VsL. By charging the second capacitor 32, the voltage VC2 between both ends of the second capacitor 32 rises to a maximum low voltage VsL. If the voltage VC1 rises to the low voltage VsL and the voltage VC2 rises to the low voltage VsL, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 rises to twice the value of the low voltage VsL. As described above, according to the low voltage charge control, the voltage VHL between the high potential input wiring 12 and the low potential input wiring 16 can be raised to a voltage higher than the low voltage VsL supplied by the charger 92. Therefore, even if the low voltage VsL is lower than the output voltage Vb of the battery 18, the voltage VHL can be raised to a voltage higher than the output voltage Vb of the battery 18. Therefore, the battery 18 can be charged. As described above, according to the multi-level inverter 10a of the first embodiment, the low voltage VsL can be boosted by using the inverter circuit 30, and the battery 18 can be charged by the boosted voltage. In this way, the battery 18 can be charged using the low voltage VsL without providing a dedicated boost converter circuit. Therefore, the multi-level inverter 10a can be miniaturized.

Further, as shown in FIG. 2, the current IL increases in the on period Ton1 and Ton2, and decreases in the off period Toff1 and Toff2. By controlling the ratio of the on-period Ton1 and Ton2 to the off-period Toff1 and Toff2, the magnitude of the current IL can be controlled. Thereby, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled. For example, if the on-periods Ton1 and Ton2 are made sufficiently longer than the off-periods Toff1 and Toff2 as shown in FIG. 2, the voltage VC1 of the first capacitor 31 can be raised to a low voltage VsL, and the voltage of the second capacitor 32 can be increased. VC2 can be raised to a low voltage VsL. Further, if the ratio of the off periods Toff1 and Toff2 is increased as compared with FIG. 2, the current IL becomes smaller, and the voltages VC1 and VC2 can be controlled to smaller values. For example, the voltage VC1 can be controlled to be 0.8 times the low voltage VsL, and the voltage VC2 can be controlled to be 0.8 times the low voltage VsL. In this case, the voltage VHL is 1.6 times the low voltage VsL. Even in this case, a voltage higher than the low voltage VsL can be applied as the voltage VHL, and the battery 18 can be charged.

In Example 1, either or both of the off periods Toff1 and Toff2 may not exist. In this case, the current IL tends to be high.

Further, in the multi-level inverter 10a of the first embodiment, the control circuit 90 keeps the switching elements 41OMS, 42MMS, 42OMS, 43MMS, and 43OMS off during the on periods Ton1 and Ton2 of the low voltage charge control. Therefore, it is possible to prevent the potential of the charging positive electrode wiring 22 and the potential of the charging negative electrode wiring 24 from being applied to the output wirings 50u, 50v, and 50w. Further, during the on periods Ton1 and Ton2 of the low voltage charge control, the control circuit 90 keeps the switching elements 41US, 41LS, 42US, 42LS, 43US, and 43LS off. Therefore, it is possible to prevent the potential of the high-potential input wiring 12 and the potential of the low-potential input wiring 16 from being applied to the output wirings 50u, 50v, and 50w. Therefore, it is possible to prevent the traveling motor 60 from generating vibration or the like during the low voltage charge control.

Further, as described above, the switching element 41MMS is turned off when the on period Ton1 is switched to the off period Toff1. Similarly, when switching from the on period Ton2 to the off period Toff2, the switching element 42MMS is turned off. When a high surge voltage is applied to the switching elements 41MMS and 42MMS by the induced electromotive force of the inductor 77 when the switching elements 41MMS and 42MMS are turned off, a high load is applied to the switching elements 41MMS and 42MMS. However, in the multi-level inverter 10a of the first embodiment, the positive electrode side diode 82 and the negative electrode side diode 84 form a bypass path that bypasses the switching elements 41 MMS and 42 MMS. By this bypass path, the surge voltage applied to the switching elements 41MMS and 42MMS is suppressed. That is, when the switching elements 41MMS and 42MMS are turned off, the positive electrode side diode 82 and the negative electrode side diode 84 are turned on during the off periods Toff1 and Toff2 as described above. As a result, as shown by the arrow 102 in FIG. 3, the current flows around the switching elements 41 MMS and 42 MMS. Therefore, the surge voltage applied to the switching elements 41MMS and 42MMS is suppressed. Further, during the low voltage charge control, at least one of the switching element 41MMS, the switching element 42MMS, and the input switching element 78 may be momentarily interrupted due to some abnormality. Even when the switching element is momentarily interrupted in this way, as shown by the arrow 102 in FIG. 3, the current flows around the switching element 41 MMS, the switching element 42 MMS, and the input switching element 78. As a result, the surge voltage applied to the switching element 41MMS, the switching element 42MMS, and the input switching element 78 is suppressed.

Further, during the low voltage charge control, the surge voltage generated in the charger 92 may be applied between the positive electrode 72a and the negative electrode 72b. When an inrush current flows through any of the switching elements due to such a surge voltage, a high load is applied to the switching element. However, in the multi-level inverter 10a of the first embodiment, when a surge voltage is applied between the positive electrode 72a and the negative electrode 72b, the inductor 77 suppresses an increase in the current IL. As a result, the inrush current is suppressed. Therefore, the inrush current is suppressed from flowing through the switching element in the multi-level inverter 10a.

(High voltage charge control)
When the control circuit 90 detects that the supply voltage Vs is the high voltage VsH, the control circuit 90 executes the high voltage charge control. In the high voltage charge control, the control circuit 90 controls the relays 74a and 74b to be on and the input switching element 78 to be off. Further, the control circuit 90 controls off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, 43OMS. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so that a current flows as shown by the arrow 102 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the positive electrode side diode 82, the battery 18, and the negative electrode side diode 84. During the high voltage charge control, the current always flows as shown by the arrow 102. As a result, the battery 18 is charged.

In this way, the multi-level inverter 10a can select and execute low-voltage charge control and high-voltage charge control. According to this configuration, the supply of the low voltage VsL and the supply of the high voltage VsH can be received by the common charging port 72. Since it is not necessary to separately provide a charging port for the low voltage VsL and the high voltage VsH, the multi-level inverter 10a can be miniaturized. Further, if the relay module 74 is turned off, the charging port 72 can be cut off from both the high-voltage charging circuit and the low-voltage charging circuit. Since it is not necessary to separately provide relay modules for the high-voltage charging circuit and the low-voltage charging circuit, the multi-level inverter 10a can be miniaturized.

Next, the functions of the input switching element 78 and the input diode 79 will be described. As described above, the multi-level inverter 10a supplies three-phase AC power to the traveling motor 60 by the inverter operation. In the absence of the input switching element 78 and the input diode 79, a current flows between the U-phase switching circuit 41 and the V-phase switching circuit 42 via the input capacitor 76 in the inverter operation as shown by the arrow 106 in FIG. When the current flows in this way, the waveform of the alternating current flowing in the output wirings 50u, 50v, and 50w is disrupted, and the drive efficiency of the traveling motor 60 is lowered. On the other hand, in the multi-level inverter 10a of the first embodiment, the input switching element 78 and the input diode 79 are interposed in the charging positive electrode wiring 22 between the input capacitor 76 and the U-phase switching circuit 41. The control circuit 90 keeps the input switching element 78 off during the operation of the inverter. Therefore, the current as shown by the arrow 106 in FIG. 5 does not flow during the operation of the inverter. Therefore, in the multi-level inverter 10a, it is possible to prevent the waveform of the alternating current flowing through the output wirings 50u, 50v, and 50w from collapsing.

Although the charging circuit 70 has the input capacitor 76 in the first embodiment, the charging circuit 70 does not have to have the input capacitor 76 as shown in FIG. Even in this case, when the charger 92 has an input capacitor 94 connected between the positive electrode 72a and the negative electrode 72b as shown in FIG. 6, a current flows through the input capacitor 94 during the inverter operation. , The AC current waveform may be corrupted. When there is such a possibility, by keeping the input switching element 78 off during the operation of the inverter, it is possible to prevent the waveform of the alternating current from collapsing.

Further, in the above-described first embodiment, the inductor 77 is interposed in the charging positive electrode wiring 22, but the inductor 77 may be interposed in the charging negative electrode wiring 24. Also in this configuration, the low voltage charge control can be executed in substantially the same manner as in the first embodiment described above by utilizing the induced electromotive force of the inductor 77. For example, as shown in FIG. 7, the inductor 77 can be interposed in the charging negative electrode wiring 24. In FIG. 7, the inductor 77 is interposed in the charging negative electrode wiring 24 on the side closer to the inverter circuit 30 than the input capacitor 76. Further, the cathode of the negative electrode side diode 84 is connected to the charging negative electrode wiring 24 on the side closer to the inverter circuit 30 than the inductor 77.

Further, in the above-described first embodiment, the input switching element 78 and the input diode 79 are interposed in the charging positive electrode wiring 22, but these may be interposed in the charging negative electrode wiring 24. Even in this configuration, by keeping the input switching element 78 off during the operation of the inverter, it is possible to prevent the waveform of the alternating current from collapsing. In this case, the input switching element 78 and the input diode 79 are installed along the direction in which the current of the charging negative electrode wiring 24 flows. For example, as shown in FIG. 7, when the inductor 77 is interposed in the charging negative electrode wiring 24, the input switching element 78 and the input diode 79 may also be interposed in the charging negative electrode wiring 24. In FIG. 7, the input switching element 78 and the input diode 79 are interposed in the charging negative electrode wiring 24 on the side closer to the inverter circuit 30 than the connection point between the charging negative electrode wiring 24 and the negative electrode side diode 84.

In the multi-level inverter of the second embodiment, the control method of the switching elements 41MMS and 42MMS in the low voltage charge control is different from that of the first embodiment. Other configurations of the multi-level inverter of the second embodiment are the same as those of the first embodiment.

In the low voltage charge control with the multi-level inverter of the second embodiment, the control circuit 90 keeps the switching elements 41US, 41OMS, 41LS, 42US, 42OMS, 42LS, 43US, 43MMS, 43OMS, 43LS in the off state. Further, as shown in FIG. 8, the control circuit 90 alternately turns on the switching element 41 MMS and the switching element 42 MMS. More specifically, the control circuit 90 has an on-period Ton1 in which the switching element 41MMS is on and the switching element 42MMS is off, a current increase period Tac1 in which the switching elements 41MMS and 42MMS are both on, and a switching element 42MMS. The switching elements 41MMS and 42MMS are controlled so that the on-period Ton2 in which the switching element 41MMS is on and the switching element 41MMS is off and the current increase period Tac2 in which both the switching elements 41MMS and 42MMS are on repeat in this order. ..

In the current increase period Tac2, when both the switching elements 41MMS and 42MMS are turned on, a current flows as shown by the arrow 110 in FIG. That is, it flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41 MMS, and the switching element 42 MMS. In this way, the current does not pass through the load other than the inductor 77. Therefore, in the current increase period Tac2, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows. Further, in the current increase period Tac2, the induced electromotive force of the inductor 77 decreases with the passage of time. Therefore, as shown in FIG. 8, the current IL increases during the current increase period Tac2.

The switching element 42MMS turns off when the current increase period Tac2 is switched to the on period Ton1. Therefore, in the on period Ton1, the switching element 41MMS is on and the switching element 42MMS is off. Therefore, as shown by the arrow 100 in FIG. 1, a current flows and the first capacitor 31 is charged. In the on period Ton1, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the first capacitor 31. Therefore, in the on period Ton1, the first capacitor 31 can be charged so that the voltage VC1 of the first capacitor 31 becomes a voltage higher than the low voltage VsL. During the on-period Ton1, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 8, the current IL gradually decreases during the on-period Ton1.

When switching from the on period Ton1 to the current increase period Tac1, the switching element 42MMS turns on. Therefore, in the current increase period Tac1, both the switching elements 41 MMS and 42 MMS are turned on. Therefore, in the current increase period Tac1, the current flows and the current IL increases as shown by the arrow 110 in FIG. 9, similarly to the current increase period Tac2.

The switching element 41MMS turns off when the current increase period Tac1 is switched to the on period Ton2. Therefore, in the on period Ton2, the switching element 42MMS is on and the switching element 41MMS is off. Therefore, as shown by the arrow 104 in FIG. 4, a current flows and the second capacitor 32 is charged. In the on-period Ton2, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the second capacitor 32. Therefore, in the on-period Ton2, the second capacitor 32 can be charged so that the voltage VC2 of the second capacitor 32 becomes a voltage higher than the low voltage VsL. During the on-period Ton2, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 8, the current IL gradually decreases during the on-period Ton2.

As described above, in the low voltage charge control of the second embodiment, the first capacitor 31 is charged so that the voltage VC1 becomes higher than the low voltage VsL in the on period Ton1, and the voltage VC2 becomes the low voltage VsL in the on period Ton2. The second capacitor 32 is charged so that the voltage becomes higher than that. Therefore, the voltage VHL between the high-potential input wiring 12 and the low-potential input wiring 16 rises to a voltage higher than twice the low voltage VsL. Therefore, the battery 18 can be charged efficiently. As described above, even in the multi-level inverter of the second embodiment, the battery 18 can be charged by using the low voltage VsL without providing a dedicated boost converter circuit.

Further, as shown in FIG. 8, the current IL decreases in the on period Ton1 and Ton2, and increases in the current increase period Tac1 and Tac2. Therefore, the magnitude of the current IL can be controlled by controlling the ratio of the on period Ton1 and Ton2 and the current increase period Tac1 and Tac2. By controlling the magnitude of the current IL in this way, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled to the intended voltage.

The multi-level inverter 10b of Example 3 shown in FIG. 10 does not have a positive electrode side diode 82 and a negative electrode side diode 84. Other configurations of the multi-level inverter 10b of the third embodiment are the same as those of the first embodiment. Further, the multi-level inverter 10b of the third embodiment executes low voltage charge control and does not execute high voltage charge control. In the third embodiment, the control method of each switching element in the low voltage charge control is different from that of the first embodiment.

In the low voltage charge control of the third embodiment, the control circuit 90 keeps the input switching element 78 on. The control circuit 90 also keeps the switching elements 43MMS and 43OMS off. Further, the control circuit 90 controls the switching elements 41MMS, 42OMS, 42MMS, and 41OMS as shown in FIG. More specifically, the control circuit 90 controls the switching elements 41MMS, 42OMS, 42MMS, and 41OMS so that the on-period Ton1, the current increase period Tac1, the on-period Ton2, and the current increase period Tac2 repeat in this order. In the on period Ton1, the switching elements 41MMS and 42OMS are on and the switching elements 42MMS and 41OMS are off. In the current increase period Tac1, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned on. In the on period Ton2, the switching elements 42MMS and 41OMS are on and the switching elements 41MMS and 42OMS are off. In the current increase period Tac2, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned on.

In the current increase period Tac2, when all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned on, a current flows as shown by the arrow 120 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41 MMS, and the switching element 42 MMS. In this way, the current does not pass through the load other than the inductor 77. Therefore, in the current increase period Tac2, the induced electromotive force of the inductor 77 is generated in the direction opposite to the direction in which the current IL flows. Further, in the current increase period Tac2, the induced electromotive force of the inductor 77 decreases with the passage of time. Therefore, as shown in FIG. 11, the current IL increases during the current increase period Tac2.

When the current increase period Tac2 is switched to the on period Ton1, the switching elements 42MMS and 41OMS are turned off. Therefore, in the on period Ton1, the switching elements 41MMS and 42OMS are on, and the switching elements 42MMS and 41OMS are off. Therefore, a current flows as shown by the arrow 122 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41MMS, the first capacitor 31, the diode 42LD, and the switching element 42OMS. The flow of the current in this way charges the first capacitor 31. In the on period Ton1, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the first capacitor 31. Therefore, in the on period Ton1, the first capacitor 31 can be charged so that the voltage VC1 of the first capacitor 31 becomes a voltage higher than the low voltage VsL. During the on-period Ton1, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 11, the current IL gradually decreases during the on-period Ton1.

When switching from the on period Ton1 to the current increase period Tac1, the switching elements 42MMS and 41OMS are turned on. Therefore, in the current increase period Tac1, all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned on. Therefore, in the current increase period Tac1, the current flows and the current IL increases as shown by the arrow 120 in FIG. 10, similarly to the current increase period Tac2.

When the current increase period Tac1 is switched to the on period Ton2, the switching elements 41MMS and 42OMS are turned off. Therefore, in the on period Ton2, the switching elements 42MMS and 41OMS are on, and the switching elements 41MMS and 42OMS are off. Therefore, a current flows as shown by arrow 124 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the inductor 77, the input switching element 78, the input diode 79, the switching element 41OMS, the diode 41UD, the second capacitor 32, and the switching element 42MMS. The flow of the current in this way charges the second capacitor 32. In the on-period Ton2, an induced electromotive force is generated in the inductor 77 in the same direction as the current IL flows. Therefore, a voltage obtained by adding the induced electromotive force of the inductor 77 to the low voltage VsL is applied to the second capacitor 32. Therefore, in the on-period Ton2, the second capacitor 32 can be charged so that the voltage VC2 of the second capacitor 32 becomes a voltage higher than the low voltage VsL. During the on-period Ton2, the induced electromotive force gradually decreases over time. Therefore, as shown in FIG. 11, the current IL gradually decreases during the on-period Ton2.

As described above, in the low voltage charge control of the third embodiment, the first capacitor 31 is charged so that the voltage VC1 becomes higher than the low voltage VsL in the on period Ton1, and the voltage VC2 becomes the low voltage VsL in the on period Ton2. The second capacitor 32 is charged so that the voltage becomes higher than that. Therefore, the voltage VHL between the high-potential input wiring 12 and the low-potential input wiring 16 rises to a voltage higher than twice the low voltage VsL. Therefore, the battery 18 can be charged efficiently. As described above, even in the multi-level inverter 10b of the third embodiment, the battery 18 can be charged by using the low voltage VsL without providing a dedicated boost converter circuit.

Further, as shown in FIG. 11, the current IL decreases in the on period Ton1 and Ton2, and increases in the current increase period Tac1 and Tac2. Therefore, the magnitude of the current IL can be controlled by controlling the ratio of the on period Ton1 and Ton2 and the current increase period Tac1 and Tac2. By controlling the magnitude of the current IL in this way, the voltage VC1 of the first capacitor 31 and the voltage VC2 of the second capacitor 32 can be controlled to the intended voltage.

As shown in FIG. 11, in the low voltage charge control of the third embodiment, the switching element 42LS is turned on during a part of the on period Ton1. When the switching element 42LS is turned on, the current flowing through the diode 42LD (see FIG. 12) branches into the diode 42LD and the switching element 42LS and flows. As a result, the loss caused by the diode 42LD is suppressed. As shown in FIG. 11, the dead time DT1 (that is, the switching elements 42LS and 42MMS are both off) between the period when the switching element 42LS is turned on and the period when the switching element 42MMS is turned on (that is, the current increase periods Tac1 and Tac2). Period) is provided. The dead time DT1 prevents both the switching elements 42LS and 42MMS from being turned on and short-circuiting the midpoint wiring 14 and the low potential input wiring 16. In the low voltage charge control of the third embodiment, the switching elements 41LS and 43LS may be controlled in the same manner as the switching element 42LS, or the switching elements 41LS and 43LS may be kept off. Even if the switching elements 41LS and 43LS are turned on as in the switching element 42LS, no current flows through the switching elements 41LS and 43LS, so that the low voltage charge control is not affected. Further, if the diode 42LD does not cause such a high loss, the switching element 42LS may be kept off in the low voltage charge control of the third embodiment.

Further, as shown in FIG. 11, in the low voltage charge control of the third embodiment, the switching element 41US is turned on during a part of the on period Ton2. When the switching element 41US is turned on, the current flowing through the diode 41UD (see FIG. 13) branches into the diode 41UD and the switching element 41US and flows. As a result, the loss caused by the diode 41UD is suppressed. As shown in FIG. 11, the dead time DT2 (that is, the switching elements 41US and 41MMS are both off) between the period when the switching element 41US is turned on and the period when the switching element 41MMS is turned on (that is, the current increasing periods Tac1 and Tac2). Period) is provided. The dead time DT2 prevents both the switching elements 41US and 41MMS from being turned on and short-circuiting the midpoint wiring 14 and the high potential input wiring 12. In the low voltage charge control of the third embodiment, the switching elements 42US and 43US may be controlled in the same manner as the switching element 41US, or the switching elements 42US and 43US may be kept off. Even if the switching elements 42US and 43US are turned on as in the switching element 41US, no current flows through the switching elements 42US and 43US, so that the low voltage charge control is not affected. Further, if the diode 41UD does not cause such a high loss, the switching element 41US may be kept off in the low voltage charge control of the third embodiment.

Further, also in the third embodiment, the inductor 77 suppresses the inrush current from flowing to the switching element in the multi-level inverter 10b. Further, also in the third embodiment, the input switching element 78 is kept off during the operation of the inverter, and the waveform of the alternating current flowing through the output wirings 50u, 50v, and 50w is prevented from collapsing. Further, also in the third embodiment, as shown in FIG. 6, the charging circuit 70 does not have to have the input capacitor 76. Further, also in the third embodiment, as shown in FIG. 7, the inductor 77 may be interposed in the charging negative electrode wiring 24. Further, also in the third embodiment, as shown in FIG. 7, the input switching element 78 and the input diode 79 may be interposed in the charging negative electrode wiring 24.

In the low voltage charge control of the third embodiment, at least one of the current increase periods Tac1 and Tac2 does not have to exist. Further, in the low voltage charge control of the third embodiment, the off periods Toff1 and Toff2 in which all of the switching elements 41MMS, 42OMS, 42MMS, and 41OMS are turned off may be provided instead of the current increase periods Tac1 and Tac2. In this case, if a bypass path for passing a current from the positive electrode 72a to the negative electrode 72b is provided by bypassing the switching elements 41MMS, 42OMS, 42MMS, and 41OMS during the off periods Toff1 and Toff2, the current is applied to the switching elements 41MMS, 42OMS, 42MMS, and 41OMS. The surge voltage can be suppressed.

Next, the multi-level inverters of the modified examples 1 to 3 obtained by modifying the multi-level inverter 10b of the third embodiment will be described. The multi-level inverters of the first to third modifications are the ones obtained by modifying the multi-level inverter 10b of the third embodiment so that the high voltage charge control can be performed.

The multi-level inverter 10c of the first modification shown in FIG. 14 has a charging diode 86. Other configurations of the multi-level inverter 10c of the first modification are the same as those of the multi-level inverter 10b of the third embodiment.

The anode of the charging diode 86 is connected to the charging positive electrode wiring 22 at a position between the inductor 77 and the relay 74a. The cathode of the charging diode 86 is connected to the high potential input wiring 12.

The control circuit 90 controls the relays 74a and 74b on, the input switching element 78 off, and the switching element 42OMS on when a high voltage VsH is applied as the supply voltage Vs. Further, the control circuit 90 controls the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 43US, 43LS, 43MMS, and 43OMS off. The control circuit 90 maintains this control state during high voltage charge control. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so that a current flows as shown by the arrow 130 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the charging diode 86, the battery 18, the diode 42LD, and the switching element 42OMS. The battery 18 is charged by the current flowing in this way.

In the multi-level inverter 10d of the second modification shown in FIG. 15, an inductor 77, an input switching element 78, and an input diode 79 are interposed in the charging negative electrode wiring 24 as in FIG. 7. Further, the multi-level inverter 10d of the second modification has a charging diode 88. The cathode of the charging diode 88 is connected to the charging negative electrode wiring 24 at a position between the inductor 77 and the relay 74b. The anode of the charging diode 88 is connected to the low potential input wiring 16. Other configurations of the multi-level inverter 10d of the fifth embodiment are the same as those of the multi-level inverter 10b of the third embodiment.

The control circuit 90 controls the relays 74a and 74b on, the input switching element 78 off, and the switching element 41OMS on when a high voltage VsH is applied as the supply voltage Vs. Further, the control circuit 90 controls the switching elements 41US, 41LS, 41MMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, and 43OMS off. The control circuit 90 maintains this control state during high voltage charge control. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so that a current flows as shown by the arrow 132 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the switching element 41OMS, the diode 41UD, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this way.

The multi-level inverter 10e of the modification 3 shown in FIG. 16 has charging diodes 86 and 88. Other configurations of the multi-level inverter 10e of the third modification are the same as those of the multi-level inverter 10b of the third embodiment. The anode of the charging diode 86 is connected to the charging positive electrode wiring 22 at a position between the inductor 77 and the relay 74a. The cathode of the charging diode 86 is connected to the high potential input wiring 12. The cathode of the charging diode 88 is connected to the charging negative electrode wiring 24 at a position between the relay 74b and the V-phase switching circuit 42. The anode of the charging diode 88 is connected to the low potential input wiring 16.

The control circuit 90 controls the relays 74a and 74b to be turned on and the input switching element 78 to be turned off when a high voltage VsH is applied as the supply voltage Vs. Further, the control circuit 90 controls off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, 43OMS. The control circuit 90 maintains this control state during high voltage charge control. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so that a current flows as shown by the arrow 134 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the charging diode 86, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this way.

When a low voltage VsL is applied as the supply voltage Vs, the control circuit 90 performs charge control in the same manner as in the fourth embodiment. Therefore, the battery 18 can be charged.

The control circuit 90 controls the relays 74a and 74b to be turned on and the input switching element 78 to be turned off when a high voltage VsH is applied as the supply voltage Vs. Further, the control circuit 90 controls off the switching elements 41US, 41LS, 41MMS, 41OMS, 42US, 42LS, 42MMS, 42OMS, 43US, 43LS, 43MMS, 43OMS. When each part is controlled in this way, the high voltage VsH is higher than the output voltage Vb of the battery 18, so that a current flows as shown by the arrow 134 in FIG. That is, a current flows from the positive electrode 72a to the negative electrode 72b via the charging diode 86, the battery 18, and the charging diode 88. The battery 18 is charged by the current flowing in this way.

As described above, according to the multi-level inverters 10c to 10e of the modified examples 1 to 3, high voltage charge control can be executed. Further, according to the multi-level inverters 10c to 10e of the modifications 1 to 3, low voltage charge control can be executed as in the multi-level inverter 10b of the third embodiment. According to the configurations of the first to third modifications, the low voltage VsL and the high voltage VsH can be supplied by the common charging port 72, so that the multi-level inverter 10c can be miniaturized. Further, according to the configurations of the modified examples 1 to 3, the charging port 72 can be cut off from both the high-voltage charging circuit and the low-voltage charging circuit by one relay module 74. Therefore, the multi-level inverter 10a can be miniaturized.

Note that at least one of the charging diodes 86 and 88 described in the modified examples 1 to 3 may be provided in the multi-level inverter of the first or second embodiment. Even in this case, charging with a high voltage can be performed via at least one of the charging diodes 86 and 88.

In the above-described embodiment, a contact type switch such as a relay may be provided instead of the input switching element 78 and the input diode 79. Even with this configuration, it is possible to prevent the waveform of the alternating current from collapsing by turning off the contact switch when the inverter is operating.

Each component of the above-described embodiment will be described. The output wiring 50u is an example of the first output wiring. The output wiring 50v is an example of the second output wiring. The output wiring 50w is an example of the third output wiring. The U-phase switching circuit 41 is an example of the first switching circuit.
The V-phase switching circuit 42 is an example of a second switching circuit. The W-phase switching circuit 43 is an example of a third switching circuit. The switching element 41US is an example of the first upper arm switching element. The switching element 41LS is an example of the first lower arm switching element. The diode 41MMD is an example of a first midpoint side intermediate diode. The diode 41OMD is an example of the first output side intermediate diode. The switching element 41MMS is an example of the first midpoint side intermediate switching element. The switching element 41OMS is an example of the first output side intermediate switching element. The switching element 42US is an example of the second upper arm switching element. The switching element 42LS is an example of a second lower arm switching element. The diode 42MMD is an example of a second midpoint side intermediate diode. The diode 42OMD is an example of a second output side intermediate diode. The switching element 42MMS is an example of a second midpoint side intermediate switching element. The switching element 42OMS is an example of the second output side intermediate switching element. Low voltage charge control is an example of boost control. The operation of the multi-level inverter in the on-period Ton1 is an example of the first operation. The operation of the multi-level inverter in the on-period Ton2 is an example of the second operation. The operation of the multi-level inverter during the off periods Toff1 and Toff2 is an example of a hibernation operation. The operation of the multi-level inverter in the current increase periods Tac1 and Tac2 is an example of the current increase operation.

Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in this specification or drawings achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

Claims (15)

1. It is a multi-level inverter
   Battery (18) and
   The high potential input wiring (12) connected to the positive electrode of the battery and
   The low potential input wiring (16) connected to the negative electrode of the battery and
   Midpoint wiring (14) and
   A first capacitor (31) connected between the midpoint wiring and the low potential input wiring,
   A second capacitor (32) connected between the high potential input wiring and the midpoint wiring,
   1st output wiring (50u) and
   2nd output wiring (50v) and
   3rd output wiring (50w) and
   The high-potential input wiring, the mid-point wiring, the low-potential input wiring, and the first switching circuit (41) connected to the first output wiring.
   The high-potential input wiring, the mid-point wiring, the low-potential input wiring, and the second switching circuit (42) connected to the second output wiring.
   The high potential input wiring, the midpoint wiring, the low potential input wiring, and the third switching circuit (43) connected to the third output wiring.
   Charging circuit (70) and
   Control circuit (90),
   Have,
   The first switching circuit
   A first upper arm switching element (41US) connected between the high potential input wiring and the first output wiring, and
   The first lower arm switching element connected between the first output wiring and the low potential input wiring (41LS),
   The first midpoint side intermediate diode (41MMD) whose anode is connected to the midpoint wiring, and
   A first output side intermediate diode (41OMD) in which the cathode is connected to the cathode of the first midpoint side intermediate diode and the anode is connected to the first output wiring,
   The first midpoint side intermediate switching element (41MMS) connected in parallel to the first midpoint side intermediate diode, and
   A first output side intermediate switching element (41OMS) connected in parallel to the first output side intermediate diode,
   Have,
   The second switching circuit
   A second upper arm switching element (42US) connected between the high potential input wiring and the second output wiring, and
   A second lower arm switching element (42LS) connected between the second output wiring and the low potential input wiring, and
   A second midpoint side intermediate diode (42MMD) whose cathode is connected to the midpoint wiring, and
   A second output side intermediate diode (42OMD) in which the anode is connected to the anode of the second midpoint side intermediate diode and the cathode is connected to the second output wiring,
   The second midpoint side intermediate switching element (42MMS) connected in parallel to the second midpoint side intermediate diode, and
   A second output side intermediate switching element (42OMS) connected in parallel to the second output side intermediate diode,
   Have,
   The charging circuit
   DC charging port (72) and
   The charging positive electrode wiring (22) connecting the positive electrode of the DC charging port and the cathode of the first midpoint side intermediate diode, and
   Charging negative electrode wiring (24) connecting the negative electrode of the DC charging port and the anode of the second midpoint side intermediate diode,
   Have,
   When the charger is connected to the DC charging port, the control circuit turns on the first midpoint side intermediate switching element and charges the first capacitor with the electric power of the charger. A boost control is executed in which the second middle point side intermediate switching element is turned on and the second operation of charging the second capacitor by the electric power of the charger is alternately repeated.
   Multi-level inverter.
2. 1 The multi-level inverter described in.
3. A positive electrode side diode (82) in which the anode is connected to the charging positive electrode wiring and the cathode is connected to the high potential input wiring,
   A negative electrode side diode (84), in which the anode is connected to the low potential input wiring and the cathode is connected to the charging negative electrode wiring.
   Have more
   The specific charging wiring is the charging positive electrode wiring, and the anode of the positive electrode side diode is connected to the charging positive electrode wiring on the side closer to the first midpoint side intermediate diode than the inductor, or the specific charging wiring is connected to the charging positive electrode wiring. The charging wiring is the charging negative electrode wiring, and the cathode of the negative electrode side diode is connected to the charging negative electrode wiring on the side closer to the second midpoint side intermediate diode than the inductor.
   The multi-level inverter according to claim 2.
4. In the first operation, the first output side intermediate switching element, the second midpoint side intermediate switching element, and the second output side intermediate switching element are turned off.
   In the second operation, the first midpoint side intermediate switching element, the first output side intermediate switching element, and the second output side intermediate switching element are turned off.
   The multi-level inverter according to claim 3.
5. In the first operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element are turned off.
   In the second operation, the first upper arm switching element, the first lower arm switching element, the second upper arm switching element, and the second lower arm switching element are turned off.
   The multi-level inverter according to claim 4.
6. In the boost control, the control circuit repeats the first operation, the second operation, and the pause operation.
   In the pause operation, the first midpoint side intermediate switching element, the first output side intermediate switching element, the second midpoint side intermediate switching element, and the second output side intermediate switching element are turned off.
   The multi-level inverter according to any one of claims 3 to 5.
7. In the boost control, the control circuit repeats the first operation, the second operation, and the current increasing operation.
   In the current increasing operation, the first midpoint side intermediate switching element and the second midpoint side intermediate switching element are turned on.
   The multi-level inverter according to any one of claims 3 to 5.
8. In the first operation, the second output side intermediate switching element is turned on, and the second output side intermediate switching element is turned on.
   In the second operation, the first output side intermediate switching element is turned on.
   The multi-level inverter according to claim 2.
9. In the boost control, the control circuit repeats the first operation, the second operation, and the current increasing operation.
   In the current increasing operation, the first midpoint side intermediate switching element and the second midpoint side intermediate switching element are turned on.
   The multi-level inverter according to claim 8.
10. The multi-level inverter according to any one of claims 2 to 9, further comprising a switch (78, 79) connected to the specific charging wiring in series with the inductor.
11. The switch
    A semiconductor switching element (78) interposed in the specific charging wiring and
    A diode (79) interposed in the specific charging wiring in series with the semiconductor switching element so as to be in the forward direction with respect to the current flowing through the specific charging wiring.
    The multi-level inverter according to claim 10.
12. The multi-level inverter according to claim 10 or 11, further comprising an input capacitor (76) for connecting the non-specific charging wiring to the inductor and the specific charging wiring closer to the DC charging port than the switch.
13. The multi-level inverter according to claim 12, further comprising a relay (74) for turning on / off the charging positive electrode wiring and the charging negative electrode wiring on the side closer to the DC charging port than the input capacitor.
14. The specific charging wiring is the charging positive electrode wiring,
    The multi-level inverter according to claim 13, wherein the anode is connected to the charging positive electrode wiring between the inductor and the relay, and the cathode further has a charging diode (82) connected to the positive electrode of the battery.
15. The specific charging wiring is the charging negative electrode wiring,
    The multi-level inverter according to claim 13, wherein the cathode is connected to the charging negative electrode wiring between the inductor and the relay, and the anode further comprises a charging diode (84) connected to the negative electrode of the battery.
    

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