Electric vehicle charging device

Abstract

The present invention provides a charging apparatus for electric vehicles, which is capable of performing a boosting operation by means of a multilevel inverter circuit during charging and which facilitates improvement in charging efficiency. This charging apparatus for electric vehicles is equipped with an NPC-type multilevel inverter circuit that outputs a driving current to a traction motor. In at least one leg, an upper clamp is an upper switching clamp capable of performing a switching operation, and a lower clamp is a lower switching clamp capable of performing a switching operation. One of a pair of power lines through which charging power is transmitted is connected to a connection point between the upper switching clamp and an upper arm, and the other is connected to a connection point between the lower switching clamp and a lower arm. In addition, a controller is capable of driving the multi-level inverter circuit so as to boost the charging power by means of a charge pump operation which uses two capacitors.

Description

Technical Field

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[0001] The present invention relates to a charging device for an electric vehicle.

Background Art

[0002] Patent Document 1 shows that by using a multi-level inverter circuit of a bidirectional switch method and boosting the input voltage by the charge pump operation of the multi-level inverter circuit, a battery can be charged with a voltage higher than the input voltage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an electric vehicle equipped with a high-voltage battery, a charging voltage lower than the battery voltage may be supplied. In such a case, it is preferable to be able to boost the charging voltage and supply it to the battery without using a dedicated boost circuit, because the dedicated boost circuit can be omitted.

[0005] By using the multi-level inverter circuit of the bidirectional switch method in Patent Document 1, the charging voltage can be boosted and supplied to the battery. However, the device is configured such that charging power is input from the midpoint of the bidirectional switch. In this configuration, it is necessary to add a diode to suppress current leakage from the multi-level inverter circuit to the power line that transmits the charging power to the multi-level inverter circuit. In this case, the charging current is transmitted through the additional diode, resulting in an increase in loss.

[0006] The present invention aims to provide a charging device for electric vehicles that can charge a battery even when a low charging voltage is supplied, and can improve charging efficiency, by using a multi-level inverter circuit for boost operation. [Means for solving the problem]

[0007] A charging device for an electric vehicle according to one aspect of the present invention is: A charging device for an electric vehicle, which is mounted on an electric vehicle comprising a drive wheel, a drive motor that drives the drive wheel, and a battery that stores the power supplied to the drive motor, A multi-level inverter circuit that receives power from the battery and outputs a drive current to the drive motor, A pair of power lines through which charging power is transmitted, A controller that controls the multilevel inverter circuit, Equipped with, The multilevel inverter circuit is an NPC type multilevel inverter circuit having a first potential point and a second potential point to which power is supplied from the battery, a third potential point to which a neutral point potential is generated, at least two capacitors to generate the neutral point potential, a plurality of output lines to which the drive current is output, and a plurality of legs corresponding to each of the plurality of output lines. Each of the plurality of legs includes an upper arm, a lower arm, an upper clamp capable of blocking current from the upper arm to the third potential point, and a lower clamp capable of blocking current from the third potential point to the lower arm. In at least one of the plurality of legs, the upper clamp is an upper switching clamp capable of switching operation. In at least one of the plurality of legs, the lower clamp is a lower switching clamp capable of switching operation. One of the pair of power lines is connected to the connection point between the upper switching clamp and the upper arm. The other end of the pair of power lines is connected to the connection point between the lower switching clamp and the lower arm. The controller can drive the multilevel inverter circuit to boost the charging power by a charge pump operation using the two capacitors. [Effects of the Invention]

[0008] According to the present invention, by utilizing a multi-level inverter circuit, the power for charging can be boosted and sent to the battery. Therefore, the circuit or elements required for boosting the voltage can be reduced. Furthermore, when boosting the power for charging, the charging current can be passed through a path with low loss. Therefore, the charging efficiency can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing an electric vehicle equipped with a charging device according to an embodiment of the present invention. [Figure 2] This diagram shows a multilevel inverter circuit. [Figure 3] This is a time chart illustrating the boost operation of a multilevel inverter circuit. [Figure 4] This flowchart shows the battery charging control process performed by the controller. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. In this specification, the state of closing the switch is referred to as "on," and the state of opening the switch is referred to as "off." In this specification, a connection point includes not only the point in question but also each point in the wiring conductor that is continuous with that point without passing through a circuit element.

[0011] Figure 1 is a block diagram showing an electric vehicle equipped with a charging device according to an embodiment of the present invention. The electric vehicle 1 comprises drive wheels 2, a driving motor 3 that drives the drive wheels 2, a battery 4 that stores power to drive the driving motor 3, a multilevel inverter circuit 6 that converts power between the battery 4 and the driving motor 3, a controller 11 that controls the multilevel inverter circuit 6, and a driving operation unit 5 on which the driver performs driving operations. The driving operation unit 5 includes a steering operation unit (e.g., a steering wheel) 5a for steering operations, an acceleration operation unit (e.g., an accelerator pedal) 5b for acceleration operations, and a deceleration operation unit (e.g., a brake pedal) 5c for deceleration operations. The multilevel inverter circuit 6 receives power from the battery 4 when the driving motor 3 is operating and outputs a drive current to the driving motor 3.

[0012] Furthermore, the electric vehicle 1 includes a power intake unit 7 for taking in power from an external source, a pair of power lines 71 and 72 for transmitting the power for charging taken in from the power intake unit 7, a communication unit 8 for communicating with external charging equipment 80, and a voltage sensor 9 for detecting the voltage between the power lines 71 and 72.

[0013] The charging device 20 of this embodiment includes a multi-level inverter circuit 6, a power intake unit 7, power lines 71 and 72, a communication unit 8, a voltage sensor 9, and a controller 11.

[0014] The controller 11 is a microcomputer having a memory unit 11a. The controller 11 operates according to a control program stored in the memory unit 11a. When the electric vehicle 1 is running, the controller 11 receives a signal of the amount of operation from the driving operation unit 5 and controls the driving motor 3 to perform powered operation or regenerative operation based on the signal. This powered operation or regenerative operation is achieved by driving the multilevel inverter circuit 6. The electric vehicle 1 moves as a result of the operation of the driving motor 3.

[0015] In addition, when power is taken in from the power intake unit 7, the controller 11 charges the battery 4 by driving the multilevel inverter circuit 6 for charging. Note that the controller 11 may be composed of a plurality of microcomputers that communicate with each other and cooperate. In this case, the microcomputer that performs running control and the microcomputer that performs charging control may have different configurations.

[0016] The communication unit 8 receives information on the power supplied from the external device 80 and sends it to the controller 11. The charging power information includes information indicating the voltage of the supplied power.

[0017] The battery 4 is a lithium-ion secondary battery, but is not limited to this type, and any type may be adopted. The voltage of the battery 4 is of the first voltage system (for example, 800V system).

[0018] The power intake unit 7 is a connector to which the power cable 81 of the external device 80 can be connected, and takes in charging power by wire. The external device 80 includes a first type of external device that can supply DC charging power at a voltage of the first voltage system (for example, 800V system) and a second type of external device that can supply DC charging power at a voltage of a second voltage system lower than the first voltage system (for example, 400V system). Note that the power intake unit 7 may be configured to take in charging power from an external device non-contact via electromagnetic action and supply DC power via a rectifier circuit or the like.

[0019] The power lines 71 and 72 are connected to the multilevel inverter circuit 6. The charging power taken in from the power intake unit 7 is sent to the battery 4 via some elements of the multilevel inverter circuit 6 and the power lines. A relay that can cut off the power lines 71 and 72 may be provided in the middle of the power lines 71 and 72.

[0020] <Multilevel Inverter Circuit> Figure 2 shows the multilevel inverter circuit of Figure 1. The multilevel inverter circuit 6 is a Neutral Point Clamped (NPC) type multilevel inverter circuit that is roughly diode clamp type. The multilevel inverter circuit 6 has a first potential point P1 and a second potential point P2 to which power is supplied from the battery 4, at least two capacitors C1 and C2 connected in series, a third potential point P3 to which a neutral point potential is generated by capacitors C1 and C2, a plurality of output lines L1 to L3 to which drive current is output to the traction motor 3, and a plurality of legs 61 to 63 corresponding to the plurality of output lines L1 to L3. Below, a configuration having three output lines L1 to L3 and three legs 61 to 63 corresponding to a three-phase traction motor 3 will be described.

[0021] The first potential point P1 and the second potential point P2 are connected to power lines 41 and 42, which are connected to the battery 4, respectively. Although not shown in the diagram, relays capable of disconnecting power lines 41 and 42 may be provided on power lines 41 and 42.

[0022] Capacitors C1 and C2 are connected in series between the first potential point P1 and the second potential point P2. Capacitors C1 and C2 generate a neutral potential with their connection point as the third potential point P3. The neutral potential is an intermediate potential between the potential of the first potential point P1 and the potential of the second potential point P2, being lower than the potential of the first potential point P1 and higher than the potential of the second potential point P2.

[0023] The first leg 61 is a circuit that can switch the connection between the corresponding output line L1 and the first potential point P1, the second potential point P2, and the third potential point P3. The second leg 62 is a circuit that can switch the connection between the corresponding output line L2 and the first potential point P1, the second potential point P2, and the third potential point P3. The third leg 63 is a circuit that can switch the connection between the corresponding output line L3 and the first potential point P1, the second potential point P2, and the third potential point P3.

[0024] The first to third legs 61 to 63 each have upper arms 611, 621, and 631, lower arms 612, 622, and 632, upper clamps 613, 623, and 633, and lower clamps 614, 624, and 634, respectively. The upper arms 611, 621, and 631 are circuit sections that supply current from the first potential point P1 to the output lines L1 to L3 when the traction motor 3 is in operation. The lower arms 612, 622, and 632 are circuit sections that supply current from the output lines L1 to L3 to the second potential point P2 when the traction motor 3 is in operation. The upper clamps 613, 623, and 633 are circuit components that allow current to flow from the third potential point P3 to the upper arms 611, 621, and 631 respectively, and interrupt the current from the upper arms 611, 621, and 631 to the third potential point P3, respectively, when the traction motor 3 is operating in power. The lower clamps 614, 624, and 634 are circuit components that allow current to flow from the lower arms 612, 622, and 632 respectively to the third potential point P3, and interrupt the current from the third potential point P3 to the lower arms 612, 622, and 632, respectively, when the traction motor 3 is operating in power.

[0025] <First Leg 61> The upper arm 611 has a first switch Q1 and a second switch Q2 connected in series between the first potential point P1 and the output line L1.

[0026] The lower arm 612 has a third switch Q3 and a fourth switch Q4 connected in series between the second potential point P2 and the output line L1.

[0027] The first to fourth switches Q1 to Q4 are power semiconductor switching elements that can be switched on and off. IGBTs (Insulated Gate Bipolar Transistors) or FETs (Field Effect Transistors) can be used for the first to fourth switches Q1 to Q4. Freewheeling diodes D1 to D4 may be connected in parallel to the first to fourth switches Q1 to Q4. Power semiconductor diodes or parasitic diodes of the first to fourth switches Q1 to Q4 may be used for the freewheeling diodes D1 to D4.

[0028] The upper clamp 613 is connected between the connection point N1 of the first switch Q1 and the second switch Q2 and the third potential point P3. The upper clamp 613 is configured to perform switching operations and will hereafter be referred to as the "upper switching clamp 613". The upper switching clamp 613 has a fifth switch Q5 and a diode D5 connected in parallel with each other. When the fifth switch Q5 is off, the upper switching clamp 613 allows current to flow from the third potential point P3 to the connection point N1, while blocking current in the reverse direction. When the fifth switch Q5 is on, the upper switching clamp 613 allows current to flow from the connection point N1 to the third potential point P3.

[0029] The lower clamp 614 is connected between the connection point N2 of the third switch Q3 and the fourth switch Q4 and the third potential point P3. The lower clamp 614 is configured to perform switching operations and will hereafter be referred to as the "lower switching clamp 614". The lower switching clamp 614 has a sixth switch Q6 and a diode D6 connected in parallel with each other. When the sixth switch Q6 is off, the lower switching clamp 614 allows current to flow from the connection point N2 to the third potential point P3, while blocking current in the reverse direction. When the sixth switch Q6 is on, the lower switching clamp 614 allows current to flow from the third potential point P3 to the connection point N2.

[0030] The fifth switch Q5 and the sixth switch Q6 can be power semiconductors such as IGBTs or FETs. Diodes D5 and D6 may be power semiconductor diodes, or they may be parasitic diodes of the fifth switch Q5 and the sixth switch Q6.

[0031] <Second Leg 62 and Third Leg 63> The upper arms 621 and 631 are the same as the upper arm 611 of the first leg 61. The lower arms 622 and 632 are the same as the lower arm 612 of the first leg 61. The upper clamps 623 and 633 have a clamping diode D5, similar to the first leg 61, but unlike the first leg 61, they do not have a fifth switch Q5. The lower clamps 624 and 634 have a clamping diode D6, similar to the first leg 61, but unlike the first leg 61, they do not have a sixth switch Q6.

[0032] <Operation of Multilevel Inverter Circuit 6> According to the multilevel inverter circuit 6 configured as described above, the first leg 61 operates as follows: When the first and second switches Q1 and Q2 are turned on and the third and fourth switches Q3 and Q4 are turned off, the first potential point P1 and the output line L1 are connected so that current can be output from the first potential point P1 to the output line L1. When the second switch Q2 is turned on and the first, third and fourth switches Q1, Q3 and Q4 are turned off, the third potential point P3 and the output line L1 are connected so that current can be output from the third potential point P3 to the output line L1. When the third switch Q3 is turned on and the first, second and fourth switches Q1, Q2 and Q4 are turned off, the third potential point P3 and the output line L1 are connected so that current can be returned from the output line L1 to the third potential point P3. When the first and second switches Q1 and Q2 are turned off and the third and fourth switches Q3 and Q4 are turned on, the second potential point P2 and output line L1 are connected so that current can flow back from output line L1 to the second potential point P2. When the first to fourth switches Q1 to Q4 are turned off, the first to third potential points P1 to P3 and output line L1 are disconnected. The same applies to legs 62 and 63.

[0033] The controller 11 then switches the states of multiple legs 61 to 63 to one of the five states described above by altering their phases, thereby outputting multiple levels of voltage between each pair of potential points, the first potential point P1, the second potential point P2, and the third potential point P3, to the output lines L1 to L3. This output can then be used to drive the traction motor 3. When the traction motor 3 is being driven, the controller 11 keeps the fifth switch Q5 and the sixth switch Q6 open.

[0034] Furthermore, the controller 11 may turn on the fifth switch Q5 and allow current to flow through it during the period when current flows through the diode D5 of the first leg 61. In addition, if such control is performed, the diode D5 of the first leg 61 may be omitted. Similarly, the controller 11 may turn on the sixth switch Q6 and allow current to flow through it during the period when current flows through the diode D6 of the first leg 61. In addition, if such control is performed, the diode D6 may be omitted.

[0035] <Connection between charging power lines and multilevel inverter circuit> One of the power lines 71 and 72 that transmit power for charging from the power intake unit 7 is connected to the connection point N1 between the upper arm 611 of the first leg 61 and the upper switching clamp 613. The other is connected to the connection point N2 between the lower arm 612 of the first leg 61 and the lower switching clamp 614.

[0036] <Boost operation of a multilevel inverter circuit> The charging device 20 of this embodiment has the function of boosting the charging power taken in from the power intake unit 7 by the operation of a charge pump and sending it to the battery 4.

[0037] Figure 3 is a time chart showing the boost operation of a multilevel inverter circuit. When boosting the voltage, the controller 11 alternately switches between turning on the fourth switch Q4 and the fifth switch Q5 (periods T1, T5) and turning on the first switch Q1 and the sixth switch Q6 (periods T3, T7). Between these switches, there may be pause periods (periods T2, T4, T6, T8) in which the first to sixth switches Q1 to Q6 are turned off.

[0038] When the fourth switch Q4 and the fifth switch Q5 are turned on, the voltages from power lines 71 and 72 are applied to the lower capacitor C2, and the capacitor C2 is charged. When the first switch Q1 and the sixth switch Q6 are turned on, the voltages from power lines 71 and 72 are applied to the upper capacitor C1, and the capacitor C1 is charged. If the first switch Q1 and the fourth switch Q4 are IGBTs that cannot conduct reverse current, the charging of capacitors C1 and C2 is achieved by current flowing through freewheeling diodes D1 and D4.

[0039] As a result of charging capacitors C1 and C2, the charge pump operation generates a charging voltage between the first potential point P1 and the second potential point P2, which is the sum of the voltages across the two capacitors C1 and C2. This charging voltage can be boosted to approximately twice the voltage of power lines 71 and 72.

[0040] <Charge control processing> Next, we will explain the battery charging control process performed by the controller 11. Figure 4 is a flowchart of this charging control process.

[0041] The controller 11 starts a charge control process based on an arbitrary charge request. Once the charge control process is started, the controller 11 acquires information about the voltage of the power for charging input via the power lines 71 and 72, i.e., the voltage of the external equipment 80 (step S1). The voltage information may be sent from the external equipment 80 supplying the charging power to the controller 11 via the communication unit 8, or it may be information detected by the voltage sensor 9.

[0042] Next, the controller 11 determines whether the above voltage is less than the charging voltage of the battery 4 (step S2). If the voltage is less than the charging voltage of the battery 4, for example, if the charging voltage of the battery 4 is 800V and the voltage of the power supply for charging is 400V, the controller 11 performs a charging process with a voltage boost operation (step S3).

[0043] In step S3, the controller 11 starts taking power from the power intake unit 7 and then controls the drive of the multi-level inverter circuit 6 shown in Figure 3. Specifically, the controller 11 controls the drive as shown in Figure 3 while adjusting the length of the pause periods T2, T4, T6, and T8 so that the charging current or charging voltage output to the battery 4 becomes the planned current or voltage value. Here, in addition to adjusting the pause periods T2, T4, T6, and T8, the controller 11 may also adjust the current or voltage output to the battery 4 by adjusting the length of the charging periods T1, T3, T5, and T7 for capacitors C1 and C2. Through the process in step S3, the low voltage of the power supplied from the external equipment 80 is boosted to a voltage higher than the charging voltage of the battery 4, and the battery 4 can be charged with the boosted voltage.

[0044] In parallel with the charging process in step S3, the controller 11 determines whether the conditions for ending the charging of the battery 4 have been met (step S4). Various conditions may be applied to the conditions for ending the charging, such as reaching a specified amount of energy, reaching a specified charging time, or reaching a specified charge level of the battery 4. If the determination result in step S4 is YES, the controller 11 performs the charging completion process (step S7) and terminates the charging control process. The charging completion process includes, for example, communication processing to notify external equipment 80 of the end of charging, and processing to turn off the relays of power lines 71 and 72.

[0045] On the other hand, if the determination result in step S2 is determined to be that the voltage is equal to or greater than the charging voltage, the controller 11 executes a charging process (step S5) that does not involve a voltage boosting operation.

[0046] In step S5, the controller 11 sends the power supplied from the power intake unit 7 to the battery 4 via the first switch Q1 or freewheeling diode D1 of the first leg 61 and the fourth switch Q4 or freewheeling diode D4 of the first leg 61. The battery 4 is then charged with this power.

[0047] In parallel with the charging process in step S5, the controller 11 determines whether the conditions for ending the charging of the battery 4 have been met (step S6). If the condition is YES, it performs the charging completion process in step S7 and terminates the charging control process.

[0048] According to the charging control process described above, the battery 4 can be charged in both cases: when it receives charging power from an external device 80 that is compatible with the voltage system of the battery 4, and when it receives charging power from an external device 80 with a voltage system lower than that of the battery 4.

[0049] The charging control process program described above is stored in a non-transient storage medium (non-transient computer-readable medium), such as the storage unit 11a of the controller 11. The controller 11 may be configured to read a program stored in a portable non-transient recording medium and execute the program. The portable non-transient storage medium described above may store the charging control process program described above.

[0050] As described above, with the charging device 20 of the electric vehicle 1 of this embodiment, the charging power taken in from the power intake unit 7 can be boosted and sent to the battery 4 by the charge pump operation using capacitors C1 and C2 of the multilevel inverter circuit 6. Therefore, even if the voltage of the charging power is lower than the voltage of the battery 4, it is possible to boost the voltage and charge the battery 4. Furthermore, a dedicated boost circuit can be omitted, which reduces the manufacturing cost and the volume of the charging device 20.

[0051] Furthermore, according to the charging device 20 of the electric vehicle 1 of this embodiment, the upper clamp 613 of one leg 61 is a switching-operable upper switching clamp 613, and the lower clamp 614 of one leg 61 is a switching-operable lower switching clamp 614. One power line 71 of the power intake unit 7 is connected to the connection point between the upper switching clamp 613 and the upper arm 611 of the multilevel inverter circuit 6. The other power line 72 is connected to the connection point between the lower switching clamp 614 and the lower arm 612 of the multilevel inverter circuit 6. Therefore, current leakage from the multilevel inverter circuit 6 through the power lines 71 and 72 is less likely to occur, and a simple connection configuration between the power lines 71 and 72 and the multilevel inverter circuit 6 can be realized. Thus, the provision of loss-generating elements such as diodes in the path through which the charging current flows can be reduced, and the charging current can be supplied to the battery 4 with less loss. Therefore, the charging efficiency can be improved.

[0052] Furthermore, according to the charging device 20 of the electric vehicle 1 of this embodiment, in the charging control process, the controller 11 acquires voltage information input to the power lines 71 and 72. The controller 11 then switches between a charging process that performs charge pump operation and a charging process that does not perform charge pump operation based on the acquired voltage information (see steps S1 to S6 in Figure 4). Therefore, power can be taken in via the same power lines 71 and 72 whether charging the battery 4 by taking in low-voltage power from the external equipment 80 or by taking in high-voltage power.

[0053] Furthermore, according to the charging device 20 of the electric vehicle 1 of this embodiment, each of the upper arms 611, 621, and 631 has a configuration in which a first switch Q1 and a second switch Q2 are connected in series. Furthermore, each of the lower arms 612, 622, and 632 has a configuration in which a third switch Q3 and a fourth switch Q4 are connected in series. Each of the upper clamps 613, 623, and 633 is connected between the connection point N1 between the first switch Q1 and the second switch Q2 in the same leg and the third potential point P3. Each of the lower clamps 614, 624, and 634 is connected between the connection point N2 between the third switch Q3 and the fourth switch Q4 in the same leg and the third potential point P3. With this configuration, current leakage from the multilevel inverter circuit 6 through the power lines 71 and 72 is less likely to occur, and the connection configuration between the power lines 71 and 72 and the multilevel inverter circuit 6 can be made simpler. Furthermore, charge pump operation can be realized with switching control of fewer elements. Therefore, the reliability of the charging device 20 can be improved.

[0054] Furthermore, in the charging device 20 of the electric vehicle 1 of this embodiment, the upper clamp 613 of one of the multiple legs 61 to 63 is configured to be switchable, and the upper clamps 623 and 633 of the other legs 62 and 63 are diodes D5. Similarly, the lower clamp 614 of one of the multiple legs 61 to 63 is configured to be switchable, and the lower clamps 624 and 634 of the other legs 62 and 63 are diodes D6. Therefore, the same configuration and control method as known diode clamp type NPC multilevel inverter circuits can be applied to the other legs 62 and 63, thereby reducing the manufacturing and development costs of the device.

[0055] Furthermore, according to the charging device 20 of the electric vehicle 1 of this embodiment, the upper clamp (upper switching clamp) 613, which is capable of switching operation, has a configuration in which the fifth switch Q5 and the clamping diode D5 are connected in parallel. Similarly, the lower clamp (lower switching clamp) 614, which is capable of switching operation, has a configuration in which the sixth switch Q6 and the clamping diode D6 are connected in parallel. The controller 11 maintains the fifth switch Q5 and the sixth switch Q6 in an open state when the traction motor 3 is being powered. Therefore, even in the leg 61 through which the charging current flows, a control method similar to that of a known diode clamp type NPC multilevel inverter circuit can be applied when the traction motor 3 is being powered. That is, multiple legs 61 to 63 can be driven with the same control method. In the multilevel inverter circuit 6, the proportion of the period during which the traction motor 3 is driven is significantly larger than the proportion of the charging operation period, and it is the period during which the traction motor 3 is driven that affects the degree of element degradation. Therefore, it is possible to suppress large variations in the degree of element degradation among multiple legs 61 to 63.

[0056] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiment, a configuration was shown in which power lines 71 and 72 that transmit power for charging are connected to one leg 61. However, one power line may be connected to the connection point between the upper arm and the upper clamp of one leg, and the other power line may be connected to the connection point between the lower arm and the lower clamp of a different leg. In this case, the upper clamp and the lower clamp to which the power lines are connected may be configured to be switchable. In this configuration as well, charging with a boost operation and charging without a boost operation are possible by similar control.

[0057] Furthermore, in the above embodiment, a configuration was shown in which one power line 71 that transmits power for charging is connected to one leg 61. However, one power line may be connected to multiple legs or all legs. In this case, the upper clamps on all legs to which one power line is connected can be configured to be switchable and driven simultaneously during the boost operation, or driven one by one in sequence. In this case, when the drive motor 3 is driven, a switch can be provided on the power line to which one power line is connected to prevent a short circuit from occurring through that power line, and the switch can be kept in the open state. The same applies to the other power line and the lower clamp.

[0058] Furthermore, although the above embodiment shows a configuration in which the upper clamps 623 and 633 are diodes D5, the upper clamps 623 and 633 may be composed of switching elements such as FETs. Similarly, although the above embodiment shows a configuration in which the lower clamps 624 and 634 are diodes D6, the lower clamps 624 and 634 may be switching elements such as FETs. In this configuration, the controller 11 only needs to control the switching elements so that they turn on during the period when current flows through the diodes D5 and D6 when the driving motor 3 is being driven. With such a configuration, losses when current flows through the upper clamps 613, 623, 633 and the lower clamps 614, 624, 634 can be reduced, and the efficiency of the multilevel inverter circuit 6 can be improved both when the driving motor 3 is being driven and when the battery 4 is being charged with a boost operation.

[0059] Furthermore, although the above embodiment shows a configuration in which the power for charging is supplied from an external device 80, the power for charging may be power generated inside the electric vehicle (for example, regenerative power). Also, the electric vehicle may be an electric vehicle equipped with an engine, such as an HEV (Hybrid Electric Vehicle) or PHEV (Plug-in Hybrid Electric Vehicle). In addition, the details shown in the embodiment can be appropriately modified without departing from the spirit of the invention. [Industrial applicability]

[0060] This invention can be applied to charging devices for electric vehicles. [Explanation of symbols]

[0061] 1. Electric Vehicle 2 drive wheels 3. Motor for driving 4 batteries 5. Operating controls 6. Multilevel Inverter Circuit 7 Power intake section 71, 72 Power lines 8 Communications Department 9. Voltage Sensor 11 Controllers 11a Storage section L1~L3 Output Lines Legs 61-63 611, 621, 631 Upper Arm 612, 622, 632 Lower Arm 613 Upper Switching Clamp (Upper Clamp) 623, 633 Upper clamp 614 Lower Switching Clamp (Lower Clamp) 624, 634 Lower clamp 80 External equipment C1, C2 Capacitors P1 First potential point P2 Second potential point P3 3rd potential point Q1 First switch Q2 Second switch Q3 Third switch Q4 Fourth switch Q5 Fifth switch Q6 Switch 6 D1~D4 Freewheeling diodes D5, D6 diodes N1, N2 connection point

Claims

1. A charging device for an electric vehicle, which is mounted on an electric vehicle comprising a drive wheel, a drive motor that drives the drive wheel, and a battery that stores the power supplied to the drive motor, A multi-level inverter circuit that receives power from the battery and outputs a drive current to the drive motor, A pair of power lines through which charging power is transmitted, A controller that controls the multilevel inverter circuit, Equipped with, The multilevel inverter circuit is an NPC type multilevel inverter circuit having a first potential point and a second potential point to which power is supplied from the battery, a third potential point to which a neutral point potential is generated, at least two capacitors to generate the neutral point potential, a plurality of output lines to which the drive current is output, and a plurality of legs corresponding to each of the plurality of output lines. Each of the plurality of legs includes an upper arm, a lower arm, an upper clamp capable of blocking current from the upper arm to the third potential point, and a lower clamp capable of blocking current from the third potential point to the lower arm. In at least one of the plurality of legs, the upper clamp is an upper switching clamp capable of switching operation. In at least one of the plurality of legs, the lower clamp is a lower switching clamp capable of switching operation. One of the pair of power lines is connected to the connection point between the upper switching clamp and the upper arm. The other end of the pair of power lines is connected to the connection point between the lower switching clamp and the lower arm. The charging device for electric vehicles is characterized in that the controller is capable of driving the multilevel inverter circuit to boost the charging power by the operation of a charge pump using the two capacitors.

2. The charging device for an electric vehicle according to claim 1, characterized in that the controller acquires voltage information of the power for charging and switches between a charging process that performs the charge pump operation and a charging process that does not perform the charge pump operation based on the voltage information.

3. The upper arm has a first switch and a second switch connected in series. The lower arm has a third switch and a fourth switch connected in series. The upper clamp is connected between the connection point between the first switch and the second switch and the third potential point. The charging device for an electric vehicle according to claim 1, characterized in that the lower clamp is connected between the connection point between the third switch and the fourth switch and the third potential point.

4. The upper clamp in one of the plurality of legs is the upper switching clamp, and the upper clamp in one or more other legs is a diode. The electric vehicle charging device according to claim 3, characterized in that the lower clamp in one of the plurality of legs is the lower switching clamp, and the lower clamp in one or more other legs is a diode.

5. The aforementioned upper switching clamp has a fifth switch and a diode connected in parallel. The lower switching clamp has a sixth switch and a diode connected in parallel. The charging device for an electric vehicle according to claim 4, characterized in that the controller maintains both the fifth switch and the sixth switch in an open state when the traction motor is being operated.

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