Electric vehicle and charging control method for electric vehicle

Abstract

The present disclosure relates to an electric vehicle and a charging control method for an electric vehicle. A terminal voltage acquisition unit (101) acquires a terminal voltage (VB) of a battery. A comparison unit (102) compares the terminal voltage (VB) with a maximum output voltage (VCmax) of a charger (30). When VB ≤ VCmax, an AC charging relay (40) is switched to supply the output power of the charger (30) to the high voltage side of a buck-boost converter (20). When VB > VCmax, an AC charging relay (40) is switched to supply the output voltage of the charger (30) to the low voltage side of the buck-boost converter (20), and the buck-boost converter (20) is operated.

Description

Technical Field

[0001] The present disclosure relates to an electric vehicle, and more particularly to an electric vehicle including a power storage device that can be charged by an external power supply, and a charging control method for the electric vehicle. Background Art

[0002] In recent years, electric vehicles, such as electric vehicles and plug-in hybrid vehicles, have become increasingly popular. These vehicles are equipped with a power storage device that can be charged using electricity supplied from an external power source. Hereinafter, charging a power storage device using electricity supplied from an external power source will also be referred to as "external charging."

[0003] For example, Japanese Patent Application Laid-Open No. 2019-047677 discloses that a power storage device is charged using a boost device based on the highest voltage output from an external charger (charging station, etc.) as an external power source.

[0004] The electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677 is equipped with an ultra-high voltage (e.g., 800V) power storage device. The maximum voltage Vmax of the power output from the charging station is compared with a predetermined reference voltage Vref. If the maximum voltage Vmax is below the reference voltage Vref, the external charging mode is set to high-voltage charging mode. If the maximum voltage Vmax is higher than the reference voltage Vref, the external charging mode is set to ultra-high-voltage charging mode.

[0005] When the external charging mode is high-voltage charging mode, the high voltage supplied from the charging station is boosted to an ultra-high voltage (800V) by the booster. The power storage device is charged using the power at the boosted voltage. When the external charging mode is ultra-high-voltage charging mode, the power supplied from the charging station is at an ultra-high voltage (800V) and is not boosted by the booster. The power storage device is charged using the power at the unboosted voltage.

[0006] The inter-terminal voltage of a power storage device mounted on an electric vehicle fluctuates depending on the SOC (State of Charge) of the power storage device. Typically, as the SOC decreases, the inter-terminal voltage decreases. In the electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677, the reference voltage Vref is a fixed value (e.g., 500V). Therefore, when the inter-terminal voltage is lower than the reference voltage Vref due to the low SOC of the power storage device, but the maximum voltage Vmax at the charging station is lower than the reference voltage Vref, a high-voltage charging mode is set. The power storage device is then charged using the power of the voltage boosted by the boost device. As such, in the electric vehicle disclosed in Japanese Patent Application Laid-Open No. 2019-047677, the boost device is operated even when the power storage device can be charged without the boost device. Furthermore, the power storage device can be charged using the power of the boosted voltage. The boosting operation of the boost device is accompanied by power loss, so if the power storage device is charged while the boost device is operating, the charging efficiency will decrease. Summary of the Invention

[0007] The present disclosure has been made to solve the above-mentioned problem, and an object of the present disclosure is to perform external charging while suppressing a decrease in charging efficiency in an electric vehicle including a power storage device that can be charged by an external power supply.

[0008] The electric vehicle disclosed herein is an electric vehicle having a power storage device that can be charged using electric power supplied from an external power source. The electric vehicle is provided with a boost device. The high-voltage side of the boost device is connected to the power storage device. The boost device is configured to boost the voltage of the electric power input to the low-voltage side of the boost device and output the boosted voltage electric power to the high-voltage side. The electric vehicle also has a first path, a second path, a charging relay, and a control device. The first path supplies the electric power supplied from the external power source to the high-voltage side of the boost device. The second path supplies the electric power supplied from the external power source to the low-voltage side of the boost device. The charging relay selectively switches the path of the electric power supplied from the external power source to the first path or the second path. The control device is configured to: when the power storage device is charged with electric power supplied from an external power supply and the voltage between the terminals of the power storage device is lower than the voltage of the electric power supplied from the external power supply, switch the charging relay to select the first path; when the power storage device is charged with electric power supplied from the external power supply and the voltage between the terminals of the power storage device is higher than the voltage of the electric power supplied from the external power supply, switch the charging relay to select the second path and operate the boost device.

[0009] According to this configuration, when the power storage device is being charged with power supplied from an external power source and the voltage across the power storage device's terminals is lower than the voltage of the power supplied from the external power source, the charging relay is switched to select the first path. Consequently, when the voltage across the power storage device's terminals is lower than the voltage of the power supplied from the external power source, the power from the external power source is supplied to the high-voltage side of the boost device. The high-voltage side of the boost device is connected to the power storage device, and the voltage of the power supplied from the external power source is higher than the voltage across the power storage device's terminals. This allows the power storage device to be charged without operating the boost device. Consequently, a decrease in charging efficiency can be minimized.

[0010] When the power storage device is being charged with power supplied from an external power source and the voltage across the terminals of the power storage device is higher than the voltage of the power supplied from the external power source, the charging relay is switched to select the second path, and the boost device operates to boost the voltage. Consequently, when the voltage of the power supplied from the external power source is lower than the voltage across the terminals of the power storage device, the power supplied from the external power source is input to the low-voltage side of the boost device, and the boost device operates to boost the voltage. This allows the power storage device to be charged.

[0011] Preferably, the external power supply is an AC power supply that supplies AC power to the electric vehicle. The electric vehicle includes a charger that converts the AC power supplied from the AC power supply into DC power. The first path is a path for supplying the power output from the charger to the high-voltage side of the boost device. The second path is a path for supplying the power output from the charger to the low-voltage side of the boost device. The control device is configured to: when the voltage between the terminals of the power storage device is lower than the voltage of the power output from the charger, switch the charging relay to select the first path; when the voltage between the terminals of the power storage device is higher than the voltage of the power output from the charger, switch the charging relay to select the second path, and operate the boost device.

[0012] With this configuration, even when the inter-terminal voltage (rated voltage or nominal voltage) of the power storage device is higher than the output voltage of the charger, the power storage device can be charged using the charger without increasing the output voltage of the charger.

[0013] Preferably, the control device is configured to: when the voltage between the terminals of the storage device is lower than an upper limit voltage that is an upper limit of the voltage output from the charger, switch the charging relay to select the first path; when the voltage between the terminals of the storage device is higher than the upper limit voltage, switch the charging relay to select the second path and operate the boost device.

[0014] In this manner, the upper limit voltage that can be output from the charger may be used as the voltage of the electric power output from the charger.

[0015] Preferably, the external power supply is a DC power supply that supplies DC power to the electric vehicle. The electric vehicle includes a DC inlet to which the DC power supplied from the DC power supply is input. The first path is a path for supplying the power input to the DC inlet to the high voltage side of the boost device. The second path is a path for supplying the power input to the DC inlet to the low voltage side of the boost device. The control device is configured to: when the voltage between the terminals of the power storage device is lower than the voltage of the DC power supplied from the DC power supply, switch the charging relay to select the first path; when the voltage between the terminals of the power storage device is higher than the voltage of the DC power supplied from the DC power supply, switch the charging relay to select the second path, and operate the boost device.

[0016] With this configuration, even when the voltage of the DC power supplied from the external power source is lower than the inter-terminal voltage (rated voltage or nominal voltage) of the power storage device, the power storage device can be charged using the power at the voltage boosted by the boost device. If the voltage of the DC power supplied from the external power source is higher than the inter-terminal voltage of the power storage device, the power storage device can be charged without using the boost device. This can minimize a decrease in charging efficiency.

[0017] Preferably, the control device is configured to: when the voltage between the terminals of the storage device is lower than the maximum voltage, which is the maximum value of the voltage of the electric power supplied from the DC power supply, switch the charging relay to select the first path; when the voltage between the terminals of the storage device is higher than the maximum voltage, switch the charging relay to select the second path and operate the boost device.

[0018] In this manner, the maximum voltage that can be output from the external power supply may be used as the voltage of the DC power supplied from the external power supply.

[0019] Preferably, the external power supply is an AC power supply that supplies AC power to the electric vehicle or a DC power supply that supplies DC power to the electric vehicle. The electric vehicle includes a DC inlet, a first DC path, a second DC path, a DC charging relay, and a charger. The DC inlet is input with DC power supplied from the DC power supply. The first DC path supplies the power input to the DC inlet to the high voltage side of the boost device. The second DC path supplies the power input to the DC inlet to the low voltage side of the boost device. The DC charging relay selectively switches the path of the power supplied from the DC power supply to the first DC path or the second DC path. The charger converts the AC power supplied from the AC power supply into DC power. The first path is a path for supplying the power output from the charger to the high voltage side of the boost device. The second path is a path for supplying the power output from the charger to the low voltage side of the boost device.

[0020] The control device is configured to: when the power storage device is being charged using the DC power input to the DC inlet and the voltage between the terminals of the power storage device is lower than the voltage of the DC power supplied from the DC power supply, switch the DC charging relay to select the first DC path; when the power storage device is being charged using the DC power input to the DC inlet and the voltage between the terminals of the power storage device is higher than the voltage of the DC power supplied from the DC power supply, switch the DC charging relay to select the second DC path and operate the step-up device; and when the power storage device is being charged using the DC power output from the charger and the voltage between the terminals of the power storage device is lower than the voltage of the power output from the charger, switch the charging relay to select the first path; and when the power storage device is being charged using the DC power output from the charger and the voltage between the terminals of the power storage device is higher than the voltage of the power output from the charger, switch the charging relay to select the second path and operate the step-up device.

[0021] This configuration enables the use of a boost device for both charging using DC power supplied from an external power source and charging using a charger that converts AC power supplied from the external power source into DC power. For example, a boost device can be provided to address situations where the voltage of the DC power supplied from the external power source is lower than the inter-terminal voltage (rated voltage or nominal voltage) of the power storage device. This configuration allows the power storage device to be charged without increasing the charger's output voltage, even when the inter-terminal voltage of the power storage device is higher than the charger's output voltage.

[0022] Preferably, the control device is configured to: when the power storage device is being charged using DC power input to the DC inlet and the voltage between the terminals of the power storage device is lower than a maximum voltage, which is the maximum value of the voltage of the power supplied from the DC power supply, switch the DC charging relay to select the first DC path; when the voltage between the terminals of the power storage device is higher than the maximum voltage, switch the DC charging relay to select the second DC path and operate the step-up device; and when the power storage device is being charged using DC power output from the charger and the voltage between the terminals of the power storage device is lower than an upper limit voltage, which is the upper limit of the voltage output from the charger, switch the charging relay to select the first path; when the power storage device is being charged using DC power input to the DC inlet and the voltage between the terminals of the power storage device is higher than the upper limit voltage, switch the charging relay to select the second path and operate the step-up device.

[0023] Preferably, the voltage boost device is a buck-boost converter. The buck-boost converter is configured to boost the voltage of power input to the low-voltage side and output the boosted voltage to the high-voltage side, and to step down the voltage of power input to the high-voltage side and output the stepped-down voltage to the low-voltage side.

[0024] According to this configuration, the buck-boost converter mounted on the electric vehicle is used as a boost device.

[0025] Preferably, the vehicle further includes an auxiliary device connected to the low voltage side of the step-up / step-down converter.

[0026] According to another aspect, a charging control method for an electric vehicle is provided. The electric vehicle includes a charger, a boost device, and a power storage device. The charger converts AC power supplied from an external power source into DC power. The high voltage side of the boost device is connected to the power storage device. The boost device is configured to boost the voltage of power input to the low voltage side of the boost device and output the power of the boosted voltage to the high voltage side. The power storage device can be charged using the power output from the charger. The charging control method includes the following steps: obtaining the voltage between the terminals of the power storage device; comparing the upper limit voltage, which is the upper limit of the voltage output from the charger, with the terminal voltage; when the terminal voltage is higher than the upper limit voltage, charging the power storage device by operating the boost device; and when the terminal voltage is lower than the upper limit voltage, charging the power storage device without operating the boost device.

[0027] This charging control method allows the storage device to be charged without using a booster when the voltage between the terminals of the storage device is lower than the upper limit voltage that can be output from the charger, preventing the storage device from being charged even without the booster. This allows the storage device to be charged without losses caused by the booster, minimizing a decrease in charging efficiency. When the voltage between the terminals of the storage device is higher than the upper limit voltage that can be output from the charger, the booster performs a voltage boost. This allows the storage device to be charged using power from the boosted voltage.

[0028] The foregoing and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. 1 is a diagram showing the overall structure of an electric vehicle according to this embodiment.

[0030] Figure 2 1 is a diagram showing the flow of power when the c-contact relay 50a is switched to the first position and the a-contact relay 50b is closed.

[0031] Figure 31 is a diagram showing the flow of power when the c-contact relay 50a is switched to the second position and the a-contact relay 50b is closed.

[0032] Figure 4 1 is a diagram showing the flow of electric power when AC charging relay 40 (C-contact relay 40a and C-contact relay 40b) is switched to the first position.

[0033] Figure 5 1 is a diagram showing the flow of electric power when AC charging relay 40 (C-contact relay 40a and C-contact relay 40b) is switched to the second position.

[0034] Figure 6 This is a diagram showing functional blocks configured within the ECU 100 .

[0035] Figure 7 This is a schematic flowchart of the processing executed by the ECU 100 .

[0036] Figure 8 1 is a diagram showing the flow of electric power when the electric vehicle V is traveling.

[0037] Figure 9 1 is a diagram showing functional blocks configured within ECU 100 in a modified example.

[0038] Figure 10 This is a schematic flowchart of processing executed by ECU 100 in the modified example.

[0039] Figure 11 This is a diagram showing another configuration example of an AC charging relay. DETAILED DESCRIPTION

[0040] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0041] Figure 1 This is a diagram showing the overall structure of an electric vehicle according to this embodiment. In this embodiment, the electric vehicle V is, for example, an electric car. The electric vehicle V includes power control units (PCUs) 1F and 1R, motor generators (MGs) 2F and 2R as rotating electrical machines, power transmission gears 3F and 3R, drive wheels 4F and 4R, a battery 10 as an example of a power storage device, a monitoring unit 11, a system main relay (SMR) 12, and an electronic control unit (ECU) 100 as an example of a control device.

[0042] MG2F and MG2R are, for example, embedded permanent magnet synchronous motors (IPM motors) that function as both electric motors and generators. The output torque of MG2F is transmitted to drive wheels 4F, the front wheels, via a power transmission gear 3F, which includes a speed reducer and a differential. Similarly, the output torque of MG2R is transmitted to drive wheels 4R, the rear wheels, via a power transmission gear 3R, which also includes a speed reducer and a differential.

[0043] When the electric vehicle V brakes, the front drive wheels 4F drive the MG2F, causing it to operate as a generator. Consequently, the MG2F also functions as a braking device that performs regenerative braking, converting the kinetic energy of the electric vehicle V into electricity. The regenerative power generated by the regenerative braking force in the MG2F is stored in the battery 10. Similarly, the MG2R also operates as a generator when the electric vehicle V brakes, and the regenerative power generated by the regenerative braking force is stored in the battery 10.

[0044] The PCU 1F is a power conversion device that converts electric power bidirectionally between the MG 2F and the battery 10. The PCU 1F includes, for example, an inverter and a converter that operate based on control signals from the ECU 100.

[0045] The converter boosts the voltage supplied from battery 10 during discharge of battery 10 and supplies the boosted voltage to the inverter. The inverter converts the DC power supplied from the converter into AC power and drives MG 2F using the converted power.

[0046] Meanwhile, when charging battery 10, the inverter converts the AC power generated by MG2F into DC power and supplies the converted power to the converter. The converter steps down the voltage supplied from the inverter to a voltage suitable for charging battery 10 and supplies the stepped-down voltage to battery 10.

[0047] The PCU 1F stops the operation of the inverter and the converter based on a control signal from the ECU 100, thereby suspending charging and discharging. The converter may be omitted from the PCU 1F.

[0048] The PCU 1R is a power conversion device that converts electric power bidirectionally between the MG 2R and the battery 10. Description of the structure and function of the PCU 1R will be omitted, as the structure and function are the same as those of the PCU 1F.

[0049] SMR 12 is electrically connected to power line PL1 and power line PN1. Power line PL1 connects battery 10 to PCU 1F and PCU 1R. When SMR 12 is closed (ON) (i.e., in the conductive state) in response to a control signal from ECU 100, power can be transmitted and received between battery 10 and PCU 1F and PCU 1R. On the other hand, when SMR 12 is disconnected (OFF) (i.e., in the disconnected state) in response to a control signal from ECU 100, the electrical connection between battery 10 and PCU 1F and PCU 1R is severed. To externally charge battery 10, SMR 12 is closed (ON) in response to a signal from ECU 100.

[0050] Battery 10 stores electricity for driving the MG2F and MG2R. Battery 10 is a rechargeable DC power source (secondary battery). Battery 10 consists of a stack of multiple single cells (battery cells), for example, electrically connected in series. The cells can be lithium-ion batteries or nickel-metal hydride batteries. Battery 10 can also be replaced by a power storage device such as an electric double-layer capacitor.

[0051] Monitoring unit 11 includes a voltage sensor, a current sensor, and a temperature sensor (none of which are shown). The voltage sensor detects voltage VB across the terminals of battery 10. The current sensor detects current IB, which is the input and output current of battery 10. The temperature sensor detects temperature TB of battery 10. Each sensor outputs its detection results to ECU 100.

[0052] Buck-boost converter 20 is, for example, a non-insulated buck-boost converter. Buck-boost converter 20 boosts the voltage of the power supplied to low-voltage power lines PL2 and PN2. Buck-boost converter 20 outputs the boosted voltage to high-voltage power lines PL1 and PN1. Buck-boost converter 20 steps down the voltage of the power input to high-voltage power lines PL1 and PN1. Buck-boost converter 20 outputs the stepped-down voltage to low-voltage power lines PL2 and PN2. Buck-boost converter 20 may be, for example, a buck-boost DC-DC converter.

[0053] Auxiliary devices are connected to low-voltage power lines PL2 and PN2. These include an electric compressor 5 for the air conditioner (AC), an inverter 6 for in-cabin outlets, and a heater 7. Inverter 6 for in-cabin outlets supplies 100V AC to the in-cabin outlets. An auxiliary battery 70 is connected to power lines PL2 and PN2 via a step-down converter 60. Auxiliary battery 70 serves as a power source for the ECU 100, an HMI (Human Machine Interface) device (not shown), and other auxiliary devices.

[0054] In this embodiment, the voltage (rated or nominal voltage) of battery 10 is 800V, and the voltage (rated or nominal voltage) of auxiliary battery 70 is 12V. Buck-boost converter 20 steps down the voltage of the 800V power discharged from battery 10 to power lines PL1 and PN1 to 400V. Buck-boost converter 20 outputs the stepped-down voltage to power lines PL2 and PN2. Auxiliary devices connected to low-voltage power lines PL2 and PN2 include the air conditioner's electric compressor 5, an inverter 6 for in-cabin outlets, and a heater 7. These auxiliary devices operate using the power from battery 10, which has been stepped down to 400V by buck-boost converter 20. Buck converter 60 steps down the voltage of the power from battery 10, which has been stepped down to 400V by buck-boost converter 20, to 12V, and uses the stepped-down power to charge auxiliary battery 70. Buck converter 60 may be a step-down (Buck) DC-DC converter.

[0055] The electric vehicle V includes a DC inlet 51 that allows the battery 10 to be quickly charged using an external DC power supply as a charging device. The DC inlet 51 is configured to connect to a connector 91 provided at the end of a charging cable of an external DC power supply (DC charging device) 90 .

[0056] The DC charging relay 50 selectively switches the path of the power supplied from the DC inlet 51 to either the high-voltage power line PL1 and power line PN1, or the low-voltage power line PL2 and power line PN2, of the buck-boost converter 20, which serves as a voltage booster. The DC charging relay 50 includes, for example, a c-contact relay 50a and an a-contact relay 50b. The c-contact relay 50a is configured to switch between a first position and a second position in response to a control signal from the ECU 100. When the c-contact relay 50a is in the first position, the power supplied to the DC inlet 51 is supplied to the high-voltage power line PL1 via the power line Lc2. When the c-contact relay 50a is in the second position, the power supplied to the DC inlet 51 is supplied to the low-voltage power line PL2 via the power line Lc1. The a-contact relay 50b is closed (ON) or opened (OFF) in response to a control signal from the ECU 100. When contact relay a 50b is closed, the power supplied to DC inlet 51 is supplied to low-voltage power line PN2 via power line Ld1. When contact relay a 50b is opened, the electrical connection between DC inlet 51 and power line PN2 is cut off.

[0057] Figure 2This diagram shows the flow of power when the c-contact relay 50a is switched to the first position and the a-contact relay 50b is closed. The buck-boost converter 20 is a non-insulated buck-boost converter. The power line PN1 on the high voltage side, which is the negative line, and the power line PN2 on the low voltage side, which is the negative line, are connected (these power lines are substantially the same). Therefore, when the c-contact relay 50a is switched to the first position and the a-contact relay 50b is closed, as shown in FIG. Figure 2 As shown by the arrows, the electric power supplied to DC inlet 51 can be supplied to battery 10 via electric power line PL1 and electric power line PN1 on the high-voltage side.

[0058] Figure 3 1 is a diagram showing the flow of power when the c-contact relay 50a is switched to the second position and the a-contact relay 50b is closed. Figure 3 As shown by the arrows, the power supplied to DC inlet 51 can be input to step-up / down converter 20 via low-voltage power line PL2 and power line PN2. Thus, the power having a voltage stepped up by step-up / down converter 20 can be supplied to battery 10.

[0059] Reference Figure 1 The DC charging device 90 is configured to convert AC power from a system power supply (e.g., a commercial power supply) into DC power. The DC charging device 90 is configured to output the converted DC charging power from a connector 91 to the electric vehicle V via a charging cable. When the connector 91 of the DC charging device 90 is connected to the DC inlet 51, a signal line (not shown) is connected in addition to the power line. These connections enable communication between the DC charging device 90 and the ECU 100 using CAN (Controller Area Network) communication and / or PLC (Power Line Communication) communication.

[0060] The electric vehicle V includes an AC inlet 31 , which allows the battery 10 to be normally charged by an external AC power source as a charging device. The AC inlet 31 is configured to connect to a connector 81 provided at the end of a charging cable of an external AC power source (AC charging device) 80 .

[0061] AC power supplied from AC charging equipment 80 to AC inlet 31 is converted into DC power by charger 30, which is a step-up ACDC converter. The voltage of the AC power is stepped up by charger 30. The stepped-up voltage is output as the voltage of DC power.

[0062] AC charging relay 40 selectively switches the path of power output from charger 30 between the high-voltage power line PL1 and power line PN1 of buck-boost converter 20, or the low-voltage power line PL2 and power line PN2. AC charging relay 40 includes, for example, a C-contact relay 40a and a C-contact relay 40b. C-contact relay 40a is configured to switch between a first position and a second position in response to a control signal from ECU 100. When C-contact relay 40a is in the first position, power output from charger 30 is supplied to high-voltage power line PL1 via power line La1. When C-contact relay 40a is in the second position, power output from charger 30 is supplied to low-voltage power line PL2 via power line La2 and power line Lc1. C-contact relay 40b is configured to switch between the first position and the second position in response to a control signal from ECU 100. When contact C relay 40b is in the first position, power output from charger 30 is supplied to high-voltage power line PN1 via power line Lb1. When contact C relay 40b is in the second position, power output from charger 30 is supplied to low-voltage power line PN2 via power line Lb2 and power line Ld1.

[0063] Figure 4 4 is a diagram showing the flow of power when the AC charging relay 40 (C contact relay 40a and C contact relay 40b) is switched to the first position. Figure 4 As shown by arrows, electric power output from charger 30 can be supplied to battery 10 via high-voltage-side electric power line PL1 and electric power line PN1.

[0064] Figure 5 4 is a diagram showing the flow of power when the AC charging relay 40 (c-contact relay 40a and c-contact relay 40b) is switched to the second position. Figure 5 As shown by the arrows, the power output from charger 30 can be supplied to power line PL2 and power line PN2 on the low voltage side. Thus, the power of the voltage boosted by boost / buck converter 20 can be supplied to battery 10.

[0065] Reference Figure 1The AC charging device 80 is configured to convert AC power from a system power source (e.g., a commercial power source). The AC charging device 80 is configured to output the converted charging power from a connector 81 via a charging cable to the electric vehicle V. When the connector 81 of the AC charging device 80 is connected to the AC inlet 31, a signal line (not shown) is connected in addition to the power line. These connections enable communication between the AC charging device 80 and the ECU 100 based on CAN communication and / or PLC communication. The AC charging device 80 supplies, for example, single-phase AC 200V power to the charger 30 via the connector 81.

[0066] ECU100 includes a CPU (Central Processing Unit) and a memory. The memory includes a ROM (Read Only Memory) and a RAM (Random Access Memory). Based on the signals received from the monitoring unit 11, the signals from various sensors (not shown), the mapping and program stored in the memory, and other information, ECU100 controls each device so that the electric vehicle V is in the desired state. The signals from the above-mentioned various sensors include an accelerator opening signal and a vehicle speed signal. ECU100 calculates the SOC of the battery 10 based on the detection values ​​of the input and output current and / or voltage of the battery 10 from the monitoring unit 11. The SOC of the battery 10 represents the storage capacity of the battery 10, for example, expressed as a percentage as the ratio of the current storage capacity to the full charge capacity of the battery 10.

[0067] The specifications of the DC charger 90, which serves as the charging infrastructure, are determined by international standards and other factors. However, the maximum output voltage of the DC charger 90 is subject to a variety of specifications. For example, when charging the battery 10 of this embodiment using the DC charger 90 with a maximum output voltage of 400V, the buck-boost converter 20 boosts the voltage of the power supplied from the DC charger 90, i.e., 400V, to 800V, and then charges the battery 10 using the boosted power. When charging the battery 10 of this embodiment using the DC charger with a maximum output voltage of 800V, the buck-boost converter 20 does not operate, and the battery 10 is charged.

[0068] Specifically, when the connector 91 of the DC charger 90 is connected to the DC inlet 51, the maximum output voltage VDCmax of the DC charger 90 is obtained based on the information received from the DC charger 90 via CAN communication or PLC communication. If the obtained maximum output voltage VDCmax is lower than 800V, the c-contact relay 50a switches to the second position and the a-contact relay 50b closes. Then, as shown in FIG. Figure 3As shown, the step-up / step-down converter 20 operates to step up the voltage of the power supplied from the DC charging device 90 to 800V, thereby charging the battery 10. When the maximum output voltage VDCmax obtained is 800V or higher, the c-contact relay 50a switches to the first position and the a-contact relay 50b closes. Figure 2 As shown, the power supplied from the DC charging device 90 charges the battery 10 without operating the step-up / step-down converter 20 .

[0069] In this embodiment, charger 30 is an ACDC converter that converts single-phase AC power supplied from AC charging equipment 80 into DC current and outputs the converted DC power. Charger 30 boosts the single-phase AC voltage of 200V to 400V and outputs the boosted voltage as DC power. While an ACDC converter capable of boosting single-phase AC voltage up to 800V could be used to charge battery 10, this would require a higher voltage rating, increasing the size of the charger. Therefore, in this embodiment, a charger 30 capable of boosting single-phase AC voltage up to 400V is used.

[0070] The maximum voltage of the power output from the charger 30 of this embodiment is 400V. Therefore, the voltage of the power output from the charger 30 is boosted by the buck-boost converter 20 to charge the battery 10. The boosting operation of the buck-boost converter 20 involves losses such as switching loss and conduction loss. When the 400V voltage of the power output from the charger 30 is boosted for charging, charging efficiency decreases. The inter-terminal voltage VB of the battery 10 fluctuates depending on the SOC. As the SOC decreases, the inter-terminal voltage decreases, and therefore the inter-terminal voltage VB of the battery 10 may fall below 400V. Therefore, when external charging is performed using the power output from the charger 30, the inter-terminal voltage of the battery 10 can be utilized to charge the battery 10 without using the boost function of the buck-boost converter 20.

[0071] In this embodiment, when the inter-terminal voltage VB of the battery 10 is higher than the output voltage of the charger 30, the buck-boost converter 20 is used to boost the voltage of the output power of the charger 30, and the battery 10 is charged with the power of the boosted voltage. Furthermore, when the inter-terminal voltage VB is lower than the output voltage of the charger 30, the battery 10 is charged without operating the buck-boost converter 20. This can suppress a decrease in charging efficiency.

[0072] Figure 6This diagram shows the functional blocks configured within ECU 100. Each functional block is implemented by the hardware of ECU 100 and software processing executed by a program. Inter-terminal voltage acquisition unit 101 acquires inter-terminal voltage VB of battery 10 from monitoring unit 11. Comparison unit 102 compares inter-terminal voltage VB acquired by inter-terminal voltage acquisition unit 101 with the maximum output voltage VCmax of charger 30. Comparison unit 102 outputs the comparison result to switching unit 103 and converter control unit 104. In this embodiment, maximum output voltage VCmax is 400V and is pre-stored in memory.

[0073] The switching unit 103 receives the comparison result from the comparing unit 102 and switches the AC charging relay 40 based on the comparison result. When the inter-terminal voltage VB is less than the maximum output voltage VCmax (VB≤VCmax), the AC charging relay 40 switches to the first position, and the output power of the charger 30 can charge the battery 10 via the high-voltage side power line PL1 and the power line PN1 (see Figure 4 When the inter-terminal voltage VB is higher than the maximum output voltage VCmax (VB>VCmax), the AC charging relay 40 switches to the second position, and the output power of the charger 30 is supplied to the power line PL2 and the power line PN2 on the low voltage side (see Figure 5 ).

[0074] Converter control unit 104 receives the comparison result from the comparator, and when the inter-terminal voltage VB is higher than the maximum output voltage VCmax (VB>VCmax) based on the comparison result, starts charging battery 10 and operates buck-boost converter 20 .

[0075] The charging power control unit 105 controls, for example, the start and end of charging of the battery 10. For example, when mutual authentication with the AC charging device 80 is established, the charging power control unit 105 transmits a charging power output request to the AC charging device 80 and activates the charger 30 to begin charging the battery 10. After charging begins, when the battery 10's SOC reaches the charging completion SOC, the charging power control unit 105 transmits a charging power stop request to the AC charging device 80 and stops the charger 30, thereby terminating charging. If the AC charging device 80 is, for example, a household outlet, communication with the AC charging device 80 is not performed.

[0076] Figure 7This is a flowchart schematically illustrating the processing executed by ECU 100. This flowchart is executed when connector 81 is connected to AC inlet 31. When connector 81 is connected to AC inlet 31, first, in step (hereinafter referred to as step S) 10, ECU 100 receives a signal from monitoring unit 11, obtains voltage VB between the terminals of battery 10 from the signal, and then proceeds to step S11.

[0077] In S11, the ECU 100 determines whether the inter-terminal voltage VB is higher than the maximum output voltage VCmax of the charger 30. The maximum output voltage VCmax of the charger 30 is pre-written in memory based on the specifications of the charger 30 and is 400V in this embodiment. If the inter-terminal voltage VB is less than the maximum output voltage VCmax (VB ≤ VCmax), a negative determination is made and the process proceeds to S12. The maximum output voltage VCmax corresponds to the "upper limit voltage" in this disclosure.

[0078] In S12, ECU 100 switches AC charging relay 40 (C-contact relay 40a and C-contact relay 40b) to the first position (maintaining the first position if already in the first position), and then proceeds to S15. This allows power output from charger 30 to be supplied via power lines La1 and Lb1 to power lines PL1 and PN1 on the high-voltage side of buck-boost converter 20. Power lines La1 and Lb1 correspond to the "first path" in this disclosure.

[0079] In S11, if the inter-terminal voltage VB is higher than the maximum output voltage VCmax (VB>VCmax), a positive determination is made, and the process proceeds to S13. In S13, the ECU 100 switches the AC charging relay 40 (C-contact relay 40a and C-contact relay 40b) to the second position (or maintains the second position if already in the second position), and the process proceeds to S14. This allows the power output from the charger 30 to be supplied to the low-voltage side power lines PL2 and PN2 of the buck-boost converter 20 via the power lines La2, Lc1, Lb2, and Ld1. The power lines La2, Lc1, Lb2, and Ld1 correspond to the "second path" in this disclosure.

[0080] In S14, ECU 100 operates step-up / step-down converter 20. This boosts the voltage of the power input to low-voltage power lines PL2 and PN2, and enables the boosted power to be output to high-voltage power lines PL1 and PN1.

[0081] In S15 , ECU 100 sends an output request to AC charger 80 to operate charger 30 for charging (while power is being supplied from AC charger 80 , power supply continues). Battery 10 may be charged using either CC (Constant Current) or CCCV (Constant Current, Constant Voltage) charging.

[0082] In the next S16, the ECU 100 determines whether charging of the battery 10 is completed. The ECU 100 determines that charging is completed when the SOC of the battery 10 reaches the charging completion SOC, for example. The charging completion SOC can be set to any value by the user. If the charging completion SOC is not set by the user, it can also be a default value (for example, 90%). If it is determined that charging is not completed, the process enters S10 and the processes of S10 to S16 are repeatedly executed. If the SOC of the battery 10 reaches the charging completion SOC and an affirmative determination is made in S16, the process enters S17.

[0083] In S17, the ECU 100 completes the current routine after executing the charging termination operation. The charging termination operation, for example, involves sending a request to stop charging power to the AC charger 80, thereby stopping the power supply from the AC charger 80 and suspending the operation of the charger 30. If the AC charging relay 40 was switched to the first position in S12, the ECU 100 switches the AC charging relay 40 to the second position. If the buck-boost converter 20 was operating in S14, the ECU 100 stops the operation of the buck-boost converter 20.

[0084] According to this embodiment, when the SOC of battery 10 is low and the inter-terminal voltage VB is below the maximum output voltage VCmax of charger 30, AC charging relay 40 switches to the first position. This allows power output from charger 30 to be supplied to power lines PL1 and PN1 on the high-voltage side of buck-boost converter 20. Because the maximum output voltage VCmax is higher than the inter-terminal voltage VB, battery 10 can be charged with the power output from charger 30 without operating buck-boost converter 20. This allows charging without using buck-boost converter 20, even when battery 10 can be charged without using the boost function of buck-boost converter 20. As a result, battery 10 can be charged without incurring losses due to buck-boost converter 20, minimizing a decrease in charging efficiency.

[0085] When the state of charge (SOC) increases during the charging process of the battery 10, or when the SOC at the start of charging is relatively high, the terminal voltage VB is higher than the maximum output voltage VCmax. In this case, the AC charging relay 40 switches to the second position. As a result, the power output from the charger 30 is supplied to the low-voltage power lines PL2 and PN2 of the buck-boost converter 20. Then, the voltage of the output power of the charger 30 is boosted by the buck-boost converter 20, and the power of the boosted voltage is supplied to the battery 10 for charging. Thus, when the output voltage of the charger 30 is lower than the terminal voltage VB, the charging of the battery 10 can be carried out using the boosting function of the buck-boost converter 20.

[0086] In the present embodiment, when the terminal voltage VB is less than or equal to the maximum output voltage VCmax in S11 (VB ≤ VCmax), the AC charging relay 40 switches to the first position in S12. However, the AC charging relay 40 may also switch to the first position when the terminal voltage VB is lower than the maximum output voltage VCmax (VB < VCmax). On the other hand, when the terminal voltage VB is greater than or equal to the maximum output voltage VCmax (VB ≥ VCmax), the AC charging relay 40 switches to the second position.

[0087] In the present embodiment, in the charging end operation of S17, the AC charging relay 40 switches to the second position. Figure 8 It is a diagram showing the flow of power when the electric vehicle V is running. When the electric vehicle V is running, as shown by the arrows in Figure 8 , the power discharged from the battery 10 is supplied to the MG2F and MG2R by the PCU1F and PCU1R respectively. At this time, since the AC charging relay 40 is switched to the second position, as shown in Figure 8 , the power discharged from the battery 10 is cut off by the AC charging relay 40 and not supplied to the charger 30. Thus, it is possible to prevent a voltage higher than the withstand voltage from being applied to the charger 30.

[0088] In the present embodiment, the buck-boost converter 20 has the functions of "boosting the voltage of the power supplied from the DC charging device 90 and charging the battery 10 with the power of the boosted voltage", "boosting the voltage of the output power of the charger 30 and charging the battery 10 with the power of the boosted voltage", and "lowering the voltage of the power discharged from the battery 10 and supplying the power of the lowered voltage to the auxiliary device". In this way, the buck-boost converter 20 realizes all the functions. As a result, the circuit structure can be relatively simplified.

[0089] In this embodiment, the maximum output voltage VCmax of the charger 30 is compared with the inter-terminal voltage VB. However, the output voltage VC of the charger 30 may also be compared with the inter-terminal voltage VB to switch the AC charging relay 40. Also, when the inter-terminal voltage VB ≤ the output voltage VC (or VB < VC), the AC charging relay 40 is switched to the first position, and when the inter-terminal voltage VB > the output voltage VC (or VB ≥ VC), the AC charging relay 40 is switched to the second position.

[0090] (Modified Example)

[0091] In the embodiment, during charging using the DC charging device 90, when the maximum output voltage VDCmax of the DC charging device 90 is lower than 800V which is the voltage (rated voltage or nominal voltage) of the battery 10, the buck-boost converter 20 is used to charge the battery 10. On the other hand, when the maximum output voltage VDCmax is 800V or higher, the battery 10 is charged without using the buck-boost converter 20.

[0092] In this modified example, similar to the case of charging using the charger 30 (AC charging device 80), the inter-terminal voltage VB of the battery 10 is compared with the maximum output voltage VDCmax, the DC charging relay 50 is switched, and charging is performed.

[0093] Figure 9 It is a diagram showing the functional blocks configured in the ECU 100 in the modified example. The output voltage acquisition unit 110 receives information from the DC charging device 90 using CAN communication and / or PLC communication, and acquires the maximum output voltage VDCmax of the DC charging device 90 based on this information. The maximum output voltage VDCmax is the maximum voltage as the maximum value of the voltage stably output from the DC charging device 90, and may be, for example, the rated output voltage.

[0094] The inter-terminal voltage acquisition unit 111 acquires the inter-terminal voltage VB of the battery 10 from the monitoring unit 11. The comparison unit 112 compares the inter-terminal voltage VB acquired by the inter-terminal voltage acquisition unit 111 with the maximum output voltage VDCmax acquired by the output voltage acquisition unit 110. The comparison unit 112 outputs the comparison result to the switching unit 113 and the converter control unit 114.

[0095] The switching unit 113 receives the comparison result from the comparison unit 112 and switches the DC charging relay 50 based on this comparison result. When the inter-terminal voltage VB is less than or equal to the maximum output voltage VDCmax (VB ≤ VDCmax), the switching unit 113 switches the c-contact relay 50a to the first position and closes the a-contact relay 50b. Thereby, the power supplied to the DC inlet 51 can charge the battery 10 via the high-voltage side power line PL1 and the power line PN1 (refer to Figure 2 ). When the inter-terminal voltage VB is lower than the maximum output voltage VDCmax (VB < VDCmax), the switching unit 113 switches the c-contact relay 50a to the second position and closes the a-contact relay 50b. Thereby, the power supplied to the DC inlet 51 is supplied to the low-voltage side power line PL2 and the power line PN2 (refer to Figure 3 ).

[0096] The converter control unit 114 receives the comparison result from the comparison unit 112 and, when the inter-terminal voltage VB is lower than the maximum output voltage VDCmax in this comparison result (VB < VDCmax), operates the buck-boost converter 20 while starting the charging of the battery 10.

[0097] The charging power control unit 115 controls, for example, the start and end of the charging of the battery 10. For example, when the mutual authentication with the DC charging device 90 is established, the charging power control unit 115 sends an output request for the charging power to the DC charging device 90 and starts the charging of the battery 10. After the start of charging, when the SOC of the battery 10 reaches the SOC at the completion of charging, the charging power control unit 115 sends a stop request for the charging power to the DC charging device 90 and ends the charging.

[0098] Figure 10 is a flowchart outlining the processing performed by the ECU 100 in the modified example. This flowchart is executed when the connector 91 is connected to the DC inlet 51. When the connector 91 is connected to the DC inlet 51, first, in S20, the ECU 100 receives information from the DC charging device 90 via CAN communication or PLC communication, obtains the maximum output voltage VDCmax of the DC charging device 90 based on this information, and proceeds to S21. The maximum output voltage VDCmax corresponds to the "maximum voltage" of the present disclosure.

[0099] In S21, the ECU 100 receives a signal from the monitoring unit 11, obtains the inter-terminal voltage VB of the battery 10 from this signal, and proceeds to S22.

[0100] In S22, ECU 100 determines whether inter-terminal voltage VB is higher than maximum output voltage VDCmax of DC charging device 90. If inter-terminal voltage VB is equal to or lower than maximum output voltage VDCmax (VB≤VDCmax), a negative determination is made and the process proceeds to S23.

[0101] In S23, ECU 100 switches contact c relay 50a of DC charging relay 50 to the first position (maintaining it if already in the first position) and closes contact a relay 50b (maintaining it if already closed). This allows power supplied from DC inlet 51 to be supplied via power lines Lc2 and Ld1 to power line PL1 on the high-voltage side of buck-boost converter 20 and power line PN1 (connected to power line PN2). Power lines Lc2 and Ld1 correspond to the "first path" or "DC first path" in this disclosure. After executing S23, ECU 100 proceeds to S26.

[0102] In S22, if the inter-terminal voltage VB is higher than the maximum output voltage VDCmax (VB>VDCmax), a positive determination is made, and the process proceeds to S24. In S24, the ECU 100 switches the c-contact relay 50a of the DC charging relay 50 to the second position (if it is in the second position, it is maintained in the second position) and closes the a-contact relay 50b (if it is closed, it is maintained closed). As a result, the power supplied from the DC inlet 51 can be supplied to the power line PL2 and the power line PN2 on the low voltage side of the buck-boost converter 20 via the power lines Lc1 and Ld1. The power lines Lc1 and Ld1 correspond to the "second path" or "DC second path" of the present disclosure. After executing the process of S24, the ECU 100 proceeds to S25.

[0103] In S25, ECU 100 operates step-up / step-down converter 20. Thus, the electric power input to low-voltage power line PL2 and power line PN2 is boosted and can be output to high-voltage power lines PL1 and PN1.

[0104] In S26 , ECU 100 sends an output request to DC charging equipment 90 to charge battery 10 (if power is being supplied from DC charging equipment 90 , power supply is continued). Charging of battery 10 may be CC charging or CCCV charging.

[0105] In the following S27, the ECU 100 determines whether charging of the battery 10 has been completed. For example, if the SOC of the battery 10 reaches the charge completion SOC, the ECU 100 determines that charging is complete. If charging is determined not to be complete, the process proceeds to S21, where the processes of S21 to S27 are repeated. If the SOC of the battery 10 reaches the charge completion SOC and a positive determination is made in S27, the process proceeds to S28.

[0106] In S28, ECU 100 terminates this routine after executing the charging termination operation. The charging termination operation, for example, involves sending a request to stop charging power to DC charger 90, stopping the power supply from DC charger 90, and disconnecting (OFF) contact relay a 50b. If buck-boost converter 20 was operating in S25, ECU 100 stops operation of buck-boost converter 20.

[0107] According to this modified example, when the SOC of battery 10 is low and inter-terminal voltage VB is below the maximum output voltage VDCmax of DC charging equipment 90, DC charging relay 50 is switched so that the power supplied from DC inlet 51 is supplied to power lines PL1 and PN1 on the high-voltage side of buck-boost converter 20. Since maximum output voltage VDCmax is higher than inter-terminal voltage VB, battery 10 can be charged with the output power of DC charging equipment 90 without buck-boost converter 20 operating. Thus, when battery 10 can be charged without using the boost function of buck-boost converter 20, charging can be performed without using buck-boost converter 20. As a result, battery 10 can be charged without incurring losses due to buck-boost converter 20, thereby suppressing a decrease in charging efficiency.

[0108] When charging battery 10 while the SOC is high, when charging starts when the SOC is high, or when the maximum output voltage VDCmax of DC charger 90 is low, inter-terminal voltage VB becomes higher than maximum output voltage VDCmax. In this case, DC charging relay 50 switches so that the power supplied from DC inlet 51 is supplied to power lines PL2 and PN2 on the low-voltage side of buck-boost converter 20. Buck-boost converter 20 then boosts the voltage of the output power of DC charger 90, and the boosted power is supplied to battery 10 for charging. Thus, when the output voltage of DC charger 90 is lower than inter-terminal voltage VB, the boost function of buck-boost converter 20 can be used to charge battery 10.

[0109] In the modified example, in S22, when the inter-terminal voltage VB is less than or equal to the maximum output voltage VDCmax (VB ≤ VDCmax), the process proceeds to S23. However, when the inter-terminal voltage VB is lower than the maximum output voltage VDCmax (VB < VDCmax), the process may also proceed to S23. In this case, when the inter-terminal voltage VB is greater than or equal to the maximum output voltage VDCmax (VB ≥ VDCmax), the process proceeds to S24.

[0110] In the present embodiment, the AC charging relay 40 includes the c-contact relay 40a and the c-contact relay 40b, but the structure of the AC charging relay 40 is not limited thereto. Figure 11 FIG. is a diagram showing another structural example of the AC charging relay. As Figure 11 shown, the charging relay may also be a charging relay 400 including four a-contact relays. Since the AC charging relay 400 includes four a-contact relays, when the connector 81 is not connected to the AC inlet 31 and all the a-contact relays are turned off (OFF), the electrical connection between the power discharged from the battery 10 and the AC inlet 31 is reliably cut off. Similarly, the c-contact relay 50a of the DC charging relay 50 may also include two a-contact relays.

[0111] In the present embodiment, the power line La2 is connected to the power line PL2 via the power line Lc1, and the power line Lb2 is connected to the power line PN2 via the power line Ld1. However, the layout of each power line is not limited thereto. For example, the power line La2 may be directly connected to the power line PL2, and the power line Lb2 may be directly connected to the power line PN2. The a-contact relay 50b of the DC charging relay 50 may also be changed to a c-contact relay. This c-contact relay may also be switched to selectively supply the power input to the DC inlet 51 to the power line PN2 or the power line PN1.

[0112] In the present embodiment, the voltage (rated voltage or nominal voltage) of the battery 10 is 800V, but it may also be 500V, 600V, or 700V. The electric vehicle V in the present embodiment is a four-wheel drive vehicle in which the front and rear wheels are driven by the MG, but it may also be a two-wheel drive vehicle in which either the front or rear wheel is driven by the MG.

[0113] Figure 1 The electric vehicle V shown is an electric vehicle, but the vehicle to which the present disclosure can be applied is not limited to the electric vehicle V. The present disclosure can also be applied to, for example, a plug-in hybrid vehicle equipped with an engine and an electric generator, a fuel cell vehicle equipped with a storage battery and capable of external charging, or an industrial vehicle such as a forklift.

[0114] While the embodiments of the present disclosure have been described, they should be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, and all modifications within the meaning and scope of the equivalents of the claims are intended to be encompassed.

Claims

1. An electric vehicle comprising a power storage device that can be charged with electric power supplied from an external power source, wherein the external power source is an AC power source that supplies AC power to the electric vehicle, wherein: The electric vehicle comprises: a charger for converting the AC power supplied from the AC power source into DC power; a boost device, the high-voltage side of the boost device being connected to the power storage device, the boost device being configured to boost the voltage of power input to the low-voltage side of the boost device and output the boosted power to the high-voltage side; a first path for supplying the electric power supplied from the charger to the high voltage side of the boost device; a second path for supplying the electric power supplied from the charger to the low voltage side of the boost device; a charging relay that selectively switches a path of the electric power supplied from the charger to the first path or the second path; as well as control device, The control device is configured as follows: When the power storage device is charged with the power supplied from the charger and the voltage between the terminals of the power storage device is lower than the voltage of the power supplied from the charger, the charging relay is switched to select the first path; When the power storage device is charged with the electric power supplied from the charger and the inter-terminal voltage of the power storage device is higher than the voltage of the electric power supplied from the charger, the charging relay is switched to select the second path and the boost device is operated.

2. The electric vehicle according to claim 1, wherein: The voltage of the electric power supplied from the charger is an upper limit voltage that is an upper limit of the voltage.

3. The electric vehicle according to claim 1 or 2, wherein: The boost device is a buck-boost converter, The buck-boost converter is constructed as follows: boosting the voltage of the electric power input to the low voltage side and outputting the boosted voltage to the high voltage side; The voltage of the electric power input to the high voltage side is stepped down, and the stepped-down voltage is output to the low voltage side.

4. The electric vehicle according to claim 3, wherein: An auxiliary device connected to the low voltage side of the step-up / step-down converter is further provided.

5. A charging control method for an electric vehicle, wherein: The electric vehicle comprises: The charger converts AC power supplied from an external power source into DC power; a power storage device capable of being charged using the power output from the charger; as well as a boost device, the high-voltage side of the boost device being connected to the power storage device, the boost device being configured to boost the voltage of power input to the low-voltage side of the boost device and output the boosted power to the high-voltage side; The charging control method comprises the following steps: obtaining a voltage between terminals of the power storage device; comparing an upper limit voltage, which is an upper limit of a voltage output from the charger, with the inter-terminal voltage; When the inter-terminal voltage is higher than the upper limit voltage, the power storage device is charged by operating the boost device; as well as When the inter-terminal voltage is lower than the upper limit voltage, the power storage device is charged without operating the boost device.

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