Vehicular power supply apparatus, vehicle including the same, and method for controlling vehicle-mounted charger

A charger is configured to receive electric power from an external power supply and charge a main power storage device and a power storage device for auxiliary machinery. The charger includes a capacitor for smoothing charging power outputted to the main power storage device. A PM-ECU controls charging of the power storage device for auxiliary machinery by the charger such that the power storage device for auxiliary machinery can receive residual electric charge in the capacitor. The PM-ECU controls the charger, after the end of charging of the main power storage device by the charger, such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery.

TECHNICAL FIELD

The present invention relates to a vehicular power supply apparatus, a vehicle including the same, and a method for controlling a vehicle-mounted charger. Particularly, the present invention relates to a vehicular power supply apparatus in which a vehicle-mounted power storage device can be charged by a power supply external to a vehicle, a vehicle including the vehicular power supply apparatus, and a method for controlling a vehicle-mounted charger.

BACKGROUND ART

Japanese Patent Laying-Open No. 10-224902 (PTL 1) discloses a motor driving control apparatus for an electric vehicle. In this motor driving control apparatus, after a key switch is turned off, a load switch by which all loads of a battery are turned on/off is opened, and at the same time, auxiliary circuits are started. Thus, residual electric charge in a DC link capacitor is discharged by the auxiliary circuits.

Therefore, without providing a discharge resistor, the residual electric charge in the DC link capacitor can be immediately discharged after the key switch is turned off. As a result, useless power consumption in the main battery is avoided and maintenance can be immediately started after the key switch is turned off (refer to PTL 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In an electric vehicle and a plug-in hybrid vehicle in which a vehicle-mounted power storage device can be charged by a power supply external to the vehicle (hereinafter also referred to simply as “external power supply”), a charger for charging the vehicle-mounted power storage device by the external power supply is mounted on the vehicle. The charger is generally provided with a capacitor for smoothing the charging power outputted to the power storage device.

After charging of the power storage device by the external power supply ends, residual electric charge in the capacitor must be discharged immediately. As a method for discharging the residual electric charge in the capacitor, providing a discharge resistance is known. However, it leads to an increase in cost. Therefore, it is desirable to immediately discharge the residual electric charge in the capacitor of the charger without using the discharge resistance. This is not, however, particularly discussed in Japanese Patent Laying-Open No. 10-224902 described above.

The present invention has been made to solve the above problem, and an object of the present invention is to provide a vehicular power supply apparatus in which the residual electric charge in the capacitor provided in the charger can be reliably discharged without using the discharge resistance, and a vehicle including the vehicular power supply apparatus.

Another object of the present invention is to provide a method for controlling a vehicle-mounted charger, in which the residual electric charge in the capacitor provided in the charger can be reliably discharged without using the discharge resistance.

Solution to Problem

According to the present invention, a vehicular power supply apparatus includes: a main power storage device; a power storage device for auxiliary machinery; a charger; and a control device. The main power storage device stores electric power for traveling. The power storage device for auxiliary machinery stores electric power for auxiliary machinery. The charger is configured to receive electric power from an external power supply and charge the main power storage device and the power storage device for auxiliary machinery. The control device controls the charger. The charger includes a capacitor. The capacitor smoothes charging power outputted to the main power storage device. The control device includes: a charging control unit; and a discharging control unit. The charging control unit controls charging of the power storage device for auxiliary machinery by the charger such that the power storage device for auxiliary machinery can receive residual electric charge in the capacitor. The discharging control unit controls the charger, after the end of charging of the main power storage device by the charger, such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery.

Preferably, the charging control unit controls charging of the power storage device for auxiliary machinery such that remaining capacity of the power storage device for auxiliary machinery does not exceed a prescribed amount. The prescribed amount is determined based on an amount of electric power stored in the capacitor.

Further preferably, the charging control unit stops charging of the power storage device for auxiliary machinery by the charger when the remaining capacity exceeds the prescribed amount, and executes charging of the power storage device for auxiliary machinery by the charger when the remaining capacity is equal to or lower than the prescribed amount.

Preferably, the prescribed amount is an amount obtained by subtracting free capacity of the power storage device for auxiliary machinery required to receive the residual electric charge in the capacitor from full charge capacity of the power storage device for auxiliary machinery.

Preferably, the charger further includes: a main circuit; and a sub power supply unit. The main circuit converts a voltage of electric power supplied from the external power supply and outputs the electric power to the main power storage device. The sub power supply unit converts a voltage of the electric power outputted from the main circuit and outputs the electric power to the power storage device for auxiliary machinery. The charging control unit controls charging of the power storage device for auxiliary machinery by the sub power supply unit such that the power storage device for auxiliary machinery can receive the residual electric charge in the capacitor. The discharging control unit controls the sub power supply unit, after the end of charging of the main power storage device, such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery.

In addition, preferably, the charger further includes: a main circuit; and a sub power supply unit. The main circuit converts a voltage of electric power supplied from the external power supply and outputs the electric power to the main power storage device. The sub power supply unit is provided on an input side of the main circuit, and converts a voltage of the electric power supplied from the external power supply and outputs the electric power to the power storage device for auxiliary machinery. The main circuit is configured to allow electric power to flow bidirectionally, The charging control unit controls charging of the power storage device for auxiliary machinery by the sub power supply unit such that the power storage device for auxiliary machinery can receive the residual electric charge in the capacitor. The discharging control unit controls the main circuit and the sub power supply unit, after the end of charging of the main power storage device, such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery.

According to the present invention, a vehicle includes any one of the vehicular power supply apparatus described above.

According to the present invention, a method for controlling a vehicle-mounted charger is directed to a method for controlling a vehicle-mounted charger configured to receive electric power from a power supply external to a vehicle and charge a main power storage device for storing electric power for traveling and a power storage device for auxiliary machinery for storing electric power for auxiliary machinery. The vehicle-mounted charger includes a capacitor. The capacitor smoothes charging power outputted to the main power storage device. The control method includes the steps of: controlling charging of the power storage device for auxiliary machinery by the vehicle-mounted charger such that the power storage device for auxiliary machinery can receive residual electric charge in the capacitor; and controlling the vehicle-mounted charger, after the end of charging of the main power storage device by the vehicle-mounted charger, such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery.

Preferably, the step of controlling charging of the power storage device for auxiliary machinery includes a step of controlling charging of the power storage device for auxiliary machinery such that remaining capacity of the power storage device for auxiliary machinery does not exceed a prescribed amount. The prescribed amount is determined based on an amount of electric power stored in the capacitor.

Advantageous Effects of Invention

In the present invention, charging of the power storage device for auxiliary machinery by the charger is controlled such that the power storage device for auxiliary machinery can receive the residual electric charge in the capacitor provided in the charger. The charger is controlled such that the residual electric charge in the capacitor is discharged into the power storage device for auxiliary machinery after charging of the main power storage device by the charger ends. Therefore, according to the present invention, the residual electric charge in the capacitor provided in the charger can be reliably discharged without using the discharge resistance.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail hereinafter with reference to the drawings, in which the same reference characters are assigned to the same or corresponding portions and description thereof will not be repeated.

FIG. 1is an overall block diagram of a vehicle on which a vehicular power supply apparatus according to a first embodiment of the present invention is mounted. Referring toFIG. 1, a vehicle100includes a main power storage device10, a system main relay (hereinafter referred to as “SMR (System Main Relay)”)15, a power control unit (hereinafter referred to as “PCU (Power Control Unit)”)20, a motor generator25, a driving wheel30, an MG-ECU35, and a battery ECU40. Vehicle100further includes a DC/DC converter45, a power storage device50for auxiliary machinery, and an auxiliary machinery load55. Vehicle100further includes a charging inlet60, a charger65, a charging relay70, and a PM-ECU75.

Main power storage device10is a DC power supply that stores electric power for traveling, and is formed of a secondary battery such as, for example, a nickel-metal hydride secondary battery and a lithium ion secondary battery. Main power storage device10is charged by an external power supply85using charger65(hereinafter charging of main power storage device10by external power supply85will also be referred to as “external charging”). In addition, during braking of vehicle100or when acceleration decreases on a downward slope, main power storage device10receives electric power generated by motor generator25from PCU20and is charged with the electric power. Then, main power storage device10outputs the stored electric power to PCU20. Instead of the secondary battery, a large-capacitance capacitor can also be used as main power storage device10.

SMR15is provided between main power storage device10and PCU20. SMR15is turned on when a vehicle system is activated to cause vehicle100to travel, and is turned off when main power storage device10is charged by charger65.

PCU20is supplied with the electric power from main power storage device10and drives motor generator25based on a control signal from MG-ECU35. During braking of vehicle100, for example, PCU20converts a voltage of the electric power generated by motor generator25which receives the kinetic energy from driving wheel35, and outputs the electric power to main power storage device10. PCU20is formed of, for example, a three-phase PWM inverter including switching elements of three phases. A boosting converter may be provided between the three-phase PWM inverter and main power storage device10.

Motor generator25is a motor generator that is capable of a power running operation and a regenerative operation, and is formed of, for example, a three-phase AC synchronous motor generator having a permanent magnet embedded in a rotor. Motor generator25is driven by PCU20, and generates driving torque for traveling and drives driving wheel30. During braking of vehicle100, for example, motor generator25receives the kinetic energy of vehicle100from driving wheel30and generates electric power.

MG-ECU35is formed of an electronic control unit (ECU), and controls the operation of PCU20through software processing realized by executing prestored programs using a CPU (Central Processing Unit) and/or hardware processing with dedicated electronic circuitry. Specifically, MG-ECU35generates a control signal (e.g., a PWM (Pulse Width Modulation) signal) for driving motor generator25by PCU20, and outputs the generated control signal to PCU20.

Battery ECU40is also formed of an ECU, and estimates the remaining capacity of main power storage device10(hereinafter also referred to as “SOC (State Of Charge)” and expressed in percentage with respect to the capacity of main power storage device10) based on detected values of a voltage and an input/output current of main power storage device10. The voltage and the input/output current of main power storage device10are detected by a voltage sensor and a current sensor that are not shown. Various known methods such as a method for calculating the SOC using a relationship between the open circuit voltage (OCV) and the SOC of main power storage device10and a method for calculating the SOC using an accumulated value of the input/output current can be used as a method for estimating the SOC. Then, battery ECU40outputs the estimated value of the SOC to PM-ECU75at the time of external charging.

DC/DC converter45is connected to power supply lines PL2and NL2arranged between SMR15and PCU20. DC/DC converter45converts (steps down) electric power received from power supply lines PL2and NL2into an auxiliary machinery voltage and outputs the electric power to power storage device50for auxiliary machinery and auxiliary machinery load55.

Power storage device50for auxiliary machinery is a DC power supply that stores electric power for various auxiliary machinery and ECUs, and is formed of, for example, a lead battery and a secondary battery such as a nickel-metal hydride secondary battery and a lithium ion secondary battery. When the vehicle system is in the activated state to cause the vehicle to travel (SMR15is in the on state), power storage device50for auxiliary machinery is charged by DC/DC converter45. On the other hand, at the time of external charging (SMR15is in the off state and charging relay70is in the on state), power storage device10for auxiliary machinery is charged by charger65. Then, power storage device50for auxiliary machinery supplies the stored electric power to auxiliary machinery load55and each ECU.

Power storage device50for auxiliary machinery also includes a voltage sensor for detecting a voltage VB of power storage device50for auxiliary machinery, and a current sensor for detecting a current IB inputted/outputted to/from power storage device50for auxiliary machinery (the voltage sensor and the current sensor are both not shown), and outputs the detected values of voltage VB and current IB to PM-ECU75. Auxiliary machinery load55collectively means many pieces of auxiliary machinery mounted on vehicle100.

Charging inlet60is configured to be fittable to a connector80connected to external power supply85. Charging inlet60receives electric power supplied from external power supply85, and outputs the electric power to charger65. A charging plug configured to be connectable to an electrical outlet of external power supply85may be provided instead of charging inlet60.

Charger65is configured to receive the electric power from external power supply85and charge main power storage device10and power storage device50for auxiliary machinery. More specifically, at the time of external charging, charger65is supplied with the electric power from external power supply85and charges main power storage device10and power storage device50for auxiliary machinery based on a control signal from PM-ECU75. Charger65is provided with a capacitor (not shown inFIG. 1) for smoothing the charging power outputted to main power storage device10. When external charging ends, residual electric charge in this capacitor is discharged into power storage device50for auxiliary machinery. A configuration of charger65will be described in detail below.

Charging relay70is provided between charger65and power supply lines PL1, NL1arranged between main power storage device10and SMR15. Charging relay70is turned on at the time of external charging, and is turned off when external charging ends.

PM-ECU75is also formed of an ECU, and controls the operation of charger65through software processing realized by executing prestored programs using a CPU and/or hardware processing with dedicated electronic circuitry. Specifically, PM-ECU75receives the estimated value of the SOC of main power storage device10from battery ECU40, and receives the detected values of voltage VB and current IB of power storage device50for auxiliary machinery from power storage device50for auxiliary machinery. At the time of external charging, PM-ECU75generates a control signal for charging main power storage device10and power storage device50for auxiliary machinery by charger65based on these values, and outputs the generated control signal to charger65.

After external charging ends, PM-ECU75controls charger65such that the residual electric charge in the capacitor provided in charger65is discharged into power storage device50for auxiliary machinery. In other words, in the first embodiment, PM-ECU75controls charger65such that the residual electric charge in the capacitor is discharged into power storage device50for auxiliary machinery, without providing a discharge resistance for discharging the capacitor.

During external charging, power storage device50for auxiliary machinery is also charged by charger65. PM-ECU75controls charging of power storage device50for auxiliary machinery by charger65such that power storage device50for auxiliary machinery can receive the residual electric charge in the capacitor after external charging ends. Specifically, a reference SOC of power storage device50for auxiliary machinery is determined based on an amount of electric power stored in the capacitor such that power storage device50for auxiliary machinery can receive the residual electric charge in the capacitor after external charging ends. During external charging, PM-ECU75controls charging of power storage device50for auxiliary machinery by charger65such that the SOC of power storage device50for auxiliary machinery does not exceed the reference SOC.

FIG. 2is a block diagram showing a specific configuration of charger65shown inFIG. 1. Referring toFIG. 2, charger65includes a main circuit210, a capacitor220, a sub power supply unit230, and a controller240. Main circuit210is driven by controller240, and converts a voltage of the electric power supplied from external power supply85(FIG. 1) into a voltage level of main power storage device10(FIG. 1) and outputs the electric power to main power storage device10.

Capacitor220is provided on the output side of main circuit210(on the main power storage device10side), and specifically, is connected between a pair of power lines on the output side of main circuit210. Capacitor220smoothes the charging power outputted to main power storage device10.

Sub power supply unit230is connected to a pair of power lines on the output side of main circuit210(on the main power storage device10side). Sub power supply unit230is driven by controller240, and converts a voltage of a part of the electric power outputted from main circuit210and outputs the electric power to power storage device50for auxiliary machinery (FIG. 1). Sub power supply unit230is also driven by controller240after external charging ends, and discharges the residual electric charge in capacitor220into power storage device50for auxiliary machinery. This sub power supply unit230is for ensuring electric power for charging control during external charging (electric power for the auxiliary machinery and the ECUs driven at the time of external charging), and has capacity smaller than those of main circuit210and DC/DC converter45(FIG. 1). Sub power supply unit230is formed of a step-down-type DC/DC converter.

Controller240controls the operation of main circuit210and sub power supply unit230through hardware processing with dedicated electronic circuitry and/or software processing realized by executing prestored programs using a CPU. Specifically, controller240receives a control signal from PM-ECU75and drives main circuit210and sub power supply unit230based on the received control signal.

FIG. 3is a circuit diagram of main circuit210shown inFIG. 2. Referring toFIG. 3, main circuit210includes AC/DC converting units310and320, an insulating transformer330and a rectifying unit340. AC/DC converting units310and320are each formed of a single-phase bridge circuit. Based on a drive signal from controller240(FIG. 2), AC/DC converting unit310converts AC power provided from external power supply85to charging inlet60(FIG. 1) into DC power and outputs the DC power to AC/DC converting unit320. Based on the drive signal from controller240, AC/DC converting unit320converts the DC power supplied from AC/DC converting unit310into high-frequency AC power and outputs the AC power to insulating transformer330.

Insulating transformer330includes a core made of a magnetic material, as well as a primary coil and a secondary coil wound around the core. The primary coil and the secondary coil are electrically insulated, and are connected to AC/DC converting unit320and rectifying unit340, respectively. Insulating transformer330converts the high-frequency AC power received from AC/DC converting unit320to the voltage level corresponding to the winding ratio of the primary coil and the secondary coil, and outputs the converted power to rectifying unit340. Rectifying unit340rectifies the AC power outputted from insulating transformer330to DC power and outputs the DC power to main power storage device10(FIG. 1).

FIG. 4is a functional block diagram functionally showing a configuration of PM-ECU75shown inFIG. 1. Referring toFIG. 4, PM-ECU75includes a charging control unit110, an SOC estimating unit120for estimating the SOC of power storage device50for auxiliary machinery (FIG. 1), a charging control unit130for controlling charging of power storage device50for auxiliary machinery, and a discharging control unit140.

Charging control unit110controls charging of main power storage device10by charger65, based on the estimated value of the SOC of main power storage device10received from battery ECU40(FIG. 1). Specifically, when receiving a charging start trigger indicating the start of external charging, charging control unit110generates a control signal for charging main power storage device10by charger65, and outputs the generated control signal to charger65(more specifically, controller240(FIG. 2) of charger65).

During charging of main power storage device10by charger65, charging control unit110notifies SOC estimating unit120, charging control unit130and discharging control unit140that main power storage device10is being charged by charger65, Furthermore, when the SOC of main power storage device10reaches a predetermined upper limit value or when a charging end trigger indicating the end of external charging is received, charging control unit110notifies SOC estimating unit120, charging control unit130and discharging control unit140that external charging has ended.

During external charging, SOC estimating unit120estimates the SOC of power storage device50for auxiliary machinery based on the detected values of voltage VB and current IB of power storage device50for auxiliary machinery. Similarly to estimation of the SOC of main power storage device10, various known methods such as a method for calculating the SOC using a relationship between the OCV and the SOC of power storage device50for auxiliary machinery and a method for calculating the SOC using an accumulated value of the input/output current of power storage device50for auxiliary machinery can be used as a method for estimating the SOC.

During external charging, charging control unit130controls charging of power storage device50for auxiliary machinery by charger65, based on the SOC of power storage device50for auxiliary machinery estimated by SOC estimating unit120. Specifically, when receiving the notification that external charging is being performed, charging control unit130generates a control signal for driving sub power supply unit230(FIG. 2) of charger65and outputs the generated control signal to controller240of charger65.

At this time, the reference SOC of power storage device50for auxiliary machinery is predetermined based on an amount of electric power stored in capacitor220such that power storage device50for auxiliary machinery can receive the residual electric charge in capacitor220(FIG. 2) of charger65. As one example, the reference SOC is a value obtained by subtracting free capacity of power storage device50for auxiliary machinery required to receive the residual electric charge in capacitor220from full charge capacity of power storage device50for auxiliary machinery.

During external charging, charging control unit130controls charging of power storage device50for auxiliary machinery such that the SOC of power storage device50for auxiliary machinery does not exceed the reference SOC. Specifically, when the SOC of power storage device50for auxiliary machinery exceeds the reference SOC, charging control unit130stops generation of the control signal for driving sub power supply unit230.

When receiving the notification that external charging has ended from charging control unit110, discharging control unit140controls charger65such that the residual electric charge in capacitor220of charger65is discharged into power storage device50for auxiliary machinery. Specifically, when external charging ends, discharging control unit140generates the control signal for driving sub power supply unit230of charger65such that the residual electric charge in capacitor220is discharged into power storage device50for auxiliary machinery, and outputs the generated control signal to controller240of charger65.

FIG. 5is a flowchart for describing charging control over power storage device50for auxiliary machinery during external charging. Referring toFIG. 5, PM-ECU75determines whether external charging is being performed or not (step S10). If it is determined that external charging is not being performed (NO in step S10), PM-ECU75proceeds to step S60without executing the rest of the process.

If it is determined in step S10that external charging is being performed (YES in step S10), PM-ECU75estimates the SOC of power storage device50for auxiliary machinery based on the detected values of voltage VB and current IB of power storage device50for auxiliary machinery (step S20). Then, PM-ECU75determines whether the SOC of power storage device50for auxiliary machinery is higher than the reference SOC or not (step S30). The reference SOC is determined based on the amount of electric power stored in capacitor220as described above.

If it is determined in step S30that the SOC of power storage device50for auxiliary machinery is higher than the reference SOC (YES in step S30), PM-ECU75stops generation of the control signal for driving sub power supply unit230(FIG. 2) of charger65. As a result, sub power supply unit230stops (step S40).

On the other hand, if it is determined in step S30that the SOC of power storage device50for auxiliary machinery is equal to or lower than the reference SOC (NO in step S30), PM-ECU75generates the control signal for driving sub power supply unit230of charger65and outputs the generated control signal to controller240(FIG. 2) of charger65. As a result, sub power supply unit230is driven (step S50).

FIG. 6is a flowchart for describing discharging control over capacitor220executed after external charging ends. Referring toFIG. 6, PM-ECU75determines whether there is an instruction to end external charging or not (step S110). For example, when the SOC of main power storage device10reaches the upper limit value or when the charging end trigger is received, it is determined that there is an instruction to end external charging. If it is determined that external charging has not yet ended (NO in step S110), PM-ECU75proceeds to step S180without executing the rest of the process.

If it is determined in step S110that there is an instruction to end external charging (YES in step S110), PM-ECU75stops generation of the control signal for driving main circuit210(FIG. 2) of charger65. As a result, main circuit210stops (step S120). PM-ECU75also stops generation of the control signal for driving sub power supply unit230(FIG. 2) of charger65. As a result, sub power supply unit230stops (step S130). Furthermore, PM-ECU75turns charging relay70(FIG. 1) off (step S140). As a result, charger65is electrically disconnected from main power storage device10.

When charging relay70is turned off, PM-ECU75generates the control signal for driving sub power supply unit230of charger65. As a result, sub power supply unit230is driven again and discharging from capacitor220into power storage device50for auxiliary machinery by sub power supply unit230starts (step S150).

When sub power supply unit230is driven, PM-ECU75determines whether discharging of capacitor220has completed or not (step S160). Whether discharging of capacitor220has completed or not is determined based on, for example, a value detected by a not-shown voltage sensor that is capable of detecting a voltage of capacitor220. If it is determined in step S160that discharging has not yet completed (NO in step S160), PM-ECU75returns to step S150.

If it is determined in step S160that discharging of capacitor220has completed (YES in step S160), PM-ECU75stops generation of the control signal for driving sub power supply unit230. As a result, sub power supply unit230stops finally (step S170).

As described above, in the first embodiment, charger65is configured to be capable of charging main power storage device10and power storage device50for auxiliary machinery by external power supply85. During external charging, PM-ECU75controls charging of power storage device50for auxiliary machinery by sub power supply unit230of charger65such that the SOC of power storage device50for auxiliary machinery does not exceed the reference SOC. In other words, PM-ECU75controls charging of power storage device50for auxiliary machinery during external charging such that power storage device50for auxiliary machinery can receive the residual electric charge in capacitor220of charger65after external charging ends. After external charging ends, PM-ECU75controls charger65such that the residual electric charge in capacitor220is discharged into power storage device50for auxiliary machinery. Therefore, according to the first embodiment, the residual electric charge in capacitor220provided in charger65can be reliably discharged without using the discharge resistance.

In the above-described first embodiment, sub power supply unit230is connected to the pair of power lines on the output side of main circuit210(on the main power storage device10side). The sub power supply unit may, however, be provided on the input side of the main circuit (on the external power supply85side).

An overall configuration of a vehicle according to this second embodiment is the same as that of vehicle100according to the first embodiment shown inFIG. 1.

FIG. 7is a block diagram showing a configuration of a charger65A in the second embodiment. Referring toFIG. 7, charger65A includes a main circuit210A, capacitor220, a sub power supply unit230A, and a controller240A.

Main circuit210A is driven by controller240A, and converts a voltage of the electric power supplied from external power supply85(FIG. 1) into a voltage level of main power storage device10(FIG. 1) and outputs the electric power to main power storage device10. Main circuit210A is also driven by controller240A after external charging ends, and discharges the residual electric charge in capacitor220into sub power supply unit230A. In other words, main circuit210A is configured to allow electric power to flow bidirectionally. A configuration of main circuit210A will be described below.

Sub power supply unit230A is connected to a pair of power lines on the input side of main circuit210A (on the external power supply85side). Sub power supply unit230A is driven by controller240A, and converts a voltage of a part of the electric power supplied from external power supply85and outputs the electric power to power storage device50for auxiliary machinery. Sub power supply unit230A is also driven by controller240A after external charging ends, and discharges the residual electric charge in capacitor220received from main circuit210into power storage device50for auxiliary machinery. Sub power supply unit230A is formed of an AC/DC converter that can also make DC/DC conversion.

Controller240A controls the operation of main circuit210A and sub power supply unit230A through hardware processing with dedicated electronic circuitry and/or software processing realized by executing prestored programs using a CPU. Specifically, controller240A receives a control signal from a PM-ECU75A (FIG. 1) and drives main circuit210A and sub power supply unit230A based on the received control signal.

In the second embodiment, sub power supply unit230A is provided on the input side of main circuit210A. At the time of external charging, sub power supply unit230A converts a voltage of a part of the electric power supplied from external power supply85and charges power storage device50for auxiliary machinery. When external charging ends, main circuit210A and sub power supply unit230A are driven and the residual electric charge in capacitor220is discharged through main circuit210and sub power supply unit230A into power storage device50for auxiliary machinery.

FIG. 8is a circuit diagram of main circuit210A shown inFIG. 7. Referring toFIG. 8, this main circuit210A differs from main circuit210in the first embodiment shown inFIG. 3in that an AC/DC converting unit340A is included instead of rectifying unit340.

AC/DC converting unit340A is formed of a single-phase bridge circuit. Based on a drive signal from controller240A (FIG. 7), AC/DC converting unit340A converts AC power outputted from insulating transformer330into DC power and outputs the DC power to main power storage device10(FIG. 1).

Each of AC/DC converting units310,320and340A and insulating transformer330can make bidirectional power conversion. In the second embodiment, when external charging ends, each of AC/DC converting units340A,322and310operates to allow electric power to flow from the main power storage device10side to the external power supply85side, based on the drive signal from controller240A. As a result, after external charging ends, the residual electric charge in capacitor220(FIG. 7) provided on the main power storage device10side is outputted through main circuit210A to sub power supply unit230A (FIG. 7) and is discharged into power storage device50for auxiliary machinery by sub power supply unit230A.

Referring again toFIG. 4, PM-ECU75A in the second embodiment differs from PM-ECU75in the first embodiment in that a discharging control unit140A is included instead of control unit140. When receiving the notification that external charging has ended from charging control unit110, discharging control unit140A controls charger65A such that the residual electric charge in capacitor220of charger65A is discharged into power storage device50for auxiliary machinery. Specifically, when external charging ends, discharging control unit140A generates a control signal for driving main circuit210A and sub power supply unit230A of charger65A such that the residual electric charge in capacitor220is discharged into power storage device50for auxiliary machinery, and outputs the generated control signal to controller240A of charger65A.

FIG. 9is a flowchart for describing discharging control over capacitor220in the second embodiment. Referring toFIG. 9, this flowchart differs from the flowchart ofFIG. 6showing discharging control over capacitor220in the first embodiment in that steps S155and S175are included instead of steps S150and S170, respectively.

In other words, when charging relay70(FIG. 1) is turned off in step S140, PM-ECU75A generates the control signal for driving main circuit210A and sub power supply unit230A of charger65. As a result, main circuit210A and sub power supply unit230A are driven again, and discharging from capacitor220into power storage device50for auxiliary machinery through main circuit210A and sub power supply unit230A starts (step S155).

If it is determined in step S160that discharging of capacitor220has completed (YES in step S160), PM-ECU75A stops generation of the control signal for driving main circuit210A and sub power supply unit230A. As a result, main circuit210A and sub power supply unit230A stop finally (step S175).

As described above, in the second embodiment, sub power supply unit230A is provided on the input side of main circuit210A of charger65A (on the external power supply85side). Main circuit210A is configured to allow electric power to flow bidirectionally, and when external charging ends, the residual electric charge in capacitor220is discharged into power storage device50for auxiliary machinery by main circuit210A and sub power supply unit230A. During external charging, charging of power storage device50for auxiliary machinery by sub power supply unit230A is controlled such that the SOC of power storage device50for auxiliary machinery does not exceed the reference SOC. Therefore, according to the second embodiment as well, the residual electric charge in capacitor220provided in charger65A can be reliably discharged without using the discharge resistance.

In each embodiment described above, vehicle100has been described as an electric-powered vehicle in which motor generator25serves as a motive power source. Vehicle100may, however, be an electric vehicle in which only motor generator25serves as a motive power source, or a hybrid vehicle having an engine (not shown) further mounted thereon in addition to motor generator25.

In the foregoing, PM-ECU75,75A corresponds to one example of “control device” in the present invention, and charging control unit130for controlling charging of power storage device50for auxiliary machinery corresponds to one example of “charging control unit” in the present invention.

Reference Signs List