JP2011229275A - Charging system for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overcharging of an auxiliary battery in charging the auxiliary battery using a power supply external to a vehicle.SOLUTION: A main battery 14 is charged from a power supply 10 external to a vehicle by using a charger 12. In addition to the charger 12, a charging system includes a sub-AC/DC converter 18 which is used for charging an auxiliary battery 20. The sub-AC/DC converter 18 compares a terminal voltage of the auxiliary battery 20 with a prescribed reference voltage for intermittent operation, preventing overcharging of the auxiliary battery 20.

Description

  The present invention relates to a charging system for an electric vehicle, and more particularly to a technique for preventing overcharging of auxiliary batteries.

  In an electric vehicle such as a plug-in hybrid vehicle or an electric vehicle provided with an externally chargeable main battery (secondary battery), a configuration for charging an auxiliary battery that drives an auxiliary load is known.

  For example, in the following Patent Document 1, the high voltage of a high voltage operating unit including a high voltage main battery and a vehicle driving motor is lowered to provide a low voltage auxiliary battery (auxiliary battery) and a low voltage load. There is disclosed a DC / DC converter for supplying to a low voltage operating unit provided.

  Patent Document 2 discloses a main battery that can be charged by a charger using AC power outside the vehicle, a DC / DC converter that steps down the voltage of the battery and outputs the battery, and charging by the output voltage of the DC / DC converter. And an auxiliary battery that supplies electric power to the auxiliary load and a control device. The control device continuously operates the DC / DC converter during vehicle operation, and the main battery is charged from the outside of the vehicle. In the meantime, it is disclosed that the DC / DC converter is intermittently operated.

JP-A-4-325801 JP 2009-27774 A

  On the other hand, the voltage of the main battery is not stepped down by the DC / DC converter and the auxiliary battery is charged, but the main battery is charged by the charger using the AC power from the vehicle external power source and the AC from the vehicle outside A configuration is also conceivable in which the auxiliary battery is charged by rectifying and stepping down power using an AC / DC converter provided separately from the charger. However, even in such a configuration, a configuration that simply and effectively prevents overcharge of the auxiliary battery is required.

  An object of the present invention is to prevent overcharging of an auxiliary battery when the auxiliary battery is charged by a vehicle external power source.

  The present invention relates to a main battery that can be charged from the outside of the vehicle, a charger that charges the main battery by supplying power to the main battery from a power source outside the vehicle, and an auxiliary battery that supplies power to an auxiliary load. And a converter that is provided separately from the charger and that charges the auxiliary battery by supplying power to the auxiliary battery from a power source external to the vehicle, and charging that detects a charging state of the auxiliary battery And a state detecting unit, wherein the converter adaptively changes a charge amount according to a charging state of the auxiliary battery detected by the charging state detecting unit.

  In one embodiment of the present invention, the converter intermittently operates in accordance with a magnitude comparison result between a charge state of the auxiliary battery and a predetermined reference value, and intermittently charges the auxiliary battery.

  In another embodiment of the present invention, the converter charges the auxiliary battery by changing an output voltage according to a magnitude comparison result between a charging state of the auxiliary battery and a predetermined reference value.

  In another embodiment of the present invention, the converter operates intermittently according to a comparison result between a terminal voltage of the auxiliary battery and a predetermined reference voltage value to intermittently operate the auxiliary battery. Charge.

  In another embodiment of the present invention, the converter charges the auxiliary battery by changing an output voltage in accordance with a comparison result between a terminal voltage of the auxiliary battery and a predetermined reference voltage value.

  In another embodiment of the present invention, a relay unit provided between the power supply outside the vehicle and the converter is provided, and the relay unit includes a state of charge of the auxiliary battery and a predetermined reference value. The charge amount of the auxiliary battery by the converter is changed by opening and closing according to the magnitude comparison result.

  In another embodiment of the present invention, the charger includes a transformer for voltage conversion, the secondary side of the transformer is composed of first and second coils, and the first coil is connected to the converter. Connected, and the second coil is connected to the main battery.

  In another embodiment of the present invention, the auxiliary load includes a control circuit that controls the charger, and the auxiliary battery supplies power to the control circuit.

  In another embodiment of the present invention, the battery pack further includes a DC / DC converter that charges the auxiliary battery by reducing the voltage of the main battery and supplying electric power to the auxiliary battery. The auxiliary battery is charged by the DC / DC converter, and the auxiliary battery is charged by the converter while the vehicle is stopped.

  ADVANTAGE OF THE INVENTION According to this invention, the overcharge of an auxiliary machine battery when charging an auxiliary machine battery with a vehicle external power supply can be prevented.

It is a basic circuit block diagram of an embodiment. It is a timing chart of an embodiment. It is another circuit block diagram of embodiment. FIG. 5 is still another circuit configuration diagram of the embodiment.

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

1. Basic Configuration FIG. 1 shows a basic circuit configuration of a charging system according to this embodiment. The charging system includes a charger 12 connected to an external power source 10, a main battery 14, a controller 16 that controls the charger 12, a sub AC / DC converter 18 connected to the external power source 10, and an auxiliary battery. 20 and a voltage sensor 22.

  The charger 12 is detachably connected to the external power source 10 through an outlet or the like. The charger 12 is connected to the main battery 14 via the relay 13. On the other hand, a sub AC / DC converter 18 is connected to the external power source 10 separately from the charger 12. Specifically, the sub AC / DC converter 18 is connected at a connection point a between the external power supply 10 and the charger 12. When the external power supply 10 and the charger 12 are connected via an outlet, the connection point a is located closer to the charger 12 than the outlet. An auxiliary battery 20 is connected to the sub AC / DC converter 18, and the auxiliary battery 20 is connected to the control circuit 16. The control circuit 16 is connected to the charger 12 and controls the operation of the charger 12. A voltage sensor 22 that detects the terminal voltage is connected to the auxiliary battery 20, and the voltage sensor 22 is configured to supply the detected voltage data to the sub AC / DC converter 18.

  The connection relationship between the main battery 14 and each part of the vehicle is the same as that of a conventional hybrid vehicle or electric vehicle. For example, taking a hybrid vehicle as an example, the main battery 14 is connected to a boost converter, and the boost converter is connected to an inverter via a smoothing capacitor. The inverter is further connected to a motor generator. The motor generator and the vehicle engine are connected to a power distribution mechanism. The power distribution mechanism has three rotating shafts, a sun gear, a planetary gear, and a ring gear, and these three rotating shafts are connected to the motor generator and the engine, respectively (the two rotating shafts are connected to the two motor generators, and the rest One rotating shaft is connected to the engine).

  The operation of such a configuration will be described below.

  The external power supply 10 is a commercial power supply of AC 100V, for example.

  The charger 12 converts the AC voltage of the external power supply 10 into a DC voltage, adjusts the voltage, and supplies it to the main battery 14.

  The main battery 14 supplies electric power to the motor generator via a boost converter and an inverter to drive the motor generator, and accumulates regenerated electric energy during regenerative braking. The main battery is, for example, a nickel metal hydride battery or a lithium ion battery.

  The control circuit 16 is a circuit that controls the charging operation of the charger 12, and specifically controls the converter operation and the voltage adjustment operation of the charger 12. In addition to the charger 12, the control circuit 16 may control other auxiliary machines such as a headlight, a power window, and an electric water pump. The operating power of the control circuit 16 is supplied from the auxiliary battery 20.

  Sub AC / DC converter 18 is provided separately from charger 12 and charges auxiliary battery 20 independently of the charging operation of main battery 14 by charger 12. That is, when connected to the external power supply 10, the sub AC / DC converter 18 converts the alternating voltage into a direct voltage and supplies it to the auxiliary battery 20 to charge the auxiliary battery 20. However, basically, the sub AC / DC converter 18 is always connected to the external power source 10 to charge the auxiliary battery 20 while charging the main battery 14, so that the auxiliary battery 20 is overcharged. There is a fear.

  Therefore, in the present embodiment, the state of charge (SOC) of the auxiliary battery 20 is estimated or detected, and the operation of the sub AC / DC converter 18 is controlled according to the SOC of the auxiliary battery 20. That is, when it is estimated or detected that the auxiliary battery 20 is close to a fully charged state, the sub AC / DC converter 18 shifts from the continuous operation to the intermittent operation to prevent the auxiliary battery 20 from being overcharged. The SOC of the auxiliary battery 20 can be estimated or detected by any known method. However, since the terminal voltage of the auxiliary battery 20 has a fixed relationship with the SOC, the terminal voltage of the auxiliary battery 20 is determined by the voltage sensor 22. And the operation of the sub AC / DC converter 18 is controlled based on the voltage data.

  Specifically, the control unit of the sub AC / DC converter compares the voltage data of the auxiliary battery 20 detected by the voltage sensor 22 with a predetermined reference voltage. Here, the predetermined reference voltage is equal to or slightly lower than the terminal voltage when the auxiliary battery 20 is nearly fully charged. When it is determined that the voltage data of the auxiliary battery 20 has reached a predetermined reference voltage, the sub AC / DC converter 18 stops its operation. Further, when the voltage data of auxiliary battery 20 is lower than a predetermined reference voltage, sub AC / DC converter 18 starts its operation again. In this way, the sub AC / DC converter 18 operates intermittently according to the terminal voltage of the auxiliary battery 20.

  FIG. 2 shows the relationship between the terminal voltage of auxiliary battery 20 and the operating state of the sub AC / DC converter. 2A is a time change of the terminal voltage of the auxiliary battery 20, and FIG. 2B is a time change of the operating state of the sub AC / DC converter 18. FIG. It is assumed that the external power supply 10 and the sub AC / DC converter 18 are connected via an outlet at a certain time, and the sub AC / DC converter 18 starts operation. Since the auxiliary battery 20 is charged as the sub AC / DC converter 18 is operated, the terminal voltage of the auxiliary battery 20 gradually increases. When the terminal voltage of auxiliary battery 20 reaches the reference voltage value, sub AC / DC converter 18 stops its operation. When the terminal voltage of auxiliary battery 20 becomes lower than the reference voltage again at time t1, sub AC / DC converter 18 starts its operation. While the terminal voltage of the auxiliary battery 20 is lower than the reference voltage, the sub AC / DC converter 18 continues to operate and continues to charge the auxiliary battery 20. When the terminal voltage of auxiliary battery 20 reaches the reference voltage at time t2, sub AC / DC converter 18 stops its operation again. When the terminal voltage of auxiliary battery 20 again becomes lower than the reference voltage at time t3, sub AC / DC converter 18 starts its operation. By repeating the above processing, the sub AC / DC converter 18 is not always in an operating state while the charger 12 is operating, but the terminal voltage of the auxiliary battery 20 is separated from the operation of the charger 12. Depending on the operation. Even if the operation of the sub AC / DC converter 18 is stopped, the control circuit 16 operates with the electric power from the auxiliary battery 20, so that the operation of the charger 12 can be continuously controlled.

  Note that the control unit of the sub AC / DC converter 18 may have hysteresis characteristics using two reference voltages as reference voltages when comparing the voltage data detected by the voltage sensor 22 with the reference voltage. Good. That is, as the reference voltage, the first reference voltage and the second reference voltage are used, and the first reference voltage is equal to the terminal voltage when the auxiliary battery 20 is almost fully charged, or the same as the above reference voltage. Is a slightly lower voltage. Further, it is assumed that the second reference voltage is lower than the first reference voltage by a predetermined value ΔV. Then, the control unit of the sub AC / DC converter 18 shifts from the operation stop state to the operation state when the terminal voltage of the auxiliary battery 20 increases and reaches the first reference voltage, and the terminal voltage of the auxiliary battery 20 Decreases to the second reference voltage (instead of the first reference voltage), the operation state shifts to the operation stop state.

2. Other Circuit Configuration FIG. 3 shows another circuit configuration in the present embodiment. The charging system includes a charger 12 connected to an external power supply 10, a main battery 14, a control circuit 16 that controls the charger 12, a sub AC / DC converter 18 connected to the external power supply 10, and an auxiliary battery. 20, a voltage sensor 22, and a relay control circuit 24. Further, the transformer in the charger 12 has two channels in which the secondary coil is divided into two. More specifically, the secondary side (output side) of the transformer is divided into a first coil 12a and a second coil 12b.

  The charger 12 is detachably connected to the external power source 10 through an outlet or the like. The charger 12 is connected to the main battery 14 via the relay 13. The charger 12 includes a transformer for voltage conversion, and the secondary coil is divided into two, a coil 12a and a coil 12b, to form two channels. A main battery 14 is connected to one coil 12b via a relay 13. A sub AC / DC converter 18 is connected to the other coil 12 a via a relay 25. An auxiliary battery 20 is connected to the sub AC / DC converter 18, and the auxiliary battery 20 is connected to the control circuit 16. The control circuit 16 is connected to the charger 12 and controls the operation of the charger 12. A voltage sensor 22 for detecting the terminal voltage is connected to the auxiliary battery 20, and the voltage sensor 22 is configured to supply the detected voltage data to the relay control circuit 24.

  In such a configuration, the sub AC / DC converter 18 converts an AC voltage into a DC voltage and supplies the DC voltage to the auxiliary battery 20 to charge the auxiliary battery 20.

  On the other hand, relay control circuit 24 controls opening / closing of relay 25 in accordance with the SOC of auxiliary battery 20. Specifically, the relay control circuit 24 compares the voltage data of the auxiliary battery 20 detected by the voltage sensor 22 with a predetermined reference voltage. Then, when the voltage data of auxiliary battery 20 reaches the reference voltage, relay 25 is controlled to be turned off to cut off external power supply 10 and sub AC / DC converter 18. When the voltage data of the auxiliary battery 20 is lower than the reference voltage, the relay 25 is turned on to connect the external power supply 10 and the sub AC / DC converter 18. Therefore, the auxiliary battery 20 is intermittently charged according to the terminal voltage, and an overcharged state is prevented.

  In the configuration of FIG. 3 as well, the relay control circuit 24 may have hysteresis characteristics using two reference voltages as reference voltages when comparing the voltage data detected by the voltage sensor 22 with the reference voltage. Good. That is, as the reference voltage, the first reference voltage and the second reference voltage are used, and the first reference voltage is equal to the terminal voltage when the auxiliary battery 20 is almost fully charged, or the same as the above reference voltage. Is a slightly lower voltage. Further, it is assumed that the second reference voltage is lower than the first reference voltage by a predetermined value ΔV. Then, when the terminal voltage of the auxiliary battery 20 increases and reaches the first reference voltage, the relay control circuit 24 shifts the relay 25 from the OFF state to the ON state, and the terminal voltage of the auxiliary battery 20 decreases. When the second reference voltage is reached (not the first reference voltage), the relay 25 shifts from the on state to the off state.

  As described above, in the present embodiment, the sub AC / DC converter 18 that charges the auxiliary battery 20 is provided separately from the charger 12 that charges the main battery 12. In the configuration in which power for operation of the control circuit 16 that controls the charging operation of the charger 12 by electric power is supplied and the auxiliary battery 20 is charged, the charging operation of the auxiliary battery 20 by the sub AC / DC converter 18 is performed. By controlling intermittently according to the SOC of 20, the overcharged state of the auxiliary battery 20 can be easily and efficiently prevented.

  In addition, this invention is not limited to this, A various deformation | transformation is possible.

  For example, in the present embodiment, the terminal voltage of the auxiliary battery 20 is used as a method for estimating the SOC of the auxiliary battery 20, but the SOC of the auxiliary battery 20 is calculated using a no-load voltage (OCV) or a polarization voltage. Based on the estimated SOC, the charging of the auxiliary battery 20 may be controlled to be intermittent. For example, in the configuration of FIG. 1, a current sensor is provided in addition to the voltage sensor 22, and the control unit of the sub AC / DC converter 18 estimates the SOC of the auxiliary battery 20 based on the voltage data and the current data, and the estimated SOC And a predetermined reference SOC are compared, and the start and stop of the operation of the sub AC / DC converter 18 are determined according to the comparison result. In the configuration of FIG. 3, a current sensor is provided in addition to the voltage sensor 22, and the relay control circuit 24 estimates the SOC of the auxiliary battery 20 based on the voltage data and the current data, and the estimated SOC and a predetermined reference SOC Are compared, and the ON / OFF of the relay 25 is controlled according to the result of the size comparison.

  In the present embodiment, the auxiliary battery 20 is charged by connecting the external power source 10 and the sub AC / DC converter 18, so that the auxiliary battery 20 is originally charged when the vehicle is stopped. As in the prior art, by providing a DC / DC converter that steps down the voltage of the main battery 14 and supplies the voltage to the auxiliary battery 20, the auxiliary battery 20 can be charged while the vehicle is running. Since the auxiliary battery 20 is charged by the DC / DC converter while the vehicle is running, the operation of the sub AC / DC converter 18 is stopped. However, the auxiliary AC / DC converter 18 is operated even when the vehicle is running. It is also possible to convert the DC voltage of the battery 20 into an AC voltage and output it from the outlet.

  Further, in the present embodiment, charging of the auxiliary battery 20 by the sub AC / DC converter 18 is intermittently controlled according to the SOC of the auxiliary battery 20, but the sub AC / DC converter 18 is not intermittent control. May be controlled to prevent overcharge of the auxiliary battery 20. That is, when the SOC of auxiliary battery 20 increases and reaches a reference value close to a fully charged state, the output voltage of sub AC / DC converter 18 is reduced.

  Further, the output voltage control of the sub AC / DC converter 18 and the intermittent control can be combined. That is, the SOC of the auxiliary battery 20 is compared with the first reference value and the second reference value (where the first reference value> the second reference value), and the SOC of the auxiliary battery 20 reaches the second reference value. In this case, the output voltage (that is, the charging voltage) is controlled to be lowered, and then the operation of the sub AC / DC converter 18 is stopped when the SOC of the auxiliary battery 20 reaches the first reference value. In short, the sub AC / DC converter 18 of the present embodiment only needs to adaptively change the charge amount of the auxiliary battery 20 according to the SOC of the auxiliary battery 20, and the SOC of the auxiliary battery 20 increases. The control is performed so as to decrease the charge amount.

  In the configuration of FIG. 3, the transformer of the charger 12 is not set to two channels, but the sub AC / DC 18 is connected to the relay 25 at the connection point a between the external power source 10 and the charger 12 as in FIG. You may connect with the external power supply 10 via this. FIG. 4 shows a circuit configuration in this case.

  Further, in the configuration of FIG. 1, the transformer of the charger 12 may be two channels as in FIG. 3, and the sub AC / DC converter 18 may be connected to the secondary transformer of the charger 12. This configuration is equivalent to a configuration in which the relay control circuit 24 and the relay 25 are removed in FIG.

  10 external power supply, 12 charger, 14 main battery, 16 control circuit, 18 sub AC / DC converter, 20 auxiliary battery, 22 voltage sensor.

Claims (9)

A main battery that can be charged from outside the vehicle;
A charger for charging the main battery by supplying power to the main battery from a power source external to the vehicle;
An auxiliary battery that supplies power to the auxiliary load; and
A converter that is provided separately from the charger and that charges the auxiliary battery by supplying power to the auxiliary battery from a power source external to the vehicle;
Charge state detection means for detecting a charge state of the auxiliary battery;
And the converter adaptively changes the amount of charge according to the state of charge of the auxiliary battery detected by the state of charge detection means. The system of claim 1, wherein
The electric vehicle charging system characterized in that the converter intermittently operates in accordance with a comparison result between a charge state of the auxiliary battery and a predetermined reference value to charge the auxiliary battery intermittently. . The system of claim 1, wherein
The electric vehicle charging system, wherein the converter charges the auxiliary battery by changing an output voltage in accordance with a comparison result between a charge state of the auxiliary battery and a predetermined reference value. The system of claim 2, wherein
Charging of an electric vehicle characterized in that the converter intermittently operates in accordance with a comparison result between a terminal voltage of the auxiliary battery and a predetermined reference voltage value to intermittently charge the auxiliary battery. system. The system of claim 3, wherein
The electric vehicle charging system, wherein the converter changes the output voltage in accordance with a magnitude comparison result between a terminal voltage of the auxiliary battery and a predetermined reference voltage value, and charges the auxiliary battery. The system of claim 1, wherein
Relay means provided between the power supply outside the vehicle and the converter;
And the relay means changes the amount of charge of the auxiliary battery by the converter by opening and closing according to a magnitude comparison result between a charge state of the auxiliary battery and a predetermined reference value. Electric vehicle charging system. The system of claim 1, wherein
The charger includes a transformer for voltage conversion,
The secondary side of the transformer is composed of first and second coils,
The charging system for an electric vehicle, wherein the first coil is connected to the converter, and the second coil is connected to the main battery. The system according to any one of claims 1 to 7,
The auxiliary machine load includes a control circuit for controlling the charger,
The charging system for an electric vehicle, wherein the auxiliary battery supplies power to the control circuit. The system according to any one of claims 1 to 7,
A DC / DC converter that charges the auxiliary battery by reducing the voltage of the main battery and supplying power to the auxiliary battery;
A charging system for an electric vehicle, wherein the auxiliary battery is charged by the DC / DC converter while the vehicle is running, and the auxiliary battery is charged by the converter while the vehicle is stopped.

Images