JP4894565B2 - Power supply control device and power supply control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power control device to secure a starting property of a hybrid system in switching off an ignition switch on the system to supply electric power to an electric load from a plurality of batteries etc. and a power control method. <P>SOLUTION: A pressure down circuit steps down electric power supplied from the high voltage system battery to prescribed voltage and supplies it to the electric load. A pressure up circuit steps up electric power supplied from the low voltage system battery to prescribed voltage and supplies it to the electric load. An ignition switch state detection means detects ON/OFF states of the ignition switch of a vehicle. A control part respectively controls movement of the pressure down circuit and the pressure up circuit. The control part stops the pressure down movement of the pressure down circuit by starting the pressure up movement of the pressure up circuit when the ignition switch state detection means detects that the ignition switch is switched from ON over to OFF. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a power supply control device and a power supply control method for supplying electric power to an electric load, and more particularly to a power supply control device and a power supply control method for supplying electric power from a plurality of batteries to an electric load.

  Conventionally, a vehicle equipped with a hybrid system combining an internal combustion engine and an electric motor has been put into practical use. In such a hybrid system, a battery that supplies electric power of a high potential (for example, about 288 V) to an electric motor is used. This battery uses a high-voltage nickel metal hydride battery or the like, and is generally called a main battery.

  Also in a vehicle equipped with the hybrid system, a battery that supplies low potential (for example, about 12 V) power to an auxiliary machine mounted on a vehicle that uses only an internal combustion engine as a power train is also used. This battery uses a lead-acid battery or the like, and is generally called an auxiliary battery.

In addition, an electric power steering device that assists the rotational operation force by the electric motor in accordance with the rotational operation given to the steering wheel is also mounted on the vehicle equipped with the hybrid system. For example, a power supply control device that supplies electric power of an intermediate potential (for example, about 42 V) between the high potential and the low potential to an electric power steering device is disclosed (for example, see Patent Document 1). The power supply control device disclosed in Patent Document 1 is a vehicle equipped with the hybrid system, in which a high potential from a main battery is stepped down to a middle potential by a DC-DC converter and power is supplied to the electric power steering device. Done. When the high potential power system is abnormal, the low potential from the auxiliary battery is boosted to the middle potential as a temporary backup power source, and power is supplied to the electric power steering apparatus.
JP 2006-213273 A

  However, the power supply control device disclosed in Patent Document 1 does not consider the power supply when the ignition switch of the vehicle is turned off (that is, the current supplied to the ignition device or the like of the internal combustion engine is turned off). For example, when the ignition switch is turned off, if the energization of the electric motor of the electric power steering device is immediately stopped, the assisting force (assisting force) to the steering wheel suddenly disappears.

  In order to prevent such deterioration of the steering feeling, a gradual change process may be performed in a general vehicle not equipped with a hybrid system. This gradual change process is a control for gradually decreasing the amount of current supplied to the electric motor during a period from when the ignition switch is switched from ON to OFF until the energization of the electric motor of the electric power steering device is stopped. The assist force will change gradually. As a result, the steering feeling after turning off the ignition switch is improved.

However, when the above-described gradual change process is simply applied to a vehicle equipped with the hybrid system, a system main relay (hereinafter referred to as SMR) provided on the power supply line of the main unit battery during the gradual change process. Cannot be blocked. In addition, even if the ignition switch is turned on during the gradual change process, the hybrid system does not start, so the startability of the hybrid system is degraded.

  Therefore, an object of the present invention is to provide a power supply control device and a power supply control method for ensuring startability of a hybrid system when an ignition switch is turned off in a system that supplies power to an electric load from a plurality of batteries or the like. It is.

In order to achieve the above-described object, the present invention has the following features.
1st invention is a power supply control apparatus which supplies electric power with respect to the electric load of a vehicle. The power supply control device includes a step-down circuit, a step-up circuit, an ignition switch state detection unit, and a control unit. The step-down circuit steps down the power supplied from the high-voltage battery to a predetermined voltage and supplies it to the electric load. The booster circuit boosts the power supplied from the low voltage system battery to a predetermined voltage and supplies it to the electric load. The ignition switch state detection means detects the on / off state of the ignition switch of the vehicle. The control unit controls operations of the step-down circuit and the step-up circuit. When the ignition switch state detecting means detects that the ignition switch has been switched from on to off, the control unit starts the boost operation of the boost circuit and stops the step-down operation of the step-down circuit.

  According to a second invention, in the first invention, an energization control unit is further provided. The energization control unit performs energization control of power supplied from the step-down circuit or the step-up circuit to the electric load. The energization control unit performs energization control by gradually decreasing the amount of current to the electric load from the detection time point when the ignition switch state detecting means detects that the ignition switch has been switched from on to off.

  A third invention is the electric power steering device according to the second invention, wherein at least one of the electric loads to which the power supply control device supplies electric power provides an assisting force for a rotation operation of a steering wheel of the vehicle. The energization control unit performs energization control by gradually decreasing the amount of current to the electric power steering device so that the assist force of the electric power steering device gradually decreases from the time of detection.

  In a fourth aspect based on the second aspect, the control unit starts the step-up operation of the step-up circuit at the time of detection, and stops the step-down operation of the step-down circuit after the first time has elapsed from the time of detection.

  In a fifth aspect based on the fourth aspect, the energization control unit gradually reduces the amount of current to the electric load to zero after a predetermined time has elapsed from the detection time point. The control unit stops the boosting operation of the booster circuit after a second time period equal to or longer than a predetermined time from the detection time point.

  In a sixth aspect based on the fourth aspect, the control unit further controls the operation of a relay for connecting / disconnecting a contact provided on the power supply line between the high voltage battery and the step-down circuit. . The control unit cuts off the contact by disconnecting the relay after the elapse of a third time longer than the first time from the detection time.

  In a seventh aspect based on the first aspect, at least one of the electric loads to which the power supply control device supplies electric power is an electric power steering device for a vehicle.

The eighth invention is a power supply control method for supplying electric power to an electric load of a vehicle. The power supply control method includes a step-down step, a step-up step, and an ignition switch state detection step. In the step-down step, high voltage power is stepped down to a predetermined voltage and supplied to the electric load. In the boosting step, the low-voltage power is boosted to a predetermined voltage and supplied to the electric load. In the ignition switch state detecting step, an on / off state of the ignition switch of the vehicle is detected. In the boosting step, when the ignition switch state detecting step detects that the ignition switch has been switched from on to off, the boosting operation is started. In the step-down step, the step-down operation is stopped after the step-up step starts the step-up operation.

  According to the first aspect of the invention, when the ignition switch is turned from ON to OFF, the power supply is switched from the low voltage system supply circuit, and the main relay of the high voltage system can be quickly turned off. It is possible to improve the startability of a hybrid system or the like when the is turned on.

  According to the second aspect of the invention, when the ignition switch is turned from ON to OFF, the electric load is gradually changed by supplying the low-voltage system power to the electric load after changing the ignition switch from ON to OFF. It is possible to improve the operational feeling when shifting from the operating state to the stopped state.

  According to the third aspect of the present invention, when the ignition switch is changed from ON to OFF by supplying the low voltage system power and performing the gradual change processing of the electric power steering device when the ignition switch is turned OFF from ON. The steering feeling can be improved.

  According to the fourth aspect of the present invention, when switching from high voltage power to low voltage power supply when the ignition switch is turned from ON to OFF, the drive period of the step-down circuit and the drive period of the boost circuit overlap. Therefore, the output voltage of the power supplied to the electric load is always stabilized at the predetermined voltage. As a result, the output voltage supplied to the electric load does not drop below a voltage that enables the electric load to operate, so that the operation of the electric load can be stabilized.

  According to the fifth aspect of the invention, since power supply during the gradual change process for the electric load is ensured, the operation during the gradual change process of the electric load can be stabilized.

  According to the sixth aspect of the invention, since the step-down circuit is stopped when the relay such as the system main relay is cut off, the contact of the relay can be prevented from being welded, and the durability of the relay is improved. Can be made. In addition, since the relay is disconnected based on the passage of time, it is not necessary to check the usage state of the step-down circuit or the like, and the response of the interruption can be improved.

  According to the seventh aspect of the invention, since the electric power supply to the electric power steering device mounted on the vehicle can be switched to the electric power supply from the low voltage system supply circuit when the ignition switch is turned off from on, the electric power steering It is possible to prevent the assist of the rotational operation force by the device from suddenly disappearing.

  Moreover, according to the power supply control method of the present invention, the same effects as those of the power supply control device described above can be obtained.

Hereinafter, with reference to FIGS. 1-5, the electric power supply system containing the power supply control device which concerns on one Embodiment of this invention is demonstrated. Typically, the power supply system is installed in a vehicle equipped with a hybrid system. FIG. 1 is a schematic configuration diagram illustrating an example of a partial configuration of the power supply system. FIG. 2 is a flowchart showing an example of the operation of the HV-ECU 11 included in the power supply control device. FIG. 3 is a flowchart showing an example of the operation of the microcomputer 53 included in the power supply control device. FIG. 4 is a timing chart of power supply control in the power supply system. FIG. 5 is a timing chart of power supply control in a conventional power supply system.

  In FIG. 1, the power supply system supplies the electric power from the high voltage system battery 1 and the low voltage system battery 8 to each electric load provided in the vehicle. Typically, there are an inverter 3 and an air conditioner 4 as electric loads to which power from the high voltage battery 1 is supplied. Here, the inverter 3 converts the DC power supplied from the high voltage system battery 1 into three phases, and controls energization of the electric motor (main motor) for vehicle travel. In addition, there is an electric power steering device as an electric load to which power from the high voltage system battery 1 or the low voltage system battery 8 is supplied. In the example of FIG. 1, electric power from the high voltage system battery 1 or the low voltage system battery 8 is supplied to an electric motor 7 via an EPS-ECU (Electric Power Steering-Electronic Control Unit) 6. Is done. In addition, although the high voltage system battery 1 and the low voltage system battery 8 supply electric power also to electric loads other than the example of the electric load mentioned above, detailed description is abbreviate | omitted here.

  The high-voltage battery 1 is a battery that supplies electric power of a high potential (for example, about 288 V) mainly to an electric motor in a hybrid system. The high voltage battery 1 is a high voltage nickel metal hydride battery or the like, and is generally called a main battery. Further, a system main relay (hereinafter referred to as SMR) 2 is provided on the power supply line of the high voltage battery 1, and power is supplied from the high voltage battery 1 by turning the SMR 2 on and off. Or power interruption is switched. An electric load such as the inverter 3 and the air conditioner 4 described above is branchedly connected to the power supply line of the high voltage battery 1 on the load side of the SMR 2.

  The low-voltage system battery 8 is a battery that mainly supplies low-potential (for example, about 12 V) power to the auxiliary equipment of the vehicle. The low voltage battery 8 uses a lead storage battery or the like, and is generally called an auxiliary battery. The low voltage battery 8 supplies power to various electric loads provided in the vehicle, but detailed description thereof is omitted here. The power supply line of the high voltage system battery 1 is connected to a step-down circuit 9 that steps down the high potential to the low potential, and the low-voltage system battery 8 is charged with the power stepped down by the step-down circuit 9. . The step-down circuit 9 is also branched and connected from the load side of the SMR 2 in the power supply line of the high voltage battery 1, as with other electric loads.

  The vehicle is equipped with an electric power steering device that assists the rotational operation force by the electric motor 7 in accordance with the rotation operation given to the steering wheel by the driver. The electric motor 7 generates a driving force in the rotation direction of the steering shaft according to the rotation operation, and applies an assist force according to the rotation operation applied to the steering wheel. For example, the electric motor 7 is constituted by a three-phase motor, and its driving is controlled by the EPS-ECU 6.

  The EPS-ECU 6 calculates an energization amount to the electric motor 7 and drives and controls the electric motor 7 according to the energization amount. For example, the EPS-ECU 6 includes a three-phase inverter to which power from the DC-DC converter 5 is supplied, and power is supplied to each phase of the electric motor 7 from the three-phase inverter. The EPS-ECU 6 controls the amount of current supplied to the electric motor 7 based on information such as the motor rotation angle of the electric motor 7, the amount of current flowing through each phase of the electric motor 7, the steering torque, and the vehicle speed of the vehicle.

Specifically, the EPS-ECU 6 includes a control circuit and a drive circuit that controls energization of the electric motor 7. The electric motor 7 applies an assisting force in accordance with a rotational operation applied to the steering wheel, and is attached to the steering shaft through a speed reduction mechanism or the like so as to transmit torque. A torque sensor is attached to the steering shaft, and the torque sensor detects a steering torque acting on the steering shaft and outputs a steering torque signal indicating the steering torque to the control unit.

  The control unit includes a microcomputer, various interfaces, and a memory. The control unit is connected to a torque sensor, a vehicle speed sensor, an engine speed sensor, and a shift position sensor via an interface. The control unit is connected to the drive circuit via an interface, and controls the conduction state of the drive circuit based on a command.

  The drive circuit includes a plurality of switching elements (for example, six MOSFETs) whose gates are connected to the control unit, and receives power supply from the high-voltage battery 1 and the low-voltage battery 8. And according to control of the said control part, a switching element is selectively made into a conduction state, an electric current flows into any phase of the electric motor 7, and the electric motor 7 rotates to one direction or the other direction. In the above description, the example in which the electric motor 7 is configured by a three-phase brushless motor and is driven and controlled by a three-phase inverter is used. However, the present invention can employ various motors and driving circuits.

  The control unit of the EPS-ECU 6 calculates a target assist torque to be applied to the steering wheel using, for example, operation torque information obtained from the torque sensor and vehicle speed information obtained from the vehicle speed sensor. Specifically, the control unit sets a target assist torque corresponding to the operation torque for each vehicle speed range (low speed, medium low speed, medium high speed, high speed, etc.). Then, the control unit sets the target assist torque to increase as the operation torque increases, and to decrease the target assist torque as the vehicle speed increases with respect to the same operation torque.

  The control unit obtains the energization time (for example, duty ratio) of each switching element of the drive circuit so that the electric motor 7 generates the calculated target assist torque, and the switching element is turned ON− according to the energization time. Perform OFF control.

  Here, when the ignition switch 10 of the vehicle is changed from ON to OFF, the control unit of the EPS-ECU 6 does not immediately set the target assist torque to 0, but uses the operation torque information and the vehicle speed information. Thus, the target assist torque is set to gradually decrease. With this setting, when the ignition switch 10 is changed from ON to OFF, the assist force applied to the steering wheel gradually decreases to zero. Specifically, during the period from when the ignition switch 10 is switched from ON to OFF until the energization of the electric motor 7 of the electric power steering device is stopped, the amount of current supplied to the electric motor 7 is gradually reduced, and electric The energization to the motor 7 is stopped (gradual change process). This gradual change process improves the steering feeling after the ignition switch 10 is turned off.

  The electric power steering apparatus is supplied with electric power having a medium potential (for example, about 42 V) between the high potential and the low potential. In the power supply system of the present embodiment, a power storage mechanism dedicated to a middle potential is not provided, and the high potential from the high-voltage battery 1 is mainly DC-DC up to the middle potential in consideration of power consumption of the electric power steering device. The voltage is stepped down by the converter 5 and electric power is supplied to the electric power steering apparatus. In this case, when the high-potential power system is abnormal or during a period immediately after the ignition switch 10 is turned off, the DC-DC converter 5 reduces the low potential from the low-voltage battery 8 to the intermediate potential as a temporary backup power source. The pressure is increased and electric power is supplied to the electric power steering apparatus.

  The DC-DC converter 5 includes a step-down circuit 51, a step-up circuit 52, and a microcomputer 53. As described above, the DC-DC converter 5 steps down the high potential from the high voltage system battery 1 to the intermediate potential or boosts the low potential from the low voltage system battery 8 to the intermediate potential and supplies the electric load to the electric load. .

  The high potential DC power output from the high voltage battery 1 is input to the step-down circuit 51 of the DC-DC converter 5. Typically, the step-down circuit 51 includes an inverter, a transformer, a rectifier circuit, and the like. The high potential power input to the step-down circuit 51 is converted into alternating current by the inverter and output to the transformer. The transformer steps down the electric power converted by the inverter from a high potential to a medium potential and outputs it to the rectifier circuit. Then, the rectifier circuit converts the medium potential AC power into DC and outputs it to the EPS-ECU 6.

  Electric power is supplied from the low voltage system battery 8 to the EPS-ECU 6 when the high potential power system is abnormal or during a period immediately after the ignition switch 10 is turned off. The low potential direct current power output from the low voltage system battery 8 is input to the booster circuit 52 of the DC-DC converter 5. Typically, the booster circuit 52 includes a booster coil and a diode provided on the power supply line, a switching element (for example, MOS) that is grounded between the booster coil and the diode, and the like. Then, by causing intermittent current from the low voltage battery 8 to flow through the booster coil, electric power is generated in the booster coil to boost the low potential power to the middle potential. The boosted medium potential power is rectified by a diode and output to the EPS-ECU 6.

  The microcomputer 53 monitors the output voltage of the DC-DC converter 5 and controls the operation of the step-down circuit 51 and the step-up circuit 52 so that the output voltage becomes the target voltage. Further, the microcomputer 53 receives power supply from the low voltage battery 8. For example, the microcomputer 53 monitors the output voltage of the DC-DC converter 5 and feedback-controls the operation of the step-down circuit 51 or the step-up circuit 52 so that the output voltage becomes a predetermined voltage (the intermediate potential). Further, the microcomputer 53 monitors the output current of the DC-DC converter 5 to prevent overcurrent to the EPS-ECU 6 and the like. Further, the microcomputer 53 monitors the ON / OFF operation of the ignition switch 10. In the present embodiment, the microcomputer 53 notifies the hybrid control device (HV-Electronic Control Unit; hereinafter referred to as HV-ECU) 11 of information (specifically, the state of the DC-DC converter 5). (Notification shown) becomes unnecessary, and the communication line from the microcomputer 53 to the HV-ECU 11 can be abolished.

  The HV-ECU 11 is configured by a microcomputer or the like. The HV-ECU 11 calculates the engine output and motor torque according to the driving state of the vehicle, and controls the output of the inverter 3 and the like. The HV-ECU 11 also performs ON / OFF control of the SMR 2 in addition to the vehicle hybrid system. Here, the HV-ECU 11 and the microcomputer 53 correspond to an example of a control unit of the present invention.

Hereinafter, the operation of the power supply system will be described with reference to FIGS. 2 and 3. FIG. 2 is a flowchart showing an example of the operation of the HV-ECU 11 included in the power supply control device, and is stored as a control program in a storage area (not shown) used by the HV-ECU 11. Then, in response to the ignition switch 10 being turned on, the HV-ECU 11 executes the control program, thereby realizing a power supply operation described later. FIG. 3 is a flowchart showing an example of the operation of the microcomputer 53 included in the power supply control device, and is stored as a control program in a storage area (not shown) used by the microcomputer 53. Then, when the ignition switch 10 is turned on, the microcomputer 53 executes the control program, thereby realizing a power supply operation described later. In the following description, the power supply operation to the electric power steering apparatus according to the change of the ignition switch 10 from ON to OFF will be mainly described, and detailed description of other operations will be omitted.

  In FIG. 2, the HV-ECU 11 determines whether or not the ignition switch 10 has been changed from ON to OFF (step S51). And HV-ECU11 advances a process to the following step S52, when the ignition switch 10 is changed from ON to OFF. On the other hand, the HV-ECU 11 repeats the process of step S51 when the ignition switch 10 is in the ON state.

  In step S52, the HV-ECU 11 stops the electrical load connected to the power supply line of the high voltage battery 1 and advances the process to the next step. For example, the electric loads stopped in step S52 are the inverter 3, the air conditioner 4, the step-down circuit 9 (see FIG. 1), and the like.

  Next, the HV-ECU 11 starts counting by the HV timer Thv (step S53). Then, the HV-ECU 11 waits for the elapse of a predetermined time t1 after starting the counting of the HV timer Thv (step S54). Here, the predetermined time t1 is a time required for the electric load to stop and the power supply from the low voltage system battery 8 to be stabilized via the DC-DC converter 5, and is longer than a predetermined time t2 (to be described later) For example, 200 ms) is set. Note that the processing order of steps S52 and S53 may be changed.

  When the predetermined time t1 has elapsed (Yes in step S54), the HV-ECU 11 shuts off the SMR 2 (step S55), and ends the process according to the flowchart. By shutting off the SMR 2, the power from the high voltage battery 1 is switched to the shut off state.

  In FIG. 3, the microcomputer 53 determines whether or not the ignition switch 10 has been changed from ON to OFF (step S61). Then, when the ignition switch 10 is changed from ON to OFF, the microcomputer 53 advances the process to the next step S62. On the other hand, when the ignition switch 10 is in the ON state, the microcomputer 53 repeats the process of step S61.

  In step S62, the microcomputer 53 starts the boosting operation of the booster circuit 52 and proceeds to the next step. In response to the control of the microcomputer 53, the booster circuit 52 starts an operation of boosting the low potential power from the low voltage system battery 8 to the middle potential and outputting it to the EPS-ECU 6.

  Next, the microcomputer 53 starts counting by the microcomputer timer Tm (step S63). Then, the microcomputer 53 waits for a predetermined time t2 to elapse after the microcomputer timer Tm starts counting (step S64). Here, the predetermined time t2 is set to a time required until the power supply from the booster circuit 52 that boosts the low potential power from the low voltage battery 8 to the middle potential is stabilized, and is shorter than the predetermined time t1 ( For example, it is set to several tens of ms). Note that the processing order of steps S62 and S63 may be changed.

When the predetermined time t2 has elapsed (Yes in step S64), the microcomputer 53 stops the step-down operation by the step-down circuit 51 (step S65), and advances the processing to the next step. By stopping the step-down operation by the step-down circuit 51, power supply from the high-voltage battery 1 to the electric power steering device is stopped. That is, the electric power steering apparatus is in a state of being operated only by the power supply from the low voltage system battery 8.

  Next, the microcomputer 53 waits for a predetermined time t3 to elapse after the microcomputer timer Tm starts counting (step S66). Here, the predetermined time t3 is set to be longer than the time required for the gradual change process of the EPS-ECU 6 described above, and is set to a time longer than the predetermined times t1 and t2 (for example, 5 s or more).

  When the predetermined time t3 has elapsed (Yes in step S66), the microcomputer 53 stops the boosting operation by the booster circuit 52 (step S67), and ends the processing according to the flowchart. By stopping the boosting operation by the booster circuit 52, the power supply from the low voltage system battery 8 to the electric power steering device is stopped, and the power supply to the electric power steering device is stopped.

  Next, the operation timing of the power supply system based on the flowcharts shown in FIGS. 2 and 3 will be described with reference to FIGS. 4 and 5. FIG. 4 is a timing chart showing an example of operation timing in the power supply system according to the present embodiment. FIG. 5 is a timing chart showing an example of operation timing in which the gradual change process is simply introduced in the conventional power supply system. The timing charts shown in FIG. 4 and FIG. 5 show the ignition switch 10 in a state where the high potential power supplied from the high potential power supply system is stepped down to the middle potential by the step-down circuit 51 and supplied to the electric load. The operation timing when is changed from ON to OFF is shown.

  First, with reference to FIG. 5, the operation timing when the gradual change process is simply introduced in the conventional power supply system will be described. In FIG. 5, when the ignition switch 10 is changed from ON to OFF, the gradual change process of the EPS-ECU 6 is started (arrow C in the drawing).

  Next, the control unit of the EPS-ECU 6 performs a gradual change process in which the assist force is gradually reduced to 0% by setting the target assist torque to gradually decrease. Then, when the assist force becomes 0%, the control unit of the EPS-ECU 6 notifies the microcomputer 53 of an EPS state notification indicating that the assist given to the steering wheel has ended (arrow D in the drawing).

  Next, the microcomputer 53 of the DC-DC converter 5 stops the step-down operation by the step-down circuit 51. Thereby, the power supply from the DC-DC converter 5 to the electric power steering device is stopped. When the step-down operation is stopped, the microcomputer 53 notifies the HV-ECU 11 of a DCDC converter state notification indicating that the DC-DC converter 5 has stopped using power from the high voltage system battery 1 (illustrated arrow E). ).

  Next, the HV-ECU 11 shuts off the SMR 2. By shutting off the SMR 2, the power from the high voltage battery 1 is switched to the shut off state. Thus, when the above-described gradual change process is simply applied to a vehicle equipped with a conventional hybrid system, the SMR 2 cannot be blocked during the gradual change process. Moreover, even if the ignition switch 10 is turned on during the gradual change process, the hybrid system does not start, so that the startability of the hybrid system decreases.

With reference to FIG. 4, the operation timing in the power supply system according to the present embodiment will be described. In FIG. 4, the ignition switch 10 is changed from ON to OFF.
Then, the control unit of the EPS-ECU 6 gradually sets the assist force by setting the target assist torque to gradually decrease in response to the ignition switch 10 being changed from ON to OFF (shown arrow A). A gradual change process is performed to reduce it to 0%.

  On the other hand, the microcomputer 53 of the DC-DC converter 5 starts the boosting operation by driving the booster circuit 52 in response to the ignition switch 10 being changed from ON to OFF (arrow B in the figure). Then, the microcomputer 53 stops the step-down operation by the step-down circuit 51 when a predetermined time t2 elapses after the ignition switch 10 is changed from ON to OFF (illustration period t2). That is, the period in which the step-down circuit 51 is driven to perform the step-down operation overlaps the period in which the step-up circuit 52 is driven to perform the step-up operation. Therefore, the high-potential power supplied from the high-voltage system battery 1 is stepped down to the middle potential by the step-down circuit 51 and the power is supplied, and the low-potential power supplied from the low-voltage system battery 8 is supplied from the boost circuit 52. Since the period in which power is boosted to the medium potential overlaps, the output voltage of the DC-DC converter 5 is always stabilized at the medium potential. As a result, the supply voltage of the electric power supplied from the DC-DC converter 5 to the electric power steering device is a required voltage at which the electric power steering device can be driven even immediately after the ignition switch 10 is changed from ON to OFF. There is no immediate drop to:

  Then, the microcomputer 53 stops the boosting operation by the booster circuit 52 when a predetermined time t3 elapses after the ignition switch 10 is changed from ON to OFF (period t3 in the drawing). Thereby, the power supply from the DC-DC converter 5 to the electric power steering device is stopped. Here, since the predetermined time t3 is set to be longer than the time required for the gradual change processing of the EPS-ECU 6, stable power supply is performed during a period in which power supply to the electric power steering device is necessary. .

  In addition, the HV-ECU 11 shuts off the SMR 2 when a predetermined time t1 has elapsed since the ignition switch 10 was changed from ON to OFF (illustration period t1). By shutting off the SMR 2, the power from the high voltage battery 1 is switched to the shut off state. Here, the predetermined time t1 is shorter than the predetermined time t3, that is, a time shorter than the time required for the gradual change processing of the EPS-ECU 6, and the SMR 2 can be shut off during the gradual change processing of the EPS-ECU 6. That is, since the hybrid system can be restarted even during the gradual change process, the startability of the hybrid system is improved.

  As is clear from FIG. 4, the EPS state notification indicating that the assist notified from the EPS-ECU 6 to the microcomputer 53 has ended, and the power from the high-voltage battery 1 notified from the microcomputer 53 to the HV-ECU 11 are received. Since the DCDC converter state notification indicating that the use has been stopped is not required, the communication line for transmitting these notifications and the notification content are transmitted, so that no processing is required.

  Thus, according to the power supply control device according to the present embodiment, when the ignition switch is turned from ON to OFF, the power supply is switched from the low voltage system supply circuit, and the main relay of the high voltage system supply circuit is shut off early. Therefore, the startability of the hybrid system when the ignition switch is turned on again can be improved. Also, when the ignition switch is turned off from ON, the steering feeling after changing the ignition switch from ON to OFF is improved by supplying the low voltage system power and gradually changing the electric power steering device. be able to. Further, regarding the gradual change processing of the electric power steering apparatus, information notification from the EPS-ECU 6 to the microcomputer 53 and information notification from the microcomputer 53 to the HV-ECU 11 are not required. Therefore, if the information notification between these is unnecessary in other processes, the communication line for transmitting these notifications and the contents of the notification are transmitted, so the process becomes unnecessary.

  Note that the process of stopping each electric load in step S52 and the process of starting the HV timer Thv in step S53 may be performed simultaneously. Further, the above-described process for starting the boosting operation in step S62 and the process for starting the microcomputer timer Tm in step S63 may be performed simultaneously.

  In the above description, the electric power steering device is used as an example of the electric load that supplies the medium potential power. However, another electric load that needs to be supplied for a predetermined time after the ignition switch is turned off is supplied. It does not matter as a target.

  Further, in the operation of step S52, the HV-ECU 11 stops the electric load connected to the power supply line of the high-voltage battery 1, but the other control unit mounted on the vehicle stops the electric load. It doesn't matter. Moreover, although the example which the some control part which makes HV-ECU11, the microcomputer 53, and EPS-ECU6 an example operate | moves was shown in the above-mentioned description, you may operate | move by another aspect. For example, any one control unit of the HV-ECU 11, the microcomputer 53, and the EPS-ECU 6 may perform the operations of the HV-ECU 11, the microcomputer 53, and the EPS-ECU 6 described above. In addition, a single control unit different from the HV-ECU 11, the microcomputer 53, and the EPS-ECU 6 may perform the operations of the HV-ECU 11, the microcomputer 53, and the EPS-ECU 6 described above. In this case, the single control unit may be provided inside the DC-DC converter 5 or may be provided outside the DC-DC converter 5. Further, other control units already installed in the vehicle may perform the operations of the above-described HV-ECU 11, microcomputer 53, and EPS-ECU 6.

  Further, the above-described determination time and the like are merely examples, and it goes without saying that the present invention can be realized with other values and determination times.

  Moreover, although the example installed in the vehicle carrying a hybrid system was used in the description mentioned above, you may install in vehicles, such as an electric vehicle.

  Although the present invention has been described in detail above, the above description is merely illustrative of the present invention in all respects and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

  The power supply control device and the power supply control method according to the present invention can improve the startability of a hybrid system or the like when the ignition switch is turned off from on in a system that supplies power to an electric load from a plurality of batteries or the like. The present invention can be applied to a system that supplies electric power from a plurality of batteries to an electric load.

1 is a schematic configuration diagram showing a partial configuration of a power supply system including a power supply control device according to an embodiment of the present invention. The flowchart which shows an example of operation | movement of HV-ECU11 of FIG. A flowchart showing an example of the operation of the microcomputer 53 of FIG. Timing chart of power supply control in the power supply system of FIG. Timing chart of power supply control in a conventional power supply system

Explanation of symbols

1 ... High voltage battery 2 ... SMR
3 ... Inverter 4 ... Air conditioner 5 ... DC-DC converter 6 ... EPS-ECU
DESCRIPTION OF SYMBOLS 7 ... Electric motor 8 ... Low voltage battery 9, 51 ... Step-down circuit 10 ... Ignition switch 11 ... HV-ECU
52 ... Booster circuit 53 ... Microcomputer

Claims (8)

A power supply control device for supplying power to an electric load of a vehicle,
A step-down circuit that steps down power supplied from a high-voltage battery to a predetermined voltage and supplies the electric load;
A step-up circuit that boosts power supplied from a low-voltage battery to the predetermined voltage and supplies the electric load;
An ignition switch state detecting means for detecting an on / off state of the ignition switch of the vehicle;
A control unit for controlling operations of the step-down circuit and the step-up circuit,
The control unit, when the ignition switch state detection means detects that the ignition switch has been switched from on to off, starts the boost operation of the boost circuit and stops the step-down operation of the step-down circuit apparatus. An energization control unit that performs energization control of electric power supplied from the step-down circuit or the step-up circuit to the electric load;
2. The energization control unit performs energization control by gradually decreasing the amount of current to the electric load from a detection time point when the ignition switch state detection unit detects that the ignition switch has been switched from on to off. The power supply control device described in 1. At least one of the electric loads to which the power supply control device supplies electric power is an electric power steering device that applies an assisting force to a rotation operation of the steering wheel of the vehicle,
The power supply control device according to claim 2, wherein the energization control unit performs energization control by gradually decreasing a current amount to the electric power steering device so that the assist force of the electric power steering device gradually decreases from the detection time point.   3. The power supply control device according to claim 2, wherein the control unit starts a boosting operation of the boosting circuit at the detection time point, and stops the step-down operation of the step-down circuit after a first time has elapsed from the detection time point. The energization control unit gradually reduces the amount of current to the electric load to 0 after a predetermined time has elapsed from the detection time point,
The power supply control device according to claim 4, wherein the control unit stops the boosting operation of the booster circuit after a second time period equal to or longer than the predetermined time from the detection time point. The control unit further controls the operation of a relay for connecting / disconnecting a contact provided on a power supply line between the high-voltage battery and the step-down circuit,
The power supply control device according to claim 4, wherein the control unit cuts off the relay and disconnects the contact after a third time longer than the first time from the detection time point.   The power supply control device according to claim 1, wherein at least one of the electric loads to which the power supply control device supplies electric power is an electric power steering device of the vehicle. A power supply control method for supplying electric power to an electric load of a vehicle,
A step-down step of stepping down high-voltage power to a predetermined voltage and supplying the electric load to the electric load;
A step of boosting low-voltage power to the predetermined voltage and supplying it to the electrical load;
An ignition switch state detecting step for detecting an on / off state of an ignition switch of the vehicle,
In the boosting step, when the ignition switch state detecting step detects that the ignition switch has been switched from on to off, the boosting operation is started,
In the step-down step, the step-down operation is stopped after the step-up step starts the step-up operation.

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