US-12620823-B2 - Power supply control apparatus and electric discharge method

US12620823B2US 12620823 B2US12620823 B2US 12620823B2US-12620823-B2

Abstract

A power supply control apparatus includes a switching control device configured to switch each of switching elements of a power converter between an on state and an off state alternately, and a discharge control device configured to, when residual charge of the fuel cell is discharged, control a gas supply unit such that oxidant gas is not supplied to the fuel cell, in a first period, control the switching control device such that an on time during which at least one switching element is maintained in the on state is longer than the on time during an operation of the fuel cell and the at least one switching element is switched between the on state and the off state alternately, and, in a second period subsequent to the first period, control the switching control device such that the at least one switching element continues to maintain the on state.

Inventors

Takahiro Umehara
Nobuyuki Kitamura
Kota Manabe

Assignees

TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date: 20260505
Application Date: 20230504
Priority Date: 20220517

Claims (6)

1 . A power supply control apparatus that controls a power supply, the power supply having a fuel cell, a gas supply unit configured to supply oxidant gas to the fuel cell, and a power converter having a plurality of switching elements and configured to convert electric power output from the fuel cell, the power supply control apparatus comprising: a switching control device configured to switch each of the plurality of switching elements between an on state and an off state alternately; and a discharge control device configured to, when residual charge remaining in the fuel cell is being discharged, control the gas supply unit such that the oxidant gas is not supplied to the fuel cell, in a first period, control the switching control device such that an on time that is a time during which at least one switching element of the plurality of switching elements is maintained in the on state is longer than the on time allowed to be taken during an operation of the fuel cell and the at least one switching element is switched between the on state and the off state alternately, and in a second period subsequent to the first period, control the switching control device such that the at least one switching element continues to maintain the on state.
2 . The power supply control apparatus according to claim 1 , wherein the second period is a period during which the residual charge is less than a predetermined value.
3 . The power supply control apparatus according to claim 2 , wherein: the discharge control device is configured to determine whether the residual charge is less than the predetermined value; and the discharge control device is configured to, when the discharge control device determines that the residual charge is less than the predetermined value, control the switching control device such that the at least one switching element continues to maintain the on state.
4 . The power supply control apparatus according to claim 1 , wherein the discharge control device is configured to estimate the residual charge based on an output current of the fuel cell in the first period.
5 . The power supply control apparatus according to claim 1 , wherein the discharge control device is configured to estimate the residual charge based on a voltage of the fuel cell.
6 . An electric discharge method of discharging residual charge remaining in a fuel cell in a power supply, the power supply having the fuel cell, a gas supply unit configured to supply oxidant gas to the fuel cell, a power converter having a plurality of switching elements and configured to convert electric power output from the fuel cell, and a switching control device configured to switch each of the plurality of switching elements between an on state and an off state alternately, the electric discharge method comprising: controlling the gas supply unit such that the oxidant gas is not supplied to the fuel cell; in a first period, controlling the switching control device such that an on time that is a time during which at least one switching element of the plurality of switching elements is maintained in the on state is longer than the on time allowed to be taken during an operation of the fuel cell and the at least one switching element is switched between the on state and the off state alternately; and in a second period subsequent to the first period, controlling the switching control device such that the at least one switching element continues to maintain the on state.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2022-080960 filed on May 17, 2022, incorporated herein by reference in its entirety. BACKGROUND 1. Technical Field The disclosure relates to a technical field of a power supply control apparatus and an electric discharge method in a power supply system including a fuel cell. 2. Description of Related Art As an apparatus of this type, there is suggested, for example, a power supply system including a fuel cell and a power converter configured to convert electric power output from the fuel cell (see Japanese Unexamined Patent Application Publication No. 2011-090823 (JP 2011-090823 A)). In the power supply system, a relay is disposed between the power converter and an inverter configured to supply electric power to a drive motor. SUMMARY For example, a junction box is often provided at a connection point between a power supply system and an electrical circuit for supplying electric power to a drive motor in order to protect the connection point. Terminals corresponding to the connection point are disposed in the junction box. A lid of the junction box can be opened due to, for example, maintenance or the like. At this time, from the viewpoint of preventing an electric shock accident, laws and regulations stipulate that the voltage between the terminals must be decreased to a predetermined voltage or below within a predetermined period of time from when the lid of the junction box is opened. As in the case of the power supply system described in JP 2011-090823 A, in an electrical circuit having a relay, when the relay is set to an off state, the voltage between the terminals is relatively quickly decreased. Incidentally, when, for example, a power supply system is mounted on a vehicle, it is difficult to ensure space for mounting a relay. In addition, when a relay is mounted, a manufacturing cost increases. The disclosure provides a power supply control apparatus and an electric discharge method capable of relatively quickly decreasing the voltage between terminals in a junction box without using a relay. A first aspect of the disclosure relates to a power supply control apparatus that controls a power supply. The power supply has a fuel cell, a gas supply unit configured to supply oxidant gas to the fuel cell, and a power converter having a plurality of switching elements and configured to convert electric power output from the fuel cell. The power supply control apparatus includes a switching control device and a discharge control device. The switching control device is configured to switch each of the plurality of switching elements between an on state and an off state alternately. The discharge control device is configured to, when residual charge remaining in the fuel cell is being discharged, control the gas supply unit such that the oxidant gas is not supplied to the fuel cell, in a first period, control the switching control device such that an on time that is a time during which at least one switching element of the plurality of switching elements is maintained in the on state is longer than the on time allowed to be taken during an operation of the fuel cell and the at least one switching element is switched between the on state and the off state alternately, and, in a second period subsequent to the first period, control the switching control device such that the at least one switching element continues to maintain the on state. In the above aspect, the second period may be a period during which the residual charge is less than a predetermined value. In the above aspect, the discharge control device may be configured to determine whether the residual charge is less than the predetermined value, and the discharge control device may be configured to, when the discharge control device determines that the residual charge is less than the predetermined value, control the switching control device such that the at least one switching element continues to maintain the on state. In the above aspect, the discharge control device may be configured to estimate the residual charge based on an output current of the fuel cell in the first period. In the above aspect, the discharge control device may be configured to estimate the residual charge based on a voltage of the fuel cell. A second aspect of the disclosure relates to an electric discharge method. The electric discharge method is an electric discharge method of discharging residual charge remaining in a fuel cell in a power supply. The power supply has a fuel cell, a gas supply unit configured to supply oxidant gas to the fuel cell, a power converter having a plurality of switching elements and configured to convert electric power output from the fuel cell, and a switching control device configured to switch each of the plurality of switching elements between an on state and an off state alternately. The electric discharge method includes controlling th