Protection circuit for in-vehicle battery

A protection circuit of an in-vehicle battery has a detection unit that detects at least the temperature of the in-vehicle battery, and a control unit that controls a first relay and a second relay. The control unit performs a first switching control when either the temperature or the output current of the in-vehicle battery detected by the detection unit is in a first abnormality range in a case where the first relay is on and the second relay is off, and performs a second switching control when the temperature of the in-vehicle battery detected by the detection unit is within the first abnormality range or within the second abnormality range after the first switching control.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage of PCT/JP2018/005117 filed on Feb. 14, 2018, which claims priority of Japanese Patent Application No. JP 2017-042971 filed on Mar. 7, 2017, the contents of which are incorporated herein.

TECHNICAL FIELD

The present disclosure relates to a protection circuit for an in-vehicle battery.

BACKGROUND

Battery protection circuits that protect chargeable batteries from overcurrent, over-discharging, over-charging, and the like are conventionally known. For example, JP 2006-136061A discloses an overcurrent protection device with the aim of protecting a secondary battery from overcurrent caused by short circuiting of the load of the secondary battery, and provided between the secondary battery and output terminals of the secondary battery is an overcurrent detection means for detecting overcurrent and a field effect transistor for controlling discharging, which switches off when overcurrent occurs. If this overcurrent detection means detects an overcurrent state in the secondary battery, then the overcurrent protection device protects the secondary battery by causing the field effect transistor for controlling discharge to switch off, thus disconnecting the load and the like from the secondary battery.

However, the overcurrent protection device disclosed in JP 2006-136061A is configured to detect overcurrent in conduction paths between the secondary battery and the output terminals thereof, and therefore it is possible to detect an overcurrent state of an output current that arises from a short circuit or the like occurring in an external circuit, but it is difficult to detect an overcurrent state caused by an abnormality in the secondary battery itself. For example, if metal deposits (dentride) form in an electrode of a battery cell due to the secondary battery being repeatedly charged and discharged and an internal short circuit occurs in the battery cell due to the deposits passing through a separator, or if an internal short circuit occurs in the battery cell due to a foreign body entering into the battery cell, a conventional overcurrent protection circuit such as that disclosed in JP 2006-136061A cannot detect abnormalities, and thus cannot adequately perform a protective operation.

The present disclosure was made based on the circumstances described above, and an object thereof is to provide a protection circuit for an in-vehicle battery that can detect internal short circuits that occur in the in-vehicle battery itself, and can perform a protective operation if an internal short circuit occurs.

SUMMARY

A protection circuit for an in-vehicle battery according to the present disclosure, includes a first relay that is positioned on a first conduction path that is a path for supplying power from the in-vehicle battery to an external circuit, the first relay being configured to switch on or off the supply of power from the in-vehicle battery to the external circuit. A discharge circuit includes a second relay and a resistor unit that are connected in series on a path that is different from the first conduction path, the discharge circuit is configured to allow current from the in-vehicle battery to flow via the resistor unit when the second relay is in an on state. A detection unit is configured to detect at least one of a temperature of the in-vehicle battery and an output current from the in-vehicle battery. A control unit is configured to, when at least one of the temperature and the output current detected by the detection unit is within a first abnormality range in a case where the first relay is in the on state and the second relay is in an off state, perform a first switching control for switching the first relay to the off state while keeping the second relay in the off state, and, when the temperature of the in-vehicle battery detected by the detection unit is within the first abnormality range or a second abnormality range after the first switching control, perform a second switching control for switching the second relay to the on state while keeping the first relay in the off state.

Advantageous Effects of Disclosure

The protection circuit for the in-vehicle battery of the present disclosure performs the first switching control if at least one of the temperature or the output current detected by the detection unit is within the first abnormality range while the first relay is on and the second relay is off, and switches the first relay off while keeping the second relay switched off. In other words, if the temperature or output current of the in-vehicle battery is abnormal when the supply of current via the second relay is stopped and current is supplied via the first relay, it is possible to stop the supply of current by switching off both the first relay and the second relay. At this time, the in-vehicle battery and the external circuit are electrically disconnected, and therefore if the abnormality of the output current arises from an abnormality in the external circuit, then there is a higher likelihood that the abnormal state will be resolved. Furthermore, if the abnormal temperature is not resolved even after both the first relay and the second relay are switched off in this way, the second relay can be switched on with a second switching control and current can thus flow from the in-vehicle battery via the second relay and a resistor unit. If the abnormal temperature cannot be resolved even after both the first relay and the second relay are switched off, there is a high likelihood that an internal short circuit has occurred in the battery, and in such a case, electrical energy stored in the in-vehicle battery can be released, and thus it is possible to protect the in-vehicle battery from generated heat.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following describes preferable examples of the disclosure.

A detection unit in a protection circuit of an in-vehicle battery may also include a current detection unit that detects the output current from the in-vehicle battery, and a temperature detection unit that detects the temperature of the in-vehicle battery. The control unit may also operate so as to perform a first switching control when the output current of the in-vehicle battery detected by the current detection unit is within a first abnormality range when the first relay is on and the second relay is off, and perform a second switching control when the temperature of the in-vehicle battery detected by the temperature detection unit is within a second abnormality range after the first switching control.

In this way, by monitoring the output current with the current detection unit and switching the first relay off with the first switching control if the output current is abnormal, it is possible to promptly detect an abnormal state if there is a rise in the output current caused by a short circuit in an external circuit, a short circuit in the battery, or the like, and thus it is more likely that a protective operation will be performed at an earlier stage. On the other hand, if an abnormal temperature occurs even after the first relay is switched off when the output current is abnormal, it is possible to switch the second relay on with the second switching control and thus suppress the generation of heat in the battery by forcing energy to be consumed outside of the battery.

In the protection circuit of the in-vehicle battery, the detection unit may also include a temperature detection unit that detects the temperature of the in-vehicle battery. The control unit may also operate so as to perform a first switching control when the temperature of the in-vehicle battery detected by the temperature detection unit is within a first abnormality range when the first relay is on and the second relay is off, and perform the second switching control when the temperature of the in-vehicle battery detected by the temperature detection unit is within a first abnormality range or a second abnormality range after the first switching control.

In this way, by monitoring the temperature of the in-vehicle battery and switching the first relay off with the first switching control when the temperature is abnormal, it is possible to more promptly detect the state of heat in the battery, and thus it is more likely that a protective operation will be performed at an earlier stage. In particular, there is a high likelihood that an internal short circuit will be detected even if the output current does not fluctuate or if the amount of fluctuation thereof is small.

The protection circuit of the in-vehicle battery may be configured such that a first abnormality range is greater than or equal to a predetermined first temperature, and the a second abnormality range is greater than or equal to a second temperature that is greater than the first temperature.

Thus, it is possible to more reliably detect that an abnormal temperature has not been resolved when the first relay is off, allow discharge current to flow in a state in which there is a high likelihood that an internal short circuit has occurred, and thus protect the in-vehicle battery.

First Embodiment

The following is a description of the first embodiment for realizing the present disclosure.

An in-vehicle battery system1shown inFIG. 1includes an in-vehicle battery2in which a plurality of unit batteries3are connected in series, and a protection circuit10for an in-vehicle battery (hereinafter also referred to as the protection circuit10).

The in-vehicle battery2is configured as a battery module in which the plurality of unit batteries3(battery cells) are connected in series, is a power storage means that can function as an in-vehicle power source, and is installed in a vehicle as a power source of a drive motor of an electric car (such as an EV or an HEV) for example. This in-vehicle battery2is configured as, for example, a series connection body in which the plurality of unit batteries3, which are composed of lithium-ion secondary batteries, nickel-hydrogen secondary batteries, or the like, are connected in series. Also, the in-vehicle battery2is connected to an external circuit90, such as a charging/discharging circuit or an electrical load, via a first conduction path11and thus supplies power to the external circuit90via the first conduction path11. Note that some of the unit batteries3are omitted fromFIG. 1, and the signal lines corresponding to the omitted unit batteries3are also omitted.

The external circuit90is supplied with power from the in-vehicle battery2via the first conduction path11, and it is sufficient that the external circuit90is a circuit that can supply the power supplied from the in-vehicle battery2via the first conduction path11to various electrical components (various in-vehicle electronic components such as an ECU, an actuator, or a sensor), and is not limited to any particular type of circuit, any specific configuration, or the like.

The in-vehicle battery2shown inFIG. 1has a high voltage electrode unit2A (hereinafter also referred to as electrode unit2A) that is an end electrode unit on the high voltage side (high potential side) of a connection body in which the unit batteries3are connected in series. A low voltage electrode unit2B (hereinafter also referred to as electrode unit2B) is an end electrode unit on the low voltage side (low potential side) of the connection body in which the unit batteries3are connected in series. Inter-battery electrode units2C (hereinafter also referred to as electrode units2C) are electrode units that are between the unit batteries of the connection body in which the unit batteries3are connected in series.

The protection circuit10includes a signal line group12, a shunt resistor13, a temperature sensor14, a first relay15, a monitoring circuit unit20, a discharge circuit30, and the like.

The signal line group12includes a plurality of voltage signal lines12A, a voltage signal line12B, and a voltage signal line12C. The plurality of voltage signal lines12A are electrically connected to the electrode units2A and2C of the in-vehicle battery2. The voltage signal line12B is electrically connected to the electrode unit2B of the in-vehicle battery2and one end of the shunt resistor13. The voltage signal line12C is electrically connected to the other end of the shunt resistor13.

The shunt resistor13is connected in series to the in-vehicle battery2. Specifically, one end of the shunt resistor13is connected to the low voltage electrode unit2B of the in-vehicle battery2and to the voltage signal line12B, and the other end of the shunt resistor13is connected to the voltage signal line12C and to ground. Also, an analogue voltage signal is input to each of input terminals22and23, the analogue voltage signal indicating the voltage of the connection position of voltage signal lines12B and12C in the in-vehicle battery2.

The temperature sensor14is a known temperature sensor such as a thermistor, and is configured to detect voltage values that indicate the temperature of the position at which the temperature sensor14is arranged and output the detected voltage values to the later-described monitoring circuit unit20. The temperature sensor14is fixed in such a manner that the temperature sensor14comes into contact with a surface portion of the in-vehicle battery2and outputs a value indicating the temperature (external surface temperature) of the surface portion of the in-vehicle battery2as a detection value. Note that the temperature sensor14may also be arranged in the vicinity of the in-vehicle battery2without being in contact with the in-vehicle battery2.

The monitoring circuit unit20is an integrated circuit (monitoring IC) that protects the in-vehicle battery2. For example, the monitoring circuit unit20includes a microcomputer that has a CPU, and the CPU includes a ROM for storing information such as a program, a RAM for storing temporarily generated information, and the like.

The monitoring circuit unit20(specifically, a control unit42of the monitoring circuit unit20) monitors the temperature, output voltage, output current, and the like of the in-vehicle battery2. For example, the monitoring circuit unit20acquires a detection value (a value indicating the temperature (external surface temperature) of a surface portion of the in-vehicle battery2) that is output by the temperature sensor14. Also, the monitoring circuit unit20detects at least one of input voltages that are input via each of the voltage signal lines12A and the voltages between signal lines in the plurality of voltage signal lines12A. Specifically, the monitoring circuit unit20includes a plurality of input terminals21to which the plurality of voltage signal lines12A are connected, analogue voltage signals are input to the input terminals21, the analogue voltage signals indicating the voltages (potentials) of the connection positions of the voltage signal lines12A in the in-vehicle battery2. Thus it is possible to detect the terminal voltages of the unit batteries3by detecting the potential difference between the voltage signal lines12A based on these analogue voltage signals.

Also, the monitoring circuit unit20detects the potential different (the voltages at both ends) of both ends of the shunt resistor13. Specifically, the voltage signal line12B is connected to one end of the shunt resistor13and the voltage signal line12C is connected to the other end of the shunt resistor13, and the monitoring circuit unit20detects the potential difference (the voltage at both ends) of both ends of the shunt resistor13based on both analogue voltage signals input via the voltage signal lines12B and12C, and calculates the value of the current (the value of the output current) that flows through the shunt resistor13, the calculation being based on the detected voltages at both ends of the shunt resistor13and a predetermined resistance value of the shunt resistor13.

The first conduction path11is a path for supplying power from the in-vehicle battery2to the external circuit90, and is a power path for transmitting power that is output from the in-vehicle battery2. The first relay15is a relay for switching on and off the supply of power from the in-vehicle battery2to the external circuit90. The first relay (protection relay)15may be, for example, a known mechanical relay, is provided on the first conduction path11, and switches the first conduction path11on or off based on a control signal from the monitoring circuit unit20. The first relay15switches on when given an on signal from the monitoring circuit unit20(specifically, the control unit42), and current is applied to the first conduction path11when the first relay15is ON. Accordingly, when the first relay15is ON, power can be supplied from the in-vehicle battery2to the external circuit90via the first conduction path11. The first relay15switches off when given an off signal from the monitoring circuit unit20(specifically, the control unit42), and no current is applied to the first conduction path11when the first relay15is off. Accordingly, when the first relay15is off, the supply of power from the in-vehicle battery2to the external circuit90is cut off.

The discharge circuit30includes a second relay33and a resistor unit32that are connected in series on a path that is different from the first conduction path11, and is configured such that current from the in-vehicle battery2is allowed to flow via the resistor unit32when the second relay33is ON, and functions so as to consume power that is output from the in-vehicle battery2. The discharge circuit30includes a second conduction path31that has one end electrically connected to the electrode unit2A of the in-vehicle battery2and to the first conduction path11, and another end electrically connected to the other end of the shunt resistor13and to ground, with the second relay33and the resistor unit32being provided on the second conduction path31. The resistor unit32is a known resistor and functions so as to restrict current that flows from the in-vehicle battery2via the second conduction path31when the discharge circuit30is undertaking a discharging operation.

The second relay (discharge relay)33is a relay for switching on and off the supply of power from the in-vehicle battery2to the resistor unit32. The second relay (discharge relay)33may be, for example, a known mechanical relay, is provided on the second conduction path31, and switches the second conduction path31on or off based on a control signal from the monitoring circuit unit20. The second relay33switches on when given an on signal from the monitoring circuit unit20, and current is applied to the second conduction path31when the second relay33is ON. Accordingly, when the second relay33is ON, power can be supplied from the in-vehicle battery2to the resistor unit32via the second conduction path31, and energy can be consumed by the resistor unit32. The second relay33switches off when given an off signal from the monitoring circuit unit20, and no current is supplied to second conduction path31when the second relay33is off. Accordingly, when the second relay33is off, the supply of power from the in-vehicle battery2to the resistor unit32is cut off.

A detection unit41shown inFIG. 1functions so as to detect the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2. The detection unit41includes a current detection unit41A and a temperature detection unit41B.

The current detection unit41A includes the shunt resistor13and the voltage signal lines12B and12C, and functions so as to generate a value that specifies the output current output from the in-vehicle battery2as a detection value. Specifically, the voltages of both ends of the shunt resistor13(the voltages applied to the voltage signal lines12B and12C) are “values that specify the output current output from the in-vehicle battery2”, and the potential difference between both ends of the shunt resistor13is generated as “the detection value for specifying the output current”. The monitoring circuit unit20keeps track of a current value I1 (output current value) of the current that flows through the shunt resistor13based on the potential difference between both ends of the shunt resistor13and the predetermined resistance value of the shunt resistor13.

The temperature detection unit41B is a known temperature sensor and functions so as to detect the temperature of the in-vehicle battery2. The temperature detection unit41B generates an analogue voltage signal that indicates the temperature (for example, the temperature of a surface portion of the in-vehicle battery2) of the location in which the temperature detection unit41B installed, and gives the generated analogue voltage signal to the monitoring circuit unit20. The monitoring circuit unit20keeps track of a temperature T of the in-vehicle battery2based on a detection value (the analogue voltage signal generated by the temperature detection unit41B) of the temperature detection unit41B.

Note that configurations described herein are merely examples in all respects, and may be replaced with other configurations, as long as they are configurations according to which the output current of the in-vehicle battery2can be detected, or configurations according to which the temperature of the in-vehicle battery2(for example, the temperature of a surface portion, the temperature of an internal portion, the temperature of an internal portion, the temperature in the vicinity thereof, or the like) can be detected.

Next, functions that are executed by the monitoring circuit unit20will be described in detail.

As shown inFIG. 1, the monitoring circuit unit20includes the control unit42. Functions executed by the control unit42may also be realized by software processing with use of an information processing device, and may also be realized by a hardware circuit. Furthermore, the functions may also be realized by separate devices, and a plurality of functions may also be realized by a common device. The following is a description of a representative example in which the control unit42is realized by an information processing device such as a microcomputer.

If the output current of the in-vehicle battery2detected by the detection unit41, is within a first abnormality range when the first relay15is off and the second relay33is ON, the control unit42shown inFIG. 1performs control (first switching control) for switching the first relay15off while keeping the second relay33switched off. Note that in the following description, a case in which output current value of the in-vehicle battery2detected by the current detection unit41A is greater than or equal to a predetermined first current value Ith1 is described as a case in which “the output current of the in-vehicle battery2is within the first abnormality range”. In other words, in the following representative example, an output current range in which the current value I1 (the value of the current that flows through the shunt resistor13), which is specified by the detection value generated by the current detection unit41A, is greater than or equal to the first current value Ith1 will be the “first abnormality range”. Also, when the temperature of the in-vehicle battery2detected by the detection unit41is within the second abnormality range after the first switching control is performed in this manner, the control unit42performs control (second switching control) for switching the second relay33on while keeping the first relay15switched off. Note that in the following description, the range in which the temperature of the in-vehicle battery2detected by the detection unit41is greater than or equal to a predetermined second temperature T2is the “second abnormality range”. Specifically, a range in which the temperature T, which is specified by the detection value generated by the temperature detection unit41B, is greater than or equal to the second temperature T2is the “second abnormality range”.

Next, the manner in which the functions of the aforementioned monitoring circuit unit20are realized will be described with reference to the flowchart shown inFIG. 2. The control unit42of the monitoring circuit unit20is configured to execute the control shown inFIG. 2when a predetermined start condition is satisfied, or more specifically, the control shown inFIG. 2is executed when the vehicle is in a predetermined operating state (for example, when the ignition switch of the vehicle is switched from off to ON).

After the control inFIG. 2starts, the control unit42first performs the processing of step S10, in which the first relay15is switched on and the second relay33is switched off. Thus, power can be supplied from the in-vehicle battery2to the external circuit via the first conduction path11because the first relay15is ON, and current does not flow from the in-vehicle battery2to the resistor unit32because the second relay33is off.

After step S10, the control unit42acquires the current value of the output current that is output from the in-vehicle battery2(step S11). Specifically, the current value I1 of the current that flows through the shunt resistor13is specified based on a detection value (the voltage at both ends of the shunt resistor13) that is generated by the current detection unit41A, and this current value I1 is used as an output current value.

Next, the control unit42determines whether or not the current value I1 (the output current value from the in-vehicle battery2) acquired in step S11is within the first abnormality range (S12). Specifically, in step S12, it is determined whether or not the current value I1 of the current that flows through the shunt resistor13is greater than or equal to the first current value Ith1, and if it is determined that the current value I1 is not greater than or equal to the first current value Ith1 (No in step S12), then the processing of S11is performed again and the processing of S11and S12is repeated until it is determined that the current value I1 is greater than or equal to the first current value Ith1.

On the other hand, if it is determined in step S12that the current value I1 is greater than or equal to the first current value Ith1 (Yes in S12), the control unit42performs the processing of step S13and switches the first relay15from on to off while keeping the second relay switched off. The processing (control) of step S13that is executed by the control unit42is equivalent to an example of the “first switching control”. When the first relay15is switched off by the control unit42performing the processing of step S13, current stops being supplied to the first conduction path11and thus the supply of power (the supply of power from the in-vehicle battery2to the external circuit90) via the first conduction path11stops. In this way, the supply of power from the in-vehicle battery2to the external circuit90is cut off and the in-vehicle battery2and the external circuit90are electrically disconnected, and therefore, if the previously described overcurrent state (an overcurrent state in which the current value I1 is greater than or equal to the first current value Ith1) is caused by the external circuit90, this overcurrent state can be resolved.

After step S13, the control unit42confirms the detection values of the temperature detection unit41B in step S14and acquires the temperature of the in-vehicle battery2. In other words, the control unit42acquires the temperature of the in-vehicle battery2when both the first relay15and the second relay33are off. Note that the processing of step S14may also be executed immediately after step S13, and may also be executed after a predetermined amount of time has passed after step S13.

Next, the control unit42determines whether or not the temperature of the in-vehicle battery2acquired in step S14is within the second abnormality range (step S15). The “second abnormality range” is a temperature range that is set in advance by the control unit42, more specifically, a temperature range of being greater than or equal to a predetermined second temperature T2is used as the “second abnormality range”. In step15, the control unit42determines whether or not the temperature T of the in-vehicle battery2detected by the temperature detection unit41B is greater than or equal to the second temperature T2, and if it is determined that the temperature T of the in-vehicle battery2is not greater than or equal to the second temperature T2(that is, the temperature is not within the second abnormality range) (No in step S15), then the processing ofFIG. 2ends. For example, if the output of overcurrent from the in-vehicle battery2is suppressed by the processing of step S13(processing for switching the first relay15off), the generation of heat in the in-vehicle battery2is suppressed, and thus the temperature no longer rises, there is a high likelihood that temperature of the in-vehicle battery2is suppressed so as to be less than the second temperature T2, and in this case processing proceeds to ‘No’ in step S15. Note that if processing proceeds to ‘No’ in step S15, then predetermined first notification processing (a notification that there is an abnormality in the external circuit) may also be performed.

On the other hand, if it is determined in step S15that the temperature T of the in-vehicle battery2is greater than or equal to the second temperature T2(that is, the temperature of the in-vehicle battery2is within the second abnormality range) (Yes in step S15), the control unit42performs the processing of step S16and switches the second relay33on while keeping the first relay15switched off. The processing (control) of step S16that is executed by the control unit42is equivalent to an example of the “second switching control”. With the on operation of the second relay33, energy stored inside the in-vehicle battery2is released to an external component. Note that if the processing of step S16is executed, predetermined second notification processing (a notification that there is an abnormality in the in-vehicle battery2) may also be performed.

For example, as shown inFIG. 4(A), if an internal short circuit occurs in at least one unit battery3of the in-vehicle battery2, there is a high likelihood that the temperature of the in-vehicle battery2will rise due to the occurrence of internal current arising from the internal short circuit. As shown inFIG. 3, if such an abnormality occurs, an overcurrent is detected at a time t1and the temperature T of the in-vehicle battery2rises even after the first relay15is switched off at a time t2. With the present configuration, if the temperature T of the in-vehicle battery2does not fall after the first relay15is switched off, and the temperature T exceeds the second temperature T2in this manner, the second relay33is switched on in step S16and, as shown inFIG. 4(B), discharge current flows from the in-vehicle battery2via the second conduction path31. With this operation, energy from the in-vehicle battery2is consumed by the resistor unit32and therefore it is possible to suppress the generation of heat in the in-vehicle battery2.

Note that if a predetermined ending condition is satisfied while the control ofFIG. 2is being executed (for example, if the ignition switch of the vehicle is switched from on to off), then the control ofFIG. 2may also be ended.

Next, effects of the aforementioned configuration will be described.

In the protection circuit10, the control unit42performs the first switching control when the output current detected by the detection unit41is within the first abnormality range when the first relay15is on and the second relay33is off, and switches the first relay15off while keeping the second relay33switched off. In other words, if the output current of the in-vehicle battery2is abnormal when the supply of current via the second relay33has stopped and current is supplied via the first relay15, it is possible to stop the supply of current by switching off both the first relay15and the second relay33. At this time, the in-vehicle battery2and the external circuit90are electrically disconnected, and therefore if the abnormality of the output current is caused by the external circuit90, then there is a higher likelihood that the abnormal state will be resolved. Furthermore, if the abnormal temperature is not be resolved even after both the first relay15and the second relay33are switched off in this manner, the control unit42performs the second switching control, the second relay33is switched ON, and current can flow from the in-vehicle battery2via the second relay33and the resistor unit32. If the abnormal temperature is not be resolved even after both the first relay15and the second relay33are switched off, there is a high likelihood that an internal short circuit has occurred in the battery, and in such a case, electrical energy stored in the in-vehicle battery2can be released and thus it is possible to protect the in-vehicle battery2from over-heating.

The detection unit41in the protection circuit10includes the current detection unit41A that detects the output current from the in-vehicle battery2, and the temperature detection unit42B that detects the temperature of the in-vehicle battery2. The control unit42performs the first switching control when the value I1 of the output current of the in-vehicle battery2detected by the current detection unit41A is within the first abnormality range when the first relay15is on and the second relay33is off, and performs the second switching control if, after the first second switching control, the temperature T of the in-vehicle battery2detected by the temperature detection unit41B is within the second abnormality range.

In this manner, monitoring the output current with the current detection unit41A and switching the first relay15off when the output current is abnormal, it is possible to promptly detect an abnormal state if there is a rise in the output current caused by a short circuit in the external circuit90, an internal short circuit in a battery, or the like, and thus it is more likely that a protective operation will be performed at an earlier stage. On the other hand, if an abnormal temperature occurs even after the first relay15is switched off when the output current is abnormal, current can be forcefully discharged by switching the second relay33ON, thus making it possible to suppress the generation of heat in the battery by forcing energy to be consumed outside of the battery.

Second Embodiment

Next, a second embodiment will be described.

The in-vehicle battery system1of the second embodiment has the same hardware configuration as the in-vehicle battery system1of the first embodiment shown inFIG. 1. Accordingly, the following description is in reference toFIG. 1. The in-vehicle battery system1of the second embodiment is different only in that the control ofFIG. 2is changed to that ofFIG. 5, and that the control ofFIG. 5is different fromFIG. 2only in that the control ofFIG. 5uses steps S21and S22instead of steps S11and S12. In the following, detailed descriptions of the configuration and control that are the same as those of the first embodiment shall be omitted, with the description focusing on the differences from the first embodiment.

The protection circuit10(FIG. 1) of the second embodiment includes a monitoring circuit unit20(FIG. 1) that is similar to that of first embodiment, and the monitoring circuit unit20includes a control unit42that is similar to that of the first embodiment. Functions executed by the control unit42may also be realized by software processing with use of an information processing device, and may also be realized by a hardware circuit. Furthermore, the functions may also be realized by separate devices, and a plurality of functions may also be realized by a common devices. The following is a description of a representative example in which the control unit42is realized by an information processing device such as a microcomputer.

With the protection circuit10of the second embodiment as well, when the temperature of the in-vehicle battery2detected by the detection unit41is within a first abnormality range when the first relay15is on and the second relay33is off, then the control unit42functions so as to switch the first relay15off. Note that in the following description, a case in which the temperature T of the in-vehicle battery2detected by the temperature detection unit41B is greater than or equal to a predetermined first temperature T1will be described as a case in which “the temperature T of the in-vehicle battery2is within the first abnormality range”. In other words, in the following representative example, the temperature range in which the temperature T, which is specified by the detection value generated by the temperature detection unit41B, is greater than or equal to the first temperature T1is the “first abnormality range”.

Also, when the temperature T of the in-vehicle battery2detected by the detection unit41is within the second abnormality range after the first relay15is switched off, the control unit42functions so as to switch the second relay33on while keeping the first relay15switched off. Note that in the following description, the range in which the temperature T of the in-vehicle battery2detected by the detection unit41is greater than or equal to the predetermined second temperature T2is the “second abnormality range”. Specifically, a range in which the temperature T, which is specified by the detection value that is generated by the temperature detection unit41B, is greater than or equal to the second temperature T2(provided T2>T1) is the “second abnormality range”. In this way, the first abnormality range is a range of being greater than or equal to a predetermined first temperature T1, and the second abnormality range is a range of being greater than or equal to the second temperature T2, which is greater than the first temperature T1.

Next, the manner in which the functions of the aforementioned monitoring circuit unit20are realized will be described with reference to the flowchart shown inFIG. 5. The control unit42of the monitoring circuit unit20is configured to execute the control shown inFIG. 5when a predetermined start condition is satisfied, or more specifically, the control shown inFIG. 5is executed when the vehicle is in a predetermined operating state (for example, when the ignition of the vehicle is switched from off to ON).

After the control inFIG. 5starts, the control unit42first performs step S20, in which the first relay15is switched on and the second relay33is switched off. Thus, power can be supplied from the in-vehicle battery2to the external circuit via the first conduction path11because the first relay15is ON, and current does not flow from the in-vehicle battery2to the resistor unit32because the second relay33is off.

After step S20, the control unit42confirms the detection values of the temperature detection unit41B in step S21and acquires the temperature T of the in-vehicle battery2. In other words, the control unit42acquires the temperature of the in-vehicle battery2when the first relay15is on and the second relay33is off. Then, after step S21, the control unit42determines whether or not the temperature T (the temperature of the in-vehicle battery2) acquired in step S21is within the first abnormality range (S22). The “first abnormality range” is a temperature range that is set in advance by the control unit42, or more specifically, a temperature range of being greater than or equal to the predetermined first temperature T1is used as the “first abnormality range”. In step S22, the control unit42determines whether or not the temperature T of the in-vehicle battery2detected by the temperature detection unit41B is greater than or equal to the first temperature T1, and if it is determined that the temperature T of the in-vehicle battery2is not greater than or equal to the first temperature T1(that is, the temperature T of the in-vehicle battery2is not within the first abnormality range) (No in step S22), then the processing of step S21is performed again and the processing of steps S21and S22is repeated until it is determined that the temperature T is greater than or equal to the first temperature T1.

On the other hand, if it is determined that the temperature T of the in-vehicle battery2is greater than or equal to the first temperature T1(that is, the temperature T of the in-vehicle battery2is within the first abnormality range) (Yes in step S22), then the control unit42performs the processing of step S23, and switches off the first relay15while keeping the second relay switched off. The processing (control) of step S23is executed by the control unit42is equivalent to an example of the “first switching control”. When the control unit42switches the first relay15off, current stops being applied to the first conduction path11and thus the supply of power (the supply of power from the in-vehicle battery2to the external circuit90) via the first conduction path11stops. In this way, the supply of power from the in-vehicle battery2to the external circuit90is cut off and the in-vehicle battery2and the external circuit90are electrically disconnected, and therefore, if that previously-described excessive temperature rise (an excessive temperature rise in which the temperature T of the in-vehicle battery2is greater than or equal to the first temperature T1) is caused by the external circuit90, this excessive temperature rise can be resolved.

After step S23, the control unit42confirms the detection values of the temperature detection unit41B in step S24and acquires the temperature of the in-vehicle battery2. In other words, the control unit42acquires the temperature of the in-vehicle battery2when both of the first relay15and the second relay33are off. Note that the processing in step S24may also be executed immediately after step S23, and may also be executed after a predetermined amount of time has passed after step S23.

Next, the control unit42determines whether or not the temperature of the in-vehicle battery2acquired in step S24is within the second abnormality range (step S25). The “second abnormality range” is a temperature range that is set in advance by the control unit42, or more specifically, a temperature range of being greater than or equal to a predetermined second temperature T2(T2>T1) is used as the “second abnormality range”. In step S25, the control unit42determines whether or not the temperature T of the in-vehicle battery2detected by the temperature detection unit41B is greater than or equal to the second temperature T2, and if it is determined that the temperature T of the in-vehicle battery2is not greater than or equal to the second temperature T2(that is, the temperature is not within the second abnormality range) (No in step S25), then the processing ofFIG. 5ends. For example, if the output of overcurrent from the in-vehicle battery2is suppressed by the processing of step S23(processing for switching the first relay15off), the generation of heat in the in-vehicle battery2is suppressed and the temperature no longer rises, then there is a high likelihood that the temperature of the in-vehicle battery2is suppressed to be less than the second temperature T2and in this case processing proceeds to ‘No’ in step S25. Note that if processing proceeds to ‘No’ in step S25, then predetermined first notification processing (a notification that there is an abnormality in the external circuit) may also be performed.

On the other hand, if it is determined in step S25that the temperature T of the in-vehicle battery2is greater than or equal to the second temperature T2(that is, the temperature of the in-vehicle battery2is within the second abnormality range) (Yes in step S25), the control unit42performs the processing of step S26and switches the second relay33on while keeping the first relay15switched off. The processing (control) of step S26that is executed by the control unit42is equivalent to an example of the “second switching control”. With the on operation of the second relay33, energy stored inside the in-vehicle battery2is released to an external component.

For example, as shown inFIG. 4(A), if an internal short circuit occurs in at least one unit battery3of the in-vehicle battery2, there is a high likelihood that the temperature of the in-vehicle battery2will rise due to the occurrence of internal current caused by the an internal short circuit. As shown inFIG. 6, if such an abnormality occurs, an excessive temperature rise (first temperature rise) is detected at a time t1, and if the temperature T of the in-vehicle battery2continues to rise even after the first relay15is switched off at the time t2, then there is a high likelihood of a further excessive temperature rise (second temperature rise) at a time t3, as shown inFIG. 6. With the present configuration, if the temperature T of the in-vehicle battery2does not fall after the first relay15is switched off, and the temperature T exceeds the second temperature T2, the second relay33is switched on in step S26and, as shown inFIG. 4(B), discharge current flows from the in-vehicle battery2via the second conduction path31. With this operation, energy from the in-vehicle battery2is consumed by the resistor unit32and therefore it is possible to suppress the generation of heat in the in-vehicle battery2.

As described above, the protection circuit10of the present configuration also has fundamental effects similar to those of the first embodiment.

In the protection circuit10of the present configuration, the detection unit41includes a temperature detection unit41B that detects the temperature of the in-vehicle battery2. The control unit42performs the first switching control when the temperature of the in-vehicle battery2detected by the temperature detection unit41B is within the first abnormality range when the first relay15is on and second relay33is off, and performs the second switching control when the temperature of the in-vehicle battery2detected by the temperature detection unit41B is within the second abnormality range after the first switching control.

By monitoring the temperature of the in-vehicle battery2and switching the first relay15off with the first switching control when the temperature is abnormal, it is possible to more promptly detect the state of heat in the battery, and thus it is more likely that the protective operation will be performed at an earlier stage. In particular, there is a high likelihood that an internal short circuit will be detected even if the output current does not fluctuate or if the amount of fluctuation thereof is small.

With the protection circuit10of the present configuration, the first abnormality range is a range of being greater than or equal to a predetermined first temperature T1, and the second abnormality range is a range of being greater than or equal to the second temperature T2, which is greater than the first temperature T1.

By doing so, it is possible to more reliably detect that an abnormal temperature has not been resolved when the first relay15is off, allow discharge current to flow in a state in which there is a high likelihood that an internal short circuit has occurred, and thus the in-vehicle battery2can be protected.

Other Embodiments

The present disclosure is not limited to the embodiments described according to the above description and the drawings, and for example, embodiments such as of the following are also included within the scope of the present embodiment. Also, the previously described embodiments and the embodiments that will be described below can be combined as long as there is no contradiction therein.

With the first and second embodiments, examples were given in which the first relay15and the second relay33of the protection circuit10are constituted by known mechanical relays, but other configurations are also possible. For example, as shown inFIG. 7, a configuration is also possible in which the first relay115and the second relay133are constituted by switching elements. Note that the example inFIG. 7can be similar to the first and second embodiments except that the first relay15is changed to a first relay115and the second relay33is changed to a second relay133. Specifically, the first relay115includes a switching element115A that is constituted by an n-channel MOSFET and a switching element115B that is constituted by an n-channel MOSFET, which are connected in series with their drains connected to each other. The first relay115is switched on and off by a signal being output from the monitoring circuit unit20to the gates of the first relay115. When the on signal is given from the monitoring circuit unit20to the first relay115, the switching elements115A and115B are switched on simultaneously, and when the off signal is given from the monitoring circuit unit20to the first relay115, the switching elements115A and115B are switched off simultaneously. In a similar way, the second relay133includes a switching element133A that is constituted by an n-channel MOSFET and a switching element133B that is constituted by an n-channel MOSFET, and the switching element133A and the switching element133B are connected in series with the drains thereof connected to each other. The second relay133is switched on and off by a signal being output from the monitoring circuit unit20to the gates of the second relay133. When the on signal is given from the monitoring circuit unit20to the second relay133, the switching elements133A and133B are switched on simultaneously, and when the off signal is given from the monitoring circuit unit20to the second relay133, the switching elements133A and133B are switched off simultaneously.

The first embodiment shows a configuration in which, in the control of the monitoring circuit unit20shown inFIG. 2, it is determined in the processing of step S12whether or not the current value of the output current from the in-vehicle battery2is within the first abnormality range. However, a configuration is also possible in which it is determined in step S12whether or not at least one of the current value of the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2is within the first abnormality range. That is to say, a configuration is also possible in which the current value of the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2are acquired in S11, and it is determined in S12whether or not at least one of the current value of the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2acquired in S11is within the first abnormality range (whether or not both the current value of the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2is within the first abnormality range). Then, if at least one of the current value of the output current from the in-vehicle battery2and the temperature of the in-vehicle battery2are within the first abnormality range, then processing proceeds to S13. Note that the first abnormality range corresponding to the temperature of the in-vehicle battery2is a range that is envisioned as the temperature of the in-vehicle battery2in an abnormal state of the in-vehicle battery2, in which overcurrent caused by an abnormality in an external circuit that is supplied power from the in-vehicle battery2occurs. Also, a configuration is possible in which the first abnormality range corresponding to the current value of the output current from the in-vehicle battery2and the first abnormality range corresponding to the temperature of the in-vehicle battery2are set so as not to correlate. That is to say, a configuration is also possible in which, when the output current of the in-vehicle battery2reaches the first current value Ith1, the temperature of the in-vehicle battery2does not reach T1.

The second embodiment shows a configuration in which, in the control of the monitoring circuit unit20shown inFIG. 5, the second abnormality range is used in determining whether or not there is an internal short circuit in the in-vehicle battery2in the processing of S25. However, a configuration is also possible in which another range is used in determining whether or not there is an internal short circuit in the in-vehicle battery2. For example, a configuration is also possible in which the first abnormality range is used in determining whether or not there is an internal short circuit in the in-vehicle battery2. For example, a configuration is also possible in which, if the temperature of the in-vehicle battery2is greater than or equal to a predetermined first temperature T1, then the temperature of the in-vehicle battery2is within the second abnormality range.

With the second embodiment, in the control of the monitoring circuit unit20shown inFIG. 5, the second abnormality range, which is used in determining whether or not there is an internal short circuit in the in-vehicle battery2in the processing of S25, need not be a range in which a second temperature is set to be greater than a first temperature. For example, a configuration is also possible in which, as the second abnormality range, the second temperature T2is set to be smaller than the first temperature T1. With this configuration, it is possible to detect an abnormal state in which the temperature of the in-vehicle battery2is below the first temperature T1even if there is an internal short circuit in the in-vehicle battery2. Alternatively, a configuration is also possible in which it is determined in step S25whether or not the temperature of the in-vehicle battery2is within the first abnormality range.

The first embodiment described a case in which, in the control of the monitoring circuit unit20shown inFIG. 5, in the processing of S15, an internal short circuit occurs in the unit battery3on the high potential side that has a high voltage electrode unit2A and is in the in-vehicle battery2, but a case is also conceivable in which an internal short circuit occurs in another unit battery3. For example, a case in which the unit battery3on the low potential side that has a low voltage electrode unit2B and is in the in-vehicle battery2, and a case in which an internal short circuit occurs in a unit battery3on the inner side that constitutes the in-vehicle battery2can also be detected by the processing of S15. Also, a case is envisioned in which an internal short circuit occurs in a plurality of the unit batteries3in the processing of S15.