JP7735946B2 - Battery unit connection switching device and battery charging system - Google Patents

Description

This disclosure relates to a battery unit connection switching device and a battery charging system.

In order to improve the driving torque of electric vehicles (EVs) and shorten battery charging times, the voltage of EV motor drive batteries is becoming higher. For example, the charging time for a 60 kWh battery is 20 minutes when charged at 400 V and 400 A, but 10 minutes when charged at 800 V and 400 A. However, much of the existing charging infrastructure, such as charging stations, is not compatible with 800 V high-voltage charging.

Patent Documents 1 and 2 disclose a charging device that can switch the connection state of two 400V-class energy storage modules between series and parallel. For example, the charging device disclosed in Patent Document 1 includes one serialization relay RY2 and two parallelization relays RY1 and RY3. The energy storage modules are connected in series by turning on the serialization relay RY2 and turning off the parallelization relays RY1 and RY3, and the energy storage modules are connected in parallel by turning off the serialization relay RY2 and turning on the parallelization relays RY1 and RY3. When charging the energy storage modules with 800V-class charging infrastructure, the energy storage modules are connected in series, and when charging the energy storage modules with 400V-class charging infrastructure, the energy storage modules are connected in parallel. This makes it possible to use both 400V-class and 800V-class charging infrastructure. By connecting the energy storage modules in series when driving a load, it is possible to drive the load at 800V.

International Publication No. 2019/082776 US Patent Publication No. 2019/160953

However, if the relay malfunctions and switches while the storage module is charging, the connection status of the storage module may change, potentially causing damage to the charging infrastructure.

A battery unit connection switching device according to one aspect of the present disclosure includes a connection switching unit that includes a first relay, a second relay, and a third relay, and that connects the first battery unit and the second battery unit in parallel when the first relay and the second relay are in an on state and the third relay is in an off state, and that connects the first battery unit and the second battery unit in series when the first relay and the second relay are in an off state and the third relay is in an on state; a first fuse and a second fuse connected in series to the first relay and the second relay, respectively; a cutoff unit connected in series to the third relay and capable of cutting off current flowing through the third relay; and a detection unit that detects blowing of at least one of the first fuse and the second fuse, and the cutoff unit cuts off current flowing through the third relay when the detection unit detects blowing of at least one of the first fuse and the second fuse.

The present disclosure can be realized not only as a battery unit connection switching device having the above-described characteristic configuration, but also as a battery unit connection switching method in which the characteristic processing steps of the battery unit connection switching device are performed. The present disclosure can be realized as a computer program that causes a computer to function as a battery unit connection switching device, as a semiconductor integrated circuit in part or in whole, or as a battery charging system that includes a battery unit connection switching device.

This disclosure makes it possible to protect the charging infrastructure even if the connection state of the battery unit changes due to a relay malfunction.

FIG. 1 is a diagram showing an example of the overall configuration of a vehicle charging system according to the first embodiment. FIG. 2 is a circuit diagram showing an example of the configuration of the battery charging system according to the first embodiment. FIG. 3 is a circuit diagram showing an example of the configuration of the connection switching device according to the first embodiment. FIG. 4 is a circuit diagram for explaining the occurrence of an overcurrent in a connection switching device of a comparative example. FIG. 5 is a circuit diagram for explaining the current flow when the fuse for overcurrent protection is blown in the connection switching device of the comparative example. FIG. 6 is a circuit diagram for explaining the operation of the connection switching device according to the first embodiment when the third relay malfunctions. FIG. 7 is a circuit diagram showing an example of the configuration of a connection switching device according to the second embodiment. FIG. 8 is a circuit diagram showing an example of the configuration of a connection switching device according to the third embodiment. FIG. 9 is a circuit diagram showing an example of the configuration of a connection switching device according to the fourth embodiment. FIG. 10 is a circuit diagram showing an example of the configuration of a connection switching device according to the fifth embodiment. FIG. 11 is a block diagram showing an example of the hardware configuration of a control circuit according to the fifth embodiment. FIG. 12 is a flowchart showing an example of a control process performed by the control circuit according to the fifth embodiment.

Overview of the embodiments of the present disclosure
The following provides an outline of embodiments of the present disclosure.

(1) The battery unit connection switching device of this embodiment includes a first relay, a second relay, and a third relay, and is equipped with a connection switching unit that connects the first battery unit and the second battery unit in parallel when the first relay and the second relay are in an on state and the third relay is in an off state, and connects the first battery unit and the second battery unit in series when the first relay and the second relay are in an off state and the third relay is in an on state; a first fuse and a second fuse connected in series to the first relay and the second relay, respectively; a cutoff unit connected in series to the third relay and capable of cutting off the current flowing through the third relay; and a detection unit that detects the blowing of at least one of the first fuse and the second fuse, and the cutoff unit cuts off the current flowing through the third relay when the detection unit detects the blowing of at least one of the first fuse and the second fuse. As a result, if the third relay malfunctions and turns on while the first battery unit and the second battery unit are being charged when the first battery unit and the second battery unit are connected in parallel, an overcurrent will flow through the first fuse and the second fuse, causing at least one of the first fuse and the second fuse to blow. When at least one of the first fuse and the second fuse blows, the current flowing through the third relay is interrupted by the circuit breaker, thereby protecting the charging infrastructure from overcurrent.

(2) In the above (1), the interrupter may be a pyro-fuse. When at least one of the first fuse and the second fuse is blown, the pyro-fuse detonates, thereby interrupting the current flowing through the third relay.

(3) In the above (1), the interrupter may be a semiconductor relay. As a result, when at least one of the first fuse and the second fuse is blown, the semiconductor relay is turned off, thereby interrupting the current flowing through the third relay.

(4) In the above (3), the semiconductor relay may include a body diode, and the semiconductor relay may be connected in series with the third relay so that the body diode does not pass a first direction current discharged from at least one of the first battery unit and the second battery unit, but passes a second direction current opposite to the first direction. This prevents current from flowing to the third relay through the body diode when the semiconductor relay is turned off.

(5) In the above (1), the interrupter may be a series-connected circuit of a first semiconductor relay and a second semiconductor relay, the first semiconductor relay including a first body diode, and the second semiconductor relay including a second body diode oriented opposite to the first body diode. This makes it possible to prevent current from flowing to the third relay through either the first body diode or the second body diode when the first semiconductor relay and the second semiconductor relay are turned off.

(6) In any one of (1) to (5) above, the detection unit may include a photocoupler connected in parallel with the first fuse or the second fuse, an output terminal of the photocoupler connected to the cutoff unit, and the cutoff unit may cut off the current flowing through the third relay when it receives an output signal from the photocoupler. This allows the photocoupler to quickly detect the blowout of the first fuse or the second fuse and cut off the current flowing through the third relay.

(7) In any one of (1) to (5) above, the detection unit may include a current sensor that detects the current flowing through the first battery unit or the second battery unit, and a control unit that outputs a control signal for controlling the cutoff unit based on the detection result of the current sensor. When the first fuse and the second fuse melt, current flows through the first battery unit and the second battery unit. Therefore, the current sensor can detect the melting of the first fuse or the second fuse.

(8) The battery charging system of this embodiment includes a first battery unit, a second battery unit, and a connection switching device that switches the connection between the first battery unit and the second battery unit, the connection switching device including a first relay, a second relay, and a third relay, and a connection switching unit that connects the first battery unit and the second battery unit in parallel when the first relay and the second relay are in an on state and the third relay is in an off state, and connects the first battery unit and the second battery unit in series when the first relay and the second relay are in an off state and the third relay is in an on state, a first fuse and a second fuse connected in series to the first relay and the second relay, respectively, a cutoff unit connected in series to the third relay and capable of cutting off the current flowing through the third relay, and a detection unit that detects the blowing of at least one of the first fuse and the second fuse, and the cutoff unit cuts off the current flowing through the third relay when the detection unit detects the blowing of at least one of the first fuse and the second fuse. As a result, if the third relay malfunctions and turns on while the first battery unit and the second battery unit are being charged when the first battery unit and the second battery unit are connected in parallel, an overcurrent will flow through the first fuse and the second fuse, causing at least one of the first fuse and the second fuse to blow. When at least one of the first fuse and the second fuse blows, the current flowing through the third relay is interrupted by the circuit breaker, thereby protecting the charging infrastructure from overcurrent.

<Details of the embodiment of the present disclosure>
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. At least some of the following preferred embodiments may be combined in any desired manner.

1. First embodiment
[1-1. Vehicle charging system]
1 is a diagram showing an example of the overall configuration of a vehicle charging system according to Embodiment 1. The vehicle charging system 10 includes an electric vehicle 20 such as an EV or a plug-in hybrid vehicle, and a charging device 30.

The electric vehicle 20 includes a high-voltage load 500 including a motor for driving the vehicle, and a battery charging system 100 for charging a first battery unit 200A and a second battery unit 200B for driving the high-voltage load. The electric vehicle 20 further includes an inlet 300 and an on-board control device 400. The first battery unit 200A and the second battery unit 200B are 400V-class secondary batteries, such as lithium-ion batteries. Note that, hereinafter, the "first battery unit 200A" and the "second battery unit 200B" are collectively referred to as "battery units 200A, 200B."

The charging device 30 is a DC charging station for the electric vehicle 20. The charging device 30 converts AC power supplied from a system power supply (e.g., a commercial AC power supply) into DC power for charging the battery units 200A, 200B of the electric vehicle 20. The charging device 30 includes a connector 30a. The connector 30a is detachable from the inlet 300. The charging device 30 can output DC power from the connector 30a. The charging device 30 may be a 400V charging device capable of outputting 400V DC power, or an 800V charging device capable of outputting 800V DC power.

Inlet 300 is an input port for charging power to battery units 200A and 200B0, and is connected to battery units 200A and 200B by power lines. When connector 30a is connected to inlet 300, charging device 30 charges battery units 200A and 200B0 of electric vehicle 20.

The inlet 300 is connected to the on-board control device 400 via a communication line (not shown). When the connector 30a is connected to the inlet 300, the on-board control device 400 can communicate with the charging device 30 using a specific communication protocol. For example, the on-board control device 400 can communicate via CAN (Controller Area Network). In another example, the on-board control device 400 can communicate via Ethernet (registered trademark).

The on-board control device 400 is connected to the battery charging system 100 via a communication line. The on-board control device 400 transmits control signals to the battery charging system 100 and controls the operation of the battery charging system 100.

[1-2. Battery charging system]
FIG. 2 is a circuit diagram showing an example of the configuration of the battery charging system according to the first embodiment.

The battery charging system 100 includes a DC bus including a positive power line 150P and a negative power line 150N. Power lines 150P and 150N are connected to a high-voltage load 500. DC power output from battery units 200A and 200B is supplied to the high-voltage load 500 via power lines 150P and 150N. The high-voltage load 500 includes a resistive component 501 and a capacitive component 502.

Each of the power lines 150P, 150N branches off midway, and the branch is connected to the inlet 300. A DC relay 151A is provided on the positive power line extending from the inlet 300 to the branch point, and a DC relay 151B is provided on the negative power line. DC relays 151A, 151B are relays that switch between connection and disconnection between the inlet 300 and the battery units 200A, 200B. DC relays 151A, 151B are controlled by the on-board control device 400 (see Figure 1), and are turned on when the battery units 200A, 200B are being charged, and turned off when they are not being charged.

Main relays 152A, 152B are provided on power lines 150P, 150N, respectively. Furthermore, a series circuit of main relay 152C and resistor 154 is provided on power line 150N in parallel with main relay 152B. Main relays 152A, 152B, 152C are relays that switch between connection and disconnection between battery units 200A, 200B and high-voltage load 500. Main relays 152A, 152B, 152C are controlled by on-board control device 400 (see Figure 1), and are turned on when electric vehicle 20 is operating and turned off when not operating.

DC relays 151A, 151B and main relays 152A, 152B, 152C are, for example, mechanical relays. However, at least one of DC relays 151A, 151B and main relays 152A, 152B, 152C may be a semiconductor relay such as a power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

The battery charging system 100 includes a voltage sensor 155 that detects the voltage between the power lines 150P and 150N. The detection results of the voltage sensor 155 are provided to the on-board control device 400. The on-board control device 400 uses the detection results of the voltage sensor 155 to control the battery charging system 100.

Power lines 150P and 150N are connected to a connection switching device 110. The connection switching device 110 switches between a series connection and a parallel connection of battery units 200A and 200B.

[1-3. Connection Switching Device]
FIG. 3 is a circuit diagram showing an example of the configuration of the connection switching device according to the first embodiment.

Power line 150P is connected to connection point 157P of power lines 156A and 156B. The positive and negative electrodes of the first battery unit 200A are connected to power line 156A. The positive and negative electrodes of the second battery unit 200B are connected to power line 156B. On the negative side of the first battery unit 200A and the negative side of the second battery unit 200B, power lines 156A and 156B are connected at connection point 157N. Power line 150N is connected to connection point 157N.

A first relay 111A is provided between the negative electrode of the first battery unit 200A and connection point 157N. A second relay 111B is provided between connection point 157P and the positive electrode of the second battery unit 200B. The first relay 111A and the second relay 111B are controlled by the on-board control device 400.

An intermediate point 157A between the negative electrode of the first battery unit 200A and the first relay 111A is connected to an intermediate point 157B between the second relay 111B and the positive electrode of the second battery unit 200B by a power line 156C. A third relay 111C is provided on the power line 156C. The third relay 111C is controlled by the on-board control device 400.

When the first relay 111A and the second relay 111B are in the ON state and the third relay 111C is in the OFF state, the first battery unit 200A and the second battery unit 200B are connected in parallel. When the battery units 200A, 200B are charged by the charging device 30, the on-board control device 400 controls the first relay 111A, the second relay 111B, and the third relay 111C to connect the first battery unit 200A and the second battery unit 200B in parallel.

When the first relay 111A and the second relay 111B are in the OFF state and the third relay 111C is in the ON state, the first battery unit 200A and the second battery unit 200B are connected in series. When driving the high-voltage load 500, the on-board control device 400 controls the first relay 111A, the second relay 111B, and the third relay 111C to connect the first battery unit 200A and the second battery unit 200B in series.

The first relay 111A, the second relay 111B, and the third relay 111C constitute the connection switching unit 111s. The connection switching unit 111s switches between the series connection and parallel connection of the first battery unit 200A and the second battery unit 200B.

Current sensor 140A is provided between the negative electrode of the first battery unit 200A and midpoint 157A. Current sensor 140B is provided between the positive electrode of the second battery unit 200B and midpoint 157B. Current sensor 140A detects the current flowing through the first battery unit 200A, and current sensor 140B detects the current flowing through the second battery unit 200B. The detection results of current sensors 140A and 140B are provided to the on-board control device 400. The on-board control device 400 uses the detection results of current sensors 140A and 140B to control the battery charging system 100.

A first fuse 112A is provided between the first relay 111A and the connection point 157N. A second fuse 112B is provided between the connection point 157P and the second relay 111B. The first fuse 112A and the second fuse 112B are overcurrent protection fuses that melt when an overcurrent flows.

A photocoupler 120A and a resistor 122A are connected in series to the first fuse 112A, and are connected in parallel. The photocoupler 120A includes an LED (Light Emitting Diode) 121A, which is a light-emitting element, and a phototransistor 123A, which is a light-receiving element. The phototransistor 123A is normally off and turns on when the LED 121A emits light. The output of the phototransistor 123A is 0 (V) in the off state and Vcc (V) in the on state.

The second fuse 112B is connected in parallel to a photocoupler 120B and resistor 122B, which are connected in series. The photocoupler 120B includes an LED 121B, which is a light-emitting element, and a phototransistor 123B, which is a light-receiving element. The phototransistor 123B is normally off and turns on when the LED 121B emits light. The output of the phototransistor 123B is 0 (V) in the off state and Vcc (V) in the on state.

In the power line 156C, a pyrofuse 130 is connected in series to the third relay 111C. When a predetermined voltage signal is applied, the pyrofuse 130 explodes, cutting off the conductive path. The pyrofuse 130 is an example of a circuit breaker that cuts off the current flowing through the third relay 111C.

Photocouplers 120A and 120B constitute detection unit 125. Detection unit 125 detects the blowing of at least one of first fuse 112A and second fuse 112B. The output terminals of photocouplers 120A and 120B are connected to pyrofuse 130.

[1-4. Operation of the connection switching device]
First, the occurrence of an overcurrent will be described using a connection switching device 110S of a comparative example, which is the connection switching device 110 of the present embodiment without the pyrofuse 130 and the detection unit 125. Fig. 4 is a circuit diagram for explaining the occurrence of an overcurrent in the connection switching device of the comparative example.

While charging the battery units 200A and 200B, the first relay 111A and the second relay 111B are turned on, and the third relay 111C is turned off. In other words, the first battery unit 200A and the second battery unit 200B are connected in parallel.

Let us consider a case where third relay 111C malfunctions and enters the ON state when battery units 200A, 200B are connected in parallel. A malfunction of third relay 111C can be caused by software malfunction, vibration, or the like. When third relay 111C enters the ON state, overcurrent (1), which is a direct current supplied from charging device 30, flows through a path extending from connection point 157P of power line 156B to midpoint 157B, power line 156C, and from midpoint 157A of power line 156A to connection point 157N. Furthermore, overcurrent (2) discharged from the first cell unit 200A flows through the power line 156A from the positive electrode of the first cell unit 200A to the connection point 157P, the power line 156B from the connection point 157P to the midpoint 157B, the power line 156C, and the power line 156A from the midpoint 157A to the negative electrode of the first cell unit 200A. Similarly, overcurrent (2) discharged from the second cell unit 200B flows through the power line 156B from the positive electrode of the second cell unit 200B to the midpoint 157B, the power line 156C, the power line 156A from the midpoint 157A to the connection point 157N, and the power line 156B from the connection point 157N to the negative electrode of the second cell unit 200B.

Figure 5 is a circuit diagram illustrating the current flow when the overcurrent protection fuse blows in a connection switching device of the comparative example. As described above, when overcurrents (1) and (2) occur, first fuse 112A and second fuse 112B blow. This causes overcurrent (3) due to the discharge of battery units 200A and 200B to flow through a path extending from connection point 157N of power line 156B to midpoint 157B, power line 156C, and from midpoint 157A of power line 156A to connection point 157P. This overcurrent (3) may flow into charging device 30, potentially damaging it.

Next, with reference to Figure 3, the overcurrent protection operation of the connection switching device 110 according to this embodiment will be described. When battery units 200A, 200B are connected in parallel, if third relay 111C malfunctions and enters the ON state, overcurrents (1) and (2) will occur as described above. When first fuse 112A blows, current flows through LED 121A, causing LED 121A to emit light. This turns on phototransistor 123A, which then outputs a detection signal with a voltage value of Vcc. Similarly, when second fuse 112AB blows, current flows through LED 121B, causing LED 121B to emit light. This turns on phototransistor 123B, causing phototransistor 123B to output a detection signal with a voltage value of Vcc.

When a detection signal is output from at least one of photocouplers 120A and 120B, the detection signal detonates pyro-fuse 130.

Figure 6 is a circuit diagram for explaining the operation of the connection switching device according to the first embodiment when the third relay 111C malfunctions. For simplicity, the detection unit 125 is omitted from Figure 6. When the pyro-fuse 130 explodes, the power line 156C is cut off, and the current flowing through the third relay 111C is interrupted. Therefore, all overcurrent paths in the connection switching device 110 are cut off, protecting the charging device 30 from overcurrent.

[2. Second embodiment]
7 is a circuit diagram showing an example of the configuration of a connection switching device according to the second embodiment. A connection switching device 110A according to the second embodiment includes a semiconductor relay 130A as a cutoff unit instead of the pyro-fuse 130. Other configurations of the connection switching device 110A according to the second embodiment are the same as those of the connection switching device 110 according to the first embodiment, and therefore the same components are designated by the same reference numerals and description thereof will be omitted.

The semiconductor relay 130A is, for example, a power MOSFET. The semiconductor relay 130A includes a body diode 131. The body diode 131 is arranged in the opposite direction to the flow of the overcurrent (3). In other words, the semiconductor relay 130A is connected in series with the third relay 111C so that the body diode 131 does not pass current in the first direction X1, which is discharged from the second battery unit 200B, but passes current in a second direction X2, which is opposite to the first direction X1.

The gate terminal of semiconductor relay 130A is connected to the output terminals of photocouplers 120A and 120B.

Semiconductor relay 130A is normally in the ON state. Therefore, when first relay 111A and second relay 111B are in the OFF state and third relay 111C is in the ON state, battery units 200A and 200B are connected in series.

When the first fuse 112A and the second fuse 112B blow due to an overcurrent, a detection signal is output from the photocouplers 120A and 120B. The detection signal is applied to the gate terminal of the semiconductor relay 130A, causing the semiconductor relay 130A to transition from the on state to the off state. This disconnects the power line 156C. Furthermore, because the body diode 131 is positioned in the X2 direction, the overcurrent in the X1 direction does not pass through the body diode 131. As a result, the current flowing through the third relay 111C is interrupted.

3. Third embodiment
8 is a circuit diagram showing an example of the configuration of a connection switching device according to the third embodiment. A connection switching device 110B according to the third embodiment includes a cutoff unit 130B formed by a first semiconductor relay 133A and a second semiconductor relay 133B instead of the pyro-fuse 130. Other configurations of the connection switching device 110B according to the third embodiment are similar to those of the connection switching device 110 according to the first embodiment, and therefore the same components are designated by the same reference numerals and description thereof will be omitted.

The first semiconductor relay 133A and the second semiconductor relay 133B are connected in series with each other. The first semiconductor relay 133A and the second semiconductor relay 133B are, for example, power MOSFETs. The first semiconductor relay 133A includes a first body diode 134A, and the second semiconductor relay 133B includes a second body diode 134B. The first body diode 134A is oriented so that it does not allow current to flow in the first direction X1 but allows current to flow in a second direction X2 opposite to the first direction X1. The second body diode 134B is oriented so that it does not allow current to flow in the second direction X2 but allows current to flow in the first direction X1. In other words, the first body diode 134A and the second body diode 134B are oriented opposite to each other.

The gate terminals of the first semiconductor relay 133A and the second semiconductor relay 133B are connected to the output terminals of the photocouplers 120A and 120B.

When the first fuse 112A and the second fuse 112B blow due to an overcurrent, a detection signal is output from the photocouplers 120A and 120B. The detection signal is applied to the gate terminals of the first semiconductor relay 133A and the second semiconductor relay 133B, respectively, causing the first semiconductor relay 133A and the second semiconductor relay 133B to transition from the on state to the off state. This disconnects the power line 156C. Furthermore, because the first body diode 134A and the second body diode are arranged facing opposite directions, the passage of current in both the X1 and X2 directions is blocked. This blocks the current flowing through the third relay 111C.

4. Fourth embodiment
9 is a circuit diagram showing an example of the configuration of a connection switching device according to the fourth embodiment. A connection switching device 110C according to the fourth embodiment includes a detection unit 125C including current sensors 140A and 140B and comparators 420A and 420B, instead of the detection unit 125 including photocouplers 120A and 120B. The other configuration of the connection switching device 110C according to the fourth embodiment is similar to that of the connection switching device 110 according to the first embodiment, and therefore the same components are designated by the same reference numerals and description thereof will be omitted.

The comparator 420A includes a first input terminal, a second input terminal, and an output terminal. A signal line extending from the output terminal of the current sensor 140A is connected to the first input terminal of the comparator 420A. A reference threshold voltage Vth is input to the second input terminal of the comparator 420A. The output terminal of the comparator 420A is connected to the pyrofuse 130. Note that in this embodiment, the connection switching device 110C may include, instead of the pyrofuse 130, the semiconductor relay 130A in the second embodiment, or the cutoff unit 130B including the first semiconductor relay 133A and the second semiconductor relay 133B in the third embodiment.

Comparator 420B includes a first input terminal, a second input terminal, and an output terminal. A signal line extending from the output terminal of current sensor 140B is connected to the first input terminal of comparator 420B. A reference threshold voltage Vth is input to the second input terminal of comparator 420B. The output terminal of comparator 420B is connected to pyrofuse 130.

Comparators 420A and 420B are an example of a control unit. Comparator 420A outputs a control signal for controlling pyrofuse 130 based on the detection result of current sensor 140A. Specifically, current sensor 140A outputs a voltage signal whose value corresponds to the detected current value. Comparator 420A compares the output voltage of current sensor 140A with threshold voltage Vth and outputs a control signal according to the comparison result. In other words, comparator 420A outputs a control signal when the output voltage of current sensor 140A exceeds threshold voltage Vth. Comparator 420B operates in a similar manner, so a description will be omitted.

The threshold voltage Vth is a value used to determine whether the current detected by current sensors 140A and 140B is an overcurrent. In other words, the threshold voltage Vth is set to a value corresponding to the current value of overcurrent (3).

When the first fuse 112A and the second fuse 112B blow due to an overcurrent, the overcurrent (3) caused by the discharge of the battery units 200A and 200B flows through the path extending from connection point 157N to midpoint 157B of power line 156B, power line 156C, and from midpoint 157A to connection point 157P of power line 156A. Current sensors 140A and 140B detect the current value of the overcurrent (3) and output a voltage signal corresponding to the detected current value.

Comparators 420A and 420B compare the output voltage from current sensors 140A and 140B with threshold voltage Vth. When overcurrent (3) occurs, the output voltage from current sensors 140A and 140B exceeds threshold voltage Vth. As a result, comparators 420A and 420B output a control signal. The control signal detonates pyrolytic fuse 130, cutting off the current flowing through third relay 111C.

5. Fifth embodiment
10 is a circuit diagram showing an example of the configuration of a connection switching device according to the fifth embodiment. A connection switching device 110D according to the fifth embodiment includes a detection unit 125D including current sensors 140A and 140B and a control circuit 520, instead of the detection unit 125 including photocouplers 120A and 120B. The other configuration of the connection switching device 110D according to the fifth embodiment is similar to that of the connection switching device 110 according to the first embodiment, and therefore the same components are designated by the same reference numerals and description thereof will be omitted.

Signal lines extending from the output terminals of current sensor 140A and current sensor 140B are connected to control circuit 520. Control circuit 520 is connected to pyrofuse 130 via a signal line. Note that in this embodiment, connection switching device 110D may include, instead of pyrofuse 130, semiconductor relay 130A in the second embodiment, or interrupter 130B including first semiconductor relay 133A and second semiconductor relay 133B in the third embodiment.

The control circuit 520 is an example of a control unit. The control circuit 520 outputs a control signal for controlling the pyrofuse 130 based on the detection results of at least one of the current sensors 140A and 140B. Specifically, the current sensors 140A and 140B output detection signals indicating the detected current values. The control circuit 520 compares the first current value A1 and the second current value A2 detected by the current sensors 140A and 140B, respectively, with a threshold value Th, and outputs a control signal according to the comparison result. That is, the control circuit 520 outputs a control signal when the first current value A1 detected by the current sensor 140A exceeds the threshold value Th, or when the second current value A2 detected by the current sensor 140B exceeds the threshold value Th.

The threshold voltage Th is a value used to determine whether the current detected by current sensors 140A and 140B is an overcurrent. In other words, the threshold Th is set to a value corresponding to the current value of overcurrent (3).

Figure 11 is a block diagram showing an example of the hardware configuration of a control circuit according to the fifth embodiment.

The control circuit 520 includes a processor 521, non-volatile memory 522, volatile memory 523, and an input/output interface (I/O) 524.

Volatile memory 523 is a volatile memory such as SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory). Non-volatile memory 522 is a non-volatile memory such as flash memory, a hard disk, or ROM (Read Only Memory). Non-volatile memory 522 stores a control program 525, which is a computer program, and data used to execute control program 525. Each function of control circuit 520 is realized when processor 521 executes control program 525. Control program 525 can be stored on a recording medium such as flash memory, ROM, or CD-ROM.

The processor 521 is, for example, a CPU (Central Processing Unit). However, the processor 521 is not limited to a CPU. The processor 521 may also be a GPU (Graphics Processing Unit). In one specific example, the processor 521 is a multi-core GPU. The processor 521 may also be, for example, an ASIC (Application Specific Integrated Circuit), or a programmable logic device such as a gate array or FPGA (Field Programmable Gate Array). In this case, the ASIC or programmable logic device is configured to be able to execute processing similar to that of the control program 525. The control circuit 520 is, for example, a microcomputer made up of a single-chip semiconductor component.

I/O 524 inputs and outputs signals. The output terminals of current sensors 140A and 140B are connected to I/O 524 via signal lines. I/O 524 is also connected to the input terminal of pyrofuse 130 via a signal line.

While charging the battery units 200A and 200B, the first relay 111A and the second relay 111B are in the ON state, and the third relay 111C is in the OFF state. In other words, the first battery unit 200A and the second battery unit 200B are connected in parallel. In this state, the processor 521 executes the control program 525. As the processor 521 executes the control program 525, the control circuit 520 performs the following control processing. Figure 12 is a flowchart showing an example of the control processing performed by the control circuit according to the fifth embodiment.

The processor 521 receives the first current value A1 and the second current value A2 output from the current sensors 140A and 140B, respectively (step S101).

Next, the processor 521 compares the first current value A1 with the threshold value Th, and compares the second current value A2 with the threshold value Th (step S102). If the first current value A1 is equal to or less than the threshold value Th and the second current value A2 is equal to or less than the threshold value Th (NO in step S102), the processor 521 returns to step S101.

If the first current value A1 exceeds the threshold value Th or the second current value A2 exceeds the threshold value Th (YES in step S102), the processor 521 outputs a control signal to the pyrofuse 130 (step S103). The control signal detonates the pyrofuse 130, and the current flowing through the third relay 111C is interrupted. This completes the control process.

[6. Supplementary Notes]
The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope thereof.

REFERENCE SIGNS LIST 10 Vehicle charging system 20 Electric vehicle 30 Charging device 30a Connector 100 Battery charging system 110, 110A, 110B, 110C, 110D, 110S Connection switching device 111A First relay 111B Second relay 111C Third relay 111s Connection switching unit 112A First fuse 112B Second fuse 120A, 120B Photocoupler 121A LED
122A, 122B Resistor 123A, 123B Phototransistor 125, 125C, 125D Detector 130 Pyro fuse 130A Semiconductor relay 130B Cutoff section 131 Body diode 133A First semiconductor relay 133B Second semiconductor relay 134A First body diode 134B Second body diode 140A, 140B Current sensor 150P, 150N Power line 151A, 151B Relay 152A, 152B, 152C Main relay 154 Resistor 155 Voltage sensor 156A, 156B, 156C Power line 157A, 157B Intermediate point 157P, 157N Connection point 200A First battery unit 200B Second battery unit 300 Inlet 400 On-board control device 420A, 420B Comparator 500 High-voltage load 501 Resistance component 502 Capacitance component 520 Control circuit 521 Processor 522 Non-volatile memory 523 Volatile memory 524 Input/output interface (I/O)
525 Control program X1 First direction X2 Second direction

Claims (8)

a connection switching unit including a first relay, a second relay, and a third relay, which connects the first battery unit and the second battery unit in parallel when the first relay and the second relay are in an on state and the third relay is in an off state, and which connects the first battery unit and the second battery unit in series when the first relay and the second relay are in an off state and the third relay is in an on state;
a first fuse and a second fuse connected in series to the first relay and the second relay, respectively;
a cutoff unit connected in series to the third relay and capable of cutting off a current flowing through the third relay;
a detection unit that detects blowout of at least one of the first fuse and the second fuse;
Equipped with
the interrupter interrupts the current flowing through the third relay when the detector detects that at least one of the first fuse and the second fuse has blown.
Battery unit connection switching device. The interrupter is a pyro fuse.
The battery unit connection switching device according to claim 1 . The interrupter is a semiconductor relay.
The battery unit connection switching device according to claim 1 . the semiconductor relay includes a body diode;
the semiconductor relay is connected in series with the third relay so that the body diode does not pass a current in a first direction discharged from at least one of the first battery unit and the second battery unit, but passes a current in a second direction opposite to the first direction;
The battery unit connection switching device according to claim 3 . the interrupter includes a first semiconductor relay and a second semiconductor relay connected in series,
the first semiconductor relay includes a first body diode;
the second semiconductor relay includes a second body diode oriented opposite to the first body diode;
The battery unit connection switching device according to claim 1 . the detection unit includes a photocoupler connected in parallel with the first fuse or the second fuse,
an output terminal of the photocoupler is connected to the interrupter;
The cutoff unit cuts off the current flowing through the third relay when receiving an output signal from the photocoupler.
The battery unit connection switching device according to any one of claims 1 to 5. The detection unit
a current sensor that detects a current flowing through the first battery unit or the second battery unit;
a control unit that outputs a control signal for controlling the interrupter based on a detection result of the current sensor;
Including,
The battery unit connection switching device according to any one of claims 1 to 5. a first battery unit;
a second battery unit;
a connection switching device that switches the connection between the first battery unit and the second battery unit;
Equipped with
The connection switching device
a connection switching unit including a first relay, a second relay, and a third relay, which connects the first battery unit and the second battery unit in parallel when the first relay and the second relay are in an on state and the third relay is in an off state, and which connects the first battery unit and the second battery unit in series when the first relay and the second relay are in an off state and the third relay is in an on state;
a first fuse and a second fuse connected in series to the first relay and the second relay, respectively;
a cutoff unit connected in series to the third relay and capable of cutting off a current flowing through the third relay;
a detection unit that detects blowout of at least one of the first fuse and the second fuse;
Including,
the interrupter interrupts the current flowing through the third relay when the detector detects that at least one of the first fuse and the second fuse has blown.
Battery charging system.