JP2021192571A - Cell balance control device - Google Patents

Abstract

To reduce energy loss by eliminating cell voltage imbalance while suppressing complication of device structure in a cell balance control device.SOLUTION: A cell balance control device is provided with a determination unit 43 for identifying a maximum voltage battery cell being a battery cell with a highest voltage, and a minimum voltage battery cell being a battery cell with a lowest voltage on the basis of a detection result of a voltage detection unit 30. When there is no maximum voltage battery cell on a side closer to a minus terminal T2 side of a battery pack 1 than the minimum voltage battery cell, a control unit 41 controls a constant current circuit 42 for detecting disconnection so that a constant current flows in the minimum voltage battery cell and battery cells positioning on a side closer to the minus terminal T2 side of the battery pack 1 than the minimum voltage battery cell. When there is the maximum battery cell on a side closer to the minus terminal T2 side of the battery pack 1 than the minimum voltage battery cell, the control unit controls a discharge circuit 11 so that the maximum voltage battery cell discharges.SELECTED DRAWING: Figure 2

Description

The present invention relates to a cell balance control device.

For mobile bodies equipped with batteries such as electric vehicles, for the purpose of preventing the storage capacity of the assembled battery from decreasing due to the imbalance of the voltages (cell voltage) of a plurality of battery cells constituting the assembled battery, each It is equipped with a cell balance control device that controls discharge so that the cell voltage becomes uniform.

Generally, the cell balance control device eliminates the cell voltage imbalance by discharging the battery cell having a high cell voltage. On the other hand, Patent Document 1 discloses a cell balance control device provided with a constant current source and which eliminates an imbalance in cell voltage by selectively charging a battery cell having a low cell voltage. According to the cell balance control device disclosed in Patent Document 1, since the imbalance of the cell voltage is eliminated by charging, it is possible to suppress the energy loss due to the discharge.

Japanese Unexamined Patent Publication No. 2006-129757

However, in the cell balance control device disclosed in Patent Document 1, it is necessary to separately provide a constant current source, which complicates the structure of the cell balance control device. As a result, the cell balance control device disclosed in Patent Document 1 increases in size and cost.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce energy loss due to elimination of cell voltage imbalance while suppressing complication of the structure of the cell balance control device.

In the present invention, as means for solving the above-mentioned problems, a voltage detection unit for detecting the voltage of each of a plurality of battery cells connected in series included in the assembled battery, a positive terminal of the assembled battery, and each of the above-mentioned batteries. A constant current circuit for disconnection detection having a disconnection detection switching element provided for each battery cell while connecting to the positive terminal of the cell, and a positive terminal of each of the battery cells provided for each battery cell. It includes a discharge circuit that is connected to a negative terminal and has a discharge switching element, and a control unit that controls the disconnection detection switching element and controls the discharge switching element based on the detection result of the voltage detection unit. , The cell balance control device mounted on the moving body, the highest voltage battery cell which is the battery cell having the highest voltage based on the detection result of the voltage detection unit, and the lowest voltage which is the battery cell having the lowest voltage. A determination unit for specifying a battery cell is provided, and when the control unit does not have the maximum voltage battery cell on the negative terminal side of the assembled battery from the minimum voltage battery cell, the minimum voltage battery cell and the minimum voltage battery The constant current circuit for detecting disconnection is controlled so that a constant current flows through the battery cell located on the negative terminal side of the assembled battery with respect to the cell, and the negative terminal side of the assembled battery is moved from the lowest voltage battery cell. When the maximum voltage battery cell is present, a configuration is adopted in which the discharge circuit is controlled so that the maximum voltage battery cell is discharged.

According to the present invention, when the maximum voltage battery cell does not exist on the negative terminal side of the assembled battery from the minimum voltage battery cell, the battery cell located on the negative terminal side of the assembled battery with respect to the minimum voltage battery cell and the minimum voltage battery cell. The constant current circuit for detecting disconnection is controlled so that a constant current flows. That is, according to the present invention, when the maximum voltage battery cell does not exist on the negative terminal side of the assembled battery from the minimum voltage battery cell, the battery cell is connected by the constant current circuit for disconnection detection provided for disconnection detection. By charging, it becomes possible to eliminate the imbalance of the cell voltage. Therefore, it is not necessary to separately provide a circuit for charging the battery cell, and it is possible to suppress the complexity of the structure of the device. Therefore, according to the present invention, in the cell balance control device, it is possible to reduce the energy loss due to the elimination of the cell voltage imbalance while suppressing the complication of the structure of the device.

It is a schematic block diagram of the vehicle traveling system provided with the cell balance control device in one Embodiment of this invention. It is a schematic block diagram including the cell balance control apparatus in one Embodiment of this invention. It is a flowchart explaining the cell balance control by the cell balance control apparatus in one Embodiment of this invention.

Hereinafter, an embodiment of the cell balance control device according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a vehicle traveling system A provided with a cell balance control device according to the present embodiment. As shown in FIG. 1, the vehicle traveling system A includes an assembled battery 1, a first contactor 2, a second contactor 3, a motor 4, a power converter 5, a cell balance control device 6, and a battery ECU 7. There is.

The assembled battery 1 is a battery mounted on the vehicle such as an electric vehicle or a hybrid vehicle, and is a secondary battery such as a lithium ion battery or a nickel hydrogen battery. Further, the assembled battery 1 may be an all-solid-state battery.

The assembled battery 1 includes a plurality of battery cells b1 to bn (n is an integer of 2 or more) connected in series. That is, the assembled battery 1 is an assembled battery in which n battery cells b1 to bn are connected in series. In the assembled battery 1, the positive terminal of the battery cell b1 located at the highest position (the most positive terminal T1 side of the assembled battery 1) is the positive terminal T1 of the assembled battery 1, and the lowermost position (the most negative terminal T2 of the assembled battery 1). The negative terminal of the battery cell bn located on the side) is the negative terminal T2 of the assembled battery 1. When each of the battery cells b1 to bn is not distinguished, it is simply labeled as "battery cell b". In this embodiment, the case where n = 3 will be described. However, the cell balance control device 6 of the present embodiment is not particularly limited to the number of battery cells b to be connected, and may be connected to a plurality of battery cells b connected in series.

The first contactor 2 is an energization switch provided with a pair of contacts. In the first contactor 2, the first contact is connected to the positive terminal T1 of the assembled battery 1, and the second contact is connected to the first input end of the power converter 5. The first contactor 2 is controlled to a closed state or an open state according to the control from the battery ECU 7. When the first contactor 2 is controlled to be in the closed state, the positive terminal T1 of the assembled battery 1 and the first input end of the power converter 5 are electrically connected. When the first contactor 2 is controlled to be in the open state, the electrical connection between the positive terminal T1 of the assembled battery 1 and the first input end of the power converter 5 is released.

The second contactor 3 is an energization switch provided with a pair of contacts. In the second contactor 3, the first contact is connected to the negative terminal T2 of the assembled battery 1, and the second contact is connected to the second input end of the power converter 5. The second contactor 3 is controlled to a closed state or an open state according to the control from the battery ECU 7. When the second contactor 3 is controlled to be in the closed state, the negative terminal T2 of the assembled battery 1 and the second input end of the power converter 5 are electrically connected. When the second contactor 3 is controlled to be in the open state, the electrical connection between the negative terminal T2 of the assembled battery 1 and the second input end of the power converter 5 is released.

The motor 4 generates a driving force when electric power is supplied from the assembled battery 1 via the power converter 5. Further, the motor 4 generates electric power by performing regenerative operation. The electric power generated by the regenerative operation of the motor 4 (hereinafter referred to as “regenerative electric power”) is supplied to the assembled battery 1 via the power converter 5. For example, the motor 4 is a motor for traveling of the vehicle.

The power converter 5 converts the DC power from the assembled battery 1 into a predetermined AC power and supplies it to the motor 4. Further, in the case of the regenerative operation of the motor 4, the power converter 5 converts the regenerative power supplied from the motor 4 from alternating current to direct current and supplies it to the assembled battery 1. The power converter 5 includes an inverter, and may further include a DCDC converter.

The cell balance control device 6 is electrically connected to each battery cell b1 to b3 via (n + 1) lines (4 lines in this embodiment) wires L1 to L4. The cell balance control device 6 is a passive type that detects the voltage between terminals of each battery cell b1 to b3 (hereinafter referred to as "cell voltage") via four wires L1 to L4 and equalizes each cell voltage. Performs cell balance control. The cell balance control device 6 outputs each detected cell voltage to the battery ECU 7. When each of the wirings L1 to L4 is not distinguished, it is simply marked as "wiring L".

The wiring L is connected to the output terminals (plus terminal and minus terminal) of each battery cell b1 to b3, respectively. For example, in the wiring L1, the first end is connected to the positive terminal of the battery cell b1, and the second end is connected to the cell balance control device 6. Further, the first end of the wiring L2 is connected to the negative terminal of the battery cell b1 (the positive terminal of the battery cell b2), and the second end is connected to the cell balance control device 6. The first end of the wiring L3 is connected to the negative terminal of the battery cell b2 (the positive terminal of the battery cell b3), and the second end is connected to the cell balance control device 6. The first end of the wiring L4 is connected to the negative terminal of the battery cell b3, and the second end is connected to the cell balance control device 6.

The battery ECU 7 controls the operation of the first contactor 2 and the second contactor 3 described above based on the operation instruction of the driver of the vehicle (for example, “ON” of the ignition switch). As a result, the battery ECU 7 can control the discharge from the assembled battery 1 to the power converter 5. Further, the battery ECU 7 controls the operation of the first contactor 2 and the second contactor 3 to transfer the regenerative power from the motor 4 and the power from the external charger provided outside the vehicle to the assembled battery 1. Can be charged.

Further, in addition to controlling the first contactor 2 and the second contactor 3, the battery ECU 7 notifies the cell balance control device 6 of the open / closed state of the first contactor 2 and the second contactor 3 based on the control. May be good. The battery ECU 7 does not charge the assembled battery 1 when at least one of the plurality of cell voltages acquired from the cell balance control device 6 has reached a voltage corresponding to full charge.

Next, the configuration of the cell balance control device 6 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 2 is a schematic configuration diagram including the cell balance control device 6 according to the present embodiment. As shown in FIG. 2, the cell balance control device 6 includes a discharge unit 10 and a control unit 20. The discharge unit 10 is provided in the wiring L between the assembled battery 1 and the control unit 20.

As shown in FIG. 2, the discharge unit 10 includes a plurality of discharge circuits 11 and a plurality of filter circuits 12. The discharge circuit 11 is connected in parallel to each battery cell b and can discharge the battery cell b. That is, the discharge unit 10 includes the same number of discharge circuits 11 as the plurality of battery cells b connected in series in the assembled battery 1.

Specifically, the discharge circuit 11a is connected in parallel to the battery cell b1 by being connected between the wiring L1 and the wiring L2. The discharge circuit 11a can discharge the battery cell b1 based on the control from the control unit 20. The discharge circuit 11b is connected in parallel to the battery cell b2 by being connected between the wiring L2 and the wiring L3. The discharge circuit 11b can discharge the battery cell b2 based on the control from the control unit 20. The discharge circuit 11c is connected in parallel to the battery cell b3 by being connected between the wiring L3 and the wiring L4. The discharge circuit 11c can discharge the battery cell b3 based on the control from the control unit 20.

The discharge circuits 11a to 11c each have the same configuration. When each of the discharge circuits 11a to 11c is not distinguished, it is simply labeled as "discharge circuit 11". The discharge circuit 11 includes a series circuit of one or more bypass resistors 21 and a switching element 22 (discharging switching element). Each discharge circuit 11 is in a discharged state when the switching element 22 is turned on, and is in a non-discharged state when the switching element 22 is turned off.

The filter circuit 12 is a noise-removing low-pass filter provided in each of the wirings L1 to L4, and is composed of a filter resistor 31 and a filter capacitor 32. Here, in the example shown in FIG. 2, since the four wirings L1 to L4 are connected to the control unit 20, the filter circuit 12 is connected to each of the wirings L1 to L4. In the example shown in FIG. 2, the filter circuit 12a is connected to the wiring L1, the filter circuit 12b is connected to the wiring L2, the filter circuit 12c is connected to the wiring L3, and the filter circuit 12d is connected to the wiring L4.

As shown in FIG. 2, the control unit 20 includes a voltage detection unit 30 and a control IC 40. The voltage detection unit 30 detects each cell voltage of a plurality of battery cells connected in series. Specifically, the voltage detection unit 30 is electrically connected to each battery cell b1 to b3 via four wires L1 to L4, and each battery cell b1 is electrically connected to each battery cell b1 via four wires L1 to L4. Each cell voltage of ~ b3 is detected. Then, the voltage detection unit 30 outputs each detected cell voltage to the control IC 40. The voltage detection unit 30 may be composed of one or a plurality of integrated circuits.

The voltage detection unit 30 detects the difference between the voltage of the wiring L1 and the voltage of the wiring L2 as the cell voltage of the battery cell b1, and detects the difference between the voltage of the wiring L2 and the voltage of the wiring L3 as the cell voltage of the battery cell b2. Then, the difference between the voltage of the wiring L3 and the voltage of the wiring L4 is detected as the cell voltage of the battery cell b3.

The control IC 40 includes a processor such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit) and a non-volatile or volatile semiconductor memory (for example, RAM (RandomAccess Memory), ROM (Read Only Memory), flash memory, EPROM (for example). Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory)) may be provided. For example, the control IC 40 may be a micro controller such as an MCU.

The control IC 40 includes a control unit 41, a constant current circuit 42 for detecting disconnection, and a determination unit 43. The control unit 41 executes cell balance control by controlling the ON state and the OFF state of each of the switching elements 22 of the plurality of discharge circuits 11. Further, the control unit 41 detects the disconnection of the wirings L1 to L4 by controlling the constant current circuit 42 for detecting the disconnection. Further, in the present embodiment, the control unit 41 executes cell balance control.

The constant current circuit 42 for detecting disconnection connects the positive terminal T1 of the assembled battery 1 to the wiring L1, the wiring L2, and the wiring L3. The disconnection detection constant current circuit 42 has a disconnection detection circuit 44 arranged between the positive terminal T1 of the assembled battery 1 and the wirings L1 to L3. These disconnection detection circuits 44 are circuits in which a diode 45 and a switching element 46 (disconnection detection switching element) are connected in series.

When the switching element 46 of the disconnection detection circuit 44 (disconnection detection circuit 44a) arranged between the positive terminal T1 of the assembled battery 1 and the wiring L1 is turned on, a constant current is applied to all the battery cells b. It flows. When the switching element 46 of the disconnection detection circuit 44 (disconnection detection circuit 44b) arranged between the positive terminal T1 of the assembled battery 1 and the wiring L2 is turned on, the battery cell b1 is removed from the battery cell b1. A constant current flows through the lower battery cell b (battery cell b2 and battery cell b3). When the switching element 46 of the disconnection detection circuit 44 (disconnection detection circuit 44c) arranged between the positive terminal T1 of the assembled battery 1 and the wiring L3 is turned on, it is higher than the battery cell b2 and the battery cell b3. Except for the battery cell b (battery cell b1), a constant current flows through the battery cell (battery cell b3) lower than the battery cell b2. The control unit 41 detects the disconnection of the wirings L1 to L4 by sequentially turning on the switching elements 46 of the disconnection detection circuit 44.

The determination unit 43 identifies the highest voltage battery cell, which is the battery cell b having the highest voltage, and the lowest voltage battery cell, which is the battery cell b having the lowest voltage, based on the detection result of the voltage detection unit 30. The determination unit 43 inputs information indicating the specified maximum voltage battery cell and minimum voltage battery cell to the control unit 41.

In the present embodiment, the control unit 41 executes cell balance control not only by using the discharge circuit 11 but also by using the constant current circuit 42 for detecting disconnection provided for detecting disconnection. FIG. 3 is a flowchart for explaining cell balance control in the present embodiment.

First, the determination unit 43 acquires the cell voltage of each battery cell b from the voltage detection unit 30 (step S1). Subsequently, the determination unit 43 identifies the minimum voltage battery cell and the maximum voltage battery cell (step S2). Subsequently, the control unit 41 determines whether or not the maximum voltage battery cell exists below the minimum voltage battery cell (step S3).

If it is determined in step S3 that the maximum voltage battery cell does not exist below the minimum voltage battery cell, the minimum voltage battery cell is charged by the constant current supplied to the control IC 40 (step S4). After that, the process returns to step S1 again.

Specifically, the control unit 41 controls the constant current circuit 42 for detecting disconnection so that a constant current flows through the minimum voltage battery cell and the battery cell b located below the minimum voltage battery cell. For example, when the battery cell b2 is the lowest voltage battery cell and the battery cell b1 is the highest voltage battery cell, the control unit 41 turns on the switching element 46 of the disconnection detection circuit 44b. As a result, the battery cell b2 is charged with a constant current.

As a result, the voltage of the lowest voltage battery cell rises and approaches the voltage of the highest voltage battery cell, and the imbalance of the cell voltage is eliminated. When the cell voltage of the battery cell b lower than the minimum voltage battery cell is about to exceed the cell voltage of the maximum voltage battery cell during charging by a constant current, the control unit 41 sends the target battery cell b to the target battery cell b. The switching element 22 of the connected discharge circuit 11 is set to the ON state, and the cell voltage of the target battery cell b is controlled so as not to exceed the cell voltage of the maximum voltage battery cell.

On the other hand, when it is determined in step S3 that the maximum voltage battery cell exists below the minimum voltage battery cell, the control unit 41 turns on the switching element 22 of the discharge circuit 11 connected to the maximum voltage battery cell. Therefore, the cell voltage of the target battery cell b is controlled so as not to exceed the cell voltage of the maximum voltage battery cell.

The cell balance control device 6 of the present embodiment as described above has a voltage detection unit 30 for detecting the voltage of each of a plurality of battery cells b connected in series included in the assembled battery 1, and a positive terminal T1 of the assembled battery 1. And the positive terminal T1 of each battery cell b are connected, and a constant current circuit 42 for disconnection detection having a switching element 46 provided for each battery cell b and a constant current circuit 42 for disconnection detection are provided for each battery cell b and each battery cell. A control unit 41 that connects the positive terminal T1 and the negative terminal T2 of b and has a switching element 22 and controls the switching element 46 and controls the switching element 22 based on the detection result of the voltage detection unit 30. It is equipped with and is mounted on a moving body.

The cell balance control device 6 is a determination unit that identifies the highest voltage battery cell, which is the battery cell b having the highest voltage, and the lowest voltage battery cell, which is the battery cell b having the lowest voltage, based on the detection result of the voltage detection unit 30. 43, and the control unit 41 has a negative terminal of the assembled battery 1 rather than the lowest voltage battery cell and the negative terminal of the assembled battery 1 when the maximum voltage battery cell does not exist on the negative terminal T2 side of the assembled battery 1 from the lowest voltage battery cell. When the constant current circuit 42 for disconnection detection is controlled so that a constant current flows to the battery cell b located on the T2 side, and the maximum voltage battery cell exists on the negative terminal T2 side of the assembled battery 1 from the minimum voltage battery cell. In addition, the discharge circuit 11 is controlled so that the maximum voltage battery cell is discharged.

According to the cell balance control device 6 of the present embodiment as described above, when the maximum voltage battery cell does not exist on the negative terminal T2 side of the assembled battery 1 from the minimum voltage battery cell, the minimum voltage battery cell and the minimum voltage battery cell are used. The constant current circuit 42 for detecting disconnection is controlled so that a constant current flows through the battery cell b located on the negative terminal T2 side of the assembled battery 1.

That is, according to the cell balance control device 6 of the present embodiment, when the maximum voltage battery cell does not exist on the negative terminal T2 side of the assembled battery 1 from the minimum voltage battery cell, the disconnection detection provided for disconnection detection is provided. The constant current circuit 42 makes it possible to eliminate the imbalance in the cell voltage by charging the battery cell b. Therefore, it is not necessary to separately provide a circuit for charging the battery cell b, and it is possible to suppress the complexity of the structure of the device. Therefore, according to the cell balance control device 6 of the present embodiment, in the cell balance control device 6, it is possible to reduce the energy loss due to the elimination of the cell voltage imbalance while suppressing the complication of the structure of the device.

Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above embodiment. The various shapes and combinations of the constituent members shown in the above-described embodiment are examples, and can be variously changed based on design requirements and the like without departing from the spirit of the present invention.

For example, in the above embodiment, the configuration in which the assembled battery 1 includes three battery cells b has been illustrated and described. However, the present invention is not limited to this, and it is also possible to adopt a configuration in which the assembled battery 1 includes a larger number of battery cells b.

1 ... Batteries, 2 ... 1st contactor, 3 ... 2nd contactor, 4 ... Motor, 5 ... Power converter, 6 ... Cell balance control device, 10 ... Discharge section, 11 ... Discharge circuit, 12 ... Filter circuit, 20 ... Control unit, 21 ... Bypass resistance, 22 ... Switching element (switching element for discharge), 30 ... Voltage detection unit, 41 ... Control unit, 42 ...... Constant current circuit for disconnection detection, 43 ... Judgment unit, 44 ... Disconnection detection circuit, 45 ... Diode, 46 ... Switching element (switching element for disconnection detection), b ... Battery cell, L ... Wiring , T1 …… Positive terminal, T2 …… Negative terminal

Claims (1)

A voltage detector that detects the voltage of each of a plurality of battery cells connected in series, which is included in the assembled battery.
A constant current circuit for disconnection detection, which connects the positive terminal of the assembled battery and the positive terminal of each battery cell and has a disconnection detection switching element provided for each battery cell,
A discharge circuit provided for each battery cell, connecting the positive terminal and the negative terminal of each battery cell, and having a discharge switching element.
A control unit that controls the disconnection detection switching element and controls the discharge switching element based on the detection result of the voltage detection unit is provided.
It is a cell balance control device mounted on a moving body.
A determination unit for identifying the highest voltage battery cell, which is the battery cell having the highest voltage, and the lowest voltage battery cell, which is the battery cell having the lowest voltage, based on the detection result of the voltage detection unit is provided.
The control unit
When the maximum voltage battery cell does not exist on the negative terminal side of the assembled battery from the minimum voltage battery cell, the battery located on the negative terminal side of the assembled battery with respect to the minimum voltage battery cell and the minimum voltage battery cell. The constant current circuit for detecting disconnection is controlled so that a constant current flows through the cell.
A cell balance control device characterized in that the discharge circuit is controlled so that the maximum voltage battery cell is discharged when the maximum voltage battery cell is present on the negative terminal side of the assembled battery from the minimum voltage battery cell. ..

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