JP2020025375A - Circuit protection device - Google Patents

Abstract

To protect a voltage detection circuit without using a fuse.SOLUTION: A circuit protection device is provided between a DC power supply and a protection object circuit applied with a plus voltage and a minus voltage of the DC power supply, and comprises: a P-channel type field effect transistor with a source terminal connected to a plus terminal of a battery cell constituting the DC power supply and with a drain terminal connected to the protection object circuit; a switching element connected between a gate terminal and a ground of the P-channel type field effect transistor; and a switch drive circuit which, when the switching element is controlled in an on-state and when the DC power supply outputs a normal voltage, brings the P-channel type field effect transistor into a conduction state, and when the DC power supply outputs an abnormal voltage, brings the P-channel type field effect transistor into a non-conduction state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circuit protection device.

  Patent Literature 1 below discloses a circuit protection device that protects a voltage detection circuit that detects a voltage of a battery pack. This circuit protection device is a circuit interposed between a battery pack and a voltage detection circuit, and a plurality of circuit protection devices interconnecting each input terminal of the voltage detection circuit with each terminal of a plurality of battery cells constituting the battery pack. And a plurality of zener diodes provided between a pair of detection lines corresponding to individual battery cells.

JP 2011-54440 A

  By the way, the above fuse protects a voltage detection circuit by blowing a conductor connecting a pair of terminals due to overcurrent, but once blown, it is necessary to replace the blown fuse with a new fuse. ,It takes time and effort.

  The present invention has been made in view of such circumstances, and an object thereof is to protect a voltage detection circuit without using a fuse.

  One embodiment of the present invention is a circuit protection device provided between a DC power supply and a protection target circuit to which a positive voltage and a negative voltage of the DC power supply are input, wherein a positive power supply of a battery cell included in the DC power supply is provided. A P-channel field-effect transistor having a source terminal connected to the terminal, and a drain terminal connected to the circuit to be protected; a switching element connected between a gate terminal of the P-channel field effect transistor and ground; When the switching element is controlled to be in an ON state, the P-channel field-effect transistor is turned on when the DC power supply outputs a normal voltage, and the P-channel field-effect transistor is turned on when the DC power supply outputs an abnormal voltage. And a switch drive circuit that makes the switch non-conductive. That.

  One embodiment of the present invention is the above-described circuit protection device, wherein the switch drive circuit has one end connected to a positive terminal of the battery cell, and the other end connected to a source terminal of the P-channel field-effect transistor. And a second resistor having one end connected to the gate terminal of the P-channel field effect transistor and the other end connected to ground via the switching element. And

  As described above, according to the present invention, a voltage detection circuit can be protected without using a fuse.

1 is a schematic configuration diagram of a power supply monitoring device A including a circuit protection device according to an embodiment of the present invention. It is a circuit diagram showing the detailed composition of the circuit protection device concerning one embodiment of the present invention. It is a figure concerning one embodiment of the present invention explaining operation of a circuit protection device when battery pack X outputs a normal voltage. It is a figure concerning one embodiment of the present invention explaining operation of a circuit protection device when battery pack X outputs an abnormal voltage.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  A power supply monitoring device A according to an embodiment of the present invention is a device that detects a voltage of an assembled battery X (DC power supply) and monitors the voltage as shown in FIG. It has. Among the components constituting the power supply monitoring device A, the shutoff circuit 2 corresponds to a circuit protection device in the present invention. The voltage detection circuit 1 is an example of the “circuit to be protected” of the present invention.

  The assembled battery X is a battery mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and is a secondary battery such as a lithium ion battery or a nickel hydride battery. As shown, the battery pack X includes a plurality of battery cells b1 to bn connected in series by a plurality of bus bars B. Such an assembled battery X supplies DC power to, for example, an inverter that drives a traveling motor that generates traveling power of the vehicle. That is, the plus terminal of the battery pack X is connected to one input terminal of the inverter, and the minus terminal of the battery pack X is connected to the other input terminal of the inverter. Note that “n” is a natural number of 2 or more. In addition, when each of the battery cells b1 to bn is not distinguished, it is simply referred to as “battery cell b”.

  The bus bar B electrically connects two adjacent battery cells b. For example, the bus bar B is an elliptical metal plate, and has screw holes (not shown) formed at both ends in the longitudinal direction. The bus bar B is fixed to the battery cell b by screws (not shown) inserted into screw holes at both ends in a state of being in contact with the output terminals (plus terminal and minus terminal) of the adjacent battery cell b. Alternatively, the bus bar B and the output terminals (plus terminal and minus terminal) of the battery cell b may be fixed by welding. By providing a plurality of such bus bars B, the battery cells b are electrically connected to each other.

  The voltage detection circuit 1 is a circuit that monitors the battery pack X based on the output voltage of the battery pack X. That is, the voltage detection circuit 1 includes a plurality of pairs of input terminals respectively corresponding to the output terminals (plus terminal and minus terminal) of each of the battery cells b1 to bn. The output terminals (plus and minus terminals) of the battery cells b1 to bn and a plurality of pairs of input terminals of the voltage detection circuit 1 are connected to connection lines L1 to Ln + 1, respectively.

  An output voltage (positive voltage or negative voltage) is input to such a voltage detection circuit 1 from output terminals (plus and minus terminals) of each of the battery cells b <b> 1 to bn via the cutoff circuit 2. The voltage detection circuit 1 detects a voltage between terminals (a difference voltage between a positive voltage and a negative voltage) of each of the battery cells b1 to bn as a cell voltage V1 to Vn based on the output voltage of each of the battery cells b1 to bn. The state of the battery pack X is monitored based on the cell voltages V1 to Vn. The voltage detection circuit 1 outputs the monitoring result of the battery pack X to a battery control device (battery ECU) that controls charging and discharging of the battery pack X.

  The shut-off circuit 2 is provided at an intermediate portion of each of the connection lines L1 to Ln + 1 between the assembled battery X and the voltage detection circuit 1, and connects the assembled battery X and the voltage detection circuit 1 according to the state of the assembled battery X. Connected or disconnected. That is, the shutoff circuit 2 is an aggregate of element circuits provided for each of the battery cells b1 to bn. When the output voltage of each of the battery cells b1 to bn is a voltage value in a predetermined normal range, the shutoff circuit 2 is set. The battery X and the voltage detection circuit 1 are connected, and when the output voltage of each of the battery cells b1 to bn is an abnormal voltage, the connection between the battery pack X and the voltage detection circuit 1 is cut off. For example, an abnormal voltage is a voltage outside a normal voltage range and is an undervoltage that does not normally occur. As described above, the cutoff circuit 2 cuts off the electrical connection between the battery pack X and the voltage detection circuit 1, thereby preventing an overcurrent from flowing into each input terminal of the voltage detection circuit 1, and The detection circuit 1 is protected.

  FIG. 2 is a circuit diagram showing a detailed configuration of the shutoff circuit 2 and the voltage detection circuit 1 corresponding to the battery cell b1 as a representative. Note that the shutoff circuit 2 and the voltage detection circuit 1 corresponding to the battery cells b2 to bn other than the battery cell b1 also have the same detailed configuration as FIG.

  The shutoff circuit 2 (element circuit) includes P-channel field effect transistors T11 and T12, switch drive circuits SD1 and SD2, and a switching element SW1. Note that the configuration of the shutoff circuit 2 (element circuit) is the same for all the battery cells b1 to bn. Therefore, the shutoff circuit 2 (element circuit) corresponding to the battery cell b1 will be described below as a representative.

  The P-channel field effect transistor T11 is provided on the connection line L1, the source terminal is connected to the plus terminal of the battery cell b1, and the drain terminal is connected to the voltage detection circuit 1. The gate terminal of the P-channel field effect transistor T11 is connected to the switching drive circuit SD1. The P-channel field effect transistor T11 has a function of connecting or disconnecting the positive terminal of the battery cell b1 and the voltage detection circuit 1.

  The P-channel field effect transistor T21 is provided on the connection line L2, and has a source terminal connected to the negative terminal of the battery cell b1 (a positive terminal of the battery cell b2), and a drain terminal connected to the voltage detection circuit 1. I have. The gate terminal of the P-channel field effect transistor T21 is connected to the switching drive circuit SD2. The P-channel field effect transistor T21 has a function of connecting or disconnecting the voltage detection circuit 1 between the minus terminal of the battery cell b1 (the plus terminal of the battery cell b2).

  The switch drive circuit SD1 drives the P-channel field effect transistor T11. Specifically, when the battery pack X outputs a normal voltage, the switch drive circuit SD1 controls the P-channel field-effect transistor T11 to a conductive state (closed state), so that the battery pack X generates an excessively small voltage that does not normally occur. When a certain abnormal voltage is output, it is controlled to a non-conductive state (open state). Note that the case where the battery pack X outputs an abnormal voltage includes, for example, a case where the remaining amount of the battery cell of the battery cell b decreases due to the overdischarge of the battery cell b, a case where the bus bar B comes off, and the like.

As a specific configuration of the switch drive circuit SD1, the switch drive circuit SD1 includes a resistor R11 and a resistor R12.
The resistor R11 has one end connected to the source terminal of the P-channel field effect transistor T11 and the other end connected to the gate terminal of the P-channel field effect transistor T11.
One end of the resistor R12 is connected to the gate terminal of the P-channel field effect transistor T11, and the other end is connected to one end of the switching element SW1.

  The switch drive circuit SD2 drives the P-channel field effect transistor T21. Specifically, the switch drive circuit SD2 controls the P-channel field effect transistor T21 to a conductive state (on state) when the battery pack X outputs a normal voltage, and turns off when the battery pack X outputs an abnormal voltage. (OFF state).

As a specific configuration of the switch drive circuit SD2, the switch drive circuit SD2 includes a resistor R21 and a resistor R22.
One end of the resistor R21 is connected to the source terminal of the P-channel field-effect transistor T21, and the other end is connected to the gate terminal of the P-channel field-effect transistor T21.
One end of the resistor R22 is connected to the gate terminal of the P-channel field effect transistor T21, and the other end is connected to one end of the switching element SW1.

  The switching element SW1 is electrically connected between each gate terminal of the P-channel field effect transistors T11 and T12 and the ground. Specifically, one end of the switching element SW1 is connected to the other end of the resistor R12 and the other end of the resistor R22. The other end of the switching element SW1 is connected to the ground. The switching element SW1 is controlled by the voltage detection circuit 1 to an on state or an off state. Note that the switching element SW1 may be a mechanical switch or an electrical switch.

  Next, the configuration of the voltage detection circuit 1 according to the present embodiment will be described.

  The voltage monitoring unit 7 includes a pair of low-pass filters LPF1 and LPF2, a discharge circuit 10, and a cell voltage detection IC 11.

  The low-pass filter LPF1 has an input terminal connected to the drain terminal of the P-channel field effect transistor T11, and an output terminal connected to the input terminal a1 of the cell voltage detection IC11. In the present embodiment, the low-pass filter LPF1 is a CR filter including a resistor R31 and a capacitor C31. The low-pass filter LPF1 is a filter circuit that removes noise of a voltage input from the plus terminal of the battery cell b1 to the input terminal a1 via the P-channel field effect transistor T11.

  The low-pass filter LPF2 has an input terminal connected to the drain terminal of the P-channel field effect transistor T21, and an output terminal connected to the input terminal a2 of the cell voltage detection IC11. In the present embodiment, the low-pass filter LPF2 is a CR filter including a resistor R41 and a capacitor C41. The low-pass filter LPF2 is a filter circuit that removes noise of a voltage input from the negative terminal of the battery cell b1 (the positive terminal of the battery cell b2) to the input terminal a2 via the P-channel field effect transistor T21.

The discharge circuit 10 includes a pair of discharge resistors R51 and R52 and a switching element SW2.
One end of the discharge resistor R51 is connected to the input terminal of the low-pass filter LPF1. The other end of the discharge resistor R51 is connected to the input terminal a3 of the cell voltage detection IC11.

  One end of the discharge resistor R52 is connected to the input terminal of the low-pass filter LPF2. The other end of the discharge resistor R52 is connected to the input terminal a4 of the cell voltage detection IC11.

  The switching element SW2 is connected to the pair of input terminals a3, a4. Specifically, the switching element SW2 is controlled to an open state or a closed state by the cell voltage detection IC11. The open / close switch 7b is controlled to be in a closed state by the cell voltage detection IC 11 to make the input terminal a3 and the input terminal a4 conductive. As a result, the electric charge stored in the capacitor C31 of the low-pass filter LPF1 is discharged. Further, by conducting between the input terminal a3 and the input terminal a4, the plus terminal and the minus terminal of the battery cell b1 are interconnected, and the electric charge of the battery cell b1 is discharged.

  Note that the switching element SW2 may be provided integrally with the cell voltage detection IC 11, or may be provided separately from the cell voltage detection IC 11. Further, the switching element SW2 may be a mechanical switch or an electrical switch.

The cell voltage detection IC 11 includes a voltage detection unit 12 and a control unit 13.
The voltage detection unit 12 determines the state of the battery pack X based on the output voltages (cell voltages V1 to Vn) of the battery cells b1 to bn input via the (n + 1) connection lines L1 to Ln + 1 and the cutoff circuit 2. Is monitored at predetermined time intervals.

The control unit 13 controls the switching element SW1 to be turned on or off. For example, at the time of starting the vehicle (for example, when the ignition switch is turned on), the control unit 13 outputs a switching signal to the switching element SW1 to control the switching element SW1 to an on state. Then, the control unit 13 controls the switching element SW1 to be always on until the ignition switch is turned off.
In addition, the control unit 13 causes the vehicle to operate the discharge circuit 10 at a predetermined cycle to execute a discharge process of the discharge circuit 10.

Hereinafter, the operation of the cutoff circuit 2 according to one embodiment of the present invention will be described in detail.
For example, when an ignition switch (not shown) is turned on to start the vehicle, the control unit 13 outputs a switching signal to the switching element SW1. As a result, the switching element SW1 is turned on, and the other ends of the resistors R12 and R22 are grounded.

  When the other ends of the resistor R12 and the resistor R22 are grounded, when a normal voltage is output from the battery pack X, a current flows from the battery pack X to the ground. For example, as shown in FIG. 3, when the voltage output from the battery pack X to the cutoff circuit 2 via the connection line L1 is within a normal voltage range, the battery cell b1 starts with the resistor R11 and the resistor R11. The current I1 flows to the ground via the switch R12 and the switching element SW1. Therefore, the gate-source voltage (VGS) of the P-channel field effect transistor T11 becomes higher than the gate threshold voltage, and the P-channel field effect transistor T11 is turned on. Therefore, the voltage detection unit 12 can detect the voltage of the positive terminal of the battery cell b1.

Similarly, when the voltage output from the battery pack X to the cutoff circuit 2 via the connection line L2 is within a normal voltage range, the battery cell b2 outputs a resistor R21, a resistor R22, and a switching element SW1. , A current I2 flows to the ground. Therefore, the gate-source voltage (VGS) of the P-channel field-effect transistor T21 becomes higher than the gate threshold voltage, and the P-channel field-effect transistor T21 is turned on. Therefore, the voltage detection unit 12 can detect the voltage of the negative terminal of the battery cell b1.
Thereby, the voltage detection unit 12 can detect the voltage between the terminals of the battery cell b1 (cell voltage V1).

  On the other hand, in a state where the other ends of the resistors R12 and R22 are grounded, that is, in a state where the switching element SW1 is controlled to be turned on, the battery cell b may be overdischarged or the bus bar B may come off. When an abnormal voltage is output from the battery X, no current flows from the battery pack X to the ground.

  For example, as illustrated in FIG. 4, it is assumed that the bus bar B connected to the plus terminal of the battery cell b <b> 1 comes off and an abnormal voltage is output from the battery pack X. In this case, the current I flowing from the battery cell b1 to the ground stops flowing, so that the gate-source voltage (VGS) of the P-channel field effect transistor T11 becomes lower than the gate threshold voltage. Therefore, the P-channel field effect transistor T11 is turned off, and the electrical connection between the battery cell b1 and the voltage detection circuit 1 is cut off. Therefore, the cutoff circuit 2 can protect the voltage detection circuit 1 from an excessive reverse voltage generated when the bus bar B comes off.

  That is, when the bus bar B connected to the plus terminal of the battery cell b1 comes off, the cutoff circuit 2 controls the P-channel field-effect transistor T11 to an off state, so that the current I3 in FIG. Block the flow path. Thus, it is possible to prevent the voltage detection circuit 1 from generating an excessive reverse voltage at which the input terminal a2 of the cell voltage detection IC 11 has a higher potential than the input terminal a1.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments and includes a design and the like within a range not departing from the gist of the present invention.

(Modification 1) The battery pack X of the above embodiment may include a CID (Current Interrupt Device). For example, a CID may be provided on the plus terminal side of each of the battery cells b1 to bn corresponding to each of the battery cells b1 to bn constituting the assembled battery X.

(Modification 2) In the above-described embodiment, the case where the battery pack X outputs an abnormal voltage includes the case where the remaining amount of the battery cell of the battery cell b is reduced due to the overdischarge of the battery cell b or the case where the bus bar B comes off. However, the present invention is not limited to this, and the voltage detection circuit 1 can be protected against an overvoltage caused by an abnormal voltage caused by various factors.

(Modification 3) In the above embodiment, the case where the shutoff circuit 2 shown in FIG. 2 is provided for each battery cell b1 to bn has been described, but the present invention is not limited to this. For example, the cutoff circuit 2 shown in FIG. 2 may be provided for at least one or more of the battery cells b among the battery cells b1 to bn.

As described above, the cutoff circuit 2 that is the circuit protection device according to the embodiment of the present invention includes the assembled battery X and the voltage detection circuit 1 to which the plus voltage and the minus voltage of the assembled battery X are input. It is provided. The shutoff circuit 2 includes a P-channel field-effect transistor and a switching drive circuit that drives the P-channel field-effect transistor.
In the P-channel field effect transistor, the source terminal is connected to the plus terminal of the battery cell b constituting the battery pack X, the drain terminal is connected to the voltage detection circuit 1, and the gate terminal is connected to the switching element SW1. Further, when the switching element SW1 is controlled to be in the ON state, the switching drive circuit turns on the P-channel field-effect transistor when the battery pack X outputs a normal voltage, and when the battery pack X outputs an abnormal voltage. The P-channel field effect transistor is turned off.

  According to such a configuration, when the battery pack X outputs an abnormal voltage, the shutoff circuit 2 uses the P-channel type field effect transistor T11 to connect the battery cell b and the voltage detection circuit 1 without using a fuse. The electrical connection between the two can be broken. Therefore, the voltage detection circuit 1 can be protected from a decrease in the remaining amount of cells due to overdischarge and an excessive reverse voltage generated when the bus bar B comes off.

  The switch driving circuit in the cutoff circuit 2 includes a first resistor having one end connected to the positive terminal of the battery cell and the other end connected to the source terminal of the P-channel field-effect transistor; A second resistor connected to the gate terminal of the field effect transistor and having the other end connected to ground via the switching element SW1.

  According to such a configuration, when the battery pack X outputs an abnormal voltage, the shutoff circuit 2 automatically switches the P-channel field effect transistor T11 to the off state. 1 can be immediately cut off to protect the voltage detection circuit 1 from excessive reverse voltage.

X assembled battery (DC power supply)
b1 to bn Battery cell 1 Voltage detection circuit 2 Cutoff circuit T11, T12 P-channel field effect transistor SW1 Switching elements SD1, SD2 Switch drive circuits R11, R21 Resistor (first resistor)
R12, R22 resistors (second resistors)

Claims (2)

A circuit protection device provided between a DC power supply and a protection target circuit to which a positive voltage and a negative voltage of the DC power supply are input,
A P-channel field-effect transistor having a source terminal connected to a positive terminal of the battery cell constituting the DC power supply, and a drain terminal connected to the circuit to be protected;
A switching element connected between a gate terminal of the P-channel field effect transistor and ground;
When the switching element is controlled to be in an ON state, the P-channel field-effect transistor is turned on when the DC power supply outputs a normal voltage, and the P-channel field-effect transistor is turned on when the DC power supply outputs an abnormal voltage. A switch drive circuit for turning off the transistor,
A circuit protection device comprising: The switch drive circuit,
A first resistor having one end connected to a positive terminal of the battery cell and the other end connected to a source terminal of the P-channel field effect transistor;
A second resistor having one end connected to the gate terminal of the P-channel field effect transistor and the other end connected to the ground via the switching element;
The circuit protection device according to claim 1, further comprising:

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