Charge / discharge control circuit and battery device

Abstract

To provide a charge / discharge control circuit for preventing characteristics deterioration in a detection voltage due to disconnection of an intermediate terminal.SOLUTION: A charge / discharge control circuit 110 includes: a constant current source that causes a detection current to flow; a plurality of voltage detection circuits that are connected in parallel to a plurality of secondary batteries, respectively; and a control circuit 120 to which outputs of the plurality of voltage detection circuits are input. The voltage detection circuit includes: a voltage dividing circuit that outputs a divided voltage based on an input voltage between positive and negative electrode input terminals; a reference voltage source VRn that outputs a reference voltage; a first comparison circuit C1n that inputs and compares the divided voltage and the reference voltage; a second comparison circuit C2n that inputs and compares potentials of the positive and negative electrode input terminals; and switches S1n and S2n that block the input voltage of the first comparison circuit. The control circuit blocks the input voltage of the first comparison circuit based on a detection signal output by the second comparison circuit when an intermediate terminal is disconnected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charge / discharge control circuit and a battery device. [Background technology]

[0002] In a battery device with multiple secondary batteries connected in series, if a disconnection occurs between a secondary battery and a charge / discharge control circuit (hereinafter referred to as intermediate terminal disconnection), the charge / discharge control of the secondary batteries becomes impossible. In other words, even if a secondary battery is overcharged or overdischarged, this cannot be detected or controlled, and stress is placed on the secondary batteries.

[0003] As an example of a technique for detecting such an intermediate terminal disconnection, a technique has been proposed in which the change in voltage between two points that changes before and after the intermediate terminal disconnection is detected using a comparison circuit (see, for example, Patent Document 1).

[0004] This will be explained using an example of a battery device equipped with multiple secondary batteries connected in series. In the battery device shown in Figure 3, if the connection between intermediate terminal VC3 and a secondary battery is disconnected, i.e., if an intermediate terminal disconnection occurs, intermediate terminal VC3 is pulled up and exceeds the voltage of intermediate terminal VC2, i.e., the terminal-to-terminal voltage between intermediate terminals VC2 and VC3 changes. If this change in terminal voltage is detected by comparison circuit C22, the intermediate terminal disconnection state can be detected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-1446 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the intermediate terminal VC3 is disconnected, the voltage of the intermediate terminal VC3 rises to the (apparent) overcharge voltage, and a voltage exceeding the reference voltage VR3 continues to be input to the comparator circuit C13 for a long period of time, which deteriorates the characteristics of the transistors that make up the comparator circuit C13, deteriorates the offset characteristics of the comparator circuit C13, and deteriorates the characteristics of the detection voltage, so there is room for improvement.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a charge / discharge control circuit and a battery device that prevent deterioration of the characteristics of the detected voltage due to disconnection of the intermediate terminal. [Means for solving the problem]

[0008] The charge / discharge control circuit and the battery device of the present invention comprise: a positive power supply connection terminal, an intermediate terminal, and a negative power supply connection terminal to which the positive electrode terminals, inter-battery connection terminals, and negative electrode terminals of the plurality of secondary batteries connected in series are respectively connected; a constant current source that supplies a detection current between the positive power supply connection terminal and the intermediate terminal, between adjacent intermediate terminals, and between the intermediate terminal and the negative power supply connection terminal; a plurality of voltage detection circuits connected in parallel to the plurality of secondary batteries; a control circuit to which outputs of the plurality of voltage detection circuits are input, The voltage detection circuit a voltage divider circuit that outputs a divided voltage based on an input voltage between the positive input terminal and the negative input terminal; a reference voltage source that outputs a reference voltage; a first comparison circuit that receives the divided voltage and the reference voltage and compares them; a second comparison circuit that receives and compares the potentials of the positive input terminal and the negative input terminal; a switch that cuts off the input voltage of the first comparison circuit; When the intermediate terminal is disconnected, the control circuit Based on the detection signal output by the second comparison circuit, The input voltage of the first comparison circuit is cut off. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent the deterioration of the characteristics of the detected voltage due to the disconnection of the intermediate terminal. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit diagram of a charge / discharge control circuit and a battery device according to an embodiment of the present invention; [Figure 2] 1 is a circuit diagram of a charge / discharge control circuit and a battery device according to an embodiment of the present invention; [Figure 3] FIG. 1 is a circuit diagram of a conventional charge / discharge control circuit and a battery device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings used to explain the embodiments, the same parts are generally designated by the same reference numerals, and repeated explanations thereof will be omitted. In addition, in the specification, components whose reference numerals end with "n" will be written as "n=1 to 3" to represent that they have been explained three times.

[0012] 1 is a circuit diagram of a battery device including a charge / discharge control circuit of this embodiment. The battery device 100 includes secondary batteries VB1, VB2, and VB3, and a charge / discharge control circuit 110. The charge / discharge control circuit 110 includes power supply terminals VDD and VSS, input terminals VC1, VC2, and VC3, constant current sources IPD and IPU, a control circuit 120, and three voltage detection circuits. The voltage detection circuit includes a voltage divider circuit, a reference voltage source VRn, comparison circuits C1n and C2n, and switches S1n and S2n, and the voltage divider circuit includes resistors R1n and R2n (n=1 to 3).

[0013] The positive terminal of the secondary battery VB1 is connected to the input terminal VC1 and the power supply terminal VDD, and the negative terminal is connected to the input terminal VC2. The positive terminal of the secondary battery VB2 is connected to the input terminal VC2, and the negative terminal is connected to the input terminal VC3. The positive terminal of the secondary battery VB3 is connected to the input terminal VC3, and the negative terminal is connected to the power supply terminal VSS. The input terminals VC2 and VC3 are not connected to the power supply terminals VDD and VSS, so they can be considered intermediate terminals. The constant current source IPD is connected between the input terminal VC2 and the power supply terminal VSS. The constant current source IPU is connected between the power supply terminal VDD and the input terminal VC3.

[0014] Resistors R11 and R21 are connected in series between input terminals VC1 and VC2. The junction of resistors R11 and R21 is connected to the non-inverting input terminal of a comparator circuit C11 via a switch S11. A reference voltage source VR1 has a negative terminal connected to the input terminal VC2 and a positive terminal connected to the inverting input terminal of the comparator circuit C11 via a switch S21. The output terminal of the comparator circuit C11 is connected to a control circuit 120. The comparator circuit C21 has a non-inverting input terminal connected to the input terminal VC1, an inverting input terminal connected to the input terminal VC2, and an output terminal connected to the control circuit 120.

[0015] Resistors R12 and R22 are connected in series between input terminals VC2 and VC3. The junction of resistors R12 and R22 is connected to the non-inverting input terminal of a comparator circuit C12 via switch S12. A reference voltage source VR2 has a negative terminal connected to input terminal VC3 and a positive terminal connected to the inverting input terminal of the comparator circuit C12 via switch S22. The output terminal of the comparator circuit C12 is connected to the control circuit 120. The comparator circuit C22 has a non-inverting input terminal connected to input terminal VC2, an inverting input terminal connected to input terminal VC3, and an output terminal connected to the control circuit 120.

[0016] Resistors R13 and R23 are connected in series between the input terminal VC3 and the power supply terminal VSS. The junction of resistors R13 and R23 is connected to the non-inverting input terminal of a comparator circuit C13 via a switch S13. A reference voltage source VR3 has a negative terminal connected to the power supply terminal VSS and a positive terminal connected to the inverting input terminal of the comparator circuit C13 via a switch S23. An output terminal of the comparator circuit C13 is connected to a control circuit 120. A non-inverting input terminal of the comparator circuit C23 is connected to the input terminal VC3, an inverting input terminal connected to the power supply terminal VSS, and an output terminal connected to the control circuit 120.

[0017] In FIG. 1, the input terminal VC3, which is the intermediate terminal, is disconnected, and therefore the switches S1n and S2n of the comparison circuit C1n are controlled so that both input terminals are connected to the negative terminal of the reference voltage source VRn (n=1 to 3).

[0018] The constant current sources IPD and IPU pass a detection current to detect intermediate terminal disconnection. The constant current source IPD pulls down the input terminal VC2 when the connection between the input terminal VC2 and the secondary battery is disconnected. The constant current source IPU pulls up the input terminal VC3 when the connection between the input terminal VC3 and the secondary battery is disconnected.

[0019] The comparator circuit C1n detects the battery voltage, and the comparator circuit C2n detects intermediate terminal disconnection. The comparator circuits C11 and C21 monitor the voltage between the input terminals VC1 and VC2. The comparator circuits C12 and C22 monitor the voltage between the input terminals VC2 and VC3. The comparator circuits C13 and C23 monitor the voltage between the input terminal VC3 and the power supply terminal VSS. The control circuit 120 receives the outputs of the comparator circuits C1n and C2n and outputs signals to control the switches S1n and S2n (n=1 to 3).

[0020] Figure 2 is also a circuit diagram of a battery device equipped with a charge / discharge control circuit of this embodiment. The differences from Figure 1 are that the input terminal VC3, which is an intermediate terminal, is not disconnected, and that the non-inverting input terminal of the comparison circuit C1n is connected to the junction of resistors R1n and R2n, and switches S1n and S2n are controlled so that the inverting input terminal is connected to the positive electrode of the reference voltage source VRn (n = 1 to 3). Other than that, it is essentially the same as Figure 1.

[0021] Next, the operation of the battery device equipped with the charge / discharge control circuit of this embodiment will be described. 2, when the charge / discharge control circuit 110 monitors the voltages of the secondary batteries VB1, VB2, and VB3, the connection between the input terminal VC3 and the secondary batteries is not disconnected, i.e., no intermediate terminal disconnection has occurred. At this time, the voltage at the input terminal VC1 is greater than the voltage at the input terminal VC2, the voltage at the input terminal VC2 is greater than the voltage at the input terminal VC3, and the voltage at the input terminal VC3 is greater than the voltage at the power supply terminal VSS. As a result, the voltage at the non-inverting input terminal of the comparator circuit C2n is greater than the voltage at the inverting input terminal, and the comparator circuit C2n outputs an H level (n=1 to 3).

[0022] The control circuit 120 outputs a signal to control the switches S1n and S2n based on the output level of the comparison circuit C2n. When the comparison circuit C2n outputs an H level, the control circuit 120 detects that no intermediate terminal disconnection has occurred and controls the switches S1n and S2n (n=1 to 3) so that the non-inverting input terminal of the comparison circuit C1n is connected to the junction of the resistors R1n and R2n and the inverting input terminal of the comparison circuit C1n is connected to the positive terminal of the reference voltage source VRn.

[0023] 1, when the charge / discharge control circuit 110 is monitoring the voltages of the secondary batteries VB1, VB2, and VB3, if the connection between input terminal VC3 and the secondary battery is lost, i.e., an intermediate terminal disconnection occurs, input terminal VC3 is pulled up by constant current source IPU, and the voltage at input terminal VC2 becomes less than the voltage at input terminal VC3. As a result, the voltage at the non-inverting input terminal of comparator circuit C22 becomes less than the voltage at the inverting input terminal, and comparator circuit C22 outputs an L level.

[0024] Although not shown, when the connection between input terminal VC2 and the secondary battery is disconnected, input terminal VC2 is pulled down by constant current source IPD, and the voltage at input terminal VC2 becomes less than the voltage at input terminal VC3. In this case, too, the voltage at the non-inverting input terminal of comparator circuit C22 becomes less than the voltage at the inverting input terminal, and comparator circuit C22 outputs an L level.

[0025] When any of the comparison circuits C2n outputs an L level, the control circuit 120 detects that an intermediate terminal disconnection has occurred, and controls the switches S1n and S2n (n=1 to 3) so that the input voltage of the comparison circuit C1n drops to the voltage level of the negative terminal of the reference voltage source VRn and is cut off.

[0026] Even if the intermediate terminal VC3 is disconnected and the voltage at the intermediate terminal VC3 rises to the (apparent) overcharge voltage, the input voltage at the input terminal of the comparator circuit C13 is reduced to the voltage level of the negative terminal of the reference voltage source VR3 and is cut off. As a result, the characteristics of the transistors that make up the comparator circuit C13 are less likely to deteriorate, the offset characteristics of the comparator circuit C13 are less likely to deteriorate, and deterioration of the overcharge detection voltage characteristics can be prevented.

[0027] As explained above, even if the intermediate terminal becomes disconnected, the input terminal of the comparison circuit that detects the battery voltage can be cut off, and a voltage exceeding the reference voltage will not be input to the comparison circuit for a long period of time, thereby preventing deterioration of the characteristics of the detected voltage.

[0028] Although the above description is based on the case where three secondary batteries are connected, the number of secondary batteries is not limited. Furthermore, the detection voltage capable of preventing characteristic degradation, which is the effect of the present invention, is not limited to the overcharge detection voltage. Furthermore, although a constant current source is used as a means for pulling up or down the intermediate terminal, this is not a limitation. Furthermore, the present invention is not limited to whether the constant current source has a period during which it flows or does not flow a detection current.

[0029] These embodiments and their variations are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0030] 100 Battery Device 110 Charge / discharge control circuit 120 control circuit VB1, VB2, VB3 secondary battery VC1, VC2, VC3 input terminals R11, R12, R13 resistors R21, R22, R23 resistance VR1, VR2, VR3 Reference voltage sources C11, C12, C13 comparison circuit C21, C22, C23 comparison circuit S11, S12, S13 switches S21, S22, S23 switches IPD, IPU constant current source VDD, VSS power supply pin

Claims

1. a positive power supply connection terminal, an intermediate terminal, and a negative power supply connection terminal to which the positive electrode terminals, inter-battery connection terminals, and negative electrode terminals of the plurality of secondary batteries connected in series are respectively connected; a constant current source that supplies a detection current between the positive power supply connection terminal and the intermediate terminal, between adjacent intermediate terminals, and between the intermediate terminal and the negative power supply connection terminal; a plurality of voltage detection circuits connected in parallel to the plurality of secondary batteries; a control circuit to which outputs of the plurality of voltage detection circuits are input, The voltage detection circuit a voltage divider circuit that outputs a divided voltage based on an input voltage between the positive input terminal and the negative input terminal; a reference voltage source that outputs a reference voltage; a first comparison circuit that receives the divided voltage and the reference voltage and compares them; a second comparison circuit that receives and compares the potentials of the positive input terminal and the negative input terminal; a switch that cuts off the input voltage of the first comparison circuit; When the intermediate terminal is disconnected, the control circuit Based on the detection signal output by the second comparison circuit, an input voltage of the first comparison circuit is cut off; Charge and discharge control circuit.

2. the constant current source has a period during which the detection current does not flow; 2. The charge / discharge control circuit according to claim 1.

3. a plurality of secondary batteries connected in series; a charge / discharge control circuit according to claim 1 or 2, which controls charging / discharging of the plurality of secondary batteries; A battery device comprising:

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