JP2014070987A - Voltage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform self diagnosis of the capacitance change of a capacitor.SOLUTION: In voltage detection mode, SW6A and SW6B are turned on and SW53, SW54, SW81, and SW82 are turned off to put an inverter circuit 9 into a non-inverting state, and SW4A, SW4B and SW5 are turned off and SW51, SW52, SW3A, SW3B, SWB3, and SWB4 are turned on to set an electric charge. Then, SW51, SW52, SW3A, SW3B, SWB3, and SWB4 are turned off and SW4A, SW4B, and SW5 are turned on to detect VB4. In self diagnosis mode, SW51 and SW52 are turned off and SW5 and SWB4 are turned on to put the inverter circuit 9 into the non-inverting state. SW4A, SW4B, SW6A, and SW6B are turned off and SW53, SW54, SW81, SW82, SW3A, and SW3B are turned on to set the electric charge. Then, SW53, SW54, SW81, SW82, SW3A, and SW3B are turned off and SW4A, SW4B, SW6A, and SW6B are turned on to perform diagnosis with an output voltage.

Description

  The present invention relates to a voltage detection device having a self-diagnosis function of capacitance change of a capacitor.

  A hybrid vehicle or an electric vehicle includes a battery pack configured by connecting a plurality of secondary batteries (unit batteries) in series. In such an assembled battery, it is necessary to individually detect the voltage of each secondary battery for capacity calculation and protection management of each secondary battery. However, since the number of series-connected secondary batteries constituting the assembled battery in the above application is very large, the potential of the secondary battery increases according to the connection position in the assembled battery, and the voltage detection device of the secondary battery has a high voltage. Is applied.

  Patent Document 1 discloses an operational amplifier, a first capacitor having one end connected to the inverting input terminal of the operational amplifier, a second capacitor connected between the inverting input terminal and the output terminal of the operational amplifier, a discharge circuit, and a unit battery. A voltage detection circuit is disclosed that includes switches connected between a terminal and the other end of the first capacitor. The switch and discharge circuit between the positive terminal of the unit battery and the first capacitor are turned on to charge the first capacitor, and then the switch is replaced with the negative terminal of the unit battery and the first one with the discharge circuit turned off. The voltage of the unit battery is detected by turning on the switch between the capacitors.

JP 2008-145180 A

  Generally, when a high voltage is applied for a long period of time or a capacitor is placed in a high temperature environment for a long period of time, aged deterioration occurs and the capacitance value changes (durability fluctuation). For example, since the voltage detection device described in Patent Document 1 has a gain corresponding to the capacitance ratio of the first capacitor and the second capacitor, an error occurs in the detection voltage when the capacitance value of any capacitor changes due to aging degradation. . In this case, even if the output voltage is observed, it cannot be determined whether the capacitance value of the capacitor has changed or whether the battery voltage has changed. Furthermore, in a voltage detection apparatus including a plurality of capacitors, the capacitance values of not only one capacitor but also a plurality of capacitors may change simultaneously. In this case, the determination becomes more difficult.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a voltage detection device capable of self-diagnosis of a change in the capacitance of a capacitor used for voltage detection.

  The means described in claim 1 is a voltage detection device having a fully differential configuration. That is, between the operational amplifier having a differential output configuration, the first switch connected between one terminal of the detection target voltage source and the first common node, and the other terminal of the detection target voltage source and the second common node. A first switch having one end connected to the first common node, a first B capacitor having one end connected to the second common node, an inverting input terminal and a non-inverting output terminal of the operational amplifier. A third A switch connected between the two, a third B switch connected between the non-inverting input terminal and the inverting output terminal of the operational amplifier, and a series connection between the inverting input terminal and the non-inverting output terminal of the operational amplifier. The second A capacitor and the fourth A switch, the second B capacitor and the fourth B switch connected in series between the non-inverting input terminal and the inverting output terminal of the operational amplifier, the first common node, and the second A first reference voltage selection circuit capable of applying a first A reference voltage or a second A reference voltage to a common connection point of the second A capacitor and the fourth A switch; and a second B Connected between the second reference voltage selection circuit capable of applying the first B reference voltage and the second B reference voltage to the common connection point of the capacitor and the 4B switch, and the other end of the first A capacitor and the inverting input terminal of the operational amplifier. The 6A switch, the 6B switch connected between the other end of the 1B capacitor and the non-inverting input terminal of the operational amplifier, and the third reference voltage capable of applying the 3A reference voltage to the other end of the 1A capacitor A selection circuit; a fourth reference voltage selection circuit capable of applying a third B reference voltage to the other end of the first B capacitor; and a control unit.

  The control means can execute a voltage detection mode for detecting the voltage of the detection target voltage source and a self-diagnosis mode for detecting a change in the capacitance of the capacitor. In the voltage detection mode, the 4A, 4B, and 5th switches are opened, the voltage application by the 3rd and 4th reference voltage selection circuits is stopped, and the 1A and 2nd switches by the 1st and 2nd reference voltage selection circuits. A 1B reference voltage is applied, the 3A, 3B, 6A, and 6B switches are closed, and the 1st and 2nd switches are closed to set charges in the 1A, 1B, 2A, and 2B capacitors. Thereafter, the first, second, third A, and third B switches are opened, the voltage application by the first and second reference voltage selection circuits is stopped, and the fourth A, fourth B, and fifth switches are closed to redistribute charges. Is done.

  If the capacitance values of the 1A, 1B, 2A, and 2B capacitors are C1A, C1B, C2A, and C2B, and the 1A and 1B reference voltages are V1A and V1B, the differential output voltage of the operational amplifier by charge redistribution Since VOP−VOM is (series capacitance value of C1A and C1B / series capacitance value of C2A and C2B) × voltage of the detection target voltage source + (V1A−V1B), the terminal of the detection target voltage source is based on the output voltage. Inter-voltage can be detected.

  On the other hand, in the self-diagnosis mode, after opening at least one of the first and second switches, the fifth switch is closed, the 3A and 3B switches are closed, and the 4A, 4B, 6A, and 6B are closed. The switch is opened, and the first, second, third, and fourth reference voltage selection circuits apply the second A, second, third A, and third B reference voltages to the first A, first B, second A, and second B capacitors. Set the charge. After that, the 3A and 3B switches are opened, the voltage application by the 1st, 2nd, 3rd and 4th reference voltage selection circuits is stopped, and the 4A, 4B, 6A and 6B switches are closed to charge. Are redistributed.

  If the 2A, 2B, 3A, and 3B reference voltages are V2A, V2B, V3A, and V3B, the differential output voltage VOP-VOM of the operational amplifier by charge redistribution is C1A, C1B, C2A, C2B, V2A, It is determined as a function of V2B, V3A, V3B, and common mode voltage VCOM. The differential output voltage in this self-diagnosis mode does not depend on the voltage of the detection target voltage source. As long as the 2A, 2B, 3A, and 3B reference voltages are correct, the differential output voltage when the capacitance value of any one or any of the three capacitors changes due to aging or failure is the capacitance value. It becomes a voltage value different from the differential output voltage at normal time with no change. For this reason, it can be detected that the capacitance value of the capacitor has changed.

  The differential output voltage when the capacitance values of any two or all four capacitors change may be the same voltage value as the voltage value different from the differential output voltage in the normal state. If the values are the same, it cannot be detected that the capacitance value of the capacitor has changed in the self-diagnosis mode. However, in the case where the same value is obtained, even if the capacitance value of the capacitor is changed, there is no error in the voltage between the terminals of the detection target voltage source detected based on the differential output voltage in the voltage detection mode. Therefore, the fact that it cannot actually be detected is not a problem. That is, when a detection error occurs at least in the voltage detection mode, the capacitance change can be diagnosed in the self-diagnosis mode.

  According to the present means, since it has a fully differential configuration, even if the common mode noise is superimposed in any of the capacitor charge setting and charge redistribution in the voltage detection mode and the self-diagnosis mode, The common mode noise can be removed from the output voltage. Further, since the circuit configuration is symmetric, an error caused by feedthrough that occurs when each switch is switched can be canceled, and a detection voltage with higher accuracy can be obtained.

  According to a second aspect of the present invention, there is provided a seventh A switch connected between the other end of the first A capacitor and the non-inverting input terminal of the operational amplifier, and between the other end of the first B capacitor and the inverting input terminal of the operational amplifier. A cross switch including a connected seventh B switch is provided. In the voltage detection mode, the control means keeps the seventh A and seventh B switches open. In the self-diagnosis mode, charges are set in the first A, first B, second A, and second B capacitors as described above with the seventh A and seventh B switches open. After that, instead of closing the 6A and 6B switches, the capacitance change of each capacitor is self-diagnosis based on the differential output voltage of the operational amplifier after the 7A and 7B switches are closed.

  According to the self-diagnosis mode of this means, the differential output voltage when the capacitance value of any one, two or three capacitors changes is different from the differential output voltage at normal time when there is no change in the capacitance value. It becomes a voltage value. For this reason, it can be detected that the capacitance value of the capacitor has changed. In addition, the differential output voltage when the capacitance values of all four capacitors are changed may be the same voltage value as when the differential output voltage is different from the normal differential output voltage. However, if the values are the same, even if the capacitance value of the capacitor has changed, there is no error in the voltage between the terminals of the voltage source to be detected that is detected based on the differential output voltage in the voltage detection mode. Therefore, the fact that it cannot actually be detected is not a problem.

  4. The means according to claim 3, wherein the voltage source to be detected is a unit battery that is connected in series with the same polarity to constitute an assembled battery. Adjacent unit cells are connected in series with one terminal or other terminals connected to each other. As a result, the first switch is provided between one terminal of each unit cell and the first common node while sharing with the first switch of the adjacent unit cell, and the second switch is provided for each unit cell. It is provided between the other terminal and the second common node while sharing the second switch of the adjacent unit battery. According to this means, the voltage of each unit battery constituting the assembled battery can be detected using the low-voltage fully differential operational amplifier.

  Since the total number of the first switch and the second switch can be halved by the above common use, the effect of reducing the switch increases as the number of unit batteries constituting the assembled battery increases. However, since the connection polarity of the adjacent unit battery to the voltage detection device is reversed, an inversion circuit for inverting the polarity of the differential output voltage output from the operational amplifier is provided. The control means sets the inverting circuit to a non-inverting operation when detecting the voltage between the terminals of the unit battery whose high potential side terminal is one terminal, and when detecting the voltage between the terminals of the unit battery whose high potential side terminal is the other terminal. The inverting circuit is set to inverting operation.

  5. The means according to claim 4, wherein the voltage source to be detected is a unit battery that is connected in series with the same polarity to constitute an assembled battery. The first switch is provided between the high potential side terminal of each unit battery and the first common node, and the second switch is provided between the low potential side terminal of each unit battery and the second common node. It has been. According to this means, the voltage of each unit battery constituting the assembled battery can be detected using the low-voltage fully differential operational amplifier. Further, although the first switch and the second switch are required for each unit battery, the above-described inverting circuit is not necessary.

1 is a configuration diagram of a voltage detection apparatus showing a first embodiment. The figure which shows the ON / OFF state of the switch in the voltage detection mode and the waveform of the output voltage The figure which shows the ON / OFF state of the switch and the waveform of output voltage in the self-diagnosis mode Diagram showing the relationship between the capacitance value of the capacitor and the output voltage VOUT in the voltage detection mode The figure which shows the relationship between the capacitance value of the capacitor and the output voltage VOUT in the self-diagnosis mode FIG. 1 equivalent diagram showing the second embodiment 3 equivalent figure Figure equivalent to FIG. FIG. 1 equivalent view showing the third embodiment 2 equivalent diagram 3 equivalent figure FIG. 1 equivalent view showing the fourth embodiment 3 equivalent figure

In each embodiment, substantially the same parts are denoted by the same reference numerals and description thereof is omitted.
(First embodiment)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 5.
An assembled battery 1 shown in FIG. 1 is mounted on a hybrid vehicle or an electric vehicle, and supplies power to an electric motor via an inverter. The actual assembled battery 1 has a configuration in which a large number of lithium ion secondary batteries, nickel hydride secondary batteries, and the like are connected in series with the same polarity. Here, for convenience of explanation, the battery cell B1 on the low potential side is used here. To the battery cell B4 on the high potential side.

  In the lithium ion secondary battery, the state of charge (SOC) of each battery cell and the cell voltage varies due to individual differences in capacity of each battery cell, differences in self-discharge characteristics, and the like. In such an assembled battery 1, it is necessary to individually detect the voltage of each secondary battery for capacity calculation of each secondary battery and protection management (for example, equalization of battery voltage).

  Respective terminals of battery cells B1 to B4 (detection target voltage source and unit battery) are connected to terminals TB0 to TB4 of the voltage detection device 2 of the assembled battery 1, respectively. The voltages of the terminals TB0 to TB4 are V0 to V4, respectively. The fully differential voltage detection device 2 operates in a voltage detection mode and a self-diagnosis mode. In the voltage detection mode, the voltage VBn of each battery cell Bn (n = 1, 2, 3, 4) constituting the assembled battery 1 is detected, and the differential voltages VOP and VOM corresponding to the voltage VBn are output from the output terminals TP and TM. Is output. In the self-diagnosis mode, differential voltages VOP and VOM corresponding to changes in capacity due to aging or failure of capacitors C1A, C1B, C2A, and C2B, which will be described later, are output, and self-diagnosis is made that the capacitance value of the capacitor has changed.

  The voltage detection device 2 is configured as an IC together with a circuit such as a differential input type A / D converter 3. The voltage detection device 2 operates by receiving a power supply voltage VDD with respect to the ground potential VSS, and includes a differential output type operational amplifier 4 that outputs a differential voltage from a non-inverting output terminal and an inverting output terminal. . The differential voltages VOP and VOM are converted into digital data by the differential input type A / D converter 3.

  The battery cells Bn (n = 1, 2, 3, 4) of the assembled battery 1 are connected in series with one terminal or other terminals connected to each other. For example, the high potential side terminals of the battery cells B2 and B4 are one terminal, the low potential side terminals are other terminals, the high potential side terminals of the battery cells B1 and B3 are other terminals, and the low potential side terminals are one terminal. . This terminal distinction is related to the connection of the switch SWBn (n = 0, 1, 2, 3, 4) to the common lines CL1, CL2 (first and second common nodes) and the voltage output polarity of the operational amplifier 4. Necessary.

  Switches SWB0, SWB2, and SWB4 are connected between the terminals TB0, TB2, and TB4 and the common line CL1, respectively. On the other hand, switches SWB1 and SWB3 are connected between the terminals TB1 and TB3 and the common line CL2, respectively. For each battery cell Bn, the switch SWBx (x is any of 0, 2, 4) connected to one terminal side corresponds to the first switch, and the switch SWBx (x is 1, 3) connected to the other terminal side. Any) corresponds to the second switch. That is, the first switch is connected between one terminal of each battery cell Bn and the common line CL1, and the second switch is connected between the other terminal of the battery cell Bn and the common line CL2.

  When the switch SWBn is provided in this manner, the first switch of the battery cell Bn and the first switch of the adjacent battery cell Bn + 1 or Bn-1 can be shared, and the second switch of the battery cell Bn is adjacent to the first switch. The second switch of the battery cell Bn + 1 or Bn-1 to be used can be shared. For this reason, the number of the first and second switches can be almost halved.

  A first A capacitor C1A and a sixth A switch SW6A are connected in series between the common line CL1 and the inverting input terminal of the operational amplifier 4. A first B capacitor C1B and a sixth B switch SW6B are connected in series between the common line CL2 and the non-inverting input terminal of the operational amplifier 4. Between the inverting input terminal and the non-inverting output terminal of the operational amplifier 4, a second A capacitor C2A and a fourth A switch SW4A are connected in series, and a third A switch SW3A is connected in parallel to this series circuit. Yes. A second B capacitor C2B and a fourth B switch SW4B are connected in series between the non-inverting input terminal and the inverting output terminal of the operational amplifier 4, and a third B switch SW3B is connected in parallel to this series circuit. Yes. A fifth switch SW5 is connected between the common lines CL1 and CL2.

  The first reference voltage selection circuit 5A is configured to be capable of outputting the first A reference voltage VA and the second A reference voltage VC to the connection point between the second A capacitor C2A and the fourth A switch SW4A via the switches SW51 and SW53. Yes. The second reference voltage selection circuit 5B is configured to be capable of outputting the first B reference voltage VB and the second B reference voltage VD via the switches SW52 and SW54 to the connection point between the second B capacitor C2B and the fourth B switch SW4B. Yes. The third reference voltage selection circuit 8A is configured to be able to output the third A reference voltage VS to the connection point between the first A capacitor C1A and the sixth A switch SW6A via the switch SW81. The fourth reference voltage selection circuit 8B is configured to output the third B reference voltage VT to the connection point between the first B capacitor C1B and the sixth B switch SW6B via the switch SW82.

  Between the operational amplifier 4 and the output terminals TP and TM, an inverting circuit 9 for inverting the polarity of the differential output voltage output from the non-inverting output terminal and the inverting output terminal of the operational amplifier 4 is provided. That is, the non-inverting output terminal of the operational amplifier 4 is connected to the output terminals TP and TM via the switches SW91 and SW93, and the inverting output terminal of the operational amplifier 4 is connected to the output terminals TM and TP via the switches SW92 and SW94. ing.

  When the voltage between the terminals of the battery cells B2 and B4 whose high potential side terminal is the one terminal is detected, the switches SW91 and SW92 are turned on to perform the non-inversion operation, and the battery cell B1 whose high potential side terminal is the other terminal. When the voltage between the terminals B3 is detected, the switches SW93 and SW94 are turned on to perform the inversion operation. Each switch described above is composed of MOS transistors, and switching of these switches is performed by a control circuit 10 which is a control means.

  Next, operations and effects of the present embodiment will be described with reference to FIGS. 2 and 3 show the waveforms of the on / off state of the switch and the output voltage VOUT (= VOP−VOM) in the voltage detection mode and the self-diagnosis mode, respectively. Switches not shown in the figure are off.

[Voltage detection mode (Fig. 2)]
The control circuit 10 repeatedly detects the cell voltages VB <b> 1 to VB <b> 4 in descending order while switching each switch, and outputs it to the A / D converter 3. In this mode, the switches SW6A and SW6B are kept on. Further, since the second A reference voltage VC, the second B reference voltage VD, the third A reference voltage VS, and the third B reference voltage VT are not used, the switches SW53, SW54, SW81, and SW82 are held in the off state.

  When detecting the voltage VB4 of the battery cell B4, the control circuit 10 switches SW91 to SW94 to make the inverting circuit 9 non-inverting operation, turns off the switches SW4A, SW4B, and SW5, and switches SW51, SW52, SW3A, SW3B, and SWB3. , SWB4 is turned on to set charges in the first A, first B, second A, and second B capacitors C1A, C1B, C2A, and C2B (period 1). Thereafter, the switches SW51 and SW52 are turned off to stop the application of the first and first B reference voltages VA and VB, and the switches SW3A, SW3B, SWB3 and SWB4 are turned off (non-overlap period 2), and the switches SW4A, SW4B, SW5 is turned on (period 3).

  The general equation for charge storage between period 2 and period 3 is that the capacitors of the first A, first B, second A, and second B capacitors are C1A, C1B, C2A, C2B, the common mode voltage of the operational amplifier 4 is VCOM, and the switch SW5 When the voltage of the common lines CL1 and CL2 when V is turned on is VY and the voltage of the input terminal of the operational amplifier 4 is VX, the equations (1), (2), and (3) are obtained. For example, when the battery cell B4 is detected, Vn = V4, Vn-1 = V3, and Vn-Vn-1 = VB4.

C1A (Vn-VCOM) + C2A (VA-VCOM) = C1A (VY-VX) + C2A (VOP-VX) (1)
C1B (Vn-1−VCOM) + C2B (VB−VCOM) = C1B (VY−VX) + C2B (VOM−VX) (2)
C1A (VCOM-Vn) + C1B (VCOM-Vn-1) = (C1A + C1B) (VX-VY) (3)

Solving this gives equation (4).

  After switching to the period 3, the A / D converter 3 performs A / D conversion on the set output voltage VOUT of the operational amplifier 4 expressed by the equation (4). The control circuit 10 can detect the cell voltage VB4 based on this A / D conversion value. Subsequently, the control circuit 10 turns off the switches SW91, SW92, SW4A, SW4B, and SW5, turns on the switches SW93, SW94, SW51, SW52, SW3A, and SW3B (non-overlap period 4), and the subsequent periods 5, 6, 7 similarly detects the voltage VB3 of the battery cell B3.

[Self-diagnosis mode (Fig. 3)]
Since the first A reference voltage VA and the first B reference voltage VB are not used in this mode, the control circuit 10 holds the switches SW51 and SW52 in the off state. Further, the switch SW5 is turned on to connect the common lines CL1 and CL2, and one of the switches SWB0 to SWB4 (SWB4 here) is turned on in order to fix the potential of the common line. Further, SW91 to SW94 are switched to make the inverting circuit 9 non-inverting operation.

  The control circuit 10 turns off the switches SW4A, SW4B, SW6A, SW6B, and turns on the switches SW53, SW54, SW81, SW82, SW3A, SW3B to turn on the first A, first B, second A, second B capacitors C1A, C1B, C2A, Charge is set in C2B (period 11). Thereafter, the switches SW53, SW54, SW81, and SW82 are turned off to stop the application of the 2A, 2B, 3A, and 3B reference voltages VC, VD, VS, and VT, and the SW3A and SW3B are turned off (non-overlap). In a period 12), the switches SW4A, SW4B, SW6A, and SW6B are turned on (period 13).

  The general expressions for charge storage between the period 12 and the period 13 are expressed by the expressions (5) and (6) when the voltages of the common lines CL1 and CL2 are VY and the voltage of the input terminal of the operational amplifier 4 is VX. Further, the equation (7) is established for the differential output.

C1A (VS-VY) + C2A (VCOM-VC) = C1A (VX-VY) + C2A (VX-VOP) (5)
C1B (VT-VY) + C2B (VCOM-VD) = C1B (VX-VY) + C2B (VX-VOM) (6)
VOP + VOM = 2VCOM (7)
Solving this gives equation (8).

  After switching to the period 13, the A / D converter 3 performs A / D conversion on the output voltage VOUT of the stabilized operational amplifier 4 expressed by the equation (8). The control circuit 10 makes a self-diagnosis that the capacitance value has changed based on the A / D conversion value.

  Hereinafter, the effect of this embodiment will be confirmed with reference to FIGS. 4 and 5. 4 and 5 show the capacitance of one, two, three, or all four capacitors C1A, C1B, C2A, and C2B under the following numerical conditions in the voltage detection mode and the self-diagnosis mode, respectively. The output voltage VOUT (= VOP−VOM) when the value changes from the normal value 1 pF to 1.5 pF is shown.

The common mode voltage of the operational amplifier 4 VCOM = 2.5V
Battery cell Bn voltage VBn = Vn-Vn-1 = 1.25V
1A reference voltage VA = 1.25V
1B reference voltage VB = 3.75V
2A reference voltage VC = 0V
Second B reference voltage VD = 1.25V
3A reference voltage VS = 1.25V
3B reference voltage VT = 2.5V

  The numerical conditions are set such that VC ≠ VD, VS ≠ VT, VC ≠ VS, and VD ≠ VT. In addition, when the capacitance values of a plurality of capacitors change, it is assumed that the capacitance value changes to the same value (1.5 pF) because detection in the self-diagnosis mode is more difficult than when the capacitance values change to different values. It is.

  In the voltage detection mode shown in FIG. 4, when all the capacitors C1A, C1B, C2A, and C2B have a normal capacitance value of 1 pF, the output voltage VOUT becomes −1.25V. On the other hand, when any one of the capacitance values changes to 1.5 pF, an error always occurs in the output voltage VOUT. When any two or any three capacitance values change, an error may or may not occur in the output voltage VOUT. When all four capacitance values change, no error occurs in the output voltage VOUT.

  In the self-diagnosis mode shown in FIG. 5, when all the capacitors C1A, C1B, C2A, C2B have a normal capacitance value of 1 pF, the output voltage VOUT becomes 0V. On the other hand, when any one or any three capacitance values change to 1.5 pF, the output voltage VOUT always deviates from 0V. Therefore, the control circuit 10 can detect that the capacitance value of any one of the capacitors has changed based on the A / D conversion value.

  When any two capacitance values change, the output voltage VOUT may be a value deviated from 0V or may be equal to 0V. When all four capacitance values change, the output voltage VOUT becomes equal to 0V. When this result is compared with the result of the voltage detection mode, it can be seen that no error has occurred in the output voltage VOUT in the voltage detection mode when the output voltage VOUT becomes equal to 0 V in the self-diagnosis mode.

  Therefore, even if the control circuit 10 cannot detect that the capacitance value of the capacitor has changed in the self-diagnosis mode, the voltage of each battery cell Bn can be accurately detected in the voltage detection mode. Does not occur.

  In the voltage detection apparatus 2, the voltage applied to the pair of capacitors C1A and C1B when detecting the voltage VBn is higher in the battery cell Bn arranged on the high potential side (for example, several hundreds V). On the other hand, the voltage applied to the pair of capacitors C2A and C2B is about the voltage of the operation power supply of the operational amplifier 4 (about several volts). For this reason, the pair of capacitors C1A and C1B is more susceptible to endurance fluctuation due to voltage stress than the pair of capacitors C2A and C2B. In addition, since there is almost no difference between the voltage applied to the capacitor C1A and the voltage applied to the capacitor C1B (about several volts for one battery cell), the capacitance values of the capacitors C1A and C1B when durability changes occur. Are likely to change to almost the same value.

  Referring to FIG. 4B under such circumstances, an error occurs in the output voltage VOUT in the voltage detection mode when the capacitance values of the capacitors C1A and C1B both change to 1.5 pF. However, referring to FIG. 5B, it can be seen that the change in the capacitance value can be correctly detected by executing the self-diagnosis mode under this change condition. In this way, the voltage detection device 2 that monitors the voltage of the battery cell can perform an effective self-diagnosis on the variation in the capacitance value in light of the above-described endurance variation occurrence of the capacitors C1A, C1B, C2A, and C2B. it can.

  As described above, the voltage detection device 2 has the capacitance values of the capacitors C1A, C1B, C2A, and C2B due to aging deterioration or failure in addition to the voltage detection mode for detecting the voltage of each battery cell Bn constituting the assembled battery 1. It has a self-diagnosis mode that detects deviations. When this self-diagnosis mode is used, it is possible to determine that the capacitance value has changed from the normal value in the case where a detection error occurs at least in the voltage detection mode due to the deviation of the capacitance value. As a result, high reliability with respect to the detection voltage can be obtained.

  Since the voltage detection device 2 has a fully differential configuration, in the voltage detection mode and the self-diagnosis mode, not only when the common mode noise is superimposed on the battery pack 1 when setting the charges of the capacitors C1A, C1B, C2A, and C2B, Even when common mode noise is superimposed on the assembled battery 1 at the time of redistribution, the common mode noise can be removed from the differential output voltage VOUT of the operational amplifier 4. In addition, since the circuit configuration is symmetric, it is possible to cancel out errors due to feedthrough that occurs at the time of switching each switch, and to perform voltage detection and self-diagnosis with higher accuracy.

  Since the first switch of the battery cell Bn and the first switch of the adjacent battery cell are made common, and the second switch of the battery cell Bn and the second switch of the adjacent battery cell are made common, the first and second switches Can be almost halved. The number of switches that can be reduced increases as the number of cells constituting the battery pack 1 increases. However, an inversion circuit 9 for inverting the polarity of the differential output voltage VOP-VOM output from the operational amplifier 4 is required.

(Second Embodiment)
A second embodiment will be described with reference to FIGS.
The voltage detection device 11 shown in FIG. 6 further includes a seventh A switch SW7A and a seventh B switch SW7B in addition to the voltage detection device 2 shown in FIG. The switch SW7A is connected between the capacitor C1A and the non-inverting input terminal of the operational amplifier 4, and the switch SW7B is connected between the capacitor C1B and the inverting input terminal of the operational amplifier 4. Other configurations are the same as those of the first embodiment.

  In the voltage detection mode, the switches SW7A and SW7B maintain the off state, and operate as shown in FIG. 2 as in the first embodiment. On the other hand, in the self-diagnosis mode, the switches SW6A and SW6B are kept off and operate as shown in FIG. Switches not shown in the figure are off. Charges are set in the capacitors C1A, C1B, C2A, and C2B with the switches SW7A and SW7B turned off (period 11), and then the switches SW4A, SW4B, SW7A, and SW7B are turned on after the non-overlap period 12 (period 13). .

  The general expressions for charge storage between the period 12 and the period 13 are expressed by the following expressions (9) and (10) when the voltages of the common lines CL1 and CL2 are VY and the voltage of the input terminal of the operational amplifier 4 is VX. Further, the above-described equation (7) is also established for the differential output.

C1A (VS-VY) + C2A (VCOM-VC) = C1A (VX-VY) + C2B (VX-VOM) (9)
C1B (VT-VY) + C2B (VCOM-VD) = C1B (VX-VY) + C2A (VX-VOP) (10)
Solving this gives equation (11).

  After switching to the period 13, the A / D converter 3 performs A / D conversion on the output voltage VOUT of the stabilized operational amplifier 4 expressed by the equation (11). The control circuit 10 makes a self-diagnosis that the capacitance value has changed based on the A / D conversion value. Under the same numerical conditions as in the first embodiment, the output voltage VOUT in the voltage detection mode and the self-diagnosis mode is as shown in FIGS. 4 and 8, respectively.

  In the self-diagnosis mode, when all the capacitors C1A, C1B, C2A, C2B have a normal capacitance value of 1 pF, the output voltage VOUT becomes 0V. On the other hand, when any one, two, or three capacitance values change, the output voltage VOUT always deviates from 0V. Therefore, the control circuit 10 can detect that the capacitance value of any one of the capacitors has changed based on the A / D conversion value. When all four capacitance values change, the output voltage VOUT becomes equal to 0V. However, at this time, no error occurs in the output voltage VOUT in the voltage detection mode. Therefore, even if the control circuit 10 cannot detect that the capacitance values of all four capacitors have changed in the self-diagnosis mode, the voltage of each battery cell Bn can be accurately detected in the voltage detection mode. There is no problem in using

  As described above, according to the voltage detection device 11 of the present embodiment, even in the case of an adverse condition where the capacitance values of a plurality of capacitors change to the same value, one capacitor is of course in the self-diagnosis mode. , It can be detected that the capacitance value of any two or three capacitors has changed. In addition, the same effects as those of the first embodiment can be obtained.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS.
The voltage detection device 12 of the present embodiment changes the connection configuration of the first switch and the second switch with respect to the voltage detection device 1 shown in FIG. Different parts will be described below.

  In the present embodiment, the battery cell Bn (n = 1, 2, 3, 4) of the assembled battery 1 has one terminal on the high potential side and the other terminal on the low potential side. The first switch SWBx1 is connected between the terminal TBx (x = 1, 2, 3, 4) and the common line CL1, respectively, and the terminal TBx (x = 0, 1, 2, 3) and the common line CL2 are connected. A second switch SWBy2 (y = 1, 2, 3, 4) is connected between them.

  That is, as in the first embodiment, the first switch is connected between one terminal of the battery cell Bn and the common line CL1, and the second switch is connected between the other terminal of the battery cell Bn and the common line CL2. Connected. However, since the first and second switches are not shared between adjacent battery cells Bn, the number of first and second switches is required to be equal to the number of cells. Since the polarity of the output voltage VOUT of the operational amplifier 4 is the same regardless of the battery cell Bn, the inverting circuit 9 becomes unnecessary.

  10 and 11 show the waveforms of the on / off state of the switch and the output voltage VOUT (= VOP−VOM) in the voltage detection mode and the self-diagnosis mode, respectively. Switches not shown in the figure are off.

[Voltage detection mode (Fig. 10)]
The control circuit 10 turns on the first switch SWB41 and the second switch SWB42 when detecting the voltage VB4 of the battery cell B4 (period 1), and sets the charge when detecting the voltage VB3 of the battery cell B3. The charge is set by turning on the first switch SWB31 and the second switch SWB32 (period 5). Other operations (except for the inverting circuit 9) are the same as the operations shown in FIG.

[Self-diagnosis mode (Fig. 11)]
In order to fix the potentials of the common lines CL1 and CL2, one of the switches SWB11 to SWB42 (here, SWB41) is turned on. Other operations (except for the inverting circuit 9) are the same as the operations shown in FIG.

  According to this embodiment, the same operation and effect as those of the first embodiment can be obtained. In the present embodiment, the first switch and the second switch are required for each battery cell Bn, but the inverting circuit 9 is unnecessary.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS.
The voltage detection device 13 of the present embodiment further includes a seventh A switch SW7A and a seventh B switch SW7B shown in FIG. 6 in addition to the voltage detection device 2 shown in FIG. Other configurations are the same as those of the third embodiment. In the voltage detection mode, the switches SW7A and SW7B maintain the off state, and operate as shown in FIG. 10 as in the third embodiment. On the other hand, in the self-diagnosis mode, the switches SW6A and SW6B are kept off and operate as shown in FIG. According to this embodiment, the same operation and effect as those of the second and third embodiments can be obtained.

(Other embodiments)
As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to embodiment mentioned above, A various deformation | transformation and expansion | extension can be performed within the range which does not deviate from the summary of invention.

The capacitors C1A, C1B, C2A, and C2B may each have a configuration in which a plurality of capacitors are connected in series.
In each of the above embodiments, when a detection error occurs in the voltage detection mode due to a capacitance change of any of the capacitors C1A, C1B, C2A, C2B, it is detected that a capacitance change has occurred in any capacitor in the self-diagnosis mode The condition for this is that the reference voltages are set to VC ≠ VD, VS ≠ VT, VC ≠ VS, and VD ≠ VT. However, even when this condition is not satisfied, there may be a case where a change in the capacitance of the capacitor can be detected.

  In the above embodiments, the case where the capacitors C1A, C1B, C2A, and C2B are changed to the same value (1.5 pF) has been described. On the other hand, when the capacitors C1A, C1B, C2A, and C2B change to different values, a detection error tends to occur in the output voltage VOUT in the voltage detection mode. However, in this case, the output voltage VOUT in the self-diagnosis mode is likely to deviate from the normal value. As a result, as in the above embodiments, at least when a detection error occurs in the voltage detection mode, it is possible to diagnose a change in capacitance in the self-diagnosis mode.

  In each embodiment, charges are set using the 1A and 1B reference voltages VA and VB in the voltage detection mode, and the 2A, 2B reference voltages VC and VD and the 3A and 3B reference voltages VS are set in the self-diagnosis mode. The charge was set using VT. On the other hand, it is also conceivable that the first A reference voltage VA and the second A reference voltage VC are made common, and the first B reference voltage VB and the second B reference voltage VD are made common. For example, when VA = VC = 0V and VB = VD = 2.5V, each of the first reference voltage selection circuit 5A and the second reference voltage selection circuit 5B can be composed of one reference voltage generation circuit and one switch. .

  In the drawings, 2, 11, 12, and 13 are voltage detection devices, 4 is an operational amplifier, 5A and 5B are first and second reference voltage selection circuits, 8A and 8B are third and fourth reference voltage selection circuits, and 9 is inverted. Circuit 10 is a control circuit (control means), B1 to B4 are battery cells (detection target voltage source, unit battery), CL1 and CL2 are common lines (first and second common nodes), C1A, C1B, C2A, C2B Is the first switch, SWB0, SWB2, SWB4, SWB11, SWB21, SWB31, SWB41 are the first switches, SWB1, SWB3, SWB12, SWB22, SWB32, SWB42 are the second switches, SW3A, SW3B is the 3A switch, 3B switch, SW4A, SW4B is the 4A switch, 4B switch, SW5 is the 5th switch switch, SW6A, SW6B is the switch A, the 6B switch, SW7A, SW7b Part 7A, a first 7B switch.

Claims (4)

An operational amplifier (4) having a differential output configuration;
A first switch (SWB0, SWB2, SWB4, SWB11 to SWB41) connected between one terminal of the detection target voltage source (B1 to B4) and the first common node (CL1);
A second switch (SWB1, SWB3, SWB12 to SWB42) connected between the other terminal of the voltage source to be detected and a second common node (CL2);
A first A capacitor (C1A) having one end connected to the first common node;
A first B capacitor (C1B) having one end connected to the second common node;
A third A switch (SW3A) connected between the inverting input terminal and the non-inverting output terminal of the operational amplifier;
A third B switch (SW3B) connected between the non-inverting input terminal and the inverting output terminal of the operational amplifier;
A second A capacitor (C2A) and a fourth A switch (SW4A) connected in series between the inverting input terminal and the non-inverting output terminal of the operational amplifier;
A second B capacitor (C2B) and a fourth B switch (SW4B) connected in series between a non-inverting input terminal and an inverting output terminal of the operational amplifier;
A fifth switch (SW5) connected between the first common node and the second common node;
A first reference voltage selection circuit (5A) capable of applying a first A reference voltage (VA) or a second A reference voltage (VC) to a common connection point between the second A capacitor and the fourth A switch;
A second reference voltage selection circuit (5B) capable of applying a first B reference voltage (VB) and a second B reference voltage (VD) to a common connection point between the second B capacitor and the fourth B switch;
A sixth A switch (SW6A) connected between the other end of the first A capacitor and the inverting input terminal of the operational amplifier;
A sixth B switch (SW6B) connected between the other end of the first B capacitor and a non-inverting input terminal of the operational amplifier;
A third reference voltage selection circuit (8A) capable of applying a third A reference voltage (VS) to the other end of the first A capacitor;
A fourth reference voltage selection circuit (8B) capable of applying a third B reference voltage (VT) to the other end of the first B capacitor;
In the voltage detection mode, the 4A, 4B, and 5th switches are opened, the voltage application by the 3rd and 4th reference voltage selection circuits is stopped, and the 1A and 1st are output by the 1st and 2nd reference voltage selection circuits. 1B reference voltage is applied, the 3A, 3B, 6A, and 6B switches are closed, and the 1st and 2nd switches are closed to set charges on the 1A, 1B, 2A, and 2B capacitors. Then, the first, second, 3A, and 3B switches are opened, the voltage application by the first and second reference voltage selection circuits is stopped, and the fourth, fourth, and fifth switches are closed. A voltage between terminals of the detection target voltage source is detected based on a differential output voltage of the operational amplifier later, and in the self-diagnosis mode, at least one of the first and second switches is opened and the fifth switch is turned on. Close The third A and third B switches are closed, the fourth A, fourth B, sixth A, and sixth B switches are opened, and the first, second, third, and fourth reference voltage selection circuits provide the second A, second B, and second switches. 3A and 3B reference voltages are applied to set charges in the 1A, 1B, 2A, and 2B capacitors, and then the 3A and 3B switches are opened and the 1st, 2nd, and 3rd switches are opened. , The application of voltage by the fourth reference voltage selection circuit is stopped, and the capacitance change of each capacitor is self-controlled based on the differential output voltage of the operational amplifier after the fourth A, fourth B, sixth A, and sixth B switches are closed. A voltage detection apparatus comprising control means (10) for diagnosis. A seventh A switch (SW7A) connected between the other end of the first A capacitor and a non-inverting input terminal of the operational amplifier;
A seventh B switch (SW7B) connected between the other end of the first B capacitor and an inverting input terminal of the operational amplifier;
The control means maintains the 7A and 7B switches in the voltage detection mode and opens the 7A and 7B switches in the self-diagnosis mode. The capacitance of each capacitor is set based on the differential output voltage of the operational amplifier after the 7A and 7B switches are closed instead of the 6A and 6B switches. The voltage detection device according to claim 1, wherein the change is self-diagnosed. The detection target voltage source is a unit battery that is connected in series with the same polarity to constitute a battery assembly, and adjacent unit batteries are connected in series with one other terminal or between other terminals,
An inverting circuit (9) for inverting the polarity of the differential output voltage output from the non-inverting output terminal and the inverting output terminal of the operational amplifier;
The first switch (SWB0, SWB2, SWB4) is provided between one terminal of each unit cell and the first common node while sharing the first switch of an adjacent unit cell,
The second switch (SWB1, SWB3) is provided between the other terminal of each unit cell and the second common node while sharing the second switch of the adjacent unit cell,
When the control means detects the inter-terminal voltage of the unit battery whose high-potential side terminal is the one terminal, the inverting circuit is set to non-inverted operation, and the inter-terminal voltage of the unit battery whose high-potential side terminal is the other terminal 3. The voltage detecting device according to claim 1, wherein when the signal is detected, the inversion circuit is in an inversion operation. The detection target voltage source is a unit battery that is connected in series with the same polarity to form an assembled battery,
The first switches (SWB11 to SWB41) are provided between the high-potential side terminals of the unit cells and the first common node, respectively.
3. The voltage detection device according to claim 1, wherein the second switches (SWB12 to SWB42) are respectively provided between a low potential side terminal of each unit cell and the second common node. .

Images