JP6554453B2 - Differential voltage measuring device - Google Patents

Description

  The present invention relates to a technique for increasing measurement accuracy of a voltage difference between a first voltage and a second voltage that are sequentially acquired.

  For example, in various vehicles such as an electric vehicle (EV) traveling using an electric motor and a hybrid vehicle (HEV) traveling using a combination of an engine and an electric motor, a lithium ion rechargeable battery as a power source of the electric motor And rechargeable batteries such as nickel metal hydride batteries.

  It is known that such secondary batteries are deteriorated by repeating charging and discharging, and the chargeable capacity (current capacity, power capacity, etc.) gradually decreases. Then, in an electric car or the like using a secondary battery, the storage capacity is determined by detecting the degree of deterioration of the secondary battery, and the distance that can be traveled by the secondary battery, the life of the secondary battery, etc. are calculated. doing.

  One index indicating the degree of deterioration of the secondary battery is SOH (State of Health), which is the ratio of the current chargeable capacity to the initial chargeable capacity. It is known that this SOH has a correlation with the internal resistance of the secondary battery. For this reason, SOH can be calculated | required based on this internal resistance by detecting the internal resistance of a secondary battery.

  In general, since the internal resistance is very small, it has been difficult to obtain sufficient detection accuracy. However, Patent Document 1 discloses a battery state detection device with improved internal resistance detection accuracy.

  FIG. 12 is a diagram showing a schematic configuration of a battery state detection device 500 described in Patent Document 1. As shown in FIG. The secondary battery B that is a detection target includes an electromotive force portion e that generates a voltage and an internal resistance r. By detecting the internal resistance r, the SOH of the secondary battery B can be obtained.

  The secondary battery B generates a voltage V between both electrodes (positive electrode Bp and negative electrode Bn), and this voltage V is a voltage generated by current flowing in voltage Ve generated by electromotive force by electromotive force unit e and internal resistance r And Vr (V = Ve + Vr). The negative electrode Bn of the secondary battery B is connected to the reference potential G.

  The battery state detection device 500 includes a differential amplification unit 511, a changeover switch 512, a first capacitor 513, a second capacitor 514, a charging unit 515, a first analog-to-digital converter (ADC) 521, 2 includes an analog-to-digital converter (ADC) 522 and a microcomputer (μCOM) 540.

  In the configuration shown in the figure, when the μCOM 540 transmits a control signal to start charging to the charging unit 515 through the output port PO2, the charging unit 515 starts to flow a predetermined constant charging current Ic to the secondary battery B. Thereby, charging of the secondary battery B is started.

  When charging is started, the μCOM 540 controls the changeover switch 512 through the output port PO1 so that the positive electrode Bp of the secondary battery B and the first capacitor 513 are connected. As a result, the voltage V1 = Ve + r · Ic between the two electrodes of the secondary battery B being charged is held in the first capacitor 513.

  Next, when the voltage between both electrodes of the secondary battery B acquired through the input port PI1 becomes a predetermined state detection voltage, the μCOM 540 controls the changeover switch 512 through the output port PO1, and the positive electrode Bp of the secondary battery B and The second capacitor 514 is connected, and a charging stop control signal is transmitted to the charging unit 515 through the output port PO2.

  As a result, when the charging current Ic to the secondary battery B is stopped and the storage state of the second capacitor 514 is stabilized, the voltage V2 between the two electrodes of the secondary battery B during the charging suspension in the second capacitor 514 = Ve Is retained.

  In this state, the μCOM 540 detects the amplified voltage Vm output from the differential amplifier 511 through the input port PI2. Then, the detected amplification voltage Vm is divided by the amplification factor Av of the differential amplification unit 511 and further divided by the charging current Ic, whereby the internal resistance r (= (Vm / Av) / Ic) of the secondary battery B is obtained. Is detected.

  Finally, the μCOM 540 transmits a charging start control signal to the charging unit 515 through the output port PO2. The charging unit 515 starts to flow a predetermined charging current Ic that is set in advance to the secondary battery B again in response to the control signal. As a result, charging is resumed and the battery state detection process is terminated.

JP 2014-219511 A

  The battery state detection device 500 described in the cited document 1 can increase the detection accuracy of the internal resistance of the secondary battery, and can suppress a decrease in the detection accuracy of the battery state.

  In addition, by applying the technology of the battery state detection device 500, not only the internal resistance of the secondary battery, but also a minute voltage change between the first state and the second state in a voltage source such as a battery or two points in the circuit A differential voltage measuring device capable of measuring a potential difference or the like with high accuracy can be configured.

That is,
1) The voltage of the voltage source in the first state or the voltage at one point in the circuit is sampled and held by the switch 512 and the first capacitor 513 as the first voltage.
2) The voltage of the voltage source in the second state or the voltage at the other point in the circuit is sampled and held by the switch 512 and the second capacitor 514 as the second voltage.
3) The difference between the first voltage and the second voltage is amplified by the differential amplifier 511, and the amplified voltage Vm output from the differential amplifier 511 is divided by the amplification factor Av of the differential amplifier 511.
By sequentially performing these processes, a minute voltage change between the first state and the second state in the voltage source or a potential difference between one point and another point in the circuit can be measured with high accuracy.

  In the example described in Patent Document 1, the state where the constant current Ic flows through the secondary battery B corresponds to the first state, and the state where no current flows flows corresponds to the second state. In addition, the voltage source which is a detection object of a voltage change is not restricted to a secondary battery, The cell which comprises a primary battery, an assembled battery, a power supply circuit etc. may be sufficient.

  By the way, in an actual capacitor, a phenomenon in which the accumulated charge escapes due to a minute leak current occurs. For this reason, after sampling and holding the voltage of the battery in the first state by the first capacitor 513, the first capacitor 513 stores the voltage of the battery in the second state by the second capacitor 514 until sample and hold is completed. The discharged electric charges are slightly discharged due to the leakage current.

  When the charge is discharged from the first capacitor 513, the first voltage is measured lower than the actual voltage, resulting in a decrease in measurement accuracy. Then, an object of this invention is to raise the measurement precision of the voltage difference of the 1st voltage and the 2nd voltage which are acquired sequentially.

In order to solve the above-mentioned subject, the difference voltage measuring device of the present invention holds a first capacitor, a second capacitor having a smaller capacity than the first capacitor, a voltage held by the first capacitor, and the second capacitor. A differential amplification unit for outputting a voltage according to a difference voltage between the first voltage and the second voltage, the first voltage being led to the first capacitor, and the second voltage being the second voltage while the first capacitor holds the first voltage The control unit includes: a control unit that leads to a second capacitor; a protection switch that switches a connection state between the first capacitor and the second capacitor and the differential amplification unit; and a temperature sensor , wherein the control unit While the voltage is conducted to the first capacitor, the protection switch is turned off, and the second voltage is conducted to the second capacitor while the first capacitor holds the first voltage. Is the disconnected state the protective switch, then the second voltage led to the second capacitor, after a lapse of the temperature sensor waiting time determined according to the measured value of the connection state the protective switch It is characterized by
Here, a switching switch is provided to exclusively switch the connection destination of the input end to which a voltage is applied between the first capacitor and the second capacitor, and the control unit controls the switching switch to One voltage may be led to the first capacitor, and the second voltage may be led to the second capacitor in a state where the first capacitor holds the first voltage.
At this time, a leakage current prevention switch for switching the connection state to the opposite side of the first capacitor to the changeover switch connection side, and the control unit is configured so that the first capacitor holds the first voltage while the first capacitor holds the first voltage. The leakage current prevention switch may be switched to a disconnected state while two voltages are guided to the second capacitor.
Further, the first current supply for generating a first voltage, may be further provided with a second current and a current output unit that outputs switch the supply to generate the second voltage.
In addition, the control unit acquires values of current for generating the first voltage and the second voltage, and 1) a current value acquired while the first voltage is conducted to the first capacitor is 2) when the current value acquired during the period until the second voltage is led to the second capacitor does not change when 2) the first voltage is led to the first capacitor; The output result of the differential amplifying unit may be invalidated when any of the current values obtained while the two voltages are being guided to the second capacitor is changed.
Further, the control unit may correct the output result of the differential amplification unit based on a preset resistance value related to the internal connection of the first voltage and the supply source of the second voltage.

  According to the present invention, since the capacity of the first capacitor is increased and the capacity of the second capacitor is decreased, the voltage drop due to the charge omission of the first capacitor can be reduced, and the charge storage time of the second capacitor can be reduced. Can be shortened. Thereby, the voltage drop of the first capacitor while the second capacitor is accumulating charges can be reduced, and the measurement accuracy of the differential voltage between the sequentially acquired first voltage and second voltage can be improved. it can.

It is a figure which shows schematic structure of the battery state detection apparatus which is 1st Embodiment. It is a flowchart which shows an example of the battery state detection process in a battery state detection apparatus. It is a figure which shows schematic structure of the differential voltage measuring apparatus which is 2nd Embodiment. It is a circuit diagram which shows an example of a differential amplifier. It is a block diagram which shows the structure of the 1st modification of a differential voltage measuring device. It is a figure explaining ON / OFF switching control of a leakage current prevention switch. It is a block diagram which shows the structure of the 2nd modification of a differential voltage measuring device. It is a figure explaining the relationship between temperature and the leakage current of a capacitor | condenser. It is a figure explaining the electric current change at the time of a measurement. It is a flowchart explaining the 3rd modification of a differential voltage measuring device. It is a figure explaining the resistance which arises by bus bar connection in an assembled battery. It is a figure which shows schematic structure of the conventional battery state detection apparatus.

  Embodiments of the present invention will be described in detail with reference to the drawings. The first embodiment is an example in which the differential voltage measurement device of the present invention is applied to a battery state detection device. FIG. 1 is a diagram showing a schematic configuration of a battery state detection device according to a first embodiment of the present invention.

  The battery state detection device 100 according to the present embodiment is mounted on, for example, an electric vehicle, connected between electrodes of a secondary battery included in the electric vehicle, and detects the internal resistance of the secondary battery as the state of the secondary battery. Is. Of course, you may apply to the apparatus, system, etc. which were equipped with secondary batteries other than an electric vehicle.

  The secondary battery B that is a detection target includes an electromotive force portion e that generates a voltage and an internal resistance r. By detecting the internal resistance r, the SOH of the secondary battery B can be obtained.

  The secondary battery B generates a voltage V between both electrodes (positive electrode Bp and negative electrode Bn), and this voltage V is a voltage generated by current flowing in voltage Ve generated by electromotive force by electromotive force unit e and internal resistance r And Vr (V = Ve + Vr). The negative electrode Bn of the secondary battery B is connected to the reference potential G.

  As shown in the figure, the battery state detection device 100 includes a differential amplifier 111, a changeover switch 112, a first capacitor 113, a second capacitor 114, a charging unit 115, and a first analog-digital converter. (ADC) 121, a second analog-to-digital converter (ADC) 122, and a microcomputer (μCOM) 140.

  The differential amplification unit 111 is configured of, for example, an operational amplifier, and includes two input terminals (first input terminal In1 and second input terminal In2) and one output terminal (output terminal Out). An amplified voltage Vm obtained by amplifying the difference value of the voltages input to the input terminal by a predetermined amplification factor Av is output from the output terminal.

  The changeover switch 112 is, for example, a switch of one circuit and two contacts (SPDT (single pole double throw)) configured by an analog switch or the like. In the changeover switch 112, the changeover terminal a of the two changeover terminals a and b is connected to the first input terminal In1 of the differential amplification unit 111, and the changeover terminal b is the second input terminal of the differential amplification unit 111. Connected to In2. The changeover switch 112 has a common terminal c connected to the positive electrode Bp of the secondary battery B.

  The changeover switch 112 is connected to an output port PO1 of the μCOM 140, which will be described later, and switches the connection between the two changeover terminals a and b and the common terminal c in accordance with a control signal from the μCOM 140. The positive electrode Bp is exclusively connected to the first input terminal In1 and the second input terminal In2.

  The first capacitor 113 is connected between the first input terminal In1 of the differential amplification unit 111 and the reference potential G. That is, the first capacitor 113 is provided between the first input terminal In1 and the negative electrode Bn of the secondary battery B. Thereby, the voltage between the first input terminal In1 and the negative electrode Bn of the secondary battery B is held in the first capacitor 113.

  The second capacitor 114 is connected between the second input terminal In2 of the differential amplification unit 111 and the reference potential G. That is, the second capacitor 114 is provided between the second input terminal In2 and the negative electrode Bn of the secondary battery B. Thereby, the voltage between the second input terminal In2 and the negative electrode Bn of the secondary battery B is held in the second capacitor 114.

  Here, in the battery state detection device 100 of the present embodiment, the capacity of the first capacitor 113 is different from the capacity of the second capacitor 114, and the capacity of the first capacitor 113 that first accumulates the charge is the second capacity. It is designed to be larger than the capacity of the capacitor 114. In general, in a capacitor, the larger the capacitance, the smaller the effect of voltage drop due to leakage current, and the smaller the capacitance, the shorter the time required for sample and hold.

  The charging unit 115 is connected between the positive electrode Bp of the secondary battery B and the reference potential G, and can charge a predetermined charging current Ic to the secondary battery B when charging the secondary battery B. It is provided as follows. For this reason, it can function as a current output part. The charging unit 115 is connected to an output port PO2 of the μCOM 140 described later, charges the secondary battery B by charging the charging current Ic according to a control signal from the μCOM 140, and supplies the charging current Ic to the secondary battery B. Stop charging and stop charging.

  The first analog-digital converter (ADC) 121 quantizes the voltage between both electrodes of the secondary battery B, and outputs a signal indicating a digital value corresponding to this voltage. The second analog-digital converter (ADC) 122 quantizes the amplified voltage Vm output from the differential amplifier 111 and outputs a signal indicating a digital value corresponding to the amplified voltage Vm.

  The μCOM 140 includes a CPU, a ROM, a RAM, and the like, and functions as a control unit to control the entire battery state detection device 100. The μCOM 140 includes a first output port PO1 connected to the changeover switch 112, and a second output port PO2 connected to the charging unit 115, and transmits a control signal to the changeover switch 112 through the first output port PO1. During charging of the secondary battery B, the positive electrode Bp of the secondary battery B and the first input terminal In1 are connected, and during charging stop of the secondary battery B, the positive electrode Bp of the secondary battery B and the second input terminal In2 are connected. The changeover switch 112 is controlled so as to be connected.

  Further, the control signal is transmitted to the charging unit 115 through the second output port PO2, and the voltage V between both electrodes of the secondary battery B becomes the predetermined state detection voltage Vth while the charging unit 115 charges the secondary battery B. When this happens, the charging unit 115 is controlled to stop the charging of the secondary battery B.

  The μCOM 140 has a first input port PI1 to which a signal output from the first ADC 121 is input, and a second input port PI2 to which a signal output from the second ADC 122 is input. The μCOM 140 detects the voltage V between both electrodes of the secondary battery B and the amplified voltage Vm output from the differential amplifier unit 111 based on these signals. Then, the internal resistance r of the secondary battery B is detected based on the amplified voltage Vm and the charging current Ic.

  Next, an example of the battery state detection process in the μCOM 140 provided in the battery state detection device 100 according to the first embodiment will be described with reference to the flowchart of FIG.

  For example, when the μCOM 140 receives an instruction to start charging the secondary battery B from the electronic control unit mounted on the vehicle through the communication port, the μCOM 140 transmits a control signal to start charging to the charging unit 115 through the second output port PO2. In response to the control signal, charging unit 115 starts to flow a predetermined constant charging current Ic to secondary battery B. Thereby, charging of the secondary battery B is started.

  When the charging current Ic flows in the secondary battery B and charging is underway, the μCOM 140 transmits a control signal connecting the switching terminal a and the common terminal c to the switch 112 via the first output port PO1 (S110) .

  The changeover switch 112 connects the positive electrode Bp of the secondary battery B and the first input terminal In1 of the differential amplifier 111 by connecting the switching terminal a and the common terminal c in accordance with the control signal.

  As a result, the first capacitor 113 is connected between the positive electrode Bp and the negative electrode Bn of the secondary battery B, and charge flows into the first capacitor 113 from the secondary battery B and the charging unit 115. Then, when time passes to some extent, the first capacitor 113 stores electric charge up to the upper limit of its capacity, and the voltage between both electrodes of the secondary battery B being charged is held in the first capacitor 113 as the first voltage.

  Next, the μCOM 140 waits until the voltage between both electrodes of the secondary battery B reaches the state detection voltage Vth (S120). Then, when the voltage between both electrodes of the secondary battery B reaches a predetermined state detection voltage Vth, a control signal for connecting the switching terminal b and the common terminal c is transmitted to the changeover switch 112 through the first output port PO1. (S130) A control signal for stopping charging is sent to the charging unit 115 almost simultaneously through the second output port PO2 (S140).

  The changeover switch 112 connects the positive electrode Bp of the secondary battery B and the second input terminal In2 of the differential amplification unit 111 by connecting the switching terminal b and the common terminal c in accordance with the control signal.

  As a result, the second capacitor 114 is connected between the positive electrode Bp and the negative electrode Bn of the secondary battery B, and the charge flows from the secondary battery B into the second capacitor 114. In addition, charging unit 115 stops charging current Ic to secondary battery B in response to the control signal from μCOM 140.

  While the second capacitor 114 and the secondary battery B are connected by the changeover switch 112, the first capacitor 113 is disconnected from the secondary battery B, but the first capacitor 113 is designed to have a large capacity. In addition, the amount of charge escape due to leakage current can be reduced.

  Then, it waits for the preset storage period for the second capacitor 114 to store the charge up to the upper limit of its capacity (S150). Since the second capacitor 114 is designed to have a small capacity, it can store electric charge up to the capacity upper limit in a short time. For this reason, the amount of charge that escapes from the first capacitor 113 can be further reduced.

  When this storage period elapses, the second capacitor 114 stores the charge up to the upper limit of its capacity and the voltage held thereby becomes stable, and the voltage across the both electrodes of the secondary battery B during the charging suspension is the second capacitor 114 Held as two voltages.

  Next, when the voltage held by the second capacitor is stabilized (that is, when the storage period has elapsed), the μCOM 140 performs differential amplification based on the information obtained from the signal input to the second input port PI2. The amplified voltage Vm output from the unit 111 is detected (S160).

  The μCOM 140 detects the internal resistance r of the secondary battery B by dividing the detected amplification voltage Vm by the amplification factor Av of the differential amplification unit 111 and further dividing it by the charging current Ic (r = (Vm / Av ) / Ic) (S170).

  Finally, the μCOM 140 transmits a charge start control signal to the charging unit 115 through the second output port PO2 (S180). In response to the control signal, the charging unit 115 starts to flow a predetermined charging current Ic predetermined to the secondary battery B again. As a result, charging is resumed and the battery state detection process is terminated.

  As described above, the battery state detection device 100 according to the present embodiment is designed such that the capacity of the first capacitor 113 that accumulates charges first is larger than the capacity of the second capacitor 114.

  By increasing the capacity of the first capacitor 113, it is possible to reduce the voltage drop due to charge loss while the second capacitor 114 is accumulating charges, and by reducing the capacity of the second capacitor 114, The storage period of the two capacitors 114 can be shortened. Thereby, since the difference voltage can be detected in a state where the first voltage of the first capacitor 113 does not decrease, the measurement accuracy can be increased.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram showing an outline of a differential voltage measuring apparatus according to the second embodiment of the present invention. The differential voltage measurement apparatus 200 of the second embodiment is an application of the technology of the battery state detection apparatus 100, and is a voltage source to be measured of a battery pack BS in which a plurality of cell batteries (Ce1 to Ce4) are combined. It is said.

  As shown in the figure, the differential voltage measurement device 200 includes a first capacitor C1, a second capacitor C2, a μCOM 210, a current output unit 220, a changeover switch 230, a differential amplifier unit 240, an ADC 250, a detection target selection switch 261, and a reference. A potential setting switch 262 and a protection switch 270 are provided.

  The current output unit 220 supplies a constant current to the assembled battery BS based on an instruction from the μCOM 210. By switching the constant current supplied to the assembled battery BS, the first state and the second state of the assembled battery BS are created. Either the first state or the second state may be a state in which no current flows.

  The 1st capacitor | condenser C1 hold | maintains the voltage of the measurement object location in the assembled battery BS of a 1st state as a 1st voltage. The 2nd capacitor | condenser C2 hold | maintains the voltage of the measurement object location in the assembled battery BS of a 2nd state as a 2nd voltage. Here, the capacity of the first capacitor C1 is designed to be larger than the capacity of the second capacitor C2.

  The changeover switch 230 guides the voltage (first voltage) at the measurement target point in the assembled battery BS in the first state to the first capacitor C1, and the voltage (second voltage) at the measurement target point in the assembled battery BS in the second state ) To the second capacitor C2.

  The detection target selection switch 261 is provided between the end of each cell battery (Ce1 to Ce4) constituting the assembled battery BS and the changeover switch 230. Specifically, SW11 is provided between the end of cell battery Ce1 corresponding to the positive electrode side of battery assembly BS and changeover switch 230, and the connection point between cell battery Ce1 and cell battery Ce2 and changeover switch 230 SW12 is provided between them, SW13 is provided between the connection point of the cell battery Ce2 and the cell battery Ce3 and the changeover switch 230, and between the connection point of the cell battery Ce3 and the cell battery Ce4 and the changeover switch 230 SW14 is provided.

  The reference potential setting switch 262 is a switch for setting the reference potential of the first capacitor C1 and the second capacitor C2. Specifically, SW24 for setting the reference potential of the first capacitor C1 and the second capacitor C2 to the reference potential G, and SW23 for setting the reference potential of the first capacitor C1 and the second capacitor C2 to the voltage of the cell battery Ce4 The reference potentials of the first capacitor C1 and the second capacitor C2 are set to the voltage of the cell battery Ce4 + cell battery Ce3. The reference potentials of the first capacitor C1 and the second capacitor C2 are set to the cell battery Ce4 + cell battery Ce3 + cell battery Ce2 SW21 which sets to voltage is provided.

  The protection switch 270 is a switch for protecting the differential amplifier 240. The protection switch 270 is a switch for guiding the first voltage and the second voltage to the differential amplification unit 240 after the sample and hold in the first capacitor C1 and the second capacitor C2 is completed, and the first capacitor C1 is used. And SW41 provided between the first input terminal In1 and SW42 provided between the second capacitor C2 and the second input terminal In2. Both SW41 and SW42 are turned off during the sample hold, and are turned on when the sample hold is completed to guide the first voltage and the second voltage to the differential amplifier 240.

  The differential amplification unit 240 includes two input terminals (first input terminal In1 and second input terminal In2) and one output terminal (output terminal Out), and a differential value of voltages input to these two input terminals. An amplified voltage Vm obtained by amplifying the signal at a predetermined amplification factor Av is output from the output terminal. The differential amplifier 240 can be constituted by, for example, an operational amplifier or a circuit shown in FIG.

  The ADC 250 quantizes the amplified voltage Vm output from the differential amplifier 240 and outputs a signal indicating a digital value corresponding to the amplified voltage Vm.

  The μCOM 210 includes a CPU, a ROM, a RAM, and the like, and functions as a control unit to control the entire differential voltage measuring apparatus 200. The μCOM 210 includes a first output port PO1 connected to the current output unit 220, a first input port PI1 to which a signal output from the ADC 250 is input, and a switch control unit 211 that controls each switch.

  The differential voltage measurement device 200 can determine, for example, the SOH of each cell battery by measuring the internal resistance of each cell battery. When measuring the internal resistance of the cell battery Ce1, only the detection target selection switch 261 is turned on, and only the reference potential setting switch 262 is turned on. As a result, the voltage between both terminals of Ce1 is guided to the first capacitor C1 and the second capacitor C2.

  Then, as the first state, a predetermined first constant current I1 is supplied from the current output unit 220, and the SW31 of the changeover switch 230 is turned on. Thereby, the voltage of the cell battery Ce1 in the first state is held as the first voltage in the first capacitor C1.

  Next, a predetermined second constant current I2 is supplied from the current output unit 220 as the second state, and the switch 32 of the changeover switch 230 is turned on. Thus, the voltage of the cell battery Ce1 in the second state is held as the second voltage in the second capacitor C2.

  When the protection switch 270 is turned on to introduce the first voltage and the second voltage to the differential amplification unit 240, a voltage difference is input to the μCOM 210. The μCOM 210 can obtain the internal resistance r1 of the cell battery Ce1 by r1 = (Vm / Av) / (I1-I2) based on the same principle as in the first embodiment. The internal resistance of other cell batteries can be obtained in the same manner.

  Also in the second embodiment, since the capacitance of the first capacitor C1 is increased and the capacitance of the second capacitor C2 is decreased, the voltage drop of the first capacitor C1 while the second capacitor C2 is accumulating charges. And the measurement accuracy of the difference voltage between the first voltage and the second voltage can be increased.

  In the second embodiment, the switch control unit 211 can measure various potential differences by operating the detection target selection switch 261 and the reference potential setting switch 262.

  For example, in a state where the current output unit 220 does not flow current and the reference potential setting switch 262 is ON only for SW21, the detection target selection switch 261 is ON only for SW11 to acquire the first voltage, and then the detection target selection switch When the second voltage is acquired with only SW12 turned on and the second voltage is obtained and the difference voltage between the first voltage and the second voltage is measured, the measurement result indicates the potential difference between both ends of the cell battery Ce1, that is, the voltage of the cell battery Ce1. Become. The voltage of other cell batteries can be similarly determined.

  Also in this case, since the capacity of the first capacitor C1 is increased and the capacity of the second capacitor C2 is decreased, the voltage drop of the first capacitor C1 is reduced while the second capacitor C2 is accumulating charges. Therefore, the measurement accuracy of the difference voltage between the first voltage and the second voltage can be increased.

  Although the present invention has been described with reference to the first and second embodiments, the differential voltage measuring device of the present invention is not limited to the configurations of these embodiments.

  For example, in each embodiment described above, the secondary battery B is charged by supplying a current from the charging unit 115 or the current output unit 220 for the first constant current I1 and the second constant current I2. However, the secondary battery B may be discharged by a load current generated by a load connected to the secondary battery B or the like.

  Furthermore, the following modifications may be made. In addition, although a modification is demonstrated taking the case of applying to 2nd Embodiment as an example, you may apply to 1st Embodiment.

  FIG. 5 is a block diagram showing a configuration of a first modification of the differential voltage measurement device. As shown in the figure, the differential voltage measurement device 201 is the same as the differential voltage measurement device 200 of the second embodiment in that the first capacitor C1, the second capacitor C2, μCOM 210, the current output unit 220, the changeover switch 230, and the difference The dynamic amplification unit 240, the ADC 250, the detection target selection switch 261, the reference potential setting switch 262, and the protection switch 270 are provided. The description about these is omitted.

  The differential voltage measurement device 201 of the first modification further includes a leak current prevention switch SW51 on the reference potential side of the first capacitor C1. That is, the current prevention switch SW51 is provided between the first capacitor C1 and the reference potential setting switch 262. The current prevention switch SW51 is controlled by the switch control unit 211 of the μCOM 210 to switch on and off.

  FIG. 6 is a diagram illustrating on / off switching control of the leakage current prevention switch SW51. The case where the voltage of the cell battery Ce1 is measured is taken as an example. Therefore, the detection target selection switch 261 is turned on only for SW11, and the reference potential setting switch 262 is turned on only for SW21. Since the switching control of the changeover switch 230 and the protection switch 270 for performing the sample hold and the differential voltage measurement is the same as that in the description of FIG.

  First, the current prevention switch SW51 is turned on, and the voltage of the cell battery Ce1 in the first state in which the first constant current I1 flows is sampled and held by the first capacitor C1. When the sample hold of the first capacitor C1 is completed, the current prevention switch SW51 is turned off. As a result, the path between the first capacitor C1 and the reference potential is disconnected, so that the leak current of the first capacitor C1 can be reduced.

  Then, the voltage of the cell battery Ce1 in the second state in which the second constant current I2 flows is sampled and held by the second capacitor C2. During this time, the current prevention switch SW51 is kept in an OFF state and a state in which the leakage current is small. When the sample hold of the second capacitor C2 is finished, the current prevention switch SW51 is turned on to measure the differential voltage.

  As described above, the differential voltage measuring device 201 according to the first modification leaks the first capacitor C1 by turning off the current prevention switch SW51 until the differential voltage is measured after the sample and hold of the first capacitor C1. I am reducing the current. For this reason, it is possible to further prevent the decrease in measurement accuracy due to the release of the charge due to the leak current.

  A leak current prevention switch is also provided separately on the reference potential side of the second capacitor C2, and the second capacitor C2 in the meantime is turned off from the end of sample hold of the second capacitor C2 to the time of differential voltage measurement. The leakage current may be reduced.

  FIG. 7 is a block diagram showing a configuration of a second modification of the differential voltage measurement device. As shown in this figure, the differential voltage measurement device 202 is the same as the differential voltage measurement device 200 of the second embodiment, and the first capacitor C1, the second capacitor C2, μCOM 210, the current output unit 220, the changeover switch 230, and the difference The dynamic amplification unit 240, the ADC 250, the detection target selection switch 261, the reference potential setting switch 262, and the protection switch 270 are provided. The description about these is omitted.

  The differential voltage measurement device 202 of the second modification further includes a temperature sensor TS in the vicinity of the first capacitor C1 and the second capacitor C2. The measured value of the temperature sensor TS is input to the μCOM 210. However, a temperature sensor TS may be provided at another location to estimate the temperature in the vicinity of the first capacitor C1 and the second capacitor C2.

  In general, the leakage current of a capacitor is affected by temperature, and the leakage current increases as the temperature increases. Therefore, if the temperature t2 is higher than the temperature t1, as shown in FIG. 8, the amount of voltage drop of the first capacitor C1 after the end of the sample hold is larger at the temperature t2 than at the temperature t1. Become. Also in the second capacitor C2, the voltage drop amount after the end of the sample and hold becomes larger at the temperature t2 than at the temperature t1.

  Here, since the sample and hold of the second capacitor C2 is performed after the sample and hold of the first capacitor C1, the voltage drop due to the leakage current occurs only in the first capacitor C1 at the end of the sample and hold of the second capacitor C2.

  On the other hand, since the capacity of the second capacitor C2 is smaller than that of the first capacitor C1, the voltage of the second capacitor C2 decreases at a speed faster than that of the first capacitor C1 after the sample and hold of the second capacitor C2 ends. Do.

  For this reason, the voltage drop amounts of the first capacitor C1 and the second capacitor C2 coincide with each other at a certain time after the end of the sample and hold of the second capacitor C2. If the standby time wt is set so that the difference voltage is measured at this time, the voltage drop amount of both capacitors is canceled, so that it is possible to further prevent the measurement accuracy from being lowered due to the leakage of charge due to the leakage current. Here, the standby time wt is the time from the end of the sample hold of the second capacitor C2 to the measurement of the differential voltage.

  However, even with the same standby time wt, the voltage drop amount of the first capacitor C1 and the second capacitor C2 is affected by the temperature, and as described above, the voltage drop amount increases as the temperature increases. For this reason, if the waiting time wt is fixedly determined, the measurement accuracy depends on the temperature change.

  Therefore, in the second modification, the standby time wt is changed in accordance with the measurement value of the temperature sensor TS. That is, for each temperature measurement value, “the voltage drop of the first capacitor C1 from the end of the sample-hold of the first capacitor C1 to the end of the sample-hold of the second capacitor C2” and after the end of the sample-hold of the second capacitor C2. The time at which the “difference between the voltage drop amount of the second capacitor C2 and the voltage drop amount of the first capacitor C1” is equal is determined by experiment or the like, and is recorded as the standby time wt in μCOM 210 etc. .

  In the actual measurement, the differential voltage may be measured after the standby time wt corresponding to the measured temperature has elapsed after the sample hold of the second capacitor C2 is completed. As a result, it is possible to further prevent the decrease in measurement accuracy due to the escape of the charge due to the leak current.

  Next, a third modification of the differential voltage measuring device will be described. In the second embodiment, as shown in FIG. 9A, when the current output unit 220 flows a predetermined first constant current I1, the sample hold of the first capacitor C1 is performed, and then the predetermined first constant current I1 is applied. The second capacitor C2 was sampled and held when two constant currents were applied. That is, the current I changing with an ideal step waveform is used for measurement.

  However, when the differential voltage measurement device is mounted on a vehicle or the like, it is not realistic to change the current I into an ideal step waveform only for differential voltage measurement while traveling or the like. On the other hand, when the differential voltage is measured regardless of the state of the current I, for example, as shown in FIG. 9B, the current I is between the sample hold time of the first capacitor C1 and the sample hold of the second capacitor C2. There is a case where the current I does not change or a case where the current I fluctuates at the time of sample and hold as shown in FIG. 9C, and a normal measurement result cannot be obtained.

  Therefore, in the third modification of the differential voltage measurement apparatus, differential voltage measurement processing is performed according to the procedure shown in the flowchart of FIG. 10 in order to obtain a normal measurement result without forcibly outputting an ideal step waveform. Do. In this process, it is assumed that the current I flowing through the current output unit 220 is constantly measured.

  First, the first capacitor C1 is sampled and held at a predetermined timing (S201). It is determined whether or not the current I is constant during the sample hold of the first capacitor C1 (S202). If it is not constant (S202: No), the sample hold of the first capacitor C1 is determined as not suitable for measurement (S201). Do the) again.

  If the current I is constant during the sample and hold of the first capacitor C1 (S202: Yes), the current I at this time is regarded as a constant current I1 and waits for a predetermined time (S203). During standby, it is determined whether or not the current I has changed (S204). If it has not changed (S204: No), it is determined that the current is not suitable for measurement, and the first capacitor C1 sample hold (S201) and subsequent steps are performed again. .

  If the current I has changed during standby (S204: Yes), the second capacitor C2 is sampled and held at a predetermined timing (S205). It is determined whether or not the current I is constant during the sample hold of the second capacitor C2 (S206). If it is not constant (S206: No), the sample hold of the first capacitor C1 is determined as not suitable for measurement (S201). Do the following again.

  If the current I is constant during the sample and hold of the second capacitor C2 (S206: Yes), the current I at this time is regarded as a constant current I2, and the differential voltage is measured as being suitable for the measurement (S207) . If the obtained result is not an abnormal value (S208: No), the measured value is treated as valid (S209), and the sample hold of the first capacitor C1 (S201) and subsequent steps are repeated as the next measurement.

  If the obtained result is an abnormal value (S208: Yes), the measured value is invalidated and the sample hold (S201) and subsequent steps of the first capacitor C1 are performed again. The abnormal value can be determined by, for example, recording a normal voltage range of the cell battery Ce in advance and comparing the range with the measured value.

  Since the measured value determined to be effective can be considered to be equivalent to the measurement with an ideal step waveform as a result, it can be handled as a normal measurement result. In addition, in this procedure, although measurement aptitude was determined for every process, you may perform measurement aptitude collectively. For example, after the sample hold of the first capacitor C1 and the sample hold of the second capacitor C2, the suitability of the measurement is determined by determining the stability of the current I during the sample hold and the change in the current I during the sample hold. Good.

  By the way, in the assembled battery BS, the battery cells Ce are generally connected by a bus bar. In the connection by the bus bar, there are very little contact resistance and wiring resistance. For this reason, as shown in FIG. 11, the assembled battery BS has a resistor BBR12 due to busbar connection between the battery cell Ce1 and the battery cell Ce2, and a voltage drop due to this resistance is included in the voltage measurement value of the battery cell Ce1. Errors will occur. The same applies to other battery cells.

  The resistance value generated by the bus bar connection can be acquired in advance by actual measurement or the like. For this reason, the resistance value due to the bus bar connection between each battery cell is recorded in the μCOM 210 or the like, and the voltage drop caused by the current I at the time of measurement is subtracted from the voltage measurement value, thereby further improving the accuracy of the differential voltage measurement. Is possible. The recorded resistance value may be calculated by multiplying a predetermined coefficient corresponding to aging in consideration of aging deterioration.

  In addition, embodiment containing the modification mentioned above only showed the typical form of this invention, and this invention is not limited to embodiment. That is, those skilled in the art can carry out various modifications without departing from the gist of the present invention in accordance with conventionally known findings. Of course, such modifications are included in the scope of the present invention as long as the configuration of the differential voltage measuring apparatus of the present invention is provided.

DESCRIPTION OF SYMBOLS 100 Battery condition detection apparatus 111 Differential amplification part 112 Changeover switch 113 1st capacitor 114 2nd capacitor 115 Charging part 121 1st ADC
122 2nd ADC
140 μCOM
200 Differential Voltage Measuring Device 201 Differential Voltage Measuring Device 202 Differential Voltage Measuring Device 210 μCOM
211 switch control unit 220 current output unit 230 changeover switch 240 differential amplification unit 250 ADC
261 Detection target selection switch 262 Reference potential setting switch 270 Protection switch

Claims (6)

A first capacitor,
A second capacitor having a smaller capacity than the first capacitor;
A differential amplifier that outputs a voltage corresponding to a voltage difference between a voltage held by the first capacitor and a voltage held by the second capacitor;
A controller that guides a first voltage to the first capacitor, and guides a second voltage to the second capacitor in a state where the first capacitor holds the first voltage;
A protective switch for switching a connection state between the first capacitor and the second capacitor and the differential amplifier;
Temperature sensor,
Equipped with
The control unit turns off the protection switch while conducting the first voltage to the first capacitor, and holds the first voltage while the first capacitor holds the first voltage. 2) While leading to the capacitor, turn off the protection switch,
A differential voltage measurement apparatus , wherein the protection switch is connected after a standby time determined in accordance with a measurement value of the temperature sensor has passed after the second voltage is led to the second capacitor. A changeover switch for exclusively switching a connection destination of an input terminal to which a voltage is applied between the first capacitor and the second capacitor;
The control unit controls the changeover switch to lead the first voltage to the first capacitor, and the second voltage is supplied to the second capacitor while the first capacitor holds the first voltage. The differential voltage measurement device according to claim 1, which leads to: A leakage current prevention switch for switching a connection state on the opposite side of the first capacitor to the selector switch connection side;
The control unit switches the leakage current prevention switch to a disconnection state while the second voltage is being led to the second capacitor in a state where the first capacitor holds the first voltage. The differential voltage measuring device according to claim 2. A current output unit for switching and outputting a first current supplied to generate the first voltage and a second current supplied to generate the second voltage. The differential voltage measuring device according to any one of 1 to 3 . The control unit
Obtaining values of current for generating the first voltage and the second voltage;
1) When the obtained current value changes while introducing the first voltage to the first capacitor 2) After introducing the first voltage to the first capacitor, the second voltage is converted to the second capacitor 3) When the current value acquired during the time when the current is acquired does not change until the current value acquired while the second voltage is supplied to the second capacitor is satisfied. differential voltage measuring device according to any one of claims 1 to 4, characterized in that a disabling the output of the differential amplifier. The control unit
Preset, based on the resistance value related to the internal connection of the supply source of the first voltage and the second voltage, any claim 1-5, characterized in that for correcting the output of the differential amplifier The differential voltage measuring device according to any one of the preceding claims

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