JP2020159989A - Voltage measurement circuit - Google Patents

Abstract

To reduce measurement time of a voltage measurement circuit measuring voltage of a battery using a resistance voltage division circuit.SOLUTION: A voltage measurement circuit measuring voltage of a battery pack including n batteries comprises: a first resistance voltage division circuit including a first reference resistor and n resistors; a second resistance voltage division circuit including a second reference resistor and an auxiliary resistor; n relay elements; and a control section measuring voltage of the battery on the basis of first voltage indicative of voltage of a positive side terminal of the first reference resistor and second voltage indicative of voltage of a positive side terminal of the second reference resistor. When a relay element connected to a first battery and a relay element connected to a second battery provided at a higher potential side than the first battery only are controlled to be turned on, the control section calculates a potential of the positive side terminal of the first battery on the basis of the first voltage and calculates a potential of the positive side terminal of the second battery on the basis of the second voltage.SELECTED DRAWING: Figure 2

Description

The present invention relates to a voltage measuring circuit that measures the voltage of a battery.

Rechargeable secondary batteries have been widely put into practical use in various fields. For example, an electric vehicle or a plug-in hybrid vehicle includes a secondary battery for supplying an electric current to a traveling motor.

In many cases, a charging device for charging a secondary battery supplies a current to the secondary battery while monitoring the voltage of the secondary battery. Therefore, the charging device includes a voltage measuring circuit for measuring the voltage of the secondary battery. Alternatively, a voltage measuring circuit for measuring the voltage of the secondary battery is connected to the charging device.

By the way, a large-capacity secondary battery may be realized by an assembled battery including a plurality of batteries connected in series. Then, as an example of a voltage measuring circuit for measuring the voltage of each battery connected in series, a configuration including a resistance voltage dividing circuit in which a plurality of resistors are connected in series is known. For example, the voltage detection circuit described in Patent Document 1 is connected to a high voltage battery composed of a plurality of battery modules, and includes a resistance voltage dividing circuit and a control circuit. The resistance voltage divider circuit includes a plurality of voltage divider resistors and a plurality of switching elements. Then, the control circuit detects the voltage of each battery module by measuring the output voltage of the resistance voltage dividing circuit while controlling the switching element.

Japanese Unexamined Patent Publication No. 2010-008227

When measuring the battery voltage using a resistance voltage divider circuit, the measurement time may become long. For example, when measuring the voltage of each battery connected in series, the output voltage of the resistance voltage dividing circuit is detected while controlling the switching elements corresponding to each battery to be turned on one by one. Therefore, when the number of batteries connected in series is large, the measurement time becomes long.

An object relating to one aspect of the present invention is to shorten the measurement time in a voltage measuring circuit for measuring a battery voltage using a resistance voltage dividing circuit.

The voltage measuring circuit of one aspect of the present invention measures the voltage of an assembled battery including n (n is an integer of 2 or more) batteries connected in series. This voltage measurement circuit is composed of a first resistance voltage dividing circuit composed of a first reference resistor and n resistors connected in series, and a second reference resistor and an auxiliary resistor connected in series. Between the second resistor voltage divider circuit electrically connected in parallel to the first resistor voltage divider circuit and the positive terminal of the n batteries and one terminal of the n resistors. A first voltage that controls the n relay elements provided respectively and the n relay elements and represents the voltage at the connection point between the first reference resistor and one of the n resistors. , And a control unit that measures the voltage of the n batteries based on the second voltage representing the voltage at the connection point between the second reference resistor and the auxiliary resistor. The negative terminal of the assembled battery is electrically connected to the first reference resistor and the second reference resistor. The control unit is provided on the relay element connected to the first battery among the n batteries and the second control unit provided on the higher potential side of the n batteries than the first battery. When only the relay element connected to the battery is controlled to be in the ON state, the potential of the positive terminal of the first battery is calculated based on the first voltage, and the potential of the positive terminal of the first battery is calculated and the potential is calculated based on the second voltage. Calculate the potential of the positive terminal of the second battery. At this time, the control unit is connected in order from the relay element connected to the battery having the lowest potential among the n batteries, or to the battery having the highest potential among the n batteries. In order from the relay element, two relay elements adjacent to each other in the plurality of relay elements may be controlled to be turned on to calculate the corresponding two potentials.

According to the voltage measuring circuit having the above configuration, by controlling the two relay elements in the ON state at the same time, the potentials at two points in the assembled battery can be measured at the same time. Therefore, in the voltage measuring circuit that measures the voltage of the battery using the resistance voltage dividing circuit, the time required to measure the voltage of each battery in the assembled battery can be shortened.

According to the above aspect, the measurement time can be shortened in the voltage measuring circuit for measuring the voltage of the battery using the resistance voltage dividing circuit.

It is a figure which shows the use example of the voltage measurement circuit which concerns on embodiment of this invention. It is a figure which shows an example of a voltage measurement circuit. It is a flowchart which shows an example of the process of measuring a voltage.

FIG. 1 shows a usage example of a voltage measuring circuit according to an embodiment of the present invention. In this embodiment, the voltage measuring circuit 1 is used in an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle, and measures the voltage of the secondary battery 101 for supplying a current to the traveling motor 105.

The secondary battery 101 is realized by an assembled battery including a plurality of battery modules connected in series. Then, the voltage measuring circuit 1 measures the voltage of the secondary battery 101 and also measures the voltage of each battery module constituting the secondary battery 101 (or the potential of the positive terminal of each battery module). Further, each battery module is composed of, for example, a plurality of battery cells connected in series. In this case, the voltage measuring circuit 1 may measure the voltage of each battery cell. In the following description, each battery module or each battery cell may be simply referred to as a "battery".

The charger 102 charges the secondary battery 101. At this time, the charger 102 may charge the secondary battery 101 based on the voltage monitored by the voltage measuring circuit 1 and the current monitored by the current sensor 103. When the electric vehicle is traveling, a current is supplied from the secondary battery 101 to the traveling motor 105. At this time, in this embodiment, the inverter circuit 104 generates a three-phase alternating current and supplies it to the traveling motor 105.

A relay 106 is provided between the secondary battery 101 and the charger 102. Further, on the negative electrode side of the secondary battery 101, a relay 107 is provided between the charger 102 and the load (in this embodiment, the traveling motor 105). Then, the controller 108 controls the relays 106 and 107. For example, when the charger 102 charges the secondary battery 101, the controller 108 controls the relays 106 and 107 to be on. Further, when the electric vehicle is traveling, the controller 108 controls the relay 106 to the off state and the relay 107 to the on state. When the secondary battery 101 is in the overcharged state or the overdischarged state, the controller 108 may control the relay 107 to the off state.

The controller 108 may give a current command value to the charger 102 based on the voltage monitored by the voltage measuring circuit 1 and the current monitored by the current sensor 103. Further, the controller 108 can give a control signal to the voltage measurement circuit 1 as needed.

FIG. 2 shows an example of the voltage measurement circuit 1. In this embodiment, the voltage measuring circuit 1 measures the voltage of the secondary battery 101. As shown in FIG. 2, the secondary battery 101 includes n battery modules B1 to Bn connected in series. Then, the voltage measuring circuit 1 can measure the voltage of the secondary battery 101 and the voltage of each battery module B1 to Bn.

The voltage measuring circuit 1 includes a resistance circuit (first resistance voltage dividing circuit) 11, a resistance circuit (second resistance voltage dividing circuit) 12, and a plurality of relay elements (first to nth relay elements) S1 to Sn. And a control unit 13. The voltage measurement circuit 1 may include other circuit elements not shown in FIG.

The resistance circuit 11 is composed of a reference resistor R0 and resistors R1 to Rn. The reference resistors R0 and resistors R1 to Rn are connected in series in order. Further, the reference resistors R0 and the resistors R1 to Rn are used as voltage dividing resistors. That is, the resistance circuit 11 is an example of a resistance voltage dividing circuit. The resistance values of the resistors R1 to Rn may or may not be the same as each other. The resistance circuit 12 includes a reference resistor r0 and an auxiliary resistor r1. The reference resistor r0 and the auxiliary resistor r1 are connected in series. Further, the reference resistor r0 and the auxiliary resistor r1 are used as a voltage dividing resistor. That is, the resistance circuit 12 is also an example of the resistance voltage dividing circuit.

One terminal (battery side terminal) of each relay element S1 to Sn is electrically connected to the positive terminal of the corresponding battery modules B1 to Bn. For example, the battery-side terminal of the relay element S1 is connected to the positive terminal of the battery module B1, and the battery-side terminal of the relay element Sn is connected to the positive terminal of the battery module Bn. Further, the other terminal (control unit side terminal) of each relay element S1 to Sn is electrically connected to one terminal (positive side terminal) of the corresponding resistors R1 to Rn. For example, the control unit side terminal of the relay element S1 is connected to the positive terminal of the resistor R1, and the control unit side terminal of the relay element Sn is connected to the positive terminal of the resistor Rn. That is, the corresponding relay elements S1 to Sn are provided between the positive terminals of the battery modules B1 to Bn and the positive terminals of the corresponding resistors R1 to Rn. The state of each relay element S1 to Sn is controlled by the control unit 13.

The other terminal (negative terminal) of the resistor R1 is connected to one terminal (positive terminal) of the reference resistor R0. The other terminal (negative terminal) of the reference resistor R0 is electrically connected to the negative terminal of the secondary battery 101 (that is, the negative terminal of the battery module B1). Then, the voltage Va at the connection point between the reference resistor R0 and the resistor R1 is given to the control unit 13.

The resistance circuit 12 is electrically connected to the resistance circuit 11 in parallel. That is, one terminal (positive terminal) of the auxiliary resistor r1 is connected to the positive terminal of the resistor Rn and the control unit side terminal of the relay element Sn. The other terminal (negative terminal) of the auxiliary resistor r1 is connected to one terminal (positive terminal) of the reference resistor r0. The other terminal (negative terminal) of the reference resistor r0 is connected to the negative terminal of the reference resistor R0 and the negative terminal of the secondary battery 101. Then, the voltage Vb at the connection point between the reference resistor r0 and the auxiliary resistor r1 is given to the control unit 13.

The control unit 13 measures the voltage of the secondary battery 101 and the potential of the positive terminal of each battery module B1 to Bn by detecting the voltage Va and the voltage Vb while controlling the relay elements S1 to Sn. Further, the control unit 13 can detect the failure of the resistance circuits 11 and 12 by monitoring the voltage Va and the voltage Vb while controlling the relay elements S1 to Sn.

The control unit 13 is realized by, for example, a microcomputer. In this case, the control unit 13 includes a processor and a memory. The processor can measure the voltage of the battery by executing a program stored in the memory. This program includes a description for controlling the relay elements S1 to Sn, and a description for calculating the voltage of the battery based on the voltage Va and the voltage Vb. The memory may store resistance information representing the resistance value of each resistor (R0 to Rn, r0 to r1).

<Voltage measurement>
The control unit 13 can measure the potentials of the positive terminals of the battery modules B1 to Bn by using the output voltage Va of the resistance circuit 11 and the output voltage Vb of the resistance circuit 12. The potential of the positive terminal of the battery module Bi (i = 1 to n) corresponds to the voltage between the potential of the negative electrode of the secondary battery 101 and the potential of the positive terminal of the battery module Bi. In the following description, the potentials of the positive terminals of the resistors R1 to Rn are represented by V1 to Vn, respectively. The potential of the positive terminal of the resistor Ri (i = 1 to n) corresponds to the voltage between the potential of the negative electrode of the secondary battery 101 and the potential of the positive terminal of the resistor Ri.

The control unit 13 selects two relay elements from the relay elements S1 to Sn in the voltage measurement of the secondary battery 101. Then, the control unit 13 acquires the voltage Va and the voltage Vb while controlling only the two selected relay elements in the ON state.

Here, the control unit 13 controls the relay element Sj and the relay element Sk in the on state, and controls the other relay elements in the off state. The relay element Sj represents a relay element connected to the battery module Bj (that is, the j-th battery module counting from the negative electrode of the secondary battery 101). The relay element Sk represents a relay element connected to the battery module Bk (that is, the kth battery module counting from the negative electrode of the secondary battery 101). It is assumed that k is larger than j. In other words, the relay element Sk is provided on the positive side with respect to the relay element Sj. As an example, k = j + 1. In this case, two relay elements adjacent to each other are controlled to be in the ON state. However, it is not always necessary that k = j + 1, and in this case, two relay elements that are not adjacent to each other are controlled to be in the ON state.

When the relay elements Sj and Sk are controlled in the on state and the other relay elements are controlled in the off state, the voltage Va is represented by the equation (1).

The control unit 13 calculates the voltage Vj by giving the measured value of the voltage Va to the equation (1). The voltage Vj represents the potential of the positive terminal of the resistor Rj (that is, the jth resistor counting from the reference resistor R0). Here, since the relay element Sj is controlled to be in the ON state, the voltage Vj is substantially the same as the potential of the positive terminal of the battery module Bj. Therefore, the control unit 13 can calculate the potential of the positive terminal of the battery module Bj based on the voltage Va.

Further, when the relay elements Sj and Sk are controlled in the on state and the other relay elements are controlled in the off state, the voltage Vb is represented by the equation (2).

The control unit 13 calculates the voltage Vk by giving the measured value of the voltage Vb to the equation (2). The voltage Vk represents the potential of the positive terminal of the resistor Rk (that is, the kth resistor counting from the reference resistor R0). Here, since the relay element Sk is controlled to be in the ON state, the voltage Vk is substantially the same as the potential of the positive terminal of the battery module Bk. Therefore, the control unit 13 can calculate the potential of the positive terminal of the battery module Bk based on the voltage Vb.

In this way, the control unit 13 can simultaneously measure the potentials of the two points in the secondary battery 101 by controlling the two relay elements in the ON state at the same time. Specifically, when the relay element Sj and the relay element Sk are controlled to be in the ON state, the control unit 13 measures the potential of the positive terminal of the battery module Bj based on the output voltage Va of the resistance circuit 11 and resists. The potential of the positive terminal of the battery module Bk is measured based on the output voltage Vb of the circuit 12.

Here, when measuring the potentials of the positive terminals of all the battery modules B1 to Bn, the control unit 13 detects the voltage Va and the voltage Vb while selecting two relay elements in order. For example, the control unit 13 selects two relay elements in order from the relay element connected to the battery module having the lowest potential among the battery modules B1 to Bn and controls the on state. In this case, at the time of the first measurement, the control unit 13 calculates the potentials of the positive terminals of the battery modules B1 and B2 by detecting the voltages Va and Vb while controlling the relay elements S1 and S2 in the ON state, respectively. .. Then, the voltage of the battery module B1 is obtained by the difference between the potential of the positive electrode terminal of the battery module B1 and the potential of the negative electrode terminal of the secondary battery 101, and the voltage of the battery module B2 is obtained by the potential of the positive electrode terminal of the battery module B2 and the battery. It is obtained by the difference from the potential of the positive electrode terminal of the module B1. Subsequently, the control unit 13 detects the voltages Va and Vb while controlling the two relay elements adjacent to the positive side of the relay element S2 in the ON state, thereby detecting the two relay elements adjacent to the positive side of the battery module B2. Calculate the potentials of the positive terminals of the battery module of. That is, the control unit 13 calculates the potentials of the positive terminals of the battery modules B3 and B4 by detecting the voltages Va and Vb while controlling the relay elements S3 and S4 in the ON state, respectively. Then, the voltage of the battery module B3 is obtained by the difference between the potential of the positive electrode terminal of the battery module B3 and the potential of the positive electrode terminal of the battery module B2, and the voltage of the battery module B4 is obtained by the potential of the positive electrode terminal of the battery module B4 and the battery module. It is obtained by the difference from the potential of the positive electrode terminal of B3. After that, the potentials of each battery module in the secondary battery 101 are sequentially measured at two points up to the battery module Bn.

FIG. 3 is a flowchart showing an example of the process of measuring the voltage. The processing of this flowchart is executed, for example, when a measurement instruction is given from the controller 108 to the control unit 13. Alternatively, the control unit 13 may voluntarily or periodically execute the processing of this flowchart.

In S1, the control unit 13 initializes the variable x to 1. The variable x specifies one of the relay elements S1 to Sn. In S2, the control unit 13 selects two relay elements corresponding to the variable x. Specifically, the control unit 13 selects the relay element Sx and the relay element Sx + 1. The relay element Sx and the relay element Sx + 1 represent relay elements connected to the positive terminals of the battery module Bx and the battery module Bx + 1, respectively. Then, the control unit 13 controls the two selected relay elements in the ON state. At this time, the other relay elements are controlled to the off state.

In S3, the control unit 13 acquires the output voltage Va of the resistance circuit 11 and the output voltage Vb of the resistance circuit 12. In S4, the control unit 13 calculates the potential of the positive terminal of the battery module connected to the relay element x (that is, the xth battery module counting from the negative electrode of the secondary battery 101) based on the voltage Va. .. This calculation is realized by the above-mentioned equation (1). Further, in S5, the control unit 13 determines the potential of the positive terminal of the battery module connected to the relay element x + 1 (that is, the x + 1th battery module counting from the negative electrode of the secondary battery 101) based on the voltage Vb. calculate. This calculation is realized by the above-mentioned equation (2).

In S6, the control unit 13 obtains the voltages of the x-th battery module and the x + 1-th battery module based on the potentials of the positive terminals of the x-th battery module and the x + 1-th battery module.

In S7, the control unit 13 determines whether or not the variable x is n or more. n represents the number of battery modules (that is, the number of relay elements) included in the secondary battery 101. Then, when the variable x is smaller than n, the control unit 13 increments the variable x by 2 in S8. After that, the processing of the control unit 13 returns to S2. That is, the control unit 13 repeatedly executes the processes of S2 to S5 until the variable x becomes n or more. In this process, two relay elements are sequentially selected from the relay elements S1 to Sn. Then, each time the two relay elements are selected, the potentials of the corresponding two battery modules are measured.

In the embodiment shown in FIG. 3, the potential of the battery module is measured in order from the negative electrode side to the positive electrode side of the secondary battery 101, but the present invention is not limited to this embodiment. That is, the control unit 13 may measure the potential of the battery module in order from the positive electrode side to the negative electrode side of the secondary battery 101.

Specifically, the control unit 13 may select two relay elements in order from the relay element connected to the battery module having the highest potential among the battery modules B1 to Bn and control the on state. Good. In this case, at the time of the first measurement, the control unit 13 detects the voltages Va and Vb while controlling the relay elements Sn and Sn-1 in the ON state, thereby detecting the potentials of the positive terminals of the battery modules Bn and Bn-1. Are calculated respectively. Subsequently, the control unit 13 detects the voltages Va and Vb while controlling the two relay elements adjacent to the negative side of the relay element Sn-1 in the ON state, thereby moving the battery module Bn-1 to the negative side. The potentials of the positive terminals of the two adjacent battery modules are calculated respectively. That is, the potentials of the positive terminals of the third and fourth battery modules counted from the positive electrode of the secondary battery 101 are measured. After that, the potentials of each battery module in the secondary battery 101 are sequentially measured at two points up to the battery module B1.

In this way, in the voltage measuring circuit 1, by controlling the two relay elements in the ON state at the same time, the potentials at two points in the secondary battery 101 can be measured at the same time. Further, by measuring the potentials of the positive terminals of the two battery modules while controlling the two adjacent relay elements in order from the relay element connected to the battery module having the lowest potential to the ON state, 1 The voltage of the two battery modules can be obtained by measuring the degree. Therefore, in the voltage measuring circuit that measures the voltage of the battery using the resistance voltage dividing circuit, the time required to measure the voltage of each battery module can be shortened.

<Variation>
In the above-described embodiment, the voltage measuring circuit 1 is provided independently of the controller 108 shown in FIG. 1, but the present invention is not limited to this configuration. For example, the function of the control unit 13 may be realized by the controller 108. Further, the voltage measurement circuit 1 may be provided with an RC filter between each battery module and the corresponding relay element.

1 Voltage measurement circuit 11, 12 Resistance circuit 13 Control unit 101 Secondary battery

Claims (2)

A voltage measuring circuit that measures the voltage of an assembled battery including n (n is an integer of 2 or more) batteries connected in series.
A first resistor divider circuit consisting of a first reference resistor and n resistors connected in series,
A second resistor divider circuit composed of a second reference resistor and an auxiliary resistor connected in series and electrically connected in parallel to the first resistor voltage divider circuit.
N relay elements provided between the positive terminals of the n batteries and one terminal of the n resistors, respectively.
A first voltage that controls the n relay elements and represents a voltage at a connection point between the first reference resistor and one of the n resistors, and the second reference resistor and the above. A control unit for measuring the voltage of the n batteries based on a second voltage representing the voltage at the connection point with the auxiliary resistor is provided.
The negative terminal of the assembled battery is electrically connected to the first reference resistor and the second reference resistor.
The control unit is attached to a relay element connected to the first battery among the n batteries and a second battery provided on the higher potential side than the first battery among the n batteries. When only the connected relay element is controlled to be in the ON state, the potential of the positive terminal of the first battery is calculated based on the first voltage, and the second voltage is calculated based on the second voltage. A voltage measurement circuit characterized by calculating the potential of the positive terminal of a battery. The control unit starts from the relay element connected to the battery having the lowest potential among the n batteries, or from the relay element connected to the battery having the highest potential among the n batteries. The voltage measurement circuit according to claim 1, wherein, in order, two relay elements adjacent to each other in the plurality of relay elements are controlled to be in an ON state to calculate the corresponding two potentials.

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