JP6554748B2 - Voltage detector - Google Patents

Description

  The present invention relates to a voltage detection device.

  Patent Document 1 below discloses a voltage detection device capable of detecting a leak failure of a capacitor of a low-pass filter. This voltage detection device is a device for detecting the voltage (cell voltage) of each battery cell constituting the assembled battery, and a CR filter is used to detect a capacitor leakage failure in a CR filter (low-pass filter) provided in each cell voltage input path. This is detected by comparing the cell voltage detected via the cell voltage with the cell voltage detected bypassing the CR filter.

JP 2014-064404 A

  By the way, in the conventional voltage detection device, the first voltage input path for inputting the cell voltage to the detection circuit via the CR filter and the second voltage input path for bypassing the CR filter and inputting the cell voltage to the detection circuit. Must be provided. That is, in the conventional voltage detection device, since it is necessary to provide two voltage input paths for each battery cell provided in a large number of battery packs, the number of components for configuring the voltage input path increases, and the detection circuit As the number of input terminals increases, the cost of the voltage detection device is increased.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to detect an abnormality of a CR filter in a state where the input path of the cell voltage is reduced as compared with the conventional one.

  In order to achieve the above object, according to the present invention, as a first solving means related to a voltage detection device, a voltage detection device that takes in a detected voltage input from a battery and detects it through a CR filter, A switch circuit for connecting a bypass resistor between the terminals of the battery, an A / D conversion circuit for sampling the detected voltage taken in via the CR filter at a predetermined sampling period and converting it into voltage detection data, and the switch Time constant calculating means for calculating a plurality of time constants of the CR filter based on the voltage detection data before and after the circuit connects the bypass resistor between the terminals of the battery, and based on the average of the plurality of time constants A means is provided that includes an abnormality determination unit that determines abnormality of the CR filter.

  In the present invention, as a second solving means relating to the voltage detecting device, in the first solving means, the time constant calculating means is configured to detect the detected voltage by connecting the bypass resistor between terminals of the battery. The plurality of time constants are calculated on the basis of a relational expression between the amount of decrease in the above and the time constant of the CR filter.

  In the present invention, as a third solving means relating to the voltage detecting device, in the second solving means, the time constant calculating means uses the voltage detection data before and after connecting the bypass resistor between the terminals of the battery. A means of calculating the plurality of time constants by substituting into the relational expression is adopted.

  In the present invention, as a fourth solving means relating to the voltage detecting device, a means is used in which the battery is an assembled battery including a plurality of cell batteries in the first or second solving means.

 According to the present invention, a plurality of CR filter time constants are calculated based on voltage detection data before and after connecting a bypass resistor between battery terminals, and an abnormality of the CR filter is determined based on an average of the plurality of time constants. Therefore, it is possible to detect an abnormality of the CR filter in a state where the input path of the detected voltage is reduced as compared with the conventional case.

It is a circuit diagram which shows the structure of the voltage detection apparatus which concerns on one Embodiment of this invention. It is a timing chart which shows operation | movement of the voltage detection apparatus which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the voltage detection device A according to the present embodiment is a device that detects a voltage (cell voltage) of n battery cells b1 to bn constituting the assembled battery B as a detected voltage. N discharge circuits D1 to Dn (switch circuit), n + 1 transmission lines S1 to Sn + 1, n + 1 CR filters F1 to Fn + 1, a cell voltage detector K, and a microcomputer M (A / D conversion circuit, time constant calculation means, abnormality determination means).

  The assembled battery B includes a plurality (n pieces) of battery cells b1 to bn. A total of n battery cells b1 to bn are connected in series in a line, the plus terminal of the battery cell b1 is the plus terminal of the assembled battery B, and the minus terminal of the battery cell bn is the minus terminal of the assembled battery B. is there. That is, n battery cells b1 to bn are connected in series in the order of battery cell b1 → battery cell b2 → (omitted) → battery cell bn, and the total value of the cell voltages of each battery cell b1 to bn is an assembled battery. B output voltage.

  The n discharge circuits D1 to Dn are respectively connected in parallel to the n battery cells b1 to bn, and each is a series circuit of a bypass resistor and a switching element. These discharge circuits B1 to Bn are switch circuits that connect the bypass resistors in parallel to the battery cells b1 to bn when the switching elements are turned on.

  That is, these discharge circuits B1 to Bn place the battery cells b1 to bn in a discharged state by connecting the bypass resistors in parallel to the battery cells b1 to bn, while the switching element is turned off and the battery cell b1 having the bypass resistance. The battery cells b1 to bn are brought into a non-discharged state by releasing the parallel connection to .about.bn. Among such n discharge circuits D1 to Dn, the discharge circuit D1 is connected in parallel to the battery cell b1, the discharge circuit D2 is connected in parallel to the battery cell b2, and (the omission), the discharge circuit Dn is connected to the battery cell bn. Connected in parallel.

  The n + 1 transmission lines S1 to Sn are wirings (cell voltage detection wirings) that connect the assembled battery B and the printed circuit board. These n + 1 transmission lines S1 to Sn transmit the terminal voltages of the n battery cells b1 to bn to the input terminals of the n + 1 CR filters F1 to Fn + 1.

  That is, the transmission line S1 connects the positive terminal of the battery cell b1 and the input end of the CR filter F1, and the transmission line S2 connects the connection point between the negative terminal of the battery cell b1 and the positive terminal of the battery cell b2 and the CR filter F2. Connect the input terminal. The transmission line S3 connects the connection point between the negative terminal of the battery cell b2 and the positive terminal of the battery cell b3 and the input end of the CR filter F3. (Omitted) The transmission line Sn connects the connection point between the negative terminal of the battery cell bn-1 (not shown) and the positive terminal of the battery cell bn and the nth input terminal of the CR filter Fn, and the transmission line Sn + 1. Connects the negative terminal of the battery cell bn and the input end of the CR filter Fn + 1.

  The n + 1 CR filters F1 to Fn + 1 are low-pass filters for noise removal provided on the 13 transmission lines S1 to Sn + 1, respectively, and include filter resistors R1 to Rn + 1 and filter capacitors C1 to Cn + 1. That is, the CR filter F1 is provided in the transmission line S1, the CR filter F2 is provided in the transmission line S2, the CR filter F3 is provided in the transmission line S3 (omitted), and the CR filter Fn is transmitted. The CR filter Fn + 1 is provided on the transmission line Sn + 1.

  The filter resistors R1 to Rn + 1 are connected in series to each of n + 1 transmission lines S1 to Sn + 1, and the filter capacitors C1 to Cn + 1 have one end connected to each of n + 1 transmission lines S1 to Sn + 1. The other end is connected to GND (ground potential). The filter resistors R1 to Rn + 1 have the same resistance value R, and the filter capacitors C1 to Cn + 1 have the same capacitance C. The resistance value R and the capacitance C are amounts that define the time constant τ of the CR filters F1 to Fn + 1, that is, the filter characteristics of the CR filters F1 to Fn + 1.

  The cell voltage detection unit K is provided corresponding to n battery cells b1 to bn, and n pieces of n input from n + 1 transmission lines S1 to Sn via n + 1 CR filters F1 to Fn. By sampling each terminal voltage of the battery cells b1 to bn at a predetermined cycle, the voltage between the terminals (cell voltage) of each battery cell b1 to bn is detected. That is, each cell voltage detection part K detects the difference (difference voltage) of each terminal voltage of each battery cell b1-bn as cell voltage V1-Vn. Further, the cell voltage detection unit K outputs the cell voltages V1 to Vn detected by itself to the microcomputer M.

  That is, the cell voltage detection unit K detects the cell voltage V1 of the battery cell b1 based on a pair of terminal voltages input via the transmission line S1 and the transmission line S2, and detects the transmission line S2 and the transmission line S3. The cell voltage V2 of the battery cell b2 is detected based on a pair of terminal voltages input via the battery cell (omitted), and the battery cell based on the pair of terminal voltages input via the transmission line Sn and the transmission line Sn + 1. The cell voltage Vn of bn is detected.

  The microcomputer M is a so-called one-chip microcomputer in which a CPU (Central Processing Unit), a memory, an input / output interface, etc. are integrated, and exhibits a predetermined function by executing a voltage detection program stored in the internal memory. To do.

  Such a microcomputer M samples n cell voltages V1 to Vn input from the cell voltage detection unit K at a predetermined sampling period and converts them into n voltage detection data Vd1 to Vdn. In addition, the microcomputer M stores the voltage detection data Vd1 to Vdn in an internal memory and performs a predetermined calculation process according to the voltage detection program, thereby performing a balance control process for the state of charge of each battery cell b1 to bn. Then, disconnection diagnosis processing of each transmission line S1 to Sn + 1 and abnormality diagnosis processing of n + 1 CR filters F1 to Fn + 1 are performed.

  That is, the microcomputer M equalizes the cell voltages V1 to Vn of the battery cells b1 to bn by controlling the discharge circuits D1 to Dn based on the voltage detection data Vd1 to Vdn. Further, the microcomputer M diagnoses which of the transmission lines S1 to Sn + 1 is disconnected based on the difference between the voltage detection data Vd1 to Vdn of the battery cells b1 to bn adjacent to each other.

  Further, the microcomputer M calculates a plurality of time constants τ of the respective CR filters F1 to Fn + 1 based on the respective voltage detection data Vd1 to Vdn before and after the discharge circuits D1 to Dn are set to the “ON” state. The abnormality of each CR filter F1 to Fn + 1 is determined based on the average of the constants. Such a microcomputer M corresponds to an A / D conversion circuit, a time constant calculation unit, and an abnormality determination unit in the present invention.

  Such a microcomputer M is connected to an external battery ECU via a predetermined insulating element so as to be communicable, and notifies the external battery ECU of the diagnosis results. The insulating element is an element for isolating the microcomputer M and the battery ECU, and is, for example, a photocoupler.

  Next, the operation of the voltage detection apparatus A according to the present embodiment, particularly the abnormality diagnosis operation of the CR filters F1 to Fn + 1 will be described in detail.

  When performing abnormality diagnosis of the CR filters F1 to Fn + 1, the microcomputer M sequentially controls the discharge circuits D1 to Dn from the OFF state to the ON state at predetermined time intervals, and the voltage detection data Vd1 before and after the state transition. The time constant τ of the CR filters F1 to Fn + 1 is calculated based on ˜Vdn. Here, since the microcomputer M relating to the abnormality diagnosis is exactly the same for each of the CR filters F1 to Fn + 1, the abnormality diagnosis operation relating to the CR filters F1 and F2 will be described in detail below with reference to FIG.

  The microcomputer M sequentially takes the cell voltage V1 input from the cell voltage detection unit K and converts it into voltage detection data Vd1 (A / D conversion). However, in the abnormality diagnosis of the CR filter F1, the discharge drive signal is output to the discharge circuit D1n. Is switched from the OFF state to the ON state, that is, the state in which the bypass resistor is not connected in parallel to the battery cell b1 to the state in which the bypass resistor is connected in parallel. Here, the time width T during which the discharge circuit D1n is turned on is a time that is 10 times or more the time constant τ when the CR filter F1 is normal.

When the discharge circuit D1n is switched from the OFF state to the ON state, a bypass resistor is connected in parallel to the battery cell b1, so that a balance current Ib flows from the plus terminal to the minus terminal of the battery cell b1 via the bypass resistor. As a result, the voltage V _i1 at the input end of the CR filter F1 is decreased by ΔV ₁ due to the balance current Ib, and the voltage V _i2 at the input end of the CR filter F2 connected to the negative terminal of the battery cell b1 is increased by ΔV _2. To do. This voltage drop ΔV ₁ is caused by the internal resistance of the transmission line S1, and the voltage rise ΔV ₂ is caused by the internal resistance of the transmission line S2.

Then, the cell voltage V1 is a difference voltage between the voltage at the output terminal of the CR filter F1 of the output end of the voltage and the CR filter F2, due to the voltage drop [Delta] V ₁ and the voltage rise [Delta] V _2, shown in FIG. 2 To decline. That is, the drop in the cell voltage V1 is stored in the filter capacitor C1 among the filter resistor R1 and the filter capacitor C1 constituting the CR filter F1 and the filter resistor R2 and the filter capacitor C2 constituting the CR filter F2. The charge flows through the filter resistor R1 and the bypass resistor as a discharge current to the negative terminal of the battery cell b1, and the charge stored in the filter capacitor C2 is discharged as the discharge current through the filter resistor R2 and the bypass resistor. It is generated by flowing through the positive terminal.

 Here, the bypass resistor is provided to equalize the cell voltages V1 to Vn of the battery cells b1 to bn, and the resistance value is set to be significantly smaller than the resistance value R of the filter resistor R1. . Therefore, the amount of decrease ΔV of the cell voltage V1 is determined by the capacitance C of the two filter capacitors C1 and C2 and the resistance value R of the two filter resistors R1 and R2, that is, by the time constant τ of the two CR filters F1 and F2. Dominated by the Lord.

That is, the amount of decrease in the cell voltage V1 due to the bypass resistor is connected in parallel to the battery cell b1 [Delta] V, under the above voltage drop [Delta] V ₁ and the voltage rise [Delta] V ₂ and a time constant τ constant, the time t as a variable type (1) That is, it can be expressed by a relational expression between the amount of decrease ΔV and the time constant τ.

  Since the voltage detection data Vd1 is obtained by sampling the cell voltage V1 at a predetermined sampling period, the voltage detection data Vd1 is applied to the above equation (1), and the time constant τ is expressed by the following equation: (2) is obtained as an approximation of equation (1). The time constants τ (1) to τ (3) represented by the equation (2) are approximate values of the time constant τ.

  That is, the voltage detection data V (0) based on the sample value AD (0) sampled immediately before the discharge circuit D1n switches from the OFF state to the ON state, and sampled immediately after the discharge circuit D1n switches from the OFF state to the ON state. Voltage detection data V (1) based on the sample value AD (1), voltage detection data V (2) based on the sample value AD (2) sampled next to the sample value AD (1), and sample value AD (2 ), The voltage detection data V (3) based on the sampled value AD (3) sampled next, and the time width T when a sufficient time has elapsed after the discharge circuit D1n is switched from the OFF state to the ON state. Approximation of time constant τ by voltage detection data V (L) based on sample value AD (L) sampled immediately before the passage Can be obtained constant τ (1) ~τ (3) when it is.

  The microcomputer M calculates three time constants τ (1) to τ (3) by substituting such voltage detection data V (0) to V (L) into the above equation (2). The microcomputer M finally obtains the time constant τ by calculating the arithmetic average of the three time constants τ (1) to τ (3). For the voltage detection data V (0) and V (L), as shown in FIG. 2, three sample values AD (0) are obtained, and the arithmetic average of the three sample values AD (0) is obtained. Each is obtained by computing. More accurate time constants τ (1) to τ (3) can be acquired by such arithmetic processing.

  According to the present embodiment, the time constants τ (approximate values) of the CR filters F1 to Fn + 1 are sequentially calculated based on the voltage detection data Vd1 to Vdn before and after the discharge circuits D1 to Dn connect the bypass resistors. Based on the time constant τ (approximate value), an abnormality of each CR filter F1 to Fn + 1, for example, a leak failure of each filter capacitor C1 to Cn + 1 that constitutes each CR filter F1 to Fn + 1 can be detected.

  That is, according to the present embodiment, each of the CR filters F1 to Fn + 1 in a state where the input paths of the cell voltages V1 to Vn (detected voltages) of the battery cells b1 to bn constituting the assembled battery B are reduced as compared with the prior art. It is possible to detect abnormalities.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the cell voltages of the n battery cells b1 to bn constituting the assembled battery B are detected voltages, but the present invention is not limited to this. The present invention can be applied to voltage detection of various batteries other than the assembled battery.

(2) In the above embodiment, three time constants τ (1) to τ (3) are obtained as an example, but the present invention is not limited to this. The time constant (approximate value) calculated | required by a calculation should just be two or more. However, the time constant τ of each CR filter F1 to Fn + 1 has a correlation with the region where each cell voltage V1 to Vn gradually decreases immediately after connecting the bypass resistance to each battery cell b1 to bn as shown in FIG. The correlation is low in the region where the cell voltages V1 to Vn are sufficiently lowered and asymptotic to a constant value. Accordingly, the plurality of time constants (approximate values) are preferably based on sample values sampled in the above-described gradually decreasing region.

A voltage detection device B assembled battery b1 to bn battery cell D1 to Dn discharge circuit (switch circuit)
F1 to Fn CR filter K Cell voltage detection unit M Microcomputer (A / D conversion circuit, disconnection determination unit, charge balance adjustment unit)
S1 to S13 Transmission line

Claims (4)

A voltage detection device that detects and detects a detected voltage input from a battery via a CR filter,
A switch circuit for connecting a predetermined bypass resistor between the terminals of the battery;
An A / D conversion circuit that samples the detected voltage taken in via the CR filter at a predetermined sampling period and converts it into voltage detection data;
Time constant calculating means for calculating a plurality of time constants of the CR filter based on the voltage detection data before and after the switch circuit connects the bypass resistor between the terminals of the battery;
An abnormality determination unit that determines abnormality of the CR filter based on an average of the plurality of time constants.   The time constant calculating means calculates the plurality of time constants based on a relational expression between a decrease amount of the detected voltage due to the bypass resistor being connected between the terminals of the battery and a time constant of the CR filter. The voltage detection device according to claim 1, wherein:   The time constant calculating means calculates the plurality of time constants by substituting the voltage detection data before and after connecting the bypass resistor between the terminals of the battery into the relational expression. The voltage detection apparatus described in 1. The voltage detection apparatus according to claim 1, wherein the battery is an assembled battery including a plurality of cell batteries.

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