JP2012115101A - Cell balance controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell balance controller capable of maintaining appropriate cell balance control by preventing destruction of a bypass resistor due to temperature rise.SOLUTION: The cell balance controller includes: a bypass circuit which is connected in parallel to each of a plurality of cells; a cell voltage detection part for detecting a cell voltage of each of the plurality of cells; and a temperature detection part for detecting the temperature of a substrate where the bypass circuit is mounted. The cell balance controller is provided with: an allowable current value determination part for determining an allowable current value of the bypass resistor on the basis of a value detected from the temperature detection part; an each cell discharge current value calculation part for calculating a current value flowing to the bypass resistor of each discharge requiring cell on the basis of each cell voltage value of the discharge requiring cell obtained from the cell voltage detection part; and a control part for comparing each cell discharge current value with the allowable current value for each discharge requiring cell, and executing duty control on a switching element of the bypass circuit connected to the discharge requiring cell so that each cell discharge current value becomes equal to or lower than the allowable current value when it exceeds the allowable current value.

Description

 The present invention relates to a cell balance control device that equalizes cell voltages of battery cells.

  As is well known, vehicles such as electric vehicles and hybrid vehicles are equipped with a motor as a power source and a high-voltage, large-capacity battery for supplying electric power to the motor. This battery is constituted by connecting a plurality of battery cells made of lithium ion batteries or hydrogen nickel batteries in series. Conventionally, in order to maintain the performance of the battery, cell balance control for monitoring the cell voltage of each battery cell and equalizing each cell voltage is performed.

  In Patent Document 1 below, a series circuit of a resistor and a switching element is connected in parallel to each cell as a bypass circuit, the lowest cell voltage is compared with another cell voltage, and the voltage difference is a first predetermined value. For cells that exceed the value, the switching element is turned on to conduct the bypass circuit (discharge the cell), and when the voltage difference becomes equal to or less than a second predetermined value lower than the first predetermined value, the switching element A technique is disclosed in which the cell voltage is made uniform by turning off and blocking the bypass circuit.

  In Patent Document 2 below, a bypass circuit is connected in parallel to each cell as in Patent Document 1, and the capacity set according to the battery state (for example, cell voltage distribution status, battery usage time ratio, and capacity deterioration coefficient) Each cell voltage is controlled by changing the predetermined capacity adjustment current value based on the adjustment capacity improvement request level and performing duty control of the switching element so that a discharge current corresponding to the predetermined capacity adjustment current value flows to the bypass circuit. A technique for achieving uniformization is disclosed.

JP-A-8-19188 JP 2008-21589 A

  As described above, conventionally, the cell balance control is performed based on the voltage difference of the cell voltages or the cell voltage distribution state, the battery usage time ratio, the capacity deterioration coefficient, and the like. On the other hand, when cell balance control is performed, a discharge current flows through the bypass circuit and the bypass resistor generates heat. Generally, the standard guaranteed current value of the resistance element rapidly decreases as the temperature rises. Therefore, if the temperature becomes too high, the discharge current may exceed the standard guaranteed current value of the bypass resistor, which may cause destruction of the bypass resistor.

  In the above prior art, cell balance control is not performed in consideration of a decrease in the standard guaranteed current value of the bypass resistor due to such a temperature rise. In the worst case, the bypass resistor is destroyed and appropriate cell balance control is performed. May not be able to be performed.

   The present invention has been made in view of the above-described circumstances, and provides a cell balance control device capable of preventing destruction of a bypass resistor due to a temperature rise and thereby maintaining appropriate cell balance control. With the goal.

  In order to achieve the above object, according to the present invention, as a first solution means for a cell balance control device, a series circuit of a bypass resistor and a switching element is connected in parallel to each of a plurality of cells constituting a battery. A cell balance control device comprising: a bypass circuit; a cell voltage detector that detects a cell voltage of each of the plurality of cells; and a temperature detector that detects a temperature of a substrate on which the bypass circuit is mounted. Based on a value detected from the temperature detection unit, an allowable current value determination unit that determines an allowable current value of the bypass resistor, and based on each cell voltage value of the discharge required cells obtained from the cell voltage detection unit, Each cell discharge current value calculation unit for calculating a current value flowing in the bypass resistor of each discharge cell, and each cell discharge current value and the allowable power for each discharge cell. A control unit that performs duty control on a switching element of a bypass circuit connected to the discharge-required cell so as to be equal to or less than the allowable current value when each cell discharge current value exceeds the allowable current value. It is characterized by providing.

  According to the present invention, as the second solving means relating to the cell balance control device, in the first solving means, the allowable current value determining unit is configured to set the allowable current of the substrate temperature and the bypass resistance that are set in advance. The allowable current value corresponding to the current substrate temperature is determined using table data indicating a correspondence relationship with the value.

  Further, in the present invention, as a third solving means relating to the cell balance control device, in each of the first and second solving means, each cell discharge current value calculating unit calculates the cell voltage value of the discharge required cell from the cell voltage value. The cell discharge current value is calculated by dividing the resistance value of the bypass resistor.

  Further, in the present invention, as a fourth solving means related to the cell balance control device, in the second or third solving means, the control unit is configured to set the cell discharge current value and the permissible value for each discharge required cell. When each cell discharge current value exceeds the allowable current value by comparing with a current value, a duty ratio is calculated by dividing the allowable current value by each cell discharge current value, and the calculated duty ratio is A duty control unit that controls the duty of the switching element of the bypass circuit connected to the discharge required cell is provided.

  In the present invention, as a fifth solving means according to the cell balance control device, in any one of the second to fourth solving means, the control unit is based on a value detected from the temperature detecting unit. And a predetermined discharge power value calculation unit for calculating a predetermined discharge power value required to raise the substrate temperature to a maximum allowable temperature, and connected to the discharge required cell based on a cell voltage value of the discharge required cell. A required discharge cell discharge power value calculating unit for calculating a required discharge cell discharge power value consumed in the bypass circuit, and the duty control unit includes the cell discharge current value and the tolerance for the required discharge cell. When each cell discharge current value is equal to or less than the allowable current value by comparing with the current value, the discharge cell is contacted at a duty ratio obtained by dividing the discharge predetermined power value by the discharge cell discharge power value. The switching element of the bypass circuit that is characterized by duty control.

  Further, in the present invention, as a sixth solving means related to the cell balance control device, in any one of the first to fifth solving means, the control unit includes the plurality of the plurality of the voltage obtained from the cell voltage detection unit. The cell voltage value of each cell is transmitted to a host control device, and the identification result of the discharge required cell is received from the host control device.

 According to the present invention, since the discharge current flowing in the bypass circuit connected to the cells requiring discharge can always be kept lower than the standard guaranteed current value of the bypass resistance while performing the cell balance control, the bypass resistance caused by the temperature rise Therefore, it is possible to maintain proper cell balance control.

1 is a schematic configuration diagram of a cell balance control device 1 in the present embodiment. It is a flowchart showing the cell balance control which the microcomputer M implements. It is a Ta-Ic characteristic view which shows the relationship between the board | substrate temperature Ta and the discharge current Ic which flows into the bypass circuit connected to the discharge required cell.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a cell balance control device 1 according to the present embodiment. As shown in FIG. 1, the cell balance control device 1 performs cell balance control for equalizing the cell voltages of 12 cells C1 to C12 constituting a battery, and includes 12 bypass circuits B1 to B12. And 12 cell voltage detection circuits D1 to D12 (cell voltage detection unit), a temperature sensor TS (temperature detection unit), a microcomputer M (control unit), and an insulating element IR.

 The bypass circuits B1 to B12 are each composed of a series circuit of a bypass resistor and a switching element such as a transistor, and are connected in parallel to the cells C1 to C12. In FIG. 1, the signs of the bypass resistors built in the bypass circuits B1 to B12 are R1 to R12, and the signs of the switching elements are T1 to T12.

 The cell voltage detection circuits D1 to D12 are connected in parallel to each of the cells C1 to C12, detect the voltage (cell voltage value) between the terminals of the cells connected to the cells C1, and detect the detected cell voltage value by the microcomputer. Output to M. Note that these cell voltage detection circuits D1 to D12 contain capacitors connected in parallel to the cells C1 to C12. That is, the voltage between terminals of each capacitor is output to the microcomputer M as the cell voltage value of each of the cells C1 to C12.

 The temperature sensor TS is a thermistor mounted on a circuit board (not shown) together with the bypass circuits B1 to B12, the cell voltage detection circuits D1 to D12, the insulating element IR, and the microcomputer M, and detects the temperature of the circuit board. A signal indicating the detected value is output to the microcomputer M. The mounting position of the temperature sensor TS on the circuit board is not particularly limited, but it is desirable that the temperature sensor TS be mounted in the vicinity of a bypass resistor that is likely to be broken due to an increase in the substrate temperature.

 The microcomputer M is communicably connected to a battery ECU (Electronic Control Unit) 2 that is a host controller via an insulating element IR, and the cell voltages of the cells C1 to C12 obtained from the cell voltage detection circuits D1 to D12. The value is transmitted to the battery ECU 2. The battery ECU 2 monitors changes in the cell voltage values of the cells C1 to C12 based on the cell voltage values of the cells C1 to C12 received from the microcomputer M, and compares the cell voltage values with those of other cells. When a high cell is found, the cell is identified as a cell that needs to be discharged (required discharge cell), and the identification result is transmitted to the microcomputer M.

 When the microcomputer M receives the specified result of the discharge required cell from the battery ECU 2, the microcomputer M is based on the value detected from the temperature sensor TS (substrate temperature) and the cell voltage value of the discharge required cell obtained from the cell voltage detection circuits D1 to D12. At the time of discharge of the discharge required cell, the discharge current Ic flowing through the bypass circuit connected to the discharge required cell is connected to the discharge required cell so as to be lower than the standard guaranteed current value Imax of the bypass resistance corresponding to the current substrate temperature Ta. Duty control is performed on the switching element of the bypass circuit. Specifically, the microcomputer M includes an allowable current value determination unit Ma, each cell discharge current value calculation unit Mb, and a duty control unit Mc as functional units for realizing the duty control. .

 The allowable current value determination unit Ma determines the allowable current value Ith of the bypass resistor based on the substrate temperature detected by the temperature sensor TS. Each cell discharge current value calculation unit Mb calculates a current value Ifi (i is an identification number of the discharge cell required) flowing in the bypass resistance of each discharge cell based on each cell voltage value of the discharge required cell. The duty control unit Mc compares each cell discharge current value Ifi and the allowable current value Ith for each discharge required cell, and when each cell discharge current value Ifi exceeds the allowable current value Ith, the duty control unit Mc becomes equal to or less than the allowable current value Ith. Duty control is performed on the switching elements of the bypass circuit connected to the discharge cells. Specifically, when each cell discharge current value Ifi exceeds the allowable current value Ith, the duty control unit Mc calculates the duty ratio by dividing the allowable current value Ith by each cell discharge current value Ifi. The switching element of the bypass circuit connected to the discharge required cell is duty-controlled with the duty ratio.

 The microcomputer M further includes a predetermined discharge power value calculation unit Md and a discharge cell discharge power value calculation unit Me. Based on the substrate temperature Ta detected by the temperature sensor TS, the predetermined discharge power value calculation unit Md calculates a predetermined discharge power value W1 necessary for increasing the substrate temperature Ta to the maximum allowable temperature Tmax. The required discharge cell discharge power value calculation unit Me calculates the required discharge cell discharge power value W2 consumed by the bypass circuit connected to the required discharge cell based on the cell voltage value of the required discharge cell.

 The duty control unit Mc compares the cell discharge current value Ifi and the allowable current value Ith with respect to the discharge required cell, and if the cell discharge current value Ifi is less than or equal to the allowable current value Ith, the predetermined discharge power value W1 is required. It also has a function of duty-controlling the switching elements of the bypass circuit connected to the discharge cells with a duty ratio obtained by dividing by the discharge cell discharge power value W2.

Next, the operation of the cell balance control device 1 configured as described above will be described.
FIG. 2 is a flowchart showing a processing procedure of cell balance control performed by the microcomputer M. Note that the microcomputer M transmits the cell voltage values of the cells C1 to C12 obtained from the cell voltage detection circuits D1 to D12 to the battery ECU 2 at a constant period, and the timing at which the specific result of the discharge required cells is received from the battery ECU 2. Then, the process shown in FIG. 2 is started.

As shown in FIG. 2, when the microcomputer M receives the specified result of the discharge cells from the battery ECU 2, the microcomputer M acquires the substrate temperature Ta from the temperature sensor TS (step S1). The predetermined discharge power value calculation unit Md of the microcomputer M includes the substrate temperature Ta (° C), the maximum allowable temperature Tmax (° C) of the circuit board, and the thermal resistance Rth (° C / W) of the circuit board ( 1) A predetermined discharge power value W1 is calculated based on the equation (step S2). In the following equation (1), the maximum allowable temperature Tmax and the thermal resistance Rth are fixed values set in the microcomputer M in advance.
W1 = (Tmax−Ta) / Rth (1)

Subsequently, the required discharge cell discharge power value calculation unit Me of the microcomputer M acquires the cell voltage value of the required discharge cell specified by the battery ECU 2 among the cell voltage values of the cells C1 to C12 (step S3). The discharge is required based on the following equation (2) consisting of the resistance value r of the bypass resistors R1 to R12 provided in each bypass circuit B1 to B12 and the cell voltage value Vi (i is an identification number of the discharge cell). A cell discharge power value W2 is calculated (step S4).
W2 = Σ (Vi ² / r) (2)

For example, when the cells C1, C5, and C10 are specified as the discharge cells in step S4, the discharge cell discharge power value calculation unit Me of the microcomputer M determines the cell voltage values of the discharge cells C1, C5, and C10. Substituting V1, V5, and V10 into the above equation (2), and calculating (V1 ² / r) + (V5 ² / r) + (V10 ² / r), the required discharge cell discharge power value W2 is calculated. .

 The predetermined discharge power value W1 obtained in step S2 is a power value necessary for raising the substrate temperature Ta to the maximum allowable temperature Tmax, and the discharge cell required discharge power value W2 obtained in step S4. These are the total discharge power values consumed in the bypass circuit when the switching elements of the bypass circuit connected to the cells requiring discharge are duty controlled with a duty ratio of 100% (full-on). Here, if the required discharge cell discharge power value W2 is equal to or less than the predetermined discharge power value W1, the substrate temperature Ta remains even if the switching element of the bypass circuit connected to the required discharge cell is duty controlled with a duty ratio of 100%. The maximum allowable temperature Tmax is not exceeded.

 On the other hand, if the required discharge cell discharge power value W2 exceeds the predetermined discharge power value W1, the substrate temperature Ta exceeds the maximum allowable temperature Tmax if the required discharge cell discharge power value W2 is reduced to the predetermined discharge power value W1. There is no. In other words, if the duty ratio is set lower than 100% and the discharge current Ic of the discharge cells is reduced by the rate at which the discharge cell discharge power value W2 exceeds the predetermined discharge power value W1, the substrate temperature Ta is set to the maximum allowable temperature. Tmax will not be exceeded. Therefore, the duty ratio necessary for performing the cell balance control so that the substrate temperature Ta does not exceed the maximum allowable temperature Tmax is expressed as a ratio (W1 / W2) between the predetermined discharge power value W1 and the required discharge cell discharge power value W2. Is done.

That is, the duty control unit Mc of the microcomputer M calculates the duty ratio Dy based on the following equation (3) composed of the predetermined discharge power value W1 and the required discharge cell discharge power value W2 (step S5). As can be seen from the following equation (3), when the required discharge cell discharge power value W2 is smaller than the predetermined discharge power value W1, the duty ratio Dy exceeds 100%. In such a case, the duty ratio Dy is always set to 100. % Can be set.
Dy = (W1 / W2) × 100 (3)

  Subsequently, the allowable current value determination unit Ma of the microcomputer M corresponds to the current substrate temperature Ta by using table data indicating a correspondence relationship between the substrate temperature Ta and the allowable current value Ith of the bypass resistor, which is set in advance. An allowable current value Ith is determined (step S6). FIG. 3 shows a correspondence relationship between the preset substrate temperature Ta and the allowable current value Ith of the bypass resistor.

 FIG. 3 is a Ta-Ic characteristic diagram in which the horizontal axis represents the substrate temperature Ta and the vertical axis represents the discharge current Ic. In FIG. 3, symbol L1 is a characteristic line showing the correspondence between the substrate temperature Ta and the standard guaranteed current value Imax of the bypass resistor. Reference numeral L2 is a characteristic line showing a correspondence relationship between the substrate temperature Ta and the allowable current value Ith of the bypass resistor. As described above, the standard guaranteed current value Imax of the resistance element generally has a characteristic of rapidly decreasing as the temperature rises, and the allowable current value Ith is within the entire range of the substrate temperature Ta. Is set to be less than

 Subsequently, each cell discharge current value calculation unit Mb of the microcomputer M calculates each cell discharge current value Ifi by dividing the resistance value r of the bypass resistor from the cell voltage value of each discharge required cell (step S7). For example, when the cells C1 and C5 are identified as the cells requiring discharge, each cell discharge current value calculation unit Mb divides the resistance value r of the bypass resistor from the cell voltage value V1 of the cell C1 to the cell C1. Each cell discharge current value If1 flowing through the connected bypass circuit B1 is calculated, and the resistance value r of the bypass resistor is divided from the cell voltage value V5 of the cell C5, thereby flowing into the bypass circuit B5 connected to the cell C5. Each cell discharge current value If5 is calculated.

  Subsequently, the duty control unit Mc of the microcomputer M compares the allowable current value Ith corresponding to the current substrate temperature Ta determined in step S6 with each cell discharge current value Ifi calculated in step S7, and each cell discharge. It is determined whether or not the current value Ifi exceeds the allowable current value Ith (step S8). For example, when the cells C1 and C5 are specified as discharge required cells, the duty control unit Mc compares each cell discharge current value If1 flowing through the bypass circuit B1 connected to the cell C1 with the allowable current value Ith, Each cell discharge current value If5 flowing through the bypass circuit B5 connected to the cell C5 is compared with the allowable current value Ith.

Then, if “Yes” in step S8, that is, if each cell discharge current value Ifi exceeds the allowable current value Ith, the duty control unit Mc of the microcomputer M, as shown in the following equation (4), A duty ratio Dy ′ is calculated by dividing Ith by each cell discharge current value Ifi, and duty control is performed on the switching elements of the bypass circuit connected to the discharge cells with the calculated duty ratio Dy ′ (step S9).
Dy ′ = (Ith / Ifi) × 100 (4)

  For example, if the cells C1 and C5 are identified as cells requiring discharge and both are determined that the respective cell discharge current values Ifi (If1 and If5) exceed the allowable current value Ith, the duty controller Mc The switching element T1 of the bypass circuit B1 connected to the cell C1 is duty-controlled by the duty ratio Dy ′ obtained by dividing the value Ith by each cell discharge current value If1, and the allowable current value Ith is set to each cell discharge current value. The duty of the switching element T5 of the bypass circuit B5 connected to the cell C5 is controlled by the duty ratio Dy ′ obtained by dividing by If5.

  That is, when it is determined that each cell discharge current value Ifi exceeds the allowable current value Ith, that is, there is a possibility that the discharge current Ic reaching the standard guaranteed current value Imax of the bypass resistor flows in the bypass circuit connected to the discharge required cell. In some cases (when there is a possibility that the bypass resistor may be destroyed), the bypass circuit connected to these discharge cells is always discharged below the standard guaranteed current value Imax of the bypass resistor by the duty control in step S9. The current Ic (discharge current Ic corresponding to the allowable current value Ith) flows.

  On the other hand, if “No” in step S8, that is, if each cell discharge current value Ifi is less than or equal to the allowable current value Ith, the duty control unit Mc of the microcomputer M performs all necessary operations with the duty ratio Dy calculated in step S5. The duty of the switching element of the bypass circuit connected to the discharge cell is controlled (step S10).

  In other words, when it is determined that each cell discharge current value Ifi does not exceed the allowable current value Ith, that is, there is a possibility that the discharge current Ic reaching the standard guaranteed current value Imax of the bypass resistor flows in the bypass circuit connected to the discharge required cell. If there is no possibility (when there is no possibility that the bypass resistor is destroyed), the total discharge power value (discharge cell discharge required) consumed by the bypass circuit connected to the discharge required cell is controlled by the duty control in step S10. A discharge current Ic whose power value W2) is always equal to or lower than the predetermined discharge power value W1 flows to the bypass circuit of each discharge cell. In this case, the substrate temperature Ta does not exceed the maximum allowable temperature Tmax of the circuit board.

 In FIG. 3, symbol L3 is a Ta-Ic characteristic line when the number of required discharge cells is 6 and the cell voltage value is 5V, and symbol L4 is a Ta-Ic characteristic line when the number of required discharge cells is 6 and the cell voltage value is 3V. Reference numeral L5 indicates a Ta-Ic characteristic line when the number of required discharge cells is six and the cell voltage value is 1.5V, and reference numeral L6 indicates a Ta-Ic characteristic line when the number of required discharge cells is one and the cell voltage value is 5V. Reference numeral L7 Is a Ta-Ic characteristic line when the number of required discharge cells is 1 and the cell voltage value is 3V, and symbol L8 is a Ta-Ic characteristic line when the number of required discharge cells is 1 and the cell voltage value is 1.5V. As shown in FIG. 3, the larger the at least one parameter of the number of discharge cells required and the cell voltage value, the larger the discharge current Ic flowing in the bypass circuit. The bypass resistance is not destroyed.

 By the cell balance control by the microcomputer M as described above, the discharge required cells are discharged and the cell balance (cell voltage uniformity) of each of the cells C1 to C12 is maintained, and a bypass circuit connected to the discharge required cells is provided. The flowing discharge current Ic is always kept lower than the standard guaranteed current value Imax of the bypass resistor, and the substrate temperature Ta is always kept below the maximum allowable temperature Tmax of the circuit board. Even during the above-described cell balance control, the microcomputer M transmits the cell voltage values of the cells C1 to C12 obtained from the cell voltage detection circuits D1 to D12 to the battery ECU 2 at a constant cycle, and discharges from the battery ECU 2. The duty control of the switching element is ended at the timing when the end command is received (when the cell balance is adjusted).

 As described above, according to the cell balance control device 1 of the present embodiment, the discharge current Ic flowing in the bypass circuit connected to the discharge cells that are required for the cell balance control is always the standard guaranteed current value Imax of the bypass resistance. Since it can be kept lower, it is possible to prevent the bypass resistance from being destroyed due to the temperature rise, and thus to maintain appropriate cell balance control. Further, according to the cell balance control device 1 in the present embodiment, the substrate temperature Ta can be suppressed to the maximum allowable temperature Tmax or less, so that it is possible to prevent circuit elements from being destroyed or malfunctioning due to the increase in the substrate temperature Ta. it can.

In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
(1) In the said embodiment, although the cell balance control apparatus 1 which performs cell balance control about 12 cells C1-C12 was illustrated, the number of cells of control object is not limited to 12. For example, when the battery is configured by connecting 45 cells in series, cell balance control can be performed for all cells constituting the battery by using four cell balance control devices 1. .

(2) In the above embodiment, the substrate temperature Ta detected by the temperature sensor TS is used as it is for the determination of the allowable current value Ith and the calculation of the discharge predetermined power value W1, but when temperature correction is necessary, The determination of the allowable current value Ith and the discharge predetermined power value W1 may be calculated using the substrate temperature Ta ′. In the above embodiment, the duty ratio Dy obtained by the above equation (3) is used as it is, and the duty control of the switching element is performed. However, the predetermined discharge power value W1 and the required discharge cell discharge power value W2 are It is desirable to multiply the duty ratio Dy by a correction coefficient for correcting non-linearity.

(3) In the above embodiment, the case where the cell balance control device 1 obtains the specific result of the discharge required cell from the battery ECU 2 is exemplified, but the cell voltage values of the cells C1 to C12 obtained from the cell voltage detection circuits D1 to D12. The microcomputer M may be provided with a function for identifying the discharge required cells based on the above.

(4) In the above embodiment, the case where the required discharge cell discharge power value W2 consumed in the bypass circuit connected to the discharge cell is calculated using the above formula (2), but it is not necessarily 100%. It is not necessary to calculate the required discharge cell discharge power value W2 assuming a duty ratio, and the total discharge power value consumed by the bypass circuit when duty control is performed at a duty ratio of 90% or 80% is required. You may obtain | require as electric power value W2.

(5) In the above embodiment, each cell discharge current value Ifi is calculated by dividing the resistance value r of the bypass resistor from the cell voltage value of each discharge cell, that is, the switching element is duty controlled with a duty ratio of 100%. However, it is not always necessary to calculate each cell discharge current value Ifi assuming a duty ratio of 100%, such as 90% or 80%. The current value flowing in the bypass resistor when the duty control is performed with the duty ratio of may be obtained as each cell discharge current value Ifi.

 DESCRIPTION OF SYMBOLS 1 ... Cell balance control apparatus, C1-C12 ... Cell, B1-B12 ... Bypass circuit, D1-D12 ... Cell voltage detection circuit (cell voltage detection part), TS ... Temperature sensor (temperature detection part), M ... Microcomputer (control) Part), Ma ... allowable current value calculation part, Mb ... each cell discharge current value calculation part, Mc ... duty control part, Md ... discharge predetermined power value calculation part, Me ... required discharge cell discharge power value calculation part, IR ... insulation Element, 2 ... Battery ECU (high-order control device)

Claims (6)

A bypass circuit comprising a series circuit of a bypass resistor and a switching element, connected in parallel to each of a plurality of cells constituting the battery, a cell voltage detection unit for detecting a cell voltage of each of the plurality of cells, and the bypass In a cell balance control device comprising a temperature detection unit that detects the temperature of a substrate on which a circuit is mounted,
Based on a value detected from the temperature detection unit, an allowable current value determination unit that determines an allowable current value of the bypass resistor;
Each cell discharge current value calculation unit for calculating a current value flowing through the bypass resistor of each discharge cell based on each cell voltage value of the discharge cell obtained from the cell voltage detection unit;
For each of the required discharge cells, the cell discharge current value is compared with the allowable current value, and when the cell discharge current value exceeds the allowable current value, the required discharge current value is less than the allowable current value. A control unit for duty-controlling the switching element of the bypass circuit connected to the cell;
A cell balance control device comprising:   The allowable current value determining unit determines the allowable current value corresponding to the current substrate temperature, using preset table data indicating a correspondence relationship between the substrate temperature and the allowable current value of the bypass resistor. The cell balance control device according to claim 1.   The cell discharge current value calculation unit calculates the cell discharge current value by dividing a resistance value of the bypass resistor from a cell voltage value of the discharge required cell. The cell balance control device described.   The control unit compares the cell discharge current value with the allowable current value for each discharge cell, and if the cell discharge current value exceeds the allowable current value, the control unit sets the allowable current value to the cell. 3. A duty control unit that calculates a duty ratio by dividing by a discharge current value and duty-controls a switching element of a bypass circuit connected to the discharge-required cell with the calculated duty ratio. Or the cell balance control apparatus of 3. The controller is
Based on a value detected from the temperature detection unit, a discharge predetermined power value calculation unit that calculates a discharge predetermined power value required to raise the substrate temperature to a maximum allowable temperature;
Based on the cell voltage value of the required discharge cell, a required discharge cell discharge power value calculation unit for calculating a required discharge cell discharge power value consumed by a bypass circuit connected to the required discharge cell;
Further comprising
The duty control unit compares the cell discharge current value with the allowable current value for the discharge required cell, and if the cell discharge current value is equal to or less than the allowable current value, the duty control unit calculates the predetermined discharge power value. 5. The cell according to claim 2, wherein duty control is performed on a switching element of a bypass circuit connected to the discharge required cell with a duty ratio obtained by dividing by a discharge cell discharge power value. 6. Balance control device.   The control unit transmits a cell voltage value of each of the plurality of cells obtained from the cell voltage detection unit to a host control device, and receives a specification result of the discharge required cells from the host control device. The cell balance control apparatus according to any one of claims 1 to 5.

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