JP2013219994A - Battery equalization device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a sufficient cell balance and also reduce a time till balancing by a digital control according to a state of a battery cell in an equalization control of a voltage of a battery pack constituted by connecting plural battery cells.SOLUTION: A first balance circuit 104 equalizes a voltage of each battery cell 102 in each stack 103 comprising a predetermined number of battery cells 102 constituting a battery pack 101 and continuously and serially connected. A second balance circuit 105 equalizes a voltage between the stacks 103. A voltage monitoring section 106 monitors the voltage of each battery cell 102 and detects it as a digital signal value. A balance control section 107 selects any of the first balance circuit 104 and the second balance circuit 105 and actuates it by digital signal processing based on the voltage value of each battery cell 102 detected by the voltage monitoring section 106.

Description

  The present invention relates to a battery equalization apparatus and method for controlling voltage equalization of an assembled battery configured by connecting a plurality of battery cells.

  A so-called hybrid car, plug-in hybrid car, hybrid vehicle, hybrid electric vehicle or the like, which is equipped with a motor (electric motor) as a power source in addition to an engine or a transport machine (hereinafter referred to as “vehicle etc.”) is practical It has become. Furthermore, an electric vehicle that does not include an engine and drives the vehicle only by a motor is being put into practical use. As a power source for driving these motors, a lithium ion battery having a small size and a large capacity has been frequently used. And in such a use, a some battery cell is connected in series, for example, a battery block is comprised, and also it may be supplied as an assembled battery connected combining this battery block. A high voltage necessary for driving the motor of the vehicle is obtained by the series connection of the battery cells, and a necessary current capacity and a further high voltage can be obtained by connecting the battery blocks in combination in series and parallel.

  In this case, the characteristics of the lithium ion battery or the like greatly change depending on the temperature, and the remaining capacity and charging efficiency of the battery greatly change depending on the temperature of the environment in which the battery is used. This is especially true in environments where automobiles are used.

  As a result, in the battery cells constituting the battery block, the remaining capacity and the output voltage of each cell vary. When the voltage generated by each cell varies, it becomes necessary to stop or suppress the entire power supply when the voltage of one cell falls below the driveable threshold, resulting in reduced power efficiency. Resulting in. For this reason, the battery equalization control which equalizes the voltage of each cell is required. Furthermore, it is necessary to equalize the voltage between the battery blocks.

  As a prior art of battery equalization control, the so-called active battery equalization, in which discharge power from a battery cell that requires discharge is charged to a battery cell that needs to be charged by a balance circuit configured by combining an inductor and a transformer. A control technology is known (for example, the technology described in Patent Document 1).

  This prior art reduces the power loss by using the discharge power from one battery cell as the charge power to other battery cells, and corrects the voltage balance of all cells in a multi-series storage cell with many series connections. The purpose is to make this happen quickly and smoothly.

  However, this prior art does not disclose a specific control method for operating a balance circuit configured by combining an inductor and a transformer in accordance with the state of each battery cell, and optimal energy efficiency control is realized. It has a problem that it cannot be said.

JP 2008-35680 A

  An object of the present invention is to realize efficient cell balance by performing digital control according to the state of a battery cell, and further to shorten the time to balance.

  An example of an aspect is configured as a battery equalizing device that equalizes voltages of a plurality of battery cells in an assembled battery configured by connecting a plurality of battery cells, and configures a plurality of battery cells and continuously connected in series For each of the stacks in a set of stacks of a given number of battery cells, the energy discharged from one or more of the battery cells in the stack is transferred to one of the battery cells in the stack. The first balance circuit that equalizes the voltage of the battery cells in the stack by charging the other battery cells as described above, and the voltage between the stacks is equalized by discharging or charging energy in units of the stack The second balance circuit to be activated, the voltage monitoring unit for monitoring the voltage of each battery cell and detecting it as a digital signal value, and the voltage monitoring unit Based on the digital signal value of the voltage of the battery cell, the digital signal processing, and a balance controller that operates to select one of the first balancing circuit or the second balance circuit.

  According to the present invention, by performing digital control according to the state of the battery cell, efficient cell balance can be achieved, and further, the time to balance can be shortened.

It is a basic lineblock diagram of this embodiment. It is a whole system lineblock diagram of this embodiment. It is a block diagram of the converter balance circuit in this embodiment. It is a flowchart which shows the control operation of this embodiment. It is a flowchart which shows the operation | movement of the balance control between stacks. It is explanatory drawing of the OCV-internal resistance map for every temperature. It is explanatory drawing of the calculation process of the frequency and duty ratio of a pulse signal for switching control of a transformer. It is a flowchart which shows the operation | movement of the balance control in a stack. It is operation | movement explanatory drawing of the calculation process of the frequency and duty ratio of the pulse signal for switching control of a converter. It is a timing chart which shows the control operation of this embodiment. It is a figure (the 1) which shows the structural example of other embodiment. It is a figure (the 2) which shows the structural example of other embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a basic configuration diagram of the present embodiment.
A plurality of battery cells 102 are connected in series to form an assembled battery 101. In this embodiment, the assembled battery 101 is configured as a set of stacks 103 including a predetermined number of battery cells 102 continuously connected in series.

  For each stack 103 constituting the assembled battery 101, the first balance circuit 104 transfers energy discharged from one or more battery cells 102 among the battery cells 102 in the stack 103 to the battery cells 102 in the stack 103. The voltage of the battery cells 102 in the stack 103 is equalized by charging one or more other battery cells. For example, the first balance circuit 104 charges energy discharged from each battery cell 102 in the stack 103 to the adjacent battery cells in the stack 103 via a circuit including a switching element and an inductor.

  The second balance circuit 105 equalizes the voltage between the stacks 103 by discharging or charging energy in units of the stacks 103. The second balance circuit 105 causes energy to be discharged or charged between the stacks 103 through a circuit including a switching element and a transformer.

The voltage monitoring unit 106 monitors the voltage of each battery cell 102 and detects it as a digital signal value.
The balance control unit 107 selects either the first balance circuit 104 or the second balance circuit 105 by digital signal processing based on the digital signal value of the voltage of each battery cell 102 detected by the voltage monitoring unit 106. And make it work. The balance control unit 107 is configured by, for example, a digital signal processor (DSP). More specifically, the balance control unit 107 determines whether each battery cell 102 has a difference between a maximum value and a minimum value of each battery cell 102 monitored by the voltage monitoring unit 106 that is equal to or greater than a first threshold value. Based on the voltage, a voltage for each stack 103 is further calculated. The balance control unit 107 operates the second balance circuit 105 to equalize the voltages between the stacks 103 when the difference between the maximum value and the minimum value of the voltages for each stack 103 is greater than or equal to the second threshold value. Then, the balance control unit 107 sets the first balance circuit 104 after the operation of the second balance circuit 105 or when the difference between the maximum value and the minimum value of the voltage for each stack 103 is smaller than the second threshold value. By operating, the voltage of the battery cells in the stack 103 is equalized for each stack 103.

  In the present embodiment, based on the digital value of the voltage of each battery cell 102 monitored by the voltage monitoring unit 106, the balance control unit 107, which is a DSP, for example, finely tunes the first balance circuit 104 and the second balance circuit 105. For example, switching control can be performed. More specifically, the balance control unit 107 operates the second balance circuit 105 first when it is determined that the voltage balance of the battery cell 102 is lost based on the voltage monitoring result of each battery cell 102. Thus, the rough voltage balance between the stacks 103 is adjusted. Thereafter, the balance control unit 107 operates the first balance circuit 104 to drive the voltage balance in each stack 103 into a uniform state. By finely performing such control, efficient cell balance can be achieved, and the time to balance can be shortened.

FIG. 2 is an overall system configuration diagram of the present embodiment based on the basic configuration of FIG.
In FIG. 2, the first balance circuit 104 in FIG. 1 is a converter balance circuit 104 ′, the second balance circuit 105 in FIG. 1 is a transbalance circuit 105 ′, and the balance control unit 107 in FIG. Processor) Embodiments each embodied in the DSP 107 ′. The other portions 101, 102, 103, and 106 are the same as the portions having the same numbers in FIG.

  The transformer balance circuit 105 ′ includes a transformer 201, a diode 207, a switching element 205, and a switch control unit 206. The transformer 201 includes a plurality of secondary windings 202, a primary winding 203, and a magnetic core 205. The primary winding 203 is connected to both poles of the assembled battery 101. Each secondary winding 202 is reversely wound with respect to the primary winding 203 and has a predetermined winding ratio, and is connected to both poles of each stack 103 via each diode 207. The switch control unit 206 is a PWM output circuit that outputs a pulse signal having a predetermined frequency and duty ratio designated by the DSP 107 ′. The switching element 205 is, for example, an FET (field effect transistor), and performs a switching operation by a pulse signal from the switch control unit 206. If the voltage generated on the side of each secondary winding 202 by this switching operation is higher than the voltage across both ends of the stack 103 connected thereto, the stack is connected via the diode 207 until the voltage between the two becomes equal. 103 is charged. Eventually, balance control is performed so that the voltage across all stacks 103 becomes equal to the common voltage generated on the secondary winding 202 side.

Details of the converter balance circuit 104 'of FIG. 2 are shown in FIG.
In FIG. 3, the stack 103 and the voltage monitoring unit 106 are the same as the parts having the same numbers in FIG. 1 or FIG. 2.

  The converter balance circuit 104 ′ includes a balance circuit 301, a DSP (digital signal processor) 302, and a switch control unit 303. The balance circuit 301 includes a plurality of inductors L and a plurality of switching elements SW for, for example, the four battery cells 102 # 1 to # 4 constituting the stack 103. Specifically, the first terminal of the # 1 inductor L is connected to the common connection terminal of the # 1 and # 2 battery cells 102, and the # 2 inductor is connected to the common connection terminal of the # 2 and # 3 battery cells 102. The first terminal of L is connected to the common connection terminal of the battery cells 102 of # 3 and # 4, and the first terminal of the inductor L of # 3 is connected thereto. The second terminal of the # 1 inductor L is the common connection terminal for the # 1 and # 2 switching elements SW, and the second terminal of the # 2 inductor L is the common for the # 3 and # 4 switching elements SW. The second terminal of the # 3 inductor L is connected to the common connection terminal of the # 5 and # 6 switching elements SW. Further, the output terminal side of the # 1 battery cell 102 is connected to the single connection terminal of the # 1 switching element SW. The common connection terminal of the battery cells 102 of # 1 and # 2 is connected to the switching element SW of # 2. The common connection terminals of the # 2 and # 3 battery cells 102 are connected to the common connection terminals of the switching elements SW of # 2 and # 5. The output terminal side of the # 4 battery cell 102 is connected to the single connection terminal of the # 6 switching element SW.

  The switch control unit 303 is a PWM output circuit that outputs a pulse signal having a predetermined frequency and duty ratio designated by the DSP 302. Each switching element SW of # 1 to # 6 is, for example, an FET (field effect transistor), and performs a switching operation by a pulse signal from the switch control unit 303.

  The voltage monitoring unit 106 detects the voltages at both ends of the battery cells 102 # 1 to # 4 constituting the stack 103 and outputs the detected voltage to the DSP 107 ′ in FIG. 2 and the DSP 302 in FIG. 3 as digital values. .

  In the configuration of the converter balance circuit 104 ′ described above, for example, when the DSP 302 determines that the balance control between the battery cells 102 of # 1 and # 2 is to be performed, the DSP 302 sets a predetermined frequency and duty ratio to the switch control unit 303. Designate and instruct the switching elements SW of # 1 and # 2 to operate. For example, the DSP 302 determines that the voltage of the # 1 battery cell 102 is higher than the voltage of the # 2 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, first, the energy discharged from the # 1 battery cell 102 is accumulated in the # 1 inductor L by the on / off operation of the # 1 switching element SW. Subsequently, the energy stored in the # 1 inductor L is charged in the # 2 battery cell 102 by the on / off operation of the # 2 switching element SW delayed by the duty ratio. Conversely, for example, the DSP 302 determines that the voltage of the # 2 battery cell 102 is higher than the voltage of the # 1 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, first, the energy discharged from the # 2 battery cell 102 is accumulated in the # 1 inductor L by the on / off operation of the # 2 switching element SW. Subsequently, the energy stored in the # 1 inductor L is charged in the # 1 battery cell 102 by the on / off operation of the # 1 switching element SW delayed by the duty ratio.

  When the DSP 302 determines that the balance control between the battery cells 102 of # 2 and # 3 is to be performed, the DSP 302 designates a predetermined frequency and duty ratio to the switch control unit 303, and performs # 3 and # 4. Instructing the switching element SW to operate. For example, the DSP 302 determines that the voltage of the # 2 battery cell 102 is higher than the voltage of the # 3 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, first, the energy discharged from the # 2 battery cell 102 is accumulated in the # 2 inductor L by the on / off operation of the # 3 switching element SW. Subsequently, the energy stored in the # 2 inductor L is charged in the # 3 battery cell 102 by the on / off operation of the # 4 switching element SW delayed by the duty ratio. Conversely, for example, the DSP 302 determines that the voltage of the # 3 battery cell 102 is higher than the voltage of the # 2 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, first, the energy discharged from the # 3 battery cell 102 is accumulated in the # 2 inductor L by the on / off operation of the # 4 switching element SW. Subsequently, the energy stored in the # 2 inductor L is charged in the # 2 battery cell 102 by the on / off operation of the # 3 switching element SW delayed by the duty ratio.

  Furthermore, when the DSP 302 determines that the balance control between the battery cells 102 of # 3 and # 4 is to be performed, the DSP 302 designates a predetermined frequency and duty ratio to the switch control unit 303, and # 5 and # 6. Instructing the switching element SW to operate. For example, the DSP 302 determines that the voltage of the # 3 battery cell 102 is higher than the voltage of the # 4 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, energy discharged from the # 3 battery cell 102 is first stored in the # 3 inductor L by the on / off operation of the # 5 switching element SW. Subsequently, the energy stored in the # 3 inductor L is charged in the # 4 battery cell 102 by the on / off operation of the # 6 switching element SW delayed by the duty ratio. Conversely, for example, the DSP 302 determines that the voltage of the # 4 battery cell 102 is higher than the voltage of the # 3 battery cell 102 based on the voltage monitoring result of the voltage monitoring unit 106. In this case, first, the energy discharged from the # 4 battery cell 102 is accumulated in the # 3 inductor L by the on / off operation of the # 6 switching element SW. Subsequently, the energy stored in the # 3 inductor L is charged in the # 3 battery cell 102 by the on / off operation of the # 5 switching element SW delayed by the duty ratio.

  As described above, in converter balance circuit 104 ′, when it is determined that balance control is necessary as a result of voltage monitoring of each battery cell 102 in stack 103 by voltage monitoring unit 106, # 1 to # 3 Inductor L and switching elements SW of # 1 to # 6 are selectively operated sequentially. As a result, balance control is sequentially performed between the battery cells 102 adjacent to each of the battery cells 102 of # 1 to # 4, and the operation is repeated, so that the operations of # 1 to # 4 in the stack 103 are finally performed. The voltage of the battery cell 102 becomes uniform.

In the configuration described above, the DSP 302 in FIG. 3 may be realized by the same DPS as the DSP 107 ′ in FIG.
In the embodiment shown in FIGS. 2 and 3, the DSPs 107 ′ (FIG. 2) and 302 (FIG. 3) are connected to the battery cell 102 based on the digital value of the voltage of each battery cell 102 detected by the voltage monitoring unit 106. It is determined whether or not the voltage balance is lost. Based on the determination result, first, the DSP 107 ′ operates the transbalance circuit 105 ′ based on a control operation specifically described below, and adjusts the rough voltage balance between the stacks 103. Thereafter, each DSP 302 in each converter balance circuit 104 ′ operates each balance circuit 301 based on an instruction from the DSP 107 ′ to drive the voltage balance of each battery cell 102 in each stack 103 to a uniform state. go. By finely performing such digital control, efficient cell balancing becomes possible, and the time to balance can be shortened.

  FIG. 4 is a flowchart showing a control operation executed by the DSP 107 ′ in FIG. 2 and each DSP 302 in each converter balance circuit 104 ′ in FIG. This control operation is realized as an operation in which a processor (not shown) in the DSP 107 'and the DSP 302 executes a control program stored in a memory (not shown). This control program is executed once or at a predetermined time interval, for example, when the vehicle equipped with the system of the present embodiment is turned off or when idling is started.

  First, the DSP 107 ′ measures the voltage at each end of each battery cell 102 using each voltage monitoring unit 106 (FIG. 2) connected to each converter balance circuit 104 ′, and acquires it as a digital value (step). S401).

The DSP 107 ′ calculates the difference between the maximum voltage value and the minimum voltage value of each battery cell 102 (step S402).
The DSP 107 ′ determines whether or not the difference between the maximum voltage value and the minimum voltage value calculated in step S402 is equal to or greater than a predetermined threshold value 1 (first threshold value) (step S403). This threshold value 1 determines whether or not balance control is necessary.

As a result of the determination in step S403, if the difference is smaller than the threshold value 1, the DSP 107 ′ determines that the balance control is unnecessary, and ends the current balance control.
If the result of determination in step S403 is that the difference is greater than or equal to the threshold value 1, the DSP 107 ′ further calculates the voltage across each stack 103 based on the voltage monitoring result of each voltage monitoring unit 106. Specifically, for each stack 103, the DSP 107 ′ adds all the voltage values at both ends of the battery cells 102 (see FIG. 3) belonging to the stack 103, for example, # 1 to # 4. It is the voltage at both ends. Then, the DSP 107 ′ calculates the difference between the maximum voltage value and the minimum voltage value of each stack 103 (step S404).

  The DSP 107 ′ determines whether or not the difference between the maximum voltage value and the minimum voltage value calculated in step S404 is greater than or equal to a predetermined threshold value 2 (second threshold value) (step S405). This threshold value 2 determines whether or not the balance control between stacks is necessary.

  As a result of the determination in step S405, if the difference is smaller than the threshold value 2, the DSP 107 ′ determines that the inter-stack balance control is unnecessary, and shifts to the intra-stack balance control after step S407.

  As a result of the determination in step S405, if the difference is equal to or larger than the threshold value 2, the DSP 107 ′ instructs the switch control unit 206 in the transbalance circuit 105 ′ in FIG. 2 to perform the inter-stack balance control operation by the transbalance circuit 105 ′. Is executed (step S406). Details of this operation will be described later in the description of the flowchart of FIG.

  After the operation of the inter-stack balance control in step S406, or when it is determined in step S405 that the inter-stack balance control is not required (the difference is smaller than the threshold value 2), the intra-stack shown in steps S407 to S411 A control loop for balance control is executed.

First, the DSP 107 ′ sequentially selects each stack 103 constituting the assembled battery 101 of FIG. 2, and activates the DSP 302 (FIG. 3) in the selected stack 103.
Based on the voltage monitoring result of the voltage monitoring unit 106, the DSP 302 measures the cell voltages of the battery cells 102 (FIG. 3) # 1 to # 4 in the stack 103 to which the DSP 302 belongs (step S407).

Next, the DSP 302 calculates the difference between the maximum voltage value and the minimum voltage value of the battery cells 102 # 1 to # 4 in the stack 103 to which the DSP 302 belongs (step S408).
The DSP 302 determines whether or not the difference between the maximum voltage value and the minimum voltage value calculated in step S408 is greater than or equal to a predetermined threshold 3 (third threshold) (step S409). This threshold value 3 determines whether or not the balance control within the stack is necessary.

  If the difference is smaller than the threshold value 3 as a result of the determination in step S409, the DSP 302 determines that the balance control in the stack to which the DSP 302 belongs is not necessary, and notifies the DSP 107 ′ accordingly. As a result, the DSP 107 ′ proceeds to the determination process in step S411.

  As a result of the determination in step S409, if the difference is equal to or greater than the threshold value 3, the DSP 302 has the # 1 and # 2 battery cells 102, the # 2 and # 3 battery cells 102, # 3 and # 4 in the stack 103 to which the DSP 302 belongs. The battery cells 102 are sequentially designated. Then, the DSP 302 executes the operation of the in-stack balance control by the converter balance circuit 104 ′ for the designated pair of battery cells 102 (step S410). Details of this operation will be described later in the description of the flowchart of FIG.

When the process of step S410 is completed, the DSP 302 notifies the DSP 107 ′ accordingly.
Upon receiving the notification of step S409 or S410 from the DSP 302, the DSP 107 ′ determines whether or not the intra-stack balance control has been completed for all the stacks 103 at this time (step S411).

  If it is determined that the intra-stack balance control has not been completed for all the stacks 103 at this time, the DSP 107 ′ selects an unprocessed stack 103, returns to the processing in step S 407, and returns the intra-stack balance to the stack 103. Make control run.

If it is determined that the intra-stack balance control has been completed for all the stacks 103 this time, the DSP 107 ′ ends the current balance control process.
FIG. 5 is a flowchart showing the operation of the inter-stack balance control in step S406 of FIG.

  First, the DSP 107 ′ determines whether or not a current flows through the assembled battery 101 (FIG. 2) by using an ammeter (not shown) connected to one end of the assembled battery 101 (step S501).

  When the DSP 107 ′ determines that a current is flowing through the assembled battery 101 in step S501, such as when the vehicle is idling, the voltage value for each stack 103 calculated in step S404 in FIG. 4 is measured in step S501. The internal resistance of each stack 103 is calculated by dividing by the current value (step S502).

  On the other hand, when the DSP 107 ′ determines that no current is flowing in the assembled battery 101 in step S501, such as when the vehicle is turned off, the DSP 107 ′ acquires the temperature value of the assembled battery 101 from a temperature sensor (not shown). Then, the DSP 107 ′ uses the voltage value (OCV: open current voltage) in a state where no current flows through each stack 103 calculated in step S404 in FIG. The internal resistance is estimated with reference to each OCV-internal resistance map (step S503). FIG. 6 is a diagram illustrating a data configuration example of an OCV-internal resistance map for each temperature. An internal resistance [mΩ] is stored for each value of temperature [° C.] and OCV [V].

  The DSP 107 ′ calculates the frequency and duty ratio of the pulse signal for the switching operation in the transbalance circuit 105 ′ in FIG. 2 from the value of the internal resistance in step S502 or S503, and sets it in the switch control unit 206 in FIG. (Step S504).

This calculation will be described in detail below. FIG. 7 is an explanatory diagram of the calculation processing of the frequency and duty ratio of the pulse signal for switching control of the transformer. This figure shows an equivalent circuit of the primary winding 203, the secondary winding 202, the switching element 205, the diode 207, and the battery cell 102 of the transformer 201 of FIG. Now, the number of turns of the primary winding 203 of the transformer 201 is N1, and the number of turns of the secondary winding 202 is N2. The frequency of the pulse signal given from the switch control unit 206 to the switching element 205 is freq, the period is T, the pulse on time is t _on , the duty ratio is D, the voltage on the primary winding 203 side is Vin, and the secondary winding 202 is If the side voltage is Vo, the following equation is established.

By controlling the frequency freq and the duty ratio D of the pulse signal applied to the switching element 205 from the switch control unit 206 of FIG. 2 based on this equation, the charge / discharge output voltage Vo for the battery cell 102 can be changed.

  Further, since the output power is output based on the following equation, the output power can be changed by controlling the duty ratio. Here, Lp is the inductance of the primary winding 203, and P is the output power.

Based on the above equation 1 and equation 2, the switch control unit 206 calculates the current allowable value set corresponding to the value of the internal resistance calculated in step S502 or S503 in FIG. 5, the power to be output, and the pulse frequency freq. Thus, the duty ratio of the pulse signal given to the switching element 205 can be calculated. Alternatively, the pulse frequency freq may be determined by arbitrarily determining the duty ratio.

  The DSP 107 ′ designates the pulse frequency freq and the duty ratio D determined as described above to the switch control unit 206 in FIG. As a result, a pulse signal is output from the switch control unit 206 in FIG. 2 to the switching element 205, and switching control is executed (step S505 in FIG. 5).

FIG. 8 is a flowchart showing the operation of the in-stack balance control in step S410 of FIG.
First, the DSP 302 in FIG. 3 determines whether or not current is flowing through the assembled battery 101 (FIG. 2) using an ammeter (not shown) connected to one end of the assembled battery 101 (step S801).

  When the DSP 302 determines that current is flowing through the assembled battery 101 in step S801, for example, when the vehicle is idling, the voltage value for each battery cell 102 calculated in step S407 in FIG. 4 is measured in step S701. The internal resistance of each battery cell 102 is calculated by dividing by the current value (step S802).

  On the other hand, when the DSP 302 determines that no current is flowing through the assembled battery 101 in step S701, for example, when the vehicle is turned off, the DSP 302 acquires the temperature value of the assembled battery 101 from a temperature sensor (not shown). Then, the DSP 302 uses the voltage value (OCV) in the state where no current flows in each battery cell 102 calculated in step S407 in FIG. With reference to the internal resistance map, the internal resistance is estimated (step S803). A data configuration example of the OCV-internal resistance map for each temperature is the same as that in FIG.

  The DSP 302 calculates the frequency and duty ratio of the pulse signal for the switching operation in the selected switching element SW in the converter balance circuit 104 ′ in FIG. 3 from the value of the internal resistance in step S702 or S703. The switch control unit 303 is set (step S804).

  This calculation will be described in detail below. FIG. 9 is an explanatory diagram of a calculation process of the frequency and duty ratio of a pulse signal for switching control of the converter. 9, the inductor L is switched from # 1 to # 3 in FIG. 3, and the switching elements SW1 and SW2 are switched from # 1 and # 2, # 3 and # 4, or # 5 and # 6 in FIG. Corresponding to the pair of elements SW, it constitutes a part of the balance circuit 301 of FIG. E1 and E2 are voltage values corresponding to pairs of battery cells 102 of # 1 and # 2, # 2 and # 3, or # 3 and # 4.

  Now, if E1> E2, the energy discharged from the battery cell 102 of E1 is accumulated in the inductor L by the on / off operation of the switching element SW1 by the first pulse signal 901 (# 1) given from the switch control unit 303. Is done. Subsequently, the energy stored in the inductor L is charged in the battery cell 102 of E2 by the on / off operation of the switching element SW2 delayed by the duty ratio by the second pulse signal 901 (# 2) given from the switch control unit 303. The

Here, according to the pulse frequency freq and the duty ratio D, the current I _L for discharging E1 and charging E2 can be changed based on the following equation. However, the potential difference ΔV = E1−E2, Imax is an allowable current determined from the internal resistance allowance calculated in step S802 or S803 in FIG. 8, and α is a weighting coefficient. I _L is a current flowing through the inductor L, and L is an inductance.

Based on the equation (3), the allowable current value determined from the internal resistance Imax, the weighting factor alpha, to determine the current I _L from the voltage difference [Delta] V, the inductance L and the pulse frequency freq, from I _L obtained, determines the duty ratio be able to. Here, α is a simple proportional coefficient, but a threshold value may be provided for the potential difference ΔV, and the coefficient α may be changed with the threshold value as a boundary. For example, weighting is performed so that a constant current is obtained up to a certain potential difference, and the current is decreased when the potential difference is less than a certain potential difference. Conversely, the pulse frequency freq may be determined by arbitrarily determining the duty ratio.

  In the processing for calculating the frequency and duty ratio of the switching control pulse signal from the value of the internal resistance in step S504 of FIG. 5 or step S804 of FIG. 8 above, even if the calculation is performed in consideration of the temperature information from the temperature sensor. Good. In addition, the pulse signal frequency and duty ratio may be set to arbitrary fixed values.

  FIG. 10 is a timing chart of the control operation of this embodiment. After the vehicle is ignited off (IG-OFF) or started idling at time t1 shown in (a), after waiting for a certain time by an internal timer as shown in (b), (c ), The cell balance circuit of this embodiment (the entire circuit in FIG. 2) starts operating at time t2. First, as shown in (d), the transbalance circuit 105 ′ of FIG. 2 operates from time t2 to time t3 (step S406 of FIG. 4), and then, from time t3 to time t4, FIG. The converter balance circuit 104 'of FIG. 3 operates (repetitive processing from steps S407 to S411 of FIG. 4).

The balance control operation from time t2 to time t4 may be executed only once after the ignition is turned off or idling is started, or may be repeatedly executed at regular time intervals.
As described above, the embodiment shown in FIG. 2 includes the converter balance circuit 104 ′ for executing the intra-stack balance control and the transbalance circuit 105 ′ for executing the inter-stack balance control for the stack 103. Is provided. As a combination of the converter balance circuit 104 ′ and the transformer balance circuit 105 ′, for example, a combination as shown in FIG. 11 can be adopted. Furthermore, as the transformer balance circuit 105 ′, for example, a flyback type shown in FIGS. 12A and 12B, a forward type shown in FIG. 12C, or the like, a transformer T or T1, T2, a diode D, and a switching element SW In addition, various combinations of the inductors L1, L2, and the like can be applied. Any configuration may be used as long as an active balance configuration that can equalize the potential difference between the stacks 103 is employed. Further, as the converter balance circuit 104 ′, for example, a capacitor system shown in FIG. 12D, a converter system shown in FIG. 12E, and the like, a capacitor C, a multiplexer MUX, an inductor L, a switching element SW, and the like are variously combined. Can be applied. Any configuration may be used as long as an active balance configuration is adopted so that the potential difference between the battery cells 102 in the stack 103 can be made uniform.

DESCRIPTION OF SYMBOLS 101 Battery assembly 102 Battery cell 103 Stack 104 1st balance circuit 104 'Converter balance circuit 105 2nd balance circuit 105' Transbalance circuit 106 Voltage monitoring part 107 Balance control part 107 ', 302 DSP
201, T, T1, T2 Transformer 202 Secondary winding 203 Primary winding 204 Magnetic core 205, SW, SW1, SW2 Switching element 206, 303 Switch control unit 207, D diode 301 Balance circuit L, L1, L2 Inductor C Capacitor

Claims (7)

A battery equalizing device for equalizing voltages of the plurality of battery cells in an assembled battery configured by connecting a plurality of battery cells,
For each of the stacks in a set of stacks of a predetermined number of battery cells that constitute the plurality of battery cells and are serially connected in series, one or more of the battery cells in the stack are discharged. A first balance circuit that equalizes the voltage of the battery cells in the stack by charging energy to one or more other battery cells of the battery cells in the stack;
A second balance circuit for equalizing the voltage between the stacks by discharging or charging energy in units of the stack;
A voltage monitoring unit for monitoring the voltage of each battery cell and detecting it as a digital signal value;
Balance control for selecting and operating either the first balance circuit or the second balance circuit by digital signal processing based on the digital signal value of the voltage of each battery cell detected by the voltage monitoring unit And
A battery equalizing apparatus comprising: The balance control unit is configured by a digital signal processor.
The battery equalization apparatus characterized by the above-mentioned. When the difference between the maximum value and the minimum value of each battery cell monitored by the voltage monitoring unit is greater than or equal to a first threshold, the balance control unit is further configured based on the voltage of each battery cell. Calculate the voltage for each
When the difference between the maximum value and the minimum value of the voltage for each stack is equal to or greater than a second threshold, the second balance circuit is operated to equalize the voltage between the stacks,
After the operation of the second balance circuit or when the difference between the maximum value and the minimum value of the voltage for each stack is smaller than a third threshold value, the first balance circuit is operated to Equalize the voltage of the battery cells in the stack,
The battery equalizing apparatus according to claim 1, wherein the battery equalizing apparatus is provided. The first balance circuit is configured to transfer energy discharged from one or more battery cells of the battery cells in the stack via a circuit including a switching element and an inductor of the battery cells in the stack. Charging one or more other battery cells,
The battery equalizing apparatus according to claim 1, wherein the battery equalizing apparatus is a battery equalizing apparatus. The second balance circuit causes energy to be discharged or charged between the stacks via a circuit including a switching element and a transformer.
The battery equalizing apparatus according to claim 1, wherein the battery equalizing apparatus is a battery equalizing apparatus. A battery equalization method for equalizing voltages of a plurality of battery cells in an assembled battery configured by connecting a plurality of battery cells,
Monitoring the voltage of each battery cell;
Based on the monitored voltage of each battery cell, for each stack in a set of stacks comprising a predetermined number of battery cells that are configured in series and connected in series, the battery cells in the stack The battery cells in the stack are equalized by charging energy discharged from one or more of the battery cells to one or more other battery cells in the stack. Selecting and operating either one balance circuit or a second balance circuit that equalizes the voltage between the stacks by discharging or charging energy in units of the stack;
The battery equalization method characterized by the above-mentioned. When the difference between the maximum value and the minimum value of the voltage of each monitored battery cell is equal to or greater than a first threshold, the voltage for each stack is further calculated based on the voltage of each battery cell,
When the difference between the maximum value and the minimum value of the voltage for each stack is equal to or greater than a second threshold, the second balance circuit is operated to equalize the voltage between the stacks,
After the operation of the second balance circuit or when the difference between the maximum value and the minimum value of the voltage for each stack is smaller than a third threshold value, the first balance circuit is operated to Equalize the voltage of the battery cells in the stack,
The battery equalization method according to claim 6.