TW201320540A - Circuits, systems and mothods for balancing cells in battery pack - Google Patents

Abstract

A cell balancing system includes comparators coupled to battery cells. Each comparator compares a cell voltage for a corresponding battery cell with a reference threshold. A result of the comparison includes information useful for identifying a subset of the battery cells that have reached the reference threshold. The cell balancing system also includes a controlling logic circuit, coupled to the comparators, that selects a battery cell from the subset of the battery cells and turns on a corresponding switch to discharge the selected battery cell.

Description

Equalization unit in the battery pack

The present invention relates to the field of battery balancing, and more particularly to a system and method for balancing battery cells during charging and discharging of batteries.

FIG. 1 is a schematic diagram showing the structure of a battery equalization system 100 in the prior art. As shown in FIG. 1, the battery pack includes a plurality of battery cells 106_1~106_N coupled in series. The resistors 102_1~102_N are coupled to both ends of the corresponding units of the battery cells 106_1~106_N through the switches 104_1~104_N. The analog multiplexer 110 includes a plurality of switches 108_1~108_N. One end of the switch 108_K is coupled to the anode of the battery unit 106_K (K=1, 2, . . . , N), and the other end is coupled to the analog to digital converter 112. Analog to digital converter 112 is coupled to microprocessor 114.

The microprocessor 114 equalizes the battery cells through the control switches 104_1 104104_N. The microprocessor 114 selects a channel by controlling the analog multiplexer 110, for example, selecting the positive terminals of the battery cells 106_1~106_N through the turn-on switches 108_1~108_N. The analog to digital converter 112 receives the terminal voltage of the selected positive terminal of the battery cell and generates corresponding digital information. The microprocessor 114 reads the digital information of the digital-to-analog converter 112, calculates the voltages of the battery cells 106_1~106_N according to the digital information, and determines the battery cells 106_1~106_N by comparing the battery voltage with a preset level indicating a specific state of charge. status. The microprocessor 114 calculates the voltage difference between the cell voltages and determines whether the battery pack needs to be equalized by comparing the voltage difference with the reference value. For example, the microprocessor 114 determines that the battery cells 106_1~106_N have the most The high voltage battery unit discharges the battery unit through the corresponding switch of the conduction switches 104_1~104_N to equalize the battery unit in the battery pack. However, the above mentioned method is a resource intensive process that requires an analog to digital converter 112 to convert the cell voltage to a digital signal, and the microprocessor 114 reads the digital signal and determines which cells need to be equalized and when equalized. The implementation of this method is relatively complicated and costly.

It is an object of the present invention to provide a battery equalization system including: a plurality of comparators coupled to a plurality of battery cells, the Kth comparator of the plurality of comparators for comparing the Kth battery cell voltage of the battery cells And a reference threshold value, K is a positive integer, the comparison result is used to determine a subset of the cells in the battery cell that have reached the reference threshold; and a control logic circuit is coupled to the plurality of comparators for A battery unit is selected from the subset of units, and the selected battery unit is discharged by turning on the corresponding switch.

The present invention also provides a battery equalization method, comprising: a comparator circuit comparing a voltage of the plurality of battery cells with a plurality of reference thresholds, wherein a voltage of the Kth battery cell and a Kth reference threshold are made Comparing, K is a positive integer; determining a subset of cells of the battery cell based on the comparison result, the cell voltage of the cell subset has reached a corresponding subset of the reference threshold; the control logic circuit from the cell of the cell Centrally select one battery unit; and discharge the selected battery unit.

The present invention also provides a battery equalization circuit comprising: a discharge path group including M discharge paths coupled to a battery pack including M battery cells, wherein a Kth discharge path of the discharge path group is coupled in parallel to the K of the battery pack a battery unit; and a control unit coupled to the discharge path group for comparing the battery cell voltage with a set of reference thresholds including M reference thresholds, the voltage of the Kth battery cell Comparing K reference thresholds, the control unit uses the comparison result to determine a subset of cells of the battery unit, the battery cell voltage in the subset of cells has reached a corresponding subset of the reference threshold, from the battery unit The cell subset selects one battery cell and discharges the selected battery cell by conducting a corresponding discharge path.

A detailed description of the embodiments of the present invention will be given below. Although the invention has been illustrated and described with respect to the embodiments, it should be noted that the invention is not limited to the embodiments. Rather, the invention is to cover all modifications, alternatives and equivalents within the scope of the invention as defined by the appended claims. In the following detailed description of the invention, reference to the claims However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well-known schemes, procedures, components, and circuits have not been described in detail in order to facilitate the invention.

In one embodiment, the battery equalization system includes a plurality of comparators that measure the battery cells, each comparator for comparing the battery cell voltage to a reference threshold and generating a comparison. The battery equalization system also includes control logic circuitry for controlling a plurality of switches coupled to the battery cells such that the battery cells can reach substantially the same voltage. For example, the control logic circuit selects a battery unit that reaches the reference threshold from the battery pack according to the comparison result, and The over-closed corresponding switch discharges the selected battery unit, and the battery pack is in an equilibrium state. Advantageously, the battery equalization system of the present invention has a relatively simple circuit configuration as compared to the battery equalization system of the prior art of FIG. 1, which is relatively simple to implement and low in cost.

2 is a block diagram showing the structure of a battery equalization system 200 in accordance with one embodiment of the present invention. In the case of charging, the battery equalization system 200 performs a battery unit 206_1~206_N that is discharged and equalized in series by discharging the battery cells that have reached the reference threshold. N is a positive integer. The battery cells 206_1 206 206_N may be, but are not limited to, lithium ion battery cells, lead acid battery cells, or nickel metal oxygen battery cells.

As shown in FIG. 2, the battery pack includes a plurality of battery cells 206_1 206 206_N coupled in series. In one embodiment, battery equalization system 200 includes a plurality of discharge paths coupled to battery cells 206_1-206_N, and each discharge path includes a load resistor 202_1-202_N and a switch 204_1-204_N. The battery equalization system 200 further includes reference resistors 212_1~212_N, detection circuit 218, comparators 208_1~208_M (M=N-1), and control logic circuit 210. The Kth discharge path including the Kth load resistor 202_K and the Kth switch 204_K is coupled in parallel to the Kth battery unit 206_K (K=1, 2, . . . , N). For example, the resistor 202_1 is coupled to both ends of the battery unit 206_1 through the switch 204_1. The detection circuit 218 is coupled to both ends of the battery unit 206_N. The non-inverting input terminals of the comparators 208_1~208_M (M=N-1) are coupled to the positive poles of the battery cells 206_1~206_M (M=N-1). The inverting input terminals of the comparators 208_1~208_M (M=N-1) are coupled to the common terminals of the reference resistors 212_1~212_N. The output end of the detecting circuit 218 and the output end of the comparator 208_1~208_M (M=N-1) are coupled to the control end. Logic circuit 210.

In one embodiment, the reference resistors 212_1~212_N are coupled in series and have substantially the same resistance. Thus the reference resistor 212_1 ~ 212_N voltages _{V 212_1, V 212_2, ...,} V 212 _ N substantially identical to, _{e.g., V 212_1 = V 212_2 = ...} = V 212_N = V TH. The voltages V _{212_1} , V _{212_2} , . . . , V _{212 —} M of the reference resistors 212_1 212 212 — M (M=N−1) may be used as the reference threshold V _TH (or equalization threshold). That is, the reference resistors 212_1~212_N can be used to provide M reference thresholds V _TH . The reference threshold V _TH corresponds to the voltages V _{212_1} , V _{212_2} , . . . , V _{212 —} M of the reference resistors 212_1 212 212 — M (M=N−1). In other words, each reference threshold V _TH corresponds to the voltage of one of the reference resistors 212_1 212 212_M. "Substantially the same resistance value" means that as long as the difference between the resistance values of the reference resistors 212_1~212_N is relatively small and can be ignored, this difference is allowed to exist. The "reference resistor voltages are substantially the same" means that due to the non-ideality of the reference resistors 212_1~212_N themselves, the difference between the voltages of the reference resistors 212_1~212_N may exist, but the difference is relatively small and can be ignored.

In one embodiment, the Kth comparator 208_K (K=1, 2, . . . , N-1) compares the terminal voltage of the positive electrode of the Kth battery cell 206_K with the Kth reference resistance 212_K and K+1 The voltage of the node 214_K between the reference resistors 212_(K+1) is compared to compare the voltage V _{206_K} of the Kth battery unit _{206_K} with the Kth reference threshold V _TH (eg, the voltage V _{212_K of} the Kth reference resistor _{212_K} ) . Specifically, the Kth comparator 208_K compares its non-inverting input terminal voltage V _K ⁺ (K=1, 2, . . . , N-1) with its inverting input terminal voltage V _K ^- (K=1, 2, ..., N-1). The non-inverting input terminal voltage V _K ^{+ of} the Kth comparator 208_K (for example, the terminal voltage of the positive electrode of the Kth battery cell 206_K) is equal to the voltages V _{2061_1} , V _{206_2} , . . . , V _{206_K} of the corresponding battery cells 206_1 206 _{206_K} And, for example, V _K ⁺ =V _{206_1} +...+V _{206_K} . The Kth comparator 208_K inverting input terminal voltage V _K ^- (for example, the voltage of the node 214_K between the reference resistor 212_K and the reference resistor 212_(K+1)) is equal to the sum of the voltages of the corresponding reference resistors 212_1 212 212_K, for example, V _K ^- =V _{212_1} +...+V _{212_K} =K*V _TH . In one embodiment, the voltage V _{206_1} +...+V _{206_(K-1)} of the battery cells 206_1~206_(K-1) is coupled in series with the voltage V of the reference resistor 212_1-212_(K-1) coupled in series. one difference _{212_1} + ... + _(K-1) V _{212_} within a relatively small range, the difference represents the difference between the cell voltage _V 206_K 206_K cell with the reference voltage V _{212_K} resistance of 212_K. In other words, the comparison result between the sum of the voltages of the battery cells 206_1 206 206_K and the sum of the voltages of the reference resistors 212_1 212 212_K (for example, the comparison between the terminal voltage of the positive electrode of the battery cell 206_K and the voltage of the node 214_K) represents the battery cell. The voltage of 206_K and the voltage of the reference resistor 212_K (for example, reference threshold V _TH ). If the terminal voltage of the battery cell 206_K positive terminal is greater than the node 214_K voltage (eg, if the voltage of the battery cell 206_K is greater than the reference threshold V _TH ), the comparator 208_K outputs a logic high signal to the control logic circuit 210. The result of the comparison (eg, a logic high signal or a logic low signal) is used to determine a subset of cells of battery cells 206_1 206 206_M that have reached the reference threshold V _TH (eg, reference resistors 212_1 212 212_M have reached voltage V _{212_1} , V _{212_2} , ..., a corresponding subset of V _{212_M} ) wherein the subset of cells includes one or more battery cells.

In addition, a detection circuit 218 having a reference threshold V' _TH is used to detect the voltage of the battery unit 206_N. The reference threshold _V'TH is equal to or slightly greater than the reference threshold _VTH mentioned above. Comparator 208_1 ~ 208_M (M = N- 1) Similarly, if the battery voltage is greater than the reference cell 206_N threshold V _'TH, the detection circuit 218 generates a control signal (e.g., a logic high signal) to the control logic circuit 210, control The logic circuit 210 turns on the corresponding switch 204_N to discharge the battery unit 206_N for a period of time. The battery unit 206_N is discharged through the load resistor 202_N and the voltage of the battery unit 206_N is decreased.

In one embodiment, if the subset of cells of battery cells 206_1~206_M have reached the reference threshold _VTH , the corresponding subset of comparators 208_1~208_M (M=N-1) outputs a parallel logic high signal. In such an embodiment, the control logic circuit 210 randomly selects one of the battery cells from the subset of cells of the battery cells 206_1~206_M and turns on the corresponding switches 204_1~204_M to discharge the selected battery cells.

In one embodiment, the battery equalization system 200 alternates between a measurement mode and an equalization mode. For example, battery equalization system 200 includes a timer circuit (not shown). When the battery equalization system 200 enters the measurement mode, the timer circuit begins measuring time, and the battery equalization system 200 operates in the measurement mode for a first predetermined period of time (ie, a measurement period). When the measurement period is cut off, the timer circuit generates a trigger signal and restarts the measurement time. In response to the trigger signal, the battery equalization system 200 enters an equalization mode. The battery equalization system 200 operates in the equalization mode for a second predetermined period of time (ie, an equalization period). When the equalization period is cut off, the timer circuit generates another trigger signal and restarts the measurement time. In response to the trigger signal, the battery equalization system 200 enters the measurement mode again.

In one embodiment, the battery equalization system 200 alternates between a measurement period and an equalization period. During the measurement period, the comparators 208_1~208_M (M=N-1) compare the voltages of the battery cells 206_1~206_M (M=N-1) with the reference threshold _VTH (eg, the reference resistors 212_1~212_N) The voltages V ₂₁₂ _ ₁ , V ₂₁₂ _ ₂ , . . . , V ₂₁₃ _ _M ), for example, by comparing the terminal voltages of the positive electrodes of the battery cells 206_1 206 206_M (M=N-1) with the common nodes 214_1 214 214_M (M=N, respectively) -1) Voltage. Control logic circuit 210 receives the output signals from comparators 208_1~208_M (M=N-1) and determines a comparator that first outputs a logic high signal for determination in battery cells 206_1~206_M (M=N-1) A battery unit that first reaches the reference threshold V _TH . If relative to other battery cells in battery cells 206_1~206_M (M=N-1), battery cell 206_f first reaches reference threshold V _TH (eg, relative to comparator 208_1~208_M (M=N-1) In the other comparators, the comparator 208_f first outputs a logic high signal), then during the equalization period after the measurement period, the control logic circuit 210 selects the battery unit 206_f and discharges the battery unit 206_f by turning on the corresponding switch 204_f. Pre-defined time. During the equalization period, the battery unit 206_f is discharged through the load resistor 202_f, and the voltage of the battery unit 206_f is decreased. In the measurement period, the detection circuit 218 detects the state of the battery cell 206_N, 206_N if the cell voltage exceeds the reference threshold V _'TH, the detection circuit 218 generates a control signal to the control logic circuit 210. Respond to the control signal. The control logic circuit 210 turns on the switch 204_N to discharge the battery unit 206_N during the equalization period.

When the equalization period is turned off, the battery equalization system 200 enters a new measurement period and turns off the switches 204_f (f = 1, 2, ..., N-1) and/or the switches 204_N. By alternately operating during the measurement period and the equalization period, the battery cells 206_1~206_N may have substantially the same voltage, and the battery pack may be in an equalized state. The term "substantially the same" as used herein means that as long as the difference between the voltages of the battery cells 206_1~206_N is relatively small and To be ignored, then this difference is allowed to exist.

In another embodiment, during the measurement period, control logic circuit 210 receives the output signals from comparators 208_1~208_M (M=N-1) and determines the output logic high signal at the end of the measurement period (eg, at measurement time) The end of the segment determines which battery unit 206_1~206_M (M=N-1) has a cell voltage greater than the reference threshold V _TH ). In the measurement period, the control logic 210 also receives the output signal from the detection circuit 218, and determines whether the end of the measurement period 206_N cell voltage is greater than the reference threshold V _'TH.

At the end of the measurement period, control logic circuit 210 determines a subset of cells of battery cells 206_1~206_M that have reached the reference threshold _VTH . If the cell subset of the battery cells 206_1~206_M includes only one battery cell, for example, if the voltage of the battery cell 206_a (a=1, 2, . . . , N-1) is greater than the reference threshold _VTH and the other battery cells 206_1~ The voltage of 206_(N-1) is not greater than the reference threshold _VTH , and during the equalization period after the measurement period, the control logic circuit 210 selects to discharge the battery unit 206_a. If the subset of cells of battery cells 206_1~206_M includes a plurality of battery cells, for example, two or more battery cell voltages are greater than a reference threshold _VTH . In one embodiment, during the equalization period, the control logic circuit 210 randomly selects one of the plurality of battery cells to discharge, and may also select the battery cells for discharging according to other methods. In addition, if the voltage of the battery unit 206_N is greater than the reference threshold V' _TH , the battery unit 206_N discharges during the equalization period. By alternately operating in the measurement period and the equalization period, the battery cells 206_1 206 206_N may have substantially the same voltage, that is, the battery pack including the battery cells 206_1 206 206_N is equalized.

Further, in one embodiment, the above-mentioned equalization process is equally applicable to the battery discharge process, that is, the equalization process when the battery cells are discharged is similar to the equalization process when the battery cells are charged.

In one embodiment, if the voltage average value V _{AVE of the} battery cells 206_1 206 206_N increases, the reference threshold value V _TH increases; if the voltage average value V _{AVE of the} battery cells 206_1 206 206_N decreases, the reference threshold value V _TH decreases. small. And, the reference threshold V _{TH is} smaller than the voltage average value V _AVE . For example, the reference resistors 212_1~212_N receive power from the battery cells 206_1~206_N through the resistor 216. Therefore, the voltages of the reference resistors 212_1~212_N increase as the voltage average value V _AVE increases, decrease as the average value V _AVE decreases, and the voltage of each reference resistor 212_1 212 212_N (eg, reference threshold) The value V _TH ) is less than the voltage average value V _AVE . Advantageously, because the reference threshold _{VTH is} less than the voltage average V _AVE , the battery equalization system can begin the equalization process earlier. Also, since the reference threshold V _TH varies with the change in the voltage average value V _AVE of the battery cells 206_1 206 206_N, the equalization process of the battery cells 206_1 206 206_N is more stable.

However, the reference thresholds 212_1 212 212_N connected in series are used in the example of FIG. 2 to provide the reference threshold V _TH , and the present invention is not limited thereto. The reference threshold V _TH can be provided according to other methods.

Advantageously, the operational process of the present invention is a process of automatic adjustment, so there is no need to determine or establish an equalization condition. Moreover, the circuit structure of the battery equalization system 200 is simpler than that of the battery equalization system 100 of the prior art. Due to the simple circuit structure, the equalization process is less expensive and easier to accomplish.

FIG. 3 is a schematic diagram of a battery cell voltage curve associated with the battery equalization system 200 shown in FIG. 2, which will be described in conjunction with FIG. As shown in FIG. 3, the number of battery cells is set to four. For example, the battery pack includes battery cells 206_1 206 206_4 coupled in series. However, the battery pack can include other numbers of battery cells. In one embodiment, according to the description of FIG. 2, the voltage of battery unit 206_4 is detected by detection circuit 218 and controlled by control logic circuit 210 based on the detection result. In addition, the voltage 301 of the battery unit 206_1, the voltage 302 of the battery unit 206_2, and the voltage 303 of the battery unit 206_3 are used for comparison with the reference threshold V _TH .

In one embodiment, the reference threshold _{VTH is} provided by a series coupled reference resistor (eg, reference resistors 212_1 212212_4 shown in FIG. 2), and with reference to the threshold value V _TH as a function of the cell voltage average Increase and increase. In another embodiment, the reference threshold _VTH is equal to the overcharge threshold V _OVC (eg, 4.4V) of the battery cells 206_1~206_4. In another embodiment, the reference threshold _VTH (eg, 4.3V) is less than the overcharge threshold V _OVC .

In one embodiment, control logic circuit 210 detects battery cell status during each measurement period. As shown in FIG. 3, in the measurement period 1, the battery unit 206_1 having the voltage of 301 is the only battery unit that reaches the reference threshold _VTH , and thus the battery unit 206_1 is selectively discharged during the equalization period 1. In the measurement period 2, although the voltage of the plurality of battery cells reaches the reference threshold, the battery unit 206_2 having the voltage of 302 first reaches the reference threshold V _TH , so the battery unit 206_2 is within the equalization period 2 Select discharge. During the measurement period 3, the battery unit 206_3 of voltage 303 is the only battery unit that reaches the reference threshold _VTH , so the battery unit 206_3 is selectively discharged during the equalization period 3. In the measurement period 4, although the voltage of the plurality of battery cells reaches the reference threshold, the battery unit 206_1 having the voltage of 301 first reaches the reference threshold V _TH , so the battery unit 206_1 is within the equalization period 4 Select discharge.

In another embodiment, control logic circuit 210 detects the state of the battery cells at the end of each measurement period. As shown in FIG. 3, at the end of the measurement period 1, the voltage 301 of the battery unit 206_1 is greater than the reference threshold _VTH , so the battery unit 206_1 is selectively discharged during the equalization period 1. At the end of the measurement period 2, the voltage 302 of the battery unit 206_2 and the voltage 303 of the battery unit 206_3 are both greater than the reference threshold _VTH . In one embodiment, battery unit 206_2 is randomly selected for discharge during equalization period 2, and other methods may be employed to select the battery unit for discharging. At the end of the measurement period 3, the voltage 303 of the battery unit 206_3 is greater than the reference threshold _VTH , so the battery unit 206_3 is selectively discharged during the equalization period 3. At the end of measurement period 4, voltages 301, 302, and 303 are all greater than the reference threshold _VTH . In one embodiment, battery unit 206_1 is randomly selected for discharge during equalization period 4, and other methods may be employed to select the battery unit for discharging.

FIG. 4 is a flow chart showing the operation of the battery cell equalization system 200 of FIG. 2 according to an embodiment of the present invention. FIG. 4 will be described in conjunction with FIG. 2. Although FIG. 4 discloses specific steps, these steps are merely exemplary. That is, the present invention is well adapted to various other steps or variations of the steps shown in the drawings.

In step 402, the comparator circuit (eg, including comparators 208_1 - 208_M) compares the voltages of the battery cells 206_1 206 206_M with the reference threshold V _TH (eg, the voltages V _{212_1} , V _{212_2} , . . . of the reference resistors 212_1 212 212_M, V _{212_M} ). Specifically, the K-th reference voltage and the threshold comparator circuit comparing the K-th battery cells (e.g., reference resistor 212_K (K = 1,2, ..., M) of the voltage _V 212_K) comparison.

In step 404, control logic circuit 210 determines a subset of cells (including one or more battery cells) of battery cells 206_1~206_M that have reached a corresponding reference threshold _VTH . For example, if the control logic circuit 210 detects that the battery cell 206_2 has reached the voltage V _{212_2} of the reference resistor 212_2, the battery cell 206_4 has reached the voltage V _{212_4} of the reference resistor _{212_4} , and the subset of cells determined by the control logic circuit 210 includes the battery cells 206_2 and 206_4. .

In step 406, control logic circuit 210 selects battery cells from the subset of cells of determined battery cells 206_1~206_M. In one embodiment, the control logic circuit 210 selects the battery cells that first arrive at the reference threshold _VTH from the battery cells 206_1~206_M. In another embodiment, control logic circuit 210 randomly selects battery cells from a subset of battery cells.

In step 408, the control logic circuit 210 discharges the selected battery cells by turning on the corresponding switches 204_1~204_M.

Embodiments of the present invention provide a battery equalization system. In one embodiment, the battery equalization system includes a plurality of comparators for measuring the battery cells by comparing the battery voltage to a reference threshold. The battery equalization system also includes control logic circuitry for controlling a plurality of switches coupled to the battery cells such that the battery cells can reach substantially the same voltage. For example, the control logic circuit transmits the battery that has reached the reference threshold by turning on the corresponding switch. The unit is discharged. The battery equalization system alternates between the measurement period and the equalization period, the battery cells can reach substantially the same voltage, and the battery pack can reach an equilibrium state. The advantage is that the equalization process is a self-adjusting process and does not require setting equilibrium conditions. Also, the battery equalization system of the present invention has a simple circuit structure as compared with the battery equalization system of the prior art of FIG. 1, thereby simplifying the equalization process and being less expensive.

It is to be understood that the above-described embodiments are only illustrative of the invention, and are not intended to The spirit and scope of the invention should be construed as being included in the scope of the appended claims.

100‧‧‧Battery equalization system

102_1~102_N‧‧‧Resistance

104_1~104_N‧‧‧Switch

106_1~106_N‧‧‧ battery unit

108_1~108_N‧‧‧Switch

110‧‧‧ analog multiplexer

112‧‧‧ Analog to Digital Converter

114‧‧‧Microprocessor

200‧‧‧Battery equalization system

202_1~202_N‧‧‧Load resistor

204_1~204_N‧‧‧Switch

206_1~206_N‧‧‧ battery unit

208_1~208_N‧‧‧ comparator

210‧‧‧Control logic

212_1~212_N‧‧‧Reference resistor

214_1~214_N‧‧‧ nodes

216‧‧‧resistance

218‧‧‧Detection circuit

301-1~303‧‧‧ voltage

400‧‧‧Operation flow diagram

402~408‧‧‧Steps

The technical method of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments to make the features and advantages of the present invention more obvious. Wherein: FIG. 1 is a schematic structural diagram of a battery equalization system in the prior art.

2 is a block diagram showing the structure of a battery equalization system according to an embodiment of the invention.

FIG. 3 is a schematic diagram showing a battery cell voltage curve of the battery equalization system shown in FIG.

FIG. 4 is a flow chart showing the operation of a battery equalization system according to an embodiment of the invention.

200‧‧‧Battery equalization system

202_1~202_N‧‧‧Load resistor

204_1~204_N‧‧‧Switch

206_1~206_N‧‧‧ battery unit

208_1~208_N‧‧‧ comparator

210‧‧‧Control logic

212_1~212_N‧‧‧Reference resistor

214_1~214_N‧‧‧ nodes

216‧‧‧resistance

218‧‧‧Detection circuit

Claims (20)

A battery equalization system includes: a plurality of comparators coupled to a plurality of battery cells, wherein the Kth comparator of the plurality of comparators is used to compare the voltage of the Kth battery cell and the reference threshold of the battery unit , K is a positive integer, the comparison result is used to determine a subset of the cells in the battery cell that have reached the reference threshold; and control logic is coupled to the plurality of comparators to select one from the subset of cells The battery unit discharges the selected battery unit by turning on the corresponding switch. The equalization system of claim 1, wherein the battery cells are coupled in series. The equalization system of claim 1, further comprising: a plurality of series-coupled resistive elements coupled to the comparator, the resistive elements having substantially the same resistance. The equalization system of claim 3, wherein the voltage of the resistive element is substantially the same, and the reference threshold corresponds to a voltage of one of the resistive elements. The equalization system of claim 3, wherein the Kth comparator compares the Kth battery voltage by comparing a terminal voltage of the Kth battery cell with a magnitude of a node voltage between a pair of the resistance components The size of the reference threshold. The equalization system of claim 1, wherein the reference threshold is increased if the average value of the voltage of the battery unit increases, and the reference threshold is decreased if the average value of the voltage is decreased. The equalization system of claim 1, wherein the control logic determines, in the battery unit, a battery unit that first reaches the reference threshold, and the battery unit selected from the subset of units is the most The battery unit that first reaches the reference threshold. The equalization system of claim 1, wherein the subset of cells comprises a plurality of battery cells, and the battery cells selected from the subset of cells are randomly selected from the plurality of battery cells. A battery equalization method includes: comparing, by a comparator circuit, a voltage of the plurality of battery cells and a plurality of reference thresholds, wherein a voltage of the Kth battery cell is compared with a Kth reference threshold, and K is a positive integer Determining, according to the comparison result, a subset of cells of the battery cell, the cell voltage of the cell subset has reached a corresponding subset of the reference threshold; the control logic circuit selects a battery cell from the cell subset of the battery cell ; and discharge the selected battery unit. The equalization method of claim 9, further comprising: a plurality of resistive elements providing the reference threshold, wherein the reference threshold corresponds to a voltage of the resistive element. The equalization method of claim 9, further comprising: a plurality of series coupled resistance elements providing the reference threshold, wherein the resistance elements have substantially the same resistance. The equalization method of claim 11, further comprising: the battery unit supplying power to the resistance element. For example, the equalization method of claim 9 of the patent scope, wherein the selection includes Determining, in the plurality of battery cells, a battery cell that first reaches a corresponding reference threshold, the battery cell selected from the subset of cells of the battery cell is the battery cell that first reaches the corresponding reference threshold . The equalization method of claim 9, wherein the subset of cells of the battery unit comprises a plurality of battery cells, the selecting comprising randomly selecting the battery cells from the plurality of battery cells. A battery equalization circuit includes: a discharge path group including M discharge paths coupled to a battery pack including M battery cells, wherein a Kth discharge path of the discharge path group is coupled in parallel to a Kth of the battery pack a battery unit; and a control unit coupled to the discharge path group for comparing the battery cell voltage with a set of reference thresholds including M reference thresholds, the voltage of the Kth battery cell Comparing K reference thresholds, the control unit uses the comparison result to determine a subset of cells of the battery unit, the battery cell voltage in the subset of cells has reached a corresponding subset of the reference threshold, from the battery unit The cell subset selects one battery cell and discharges the selected battery cell by conducting a corresponding discharge path. The equalization circuit of claim 15, wherein the control unit determines a battery unit that first reaches a corresponding reference threshold, and the battery unit selected from the unit subset of the battery unit is the first to reach the battery unit. The battery unit corresponding to the reference threshold. The equalization circuit of claim 15, wherein the subset of cells comprises a plurality of battery cells, and the battery cells selected from the subset of cells are randomly selected from the plurality of battery cells. The equalization circuit of claim 15, further comprising: a plurality of series coupled resistance elements, the resistance element being powered by the battery unit and providing the reference threshold. The equalization circuit of claim 15 further comprising: a plurality of series coupled resistance elements having substantially the same resistance to provide the reference threshold. The equalization circuit of claim 15, wherein the reference threshold increases if the average value of the voltage of the battery unit increases, and the reference threshold decreases if the average value of the voltage decreases.