TWI390822B - Circuits and methods for balancing battery cells - Google Patents

Description

Battery cell balancing circuit and method thereof

The present invention relates to a battery management system, and more particularly to a battery cell balancing circuit and method for balancing a plurality of battery cells.

A battery pack having a plurality of battery cells (for example, a lithium ion battery pack) is widely used in a power tool to supply power to a power tool. Power tools include: electric vehicles and hybrids (Hybrid), but not limited to this. However, each battery cell in the battery pack may be different due to different degrees of aging or different battery temperatures. As the number of charging/discharging times increases, the voltage or capacity difference between the battery cells may be caused, thereby causing the battery cells to be unbalanced. .

The imbalance of the battery unit means that the battery cells are overcharged when some battery cells are not fully charged, or when some battery cells have not been completely discharged, other battery cells are Excessive discharge has occurred, and these imbalances affect the capacity or service life of the entire battery pack. Although hardware or software protection can be used to avoid overcharging or overdischarging of the battery unit, additional hardware and software can affect the efficiency of the battery pack. Therefore, when the battery cells in the battery pack are unbalanced, the battery pack needs to be balanced.

Battery cell balance is divided into passive balance and active balance. Passive balance consumes excess energy from a battery with higher energy through the parallel-coupled shunt resistor. However, the thermal energy generated during passive balancing affects the life of the battery pack. Conversely, active balancing transfers energy from one or more battery cells to other battery cells.

FIG. 1 is a structural diagram of a conventional battery cell balancing circuit 100. The battery cell balancing circuit 100 includes a battery pack including a plurality of battery cells 102_1, 102_2, 102_3, ... 102_n, a transformer including a primary coil 104 and a plurality of secondary coils 106_1, 106_2, 106_3 ... ... 106_n, and a switch 108 coupled to the primary coil 104. Each of the battery cells 102_1, 102_2, 102_3, ..., 102_n is coupled to the primary coils 106_1, 106_2, 106_3, ..., 106_n. When the switch 108 is in the closed state, the discharge current of the battery pack flows through the primary coil 104 of the transformer. After the switch 108 is turned off, induced currents I ₁ , I ₂ , I ₃ . . . In are generated on each of the secondary coils 106_1, 106_2, 106_3, ..., 106_n, respectively. Among them, the induced current generated on the secondary coil with the smallest reactance is the largest. It can be understood that the charging current received by each of the battery cells 102_1, 102_2, 102_3, ... 102_n is inversely proportional to the voltage corresponding thereto. Since each of the battery cells 102_1, 102_2, 102_3, ..., 102_n obtains energy transferred from the battery pack during the balancing process, the balance efficiency is low. In addition, this architecture can only balance the battery cells by transferring the energy of the entire battery pack. Therefore, this battery cell balancing architecture is only suitable for the discharge process of the battery pack, and is less effective during the charging process of the battery pack.

FIG. 2 is a block diagram showing another conventional battery cell balancing circuit 200. A pair of N-type metal oxide semiconductor field effect transistors (MOSFETs) and a P-type MOSFET and an inductor are used between adjacent battery cells 202_1, 202_2, 202_3, ..., 202_n to form an energy transfer circuit. Except for the parasitic impedance of the inductor itself and the minimum energy consumed by the on-resistance of the body diode, other energy is stored in the inductor. For the sake of simplicity, only three battery cells 202_1, 202_2, 202_3 are shown in FIG. When a control signal P2 having a specific frequency and duty cycle controls the MOSFET 204_4 to be in an off state, the energy stored in the inductor L2 reaches a maximum value. As shown in FIG. 2, when the topmost battery unit 202_3 needs to transfer energy to the bottommost battery unit 202_1, the control signal P2 controls the MOSFET 204_4 to be in a closed state, transferring energy from the battery unit 202_3 to the inductor L2. Since the current in the inductor L2 continues to flow, the energy stored in the inductor L2 is transferred to the battery unit 202_2 through the closed MOSFET 204_3 or its forward biased body diode, wherein the MOSFET 204_3 is closed and broken. The opening is controlled by a control signal N2.

Next, in a similar manner, the control signals N1 and P1 are used to control the closing and opening of the MOSFET 204_2 and the MOSFET 204_1 to transfer the energy in the battery cell 202_2 to the battery cell 202_1. Therefore, excess energy in the battery unit 202_3 can be transferred to the battery unit 202_1. Understandably, this balancing method can only be performed between adjacent battery cells. When a battery pack including two or more battery cells connected in series needs to be balanced, for example, the battery cells 202_1, 202_2, and 202_3, it takes a long time to transfer the energy of one battery cell to another non-adjacent battery cell. For example, the battery unit 202_3 is transferred to the battery unit 202_1.

As described above, to transfer energy of one battery unit (for example, battery unit 202_3) to another non-adjacent battery unit (for example, battery unit 202_1), energy needs to be transferred from battery unit 202_3 to battery unit 202_2, and then Transfer from the battery unit 202_2 to the battery unit 202_1. In addition to time consuming, assuming that the battery pack contains N series connected battery cells, 2*(N-1) MOSFETs are needed to transfer energy from the topmost battery cell 202_n to the bottommost battery cell 202_1 or from the bottom. The battery unit 202_1 is transferred to the topmost battery unit 202_n, where N is a positive integer greater than or equal to 2. Therefore, the control circuit that generates the control signals for controlling the MOSFETs 204_1 to 204_n is very complicated. Moreover, since the energy needs to be excessively transferred, part of the energy is converted into heat during the transfer process and consumed. Therefore, this balancing method is inefficient, time consuming, and complicated in circuit structure.

The technical problem to be solved by the present invention is to provide a battery cell balancing circuit and method, which can be applied to a charging process, a discharging process, and an idle state of a battery, and can improve balance efficiency and reduce circuit complexity.

In order to solve the above technical problem, the present invention provides a battery cell balancing circuit, including a first battery unit having a parameter, and the value of the parameter has a first value; a second battery unit coupled in series to the first a battery unit, the value of the parameter of the second battery unit has a second value, wherein the first value is greater than the second value; and a transformer comprising a first electrical connection with the first battery unit A primary coil, and a secondary coil electrically coupled to both ends of the second battery unit, operate to transfer a portion of the energy in the first battery unit to the second battery unit.

The present invention also provides a battery cell balancing circuit comprising a battery pack comprising a plurality of battery cells connected in series, one of the plurality of battery cells having a parameter and the value of the parameter having a first value a parameter of the second battery unit of the plurality of battery cells having a value less than a second value of the first value; and a transformer including a first coil and a second coil, and the battery The electrical connection is configured to transfer a portion of the energy in the first battery unit to the second battery unit.

The present invention also provides a battery cell balancing circuit comprising a first battery module and a second battery module connected in series, the first battery module and the second battery module respectively comprising a plurality of battery cells, The value of one parameter of the first battery module has a first value, the value of the parameter of the second battery module is a second value less than one of the first values; and a transformer includes the first battery The module is electrically connected to one primary coil and one secondary coil electrically connected to the second battery module, and is configured to transfer part of energy in the first battery module to the second battery module.

The invention also provides a battery cell balancing method, comprising: detecting a parameter of a first battery unit, the value of the parameter of the first battery unit has a first value; detecting a first connection with the first battery unit The parameter of the second battery unit, the value of the parameter of the second battery unit has a second value, wherein the first value is greater than the second value; and transferring part of the energy of the first battery unit to a transformer To the second battery unit.

The present invention also provides a battery cell balancing method, comprising: detecting a parameter of each of a plurality of battery cells connected in series; selecting a battery cell having a first value from among the plurality of detected parameters and having a second value of a battery unit, the first value is greater than the second value; and transferring a portion of the energy of the first battery unit having the first value through a transformer to the second having the second value Battery unit.

A detailed description of the embodiments of the present invention will be given below. While the invention will be described in conjunction with the embodiments, it is understood that the invention is not limited to the embodiments. Rather, the invention is to cover various modifications, equivalents, and equivalents of the invention as defined by the scope of the appended claims.

In addition, in the following detailed description of the embodiments of the invention However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail in order to facilitate the invention.

3 is a block diagram of a battery cell balancing circuit 300 in accordance with an embodiment of the present invention. The battery cell balancing circuit 300 includes a battery pack 302 and a transformer 303, which are respectively coupled to the respective battery cells 302_1-302_6 of the battery pack 302 through the switches 306_1-306_6, and to the battery pack 302 and the switches 306_1-306_6. Detection and control unit 308 for sexual connections. For simplicity, FIG. 3 shows only six battery cells 302_1-302_6, it being understood that the battery pack 302 can include any number of battery cells, not limited to the number of battery cells shown in FIG.

The transformer 303 includes six coils 304_1-304_6 and a core 305. Each of the coils 304_1-304_6 is connected in parallel with a battery unit 302_1-302_6 through a corresponding switch 306_1-306_6. For example, the coil 304_1 is connected in parallel with the battery unit 302_1 through the switch 306_1. In one embodiment, the number of turns of the six coils 304_1-304_6 is equal. In one embodiment, the transformer 303 is a flyback transformer. In other words, the six coils 304_1-304_6 do not have current flowing at the same time. Referring to FIG. 3, the positive electrodes of the battery cells 302_1, 302_3, and 302_5 are respectively connected to the positive ends (the dot ends) of the coils 304_1, 304_3, and 304_5, and the negative electrodes of the battery cells 302_2, 302_4, and 302_6 are respectively connected to the coils 304_2, 304_4, and 304_6 ( Tap the end) to connect. The connection mode of the battery unit and the corresponding coil shown in FIG. 3 is only a specific embodiment of the present invention, and other connection manners may be adopted to achieve battery balance. For example, the negative poles of the battery units 302_1 and 302_2 and the dot ends of the coils 304_1 and 304_2, respectively. Connected, the positive poles of the battery cells 302_3-302_6 are respectively connected to the dot ends of the coils 304_3-304_6.

Referring to FIG. 3, the detection and control unit 308 is configured to detect parameters of each of the battery cells 302_1-302_6 in the battery pack 302, and select a battery cell and a parameter value whose parameter values are a first value from the detected parameters. a second value battery unit, wherein the first value is greater than the second value. The detection and control unit 308 controls the battery unit having the parameter value of the first value such that part of the energy of the battery unit is transferred through the transformer 303 to the battery unit having the parameter value of the second value. In an embodiment, the parameter may be any one of voltage, state of charge, or capacity, but is not limited thereto. Although in all of the following embodiments, the voltage balancing target parameter is used to illustrate how the cell balancing circuit of the present invention achieves cell balancing, however, those skilled in the art will appreciate that the cell balancing circuit of the present invention employs other parameters (eg, The principle of balancing the battery cells to balance the target parameters is the same as the principle of using voltage as the balance target parameter.

With continued reference to FIG. 3, it is assumed that in the battery pack 302, the battery unit 302_1 has the highest battery cell voltage. Therefore, it is necessary to balance the battery unit 302_1 during the charging process. In order to suppress the voltage rise of the battery unit 302_1 from being too fast and to terminate the charging process in advance, it is necessary to transfer the excess energy in the battery unit 302_1 to the other battery unit. The detection and control unit 308 generates a control signal control switch 306_1 having a first predetermined frequency and a duty cycle of D1 that is closed and opened. When the switch 306_1 is closed, the current I1 flows from the battery unit 302_1 to the coil 304_1. Due to the inductance effect, the current linearly increases with time, and the maximum current value is determined by the time when the switch is closed. The energy transferred from the battery unit 302_1 is stored in the core 305 of the transformer 303. In an embodiment of the invention, the closing time Ton of the switch 306_1 may be based on the battery cell voltage V of the battery cell 302_1, the inductance L of the coil 304_1, and the average balancing current required by the battery cell 302_1. Decided:

Where f is the first predetermined frequency.

In addition, it is assumed that in the battery pack 302, the battery unit 302_4 has the lowest battery cell voltage. The most efficient cell balancing method is to transfer excess energy from battery cell 302_1 directly to battery cell 302_4. The detection and control unit 308 generates a control signal having a first predetermined frequency and a duty cycle equal to or less than (1_D1) to control the closing and opening of the switch 306_4. When the switch 306_1 is turned off, the switch 306_4 is closed, the induced current I4 appears on the coil 304_4, and finally, the energy stored in the core 305 of the transformer 303, that is, the energy transferred from the battery unit 302_1, is transferred to the battery. In unit 302_4. It is to be noted that the switch 306_1 connected to the coil 304_1 and the switch 306_4 connected to the coil 304_4 are alternately closed and opened, that is, when the switch 306_1 is in the closed state, the switch 306_4 is in the off state; and when the switch 306_1 is in the off state In the on state, the switch 306_4 is in a closed state or is in a closed state and then in an open state. Further, if the detection and control unit 308 controls the switches 306_2 and 306_6 to be always in the off state, the energy of the battery unit 302_1 is not transferred to the battery units 302_2 and 302_6.

In the above example, the coil 304_1 and the coil 304_4 operate as a primary coil and a secondary coil, respectively. Conversely, assuming that the battery unit 302_4 has the highest battery unit voltage and the battery unit 302_1 has the lowest battery unit voltage, the coil 304_4 acts as the primary coil while the excess energy in the battery unit 302_4 is transferred to the battery unit 302_1. 304_1 is used as the secondary coil. That is, the six coils 304_1-304_6 can serve as the primary coil and the secondary coil, respectively, depending on the actual application.

The above battery balancing method can directly transfer part of the energy in the battery cell having the highest battery cell voltage to the battery cell having the lowest battery cell voltage. Therefore, the battery balance can be efficiently completed in a short time. Since the present invention directly transfers part of the energy of the battery cell having the highest battery cell voltage to the battery cell having the lowest battery cell voltage, the battery cell balancing circuit of one embodiment of the present invention is also applicable to the discharge of the battery. Process and idle status.

In the following, FIG. 3 is taken as an example to further illustrate other specific applications of the battery cell balancing circuit of the present invention. With continued reference to FIG. 3, it is assumed that during charging of the battery pack 302, the battery unit 302_1 in the battery pack 302 has the highest battery unit voltage, and the battery unit 302_3 has the lowest battery unit voltage; however, in the battery units 302_2, 302_4, and 302_6 The battery unit 302_4 has the highest battery unit voltage, and the battery unit 302_6 has the lowest battery unit voltage. Obviously, the excess energy of the battery unit 302_1 cannot be directly transferred to the battery unit 302_3. However, the excess energy in the battery unit 302_1 can be transferred to the battery unit 302_6 by alternately closing and opening the control switches 306_1 and 306_6, so that the battery unit 302_1 can be prevented from being overcharged. In addition, the excess energy in the battery unit 302_4 can be transferred to the battery unit 302_3 by alternately closing and opening the control switches 306_4 and 306_3, so that the charging speed of the battery unit 302_3 can be prevented from being too slow.

Although transferring excess energy from the battery unit 302_4 to the battery unit 302_3 during charging of the battery pack 302 is not an essential step, it is very important during the discharge of the battery pack 302 because it can extend the discharge of the battery pack 302. Time increases the efficiency of use of the battery pack 302. In fact, during the charging process, the excess energy in the battery unit 302_4 is simultaneously transferred to the battery unit 302_3, which can accelerate the balance of the battery unit. It can be seen that the battery cell balancing circuit of the present invention can be applied to the charging process, the discharging process, and the idle state of the battery pack 302.

4 is a block diagram of a battery cell balancing circuit 400 in accordance with an embodiment of the present invention. Figure 4 is an extension of the six battery cells shown in Figure 3 to n battery cells, where n is a positive integer. 4 is used to illustrate how the cell balancing circuit 400 achieves the balance of the battery cells regardless of whether the battery cells are in a charging process, a discharging process, or an idle state. The cell balancing circuit 400 includes a battery pack 402 having n battery cells 402_1-402_n, a transformer 403, and a detection and control unit 408. The transformer 403 includes a core 405 and n coils 404_1-404_n coupled to the core 405. The battery cell balancing circuit 400 further includes n switches 406_1-406_n, each of which is connected to both ends of a battery unit 402_1-402_n through a corresponding switch 406_1-406_n. For example, the coil 404_1 is connected to the battery through the switch 406_1. Both ends of unit 402_1.

Referring to FIG. 4, the dot ends of the coils 404_1, 404_3, ..., 404_n-1 are respectively connected to the positive electrodes of the battery cells 402_1, 402_3, ..., 402_n-1; and the dot ends of the coils 404_2, 404_4, ..., 404_n are respectively connected to the battery The cathodes of the units 402_2, 402_4, ..., 402_n are connected. It can be understood that the connection manner of the battery units 402_1-402_n and the corresponding coils 404_1-404_n disclosed in FIG. 4 is only one specific example of the present invention. In general, the N coils 404_1-404_n can be divided into a first group of coils and a second group of coils, wherein the dot ends of the first group of coils are connected to the anodes of the corresponding battery cells, and the second group The dot end of the coil is connected to the negative pole of the corresponding battery unit. Taking FIG. 4 as an example, the coils 404_1, 404_3, . . . , 404_n-1 may be referred to as a first group of coils, and the coils 404_2, 404_4, . . . , 404_n may be referred to as a second group of coils. The switches 406_1, 406_3, ..., 406_n-1 connected to the first group of coils are referred to as a first group of switches, and the switches 406_2, 406_4, ..., 406_n connected to the second group of coils are referred to as a second group of switches. The detection and control unit 408 controls the closing and opening of the switches 406_1-406_n, wherein the first set of switches (ie, switches 406_1, 406_3, ..., 406_n-1) and the second set of switches (ie, switches 406_2, 406_4, ... , 406_n) will not close at the same time.

The detection and control unit 408 is electrically connected to the battery pack 402 and the switches 406_1-406_n for detecting the battery cell voltage of each of the battery cells 402_1-402_n in the battery pack 402, and from the first battery group connected to the first group of coils. Selecting, in the cells (ie, battery cells 402_1, 402_3, ..., 402_n-1), a battery cell having the highest cell voltage (eg, battery cell 402_1) and a battery cell having the lowest cell voltage (eg, battery cell 402_3); Selecting a battery unit having the highest battery cell voltage (eg, battery unit 402_n) from the second group of battery cells (ie, battery cells 402_2, 402_4, . . . , 402_n) connected to the second set of coils and having the lowest battery cell voltage Battery unit (eg, battery unit 402_2). The detection and control unit 408 generates a control signal control switch 406_1 having a second predetermined frequency and a duty cycle of D2 to be closed and opened, and generates a control signal having a second predetermined frequency and a duty cycle equal to or less than (1-D2). Controlling the closing and opening of the switch 406_2, when the switch 406_1 is closed, the excess energy in the battery unit 402_1 is transferred to the core 405 of the transformer 403; after the switch 406_1 is turned off, the switch 406_2 is closed, and the induction occurs on the coil 404_2 Current, and finally, the energy stored in the transformer 403 (i.e., the energy transferred from the battery unit 402_1) is transferred to the battery unit 402_2. The detection and control unit 408 generates a control signal control switch 406_n having a third predetermined frequency and a duty cycle of D3 to be closed and opened, and generates control signal control having a third predetermined frequency and a duty cycle equal to or less than (1-D3). The switch 406_3 is closed and opened. When the switch 406_n is closed, excess energy in the battery unit 402_n is transferred to the core 405 of the transformer 403. After the switch 406_n is turned off, the switch 406_3 is closed, an induced current appears on the coil 404_3, and finally, the energy stored in the transformer 403 (i.e., the energy transferred from the battery unit 402_n) is transferred to the battery unit 402_3. In an embodiment, the third predetermined frequency is equal to the second predetermined frequency.

Based on the connection relationship between the battery cells 402_1-402_n and the dot ends of the coils 404_1-404_n, the n battery cells of the battery pack 402 can be divided into a first battery unit and a second battery unit, for example, the positive electrode of the first battery unit. Connected to the dot end of the coil, the negative pole of the second group of battery cells is connected to the dot end of the coil. The detection and control unit 408 selects the battery unit having the highest battery cell voltage and the lowest battery cell voltage from the first group of battery cells, and selects the battery cell having the highest battery cell voltage and the lowest battery cell voltage from the second group of battery cells. The detection and control unit 408 controls the closing and opening of the corresponding switch to transfer excess energy in the battery unit having the highest battery cell voltage among the first group of battery cells to the battery unit having the lowest battery cell voltage of the second group of battery cells. And transferring excess energy in the battery cells having the highest battery cell voltage among the second group of battery cells to the battery cells having the lowest battery cell voltage among the first group of battery cells.

FIG. 5 is a block diagram of a battery cell balancing circuit 500 in accordance with an embodiment of the present invention. The components in FIG. 5 that are the same as those in FIG. 3 have the same functions, and are not described herein for the sake of brevity. In an embodiment, the switches 506_1-506_6 of the cell balancing circuit 500 employ a metal oxide semiconductor field effect transistor (MOSFET). Each MOSFET includes a body diode. Assuming that the battery unit 302_1 has the highest battery unit voltage and the battery unit 302_4 has the lowest battery unit voltage, when the switch 506_1 is closed, the excess energy in the battery unit 302_1 is transferred to the core 305 of the transformer, after the switch 506_1 is turned off, Switch 506_4 is closed and an induced current is present on coil 304_4. Due to the influence of the body diode, a slight induced current also appears in the coils 304_2 and 304_6 after the switch 506_1 is turned off. The induced current is inversely proportional to the equivalent load reactance across the coils 304_2 and 304_6, so that the battery unit 302_4 connected to the closed switch 506_4 obtains most of the energy transferred from the core 305.

FIG. 6 is a block diagram of a battery cell balancing circuit 600 in accordance with an embodiment of the present invention. The battery cell balancing circuit 600 includes n battery modules 602_1-602_n and a transformer 603 connected in series. The transformer 603 includes a plurality of coils, each of which is connected in parallel with a corresponding battery module 602_1-602_n through a switch (not shown). The detecting and controlling unit 608 is electrically connected to the plurality of battery modules 602_1-602_n to detect the voltage of each of the battery modules 602_1-602_n and select a battery module having a first voltage and a battery module having a second voltage. Wherein the first voltage is greater than the second voltage. In an embodiment of the invention, the first voltage and the second voltage are respectively the highest voltage and the lowest voltage of the n battery modules 602_1-602_n. The transformer 603 transfers a portion of the energy in the battery module having the first voltage to the battery module having the second voltage. It can be understood that each of the battery modules 602_1-602_n can be regarded as a battery unit, and the battery unit balancing circuit shown in FIG. 6 works in the same manner as the battery unit balancing circuit shown in FIGS. 3 and 4. In an embodiment of the invention, each of the battery modules 602_1-602_n includes a plurality of battery cells connected in series, and the principle of balance between the battery cells in each of the battery modules 602_1-602_n is as shown in FIG. 3 and FIG. The principle of the battery cell balancing circuit is the same, and for brevity, it will not be repeated here.

FIG. 7 is a block diagram of a battery cell balancing circuit 700 in accordance with an embodiment of the present invention. The battery cell balancing circuit 700 includes a battery pack 702, a transformer 703, a first switch array 706, a second switch array 707, and a detection and control unit 708. The battery pack 702 includes n battery cells 702_1-702_n connected in series. Transformer 703 includes a first coil 704 and a second coil 705. The first switch array 706 is coupled between the first coil 704 and the battery pack 702. The second switch array 707 is coupled between the second coil 705 and the battery pack 702. The first switch array 706 includes a first set of switches SA_1-SA_n and a second set of switches SB_1-SB_n. The second switch array 707 includes a third group of switches SC_1-SC_n and a fourth group of switches SD_1-SD_n. The detection and control unit 708 is electrically coupled to the battery pack 702, the first switch array 706, and the second switch array 707 to detect the battery cell voltage of each of the battery cells 702_1-702_n. It is assumed that in the battery pack 702, the battery unit 702_1 has the highest battery unit voltage, and the battery unit 702_n has the lowest battery unit voltage. The most efficient way to balance the battery cells is to transfer excess energy from battery cell 702_1 directly into battery cell 702_n. The detection and control unit 708 controls the switches SA_1 and SB_1 in the first switch array 706 to close, the other switches to open, and controls all switches in the second switch array 707 to open, the current flowing from the battery unit 702_1 to the first coil 704. The energy transferred from the battery unit 702_1 is stored in the iron core of the transformer 703. The detection and control unit 708 controls the switches SA_1 and SB_1 in the first switch array 706 to be turned off, the switches SC_n and SD_n in the second switch array 707 are closed, the induced current appears on the second coil 705, and finally, the core of the transformer 703 is turned on. The energy stored in (i.e., the energy transferred from the battery unit 702_1) is transferred to the battery unit 702_n. Furthermore, if the detection and control unit 708 controls the other switches in the second switch array to be always in the off state, the energy of the battery unit 702_1 is not transferred to the battery cells 702_2-702_n-1. In this example, the first coil 704 and the second coil 705 operate as a primary coil and a secondary coil, respectively.

Obviously, the excess energy in the battery unit 702_1 can be directly transferred to the battery unit 702_n. For example, the detection and control unit 708 controls the switches SC_1 and SD_1 in the second switch array 707 to be closed, and the other switches are turned off, and All switches in the first switch array 706 are controlled to be turned off, and current flows from the battery unit 702_1 to the second coil 705. The energy transferred from the battery unit 702_1 is stored in the iron core of the transformer 703. Next, the detection and control unit 708 controls the switches SC_1 and SD_1 in the second switch array 707 to be turned off, the switches SA_n and SB_n in the first switch array 706 are closed, an induced current appears on the first coil 704, and finally, the transformer 703 is The energy stored in the iron core (i.e., the energy transferred from the battery unit 702_1) is transferred to the battery unit 702_n. Furthermore, if the detection and control unit 708 controls the other switches in the first switch array 706 to be always in the off state, the energy of the battery unit 702_1 is not transferred to the battery cells 702_2-702_n-1.

Figure 8 illustrates a control flow 800 performed by a detection and control unit in accordance with an embodiment of the present invention. Figure 8 will be described in conjunction with Figure 4. In step 802, the cell voltage of each of the plurality of battery cells is monitored. In step 804, the battery unit is divided into a first group of battery units and a second group of battery units based on the connection relationship between the battery unit and the coil striking end. Referring to FIG. 4 at the same time, the first battery unit is a battery unit connected to the positive end of the battery unit and the dot end of the coil, such as battery units 402_1, 402_3, . . . , 402_n-1, and the second battery unit is a battery unit. A battery unit whose negative electrode is connected to the dot end of the coil, such as battery cells 402_2, 402_4, ..., 402_n.

In step 806, the battery unit B_GAAL having the highest battery cell voltage V(B_GAH) and the lowest battery cell voltage V(B_GAL) are selected from the first group of battery cells, and selected from the second group of battery cells The battery unit B_GBH of the highest battery cell voltage V (B_GBH) and the battery unit B_GBL of the lowest battery cell voltage V (B_GBL).

In step 808, a difference between the highest battery cell voltage V (B_GAH) and the lowest battery cell voltage V (B_GAL) in the first group of battery cells or the highest battery cell voltage V (B_GBH) in the second group of battery cells is determined. Whether the difference of the lowest battery cell voltage V (B_GBL) is greater than a first threshold voltage Vlim. The magnitude of the first threshold voltage Vlim can be selected according to practical applications. In an embodiment of the invention, the first threshold voltage Vlim is 0..5 volts. If the difference between the highest battery cell voltage V (B_GAH) and the lowest battery cell voltage V (B_GAL) in the first group of battery cells or the highest battery cell voltage V (B_GBH) and the lowest battery cell voltage V in the second group of battery cells If the difference of (B_GBL) is greater than the first threshold voltage Vlim, proceed to step 810 to check if the battery is damaged, otherwise proceed to step 812.

In step 812, it is determined whether the difference between the highest battery cell voltage V (B_GAH) in the first group of battery cells and the lowest battery cell voltage V (B_GBL) in the second group of battery cells is less than a second threshold voltage Vbal, Determining whether a difference between the highest battery cell voltage V(B_GBH) of the second group of battery cells and the lowest battery cell voltage V(B_GAL) of the first group of battery cells is less than a second threshold voltage Vbal, determining the first group of battery cells Whether the difference between the highest battery cell voltage V (B_GAH) and the lowest battery cell voltage V (B_GAL) is less than the second threshold voltage Vbal, and determining the highest battery cell voltage V (B_GBH) and the lowest of the second group of battery cells Whether the difference of the cell voltage V (B_GBL) is smaller than the second threshold voltage Vbal. In an embodiment, the second threshold voltage Vbal is less than the first threshold voltage Vlim, for example, 50 millivolts. If the difference determined in step 812 is less than the second threshold voltage Vbal, then the balancing of the battery cells is terminated in step 814, otherwise step 816 is entered.

In step 816, a difference between the highest battery cell voltage V (B_GAH) and the lowest battery cell voltage V (B_GAL) in the first group of battery cells or the highest battery cell voltage V (B_GBH) in the second group of battery cells is determined. Whether the difference of the lowest battery cell voltage V (B_GBL) is greater than a third threshold voltage Vthb. In an embodiment, the third threshold voltage Vthb is greater than the second threshold voltage Vbal and less than the first threshold voltage Vlim, eg, 0.2 volts. If the difference between the highest battery cell voltage V (B_GAH) and the lowest battery cell voltage V (B_GAL) in the first group of battery cells or the highest battery cell voltage V (B_GBH) and the lowest battery cell voltage V in the second group of battery cells If the difference of (B_GBL) is greater than the third threshold voltage Vthb, then the normal balance mode of step 818 is entered, otherwise step 820 is entered.

Control flow 800 proceeds to step 822 after the normal balancing mode. In step 822, part of the energy in the battery unit B_GAH having the highest battery cell voltage V(B_GAH) among the first group of battery cells is transferred to the battery unit B_GBL having the lowest battery cell voltage V (B_GBL) among the second group of battery cells. And transferring part of the energy in the battery unit B_GBH having the highest battery cell voltage V (B_GBH) among the second group of battery cells to the battery unit B_GAL having the lowest voltage battery unit V (B_GAL) among the first group of battery cells.

In step 820, a difference between the highest battery cell voltage V(B_GAH) of the first group of battery cells and the lowest battery cell voltage V(B_GBL) of the second group of battery cells or the highest battery of the second group of battery cells is determined. Whether the difference between the cell voltage V(B_GBH) and the lowest cell voltage V(B_GAL) in the first group of battery cells is greater than the third threshold voltage Vthb. If the difference between the highest battery cell voltage V (B_GAH) in the first group of battery cells and the lowest battery cell voltage V (B_GBL) in the second group of battery cells or the highest battery cell voltage V in the second group of battery cells (B_GBH) And the difference between the lowest battery cell voltage V(B_GAL) in the first group of battery cells is greater than the third threshold voltage Vthb, then proceeds to the fast balancing mode of step 824, otherwise proceeds to the normal balancing mode of step 818.

Control flow 800 proceeds to step 826 after the fast balance mode. In step 826, it is determined whether the difference between the highest battery cell voltage V(B_GAH) of the first group of battery cells and the lowest battery cell voltage V(B_GBL) of the second group of battery cells is greater than the highest of the second group of battery cells. The difference between the cell voltage V (B_GBH) and the lowest cell voltage V (B_GAL) in the first group of cells. If the difference between the highest battery cell voltage V (B_GAH) in the first group of battery cells and the lowest battery cell voltage V (B_GBL) in the second group of battery cells is greater than the highest battery cell voltage V in the second group of battery cells (B_GBH) And the difference between the lowest battery cell voltage V(B_GAL) in the first group of battery cells, then proceeds to step 828, otherwise proceeds to step 830.

In step 828, part of the energy in the battery unit B_GAH having the highest battery cell voltage V(B_GAH) among the first group of battery cells is transferred to the battery unit B_GBL having the lowest battery cell voltage V (B_GBL) among the second group of battery cells. .

In step 830, part of the energy of the battery unit B_GBH having the highest battery cell voltage V(B_GBH) among the second group of battery cells is transferred to the battery unit B_GAL having the lowest battery cell voltage V(B_GAL) among the first group of battery cells.

The control flow shown in FIG. 8 can detect the battery cell voltage of each battery cell at intervals, for example, 100 milliseconds, that is, the battery cell voltage monitored in step 802 is updated every 100 milliseconds. . The specific control flow disclosed in Figure 8 is by way of example only. That is to say, the present invention is also applicable to other reasonable control procedures or steps for improving FIG.

9 is a flow chart of a method of balancing battery cells in accordance with an embodiment of the present invention. In step 902, the cell voltages of the plurality of battery cells connected in series are detected. In step 904, the battery cell having the highest battery cell voltage and the battery cell having the lowest battery cell voltage are selected from the plurality of detected battery cell voltages. In step 906, a portion of the energy in the battery cell having the highest battery cell voltage is transferred to the battery cell having the lowest battery cell voltage.

The above detailed description and the accompanying drawings are only typical embodiments of the invention. It is apparent that various additions, modifications and substitutions are possible without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood by those of ordinary skill in the art that the present invention may be applied in the form of the form, structure, arrangement, ratio, material, element, element, and other aspects in the actual application without departing from the invention. Changed. Therefore, the embodiments disclosed herein are intended to be illustrative and not restrictive, and the scope of the invention is defined by the scope of the appended claims and their legal equivalents.

100. . . Battery cell balancing circuit

102_1~102_n. . . Battery unit

104. . . Primary coil

106_1~106_n. . . Secondary coil

108. . . switch

200. . . Battery cell balancing circuit

202_1~202_n. . . Battery unit

204_1~204_n. . . Metal oxide semiconductor field effect transistor

300. . . Battery cell balancing circuit

302. . . Battery

302_1-302_6. . . Battery unit

303. . . transformer

304_1-304_6. . . Coil

305. . . Iron core

306_1-306_6. . . switch

308. . . Detection and control unit

400. . . Battery cell balancing circuit

402. . . Battery

402_1-402_n. . . Battery unit

403. . . transformer

404_1-404_n. . . Coil

405. . . Iron core

406_1-406_n. . . switch

408. . . Detection and control unit

500. . . Battery cell balancing circuit

506_1-506_n. . . switch

600. . . Battery cell balancing circuit

602_1-602_n. . . Battery module

603. . . transformer

608. . . Detection and control unit

700. . . Battery cell balancing circuit

702. . . Battery

702_1-702_n. . . Battery unit

703. . . transformer

704. . . First coil

705. . . Second coil

706. . . First switch array

707. . . Second switch array

708. . . Detection and control unit

800. . . Process

802-830. . . step

900. . . Process

902, 904, 906. . . step

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. among them:

Figure 1 shows the structure of a conventional battery cell balancing circuit.

FIG. 2 is a structural diagram of another conventional battery cell balancing circuit.

FIG. 3 is a structural diagram of a battery cell balancing circuit according to an embodiment of the invention.

4 is a structural diagram of a battery cell balancing circuit according to an embodiment of the present invention.

FIG. 5 is a structural diagram of a battery cell balancing circuit according to an embodiment of the invention.

FIG. 6 is a structural diagram of a battery cell balancing circuit according to an embodiment of the present invention.

FIG. 7 is a structural diagram of a battery cell balancing circuit according to an embodiment of the invention.

Figure 8 is a flow chart showing the control performed by the detection and control unit in accordance with an embodiment of the present invention.

9 is a flow chart of a method of balancing battery cells in accordance with an embodiment of the present invention.

300. . . Battery cell balancing circuit

302. . . Battery

302_1-302_6. . . Battery unit

303. . . transformer

304_1-304_6. . . Coil

305. . . Iron core

306_1-306_6. . . switch

308. . . Detection and control unit

Claims (22)

A battery cell balancing circuit includes: a first battery unit having a parameter, and the value of the parameter has a first value; a second battery unit coupled in series to the first battery unit, the second battery unit The value of the parameter has a second value, wherein the first value is greater than the second value; a transformer comprising a primary coil electrically connected to both ends of the first battery unit, and the second battery unit Electrically connecting one of the two ends of the first battery unit to the second battery unit; a first switch and a second switch; and a detecting and controlling unit electrically connecting the first a battery unit, the second battery unit, and detecting the first value of the first battery unit and the second value of the second battery unit, wherein, according to the detected first value and the second value And generating a control signal to control the first switch and the second switch to alternately close and open. The battery cell balancing circuit of claim 1, wherein the parameter is a voltage. The battery cell balancing circuit of claim 1, wherein the parameter is a state of charge. The battery cell balancing circuit of claim 1, wherein the parameter is a capacity. Such as the battery cell balancing circuit of claim 1 of the patent scope, wherein A positive pole of the first battery unit is electrically connected to a dot end of the primary coil, and a negative pole of the second battery unit is electrically connected to a dot end of the secondary coil. The battery cell balancing circuit of claim 1, wherein the first open relationship is coupled between the first battery unit and the primary coil, and the second open relationship is coupled to the second battery unit and the The first switch and the second switch are electrically connected to the detecting and controlling unit between the secondary coils. A battery cell balancing circuit comprising: a battery pack comprising a plurality of battery cells connected in series, wherein two of the plurality of battery cells have a parameter and the value of the parameter has a first value, the plurality of The value of the parameter of the second battery unit of the battery unit is a second value smaller than the first value; a transformer includes a first coil and a second coil, and is electrically connected to the battery pack, Transferring energy of one of the first battery cells to the second battery unit; a first switch array and a second switch array; and a detection and control unit electrically connected to the battery pack and detecting the first a value and the second value, wherein, according to the detected first value and the second value, controlling closing and opening of each of the first switch array and the second switch array to enable the The energy in a battery unit is transferred to the second battery unit. For example, the battery cell balancing circuit of claim 7 of the patent scope, wherein The first switch array is coupled between the battery pack and the first coil, the second switch array is coupled between the battery pack and the second coil, the first switch array, the second switch The array is electrically connected to the detection and control unit. The battery cell balancing circuit of claim 8, wherein the first switch and the second open relationship are coupled between the battery pack and the first coil, the second switch array further comprising a third switch and a fourth switch, the third switch and the fourth open relationship are coupled between the battery pack and the second coil. The battery cell balancing circuit of claim 9, wherein the detecting and controlling unit generates a control signal to control the first switch and the second switch according to the detected first value and the second value. The third switch and the fourth switch are in a closed and open state. The battery cell balancing circuit of claim 7, wherein the parameter is a voltage, the first value is one of the plurality of battery cells, and the second value is the plurality of One of the lowest cell voltages in the battery unit. A battery cell balancing circuit includes: a first battery module and a second battery module connected in series, the first battery module and the second battery module respectively comprise a plurality of battery cells, the first battery module The value of one of the parameters of the group has a first value, and the value of the parameter of the second battery module is less than a second value of the first value; a transformer includes electrically connecting to the first battery module One primary coil and one secondary line electrically connected to the second battery module a first battery module, a first switch and a second switch; and a detection and control unit electrically connected to the first battery module, the a second battery module, and detecting the first value of the first battery module and the second value of the second battery module, wherein, according to the detected first value and the second value, generating A control signal controls the first switch and the second switch to alternately close and open. For example, in the battery cell balancing circuit of claim 12, a positive pole of the first battery module is connected to a dot end of the primary coil, and a negative pole of the second battery module and a dot end of the secondary coil connection. The battery cell balancing circuit of claim 12, wherein the parameter is a voltage. The battery cell balancing circuit of claim 12, wherein the parameter is a state of charge. The battery cell balancing circuit of claim 12, wherein the parameter is a capacity. A battery cell balancing method includes: detecting a parameter of a first battery unit, the value of the parameter of the first battery unit has a first value; detecting a second battery unit connected in series with the first battery unit The parameter, the value of the parameter of the second battery unit has a second value, wherein the first value is greater than the second value; Comparing a difference between a highest battery cell voltage and a lowest battery cell voltage with a threshold voltage; and transferring one of the first battery cells to the second battery cell through a transformer. The battery cell balancing method of claim 17, wherein the transferring step comprises: storing the energy in the first battery unit in an iron core of the transformer; and storing energy stored in the iron core Transfer to the second battery unit. The battery cell balancing method of claim 18, wherein the storing step comprises: controlling a first switch coupled between the first battery unit and one of the primary coils of the transformer to be in a closed state; and controlling the coupling A second switch connected between the second battery unit and one of the secondary windings of the transformer is in an open state. The battery cell balancing method of claim 19, wherein the transferring the energy in the iron core to the second battery unit comprises: controlling the first switch to be in an off state; and controlling the second switch It is in a closed state. A battery cell balancing method includes: detecting a parameter of each of a plurality of battery cells connected in series; selecting a battery cell having a first value from the plurality of detected parameters and having a second value a battery unit, the first value Greater than the second value; comparing a difference between a highest cell voltage and a lowest cell voltage to a threshold voltage; and transferring one of the cells having the first value through a transformer to have The second value of the battery unit. The battery cell balancing method of claim 21, wherein the parameter is a voltage, the first value is the highest battery cell voltage of the plurality of battery cells, and the second value is the plurality of batteries The lowest cell voltage in the cell.