Active equalization circuit for battery pack

Abstract

The utility model discloses an active equalization circuit used for a battery pack. The active equalization circuit used for the battery pack comprises the battery pack, an input switch array, an output switch array, a DC isolation conversion module, a control module and a gating module. The battery pack comprises a plurality of unit batteries connected in series; the input switch array comprises a plurality of input group switches, and the input group switches are connected in series between the corresponding unit batteries and the output end of the direct current isolation conversion module in a one-to-one correspondence manner; the output switch array comprises a plurality of output group switches, and the output group switches are connected in series between the corresponding unit batteries and the input end of the direct current isolation conversion module in a one-to-one correspondence manner; the control module is used for outputting a control signal, and the gating module is used for carrying out alternative gating on the plurality of input group switches and alternative gating on the plurality of output group switches based on the control signal. By adopting the scheme, the effect of high-efficiency discharging and charging equalization can be realized under the condition of avoiding easy short circuit.

Description

Technical Field

[0001] The utility model relates to the technical field of battery management, and in particular to an active equalization circuit for a battery pack. Background Art

[0002] With the development of secondary battery technology, rechargeable batteries such as lithium batteries and lead-acid batteries are increasingly used. Many occasions require high voltage output, which requires the use of multiple unit cells stacked together, such as power tool batteries, electric bicycle batteries, energy storage batteries, and electric vehicle batteries. These batteries all require a BMS battery management system to manage and protect each unit cell and battery pack. The differences between the unit cells in the battery pack due to differences in production and manufacturing processes, materials, battery internal resistance, battery operating temperature, self-discharge rate, etc., will cause imbalance between the unit cells during charging and discharging.

[0003] When charging, the weak battery will be fully charged first, and the voltage will first reach the protection voltage limit. The other strong batteries are not fully charged and the voltage is low. They can be allowed to continue charging, but in order to protect the weak battery and prevent overcharging, overheating, and battery explosion, the battery pack stops charging. When discharging, the weak battery has a small capacity and will first reach the lowest protection discharge voltage limit. In order to protect the weak battery and prevent battery damage caused by overdischarge, the battery pack should stop discharging. At this time, the strong battery still has power that has not been discharged, but it cannot be used. Therefore, the relevant technology will adopt the unit cell active balancing technology to make the performance of the battery pack unit cells tend to be consistent, which can significantly improve the performance of the battery pack.

[0004] The existing active battery balancing technology uses a transformer to realize the charge transfer between the unit cell and the battery pack, and realizes the charging and discharging function between the unit cell and the battery pack. That is, each unit cell requires a transformer to realize the charging and discharging function between the unit cell and the battery pack. However, in this method, the number of transformers required is the same as the number of unit cells, so the number of transformers required is large, the volume is large, the balancing circuit is complex, and the solution cost is high. At the same time, when the unit cell and the battery pack are balanced, part of the balancing effect will be offset, so the balancing efficiency of the solution is low.

[0005] Another active balancing solution is to transfer charge between cells through supercapacitor energy storage. This solution first selects the cell that needs to be discharged through the switch array, charges the supercapacitor through the bidirectional DCDC module, and after the capacitor is fully charged, disconnects the switch array to stop charging. The switch array switches to the cell that needs to be balanced and charged. By controlling the bidirectional DCDC module, the supercapacitor discharges the cell to achieve the charge transfer effect between different cells and achieve balance between cells. However, this solution is limited by the capacity of the supercapacitor, which has a small capacity, a large number of charge transfers, and low efficiency. If the supercapacitor capacity is increased, the number of charge transfers will increase, the transfer efficiency will increase, but the cost will increase. In addition, the supercapacitor energy storage solution must achieve balance through two charge transfers, and the time efficiency and work efficiency are both low. At the same time, when controlling the gating of different cells, if the switch array is improperly controlled or is interfered by the external environment, the switch is prone to misoperation, resulting in a fatal short circuit. The short circuit between the high-voltage cell and the low-voltage cell will cause fire and explosion, which is a high risk. Utility Model Content

[0006] The utility model provides an active equalization circuit for a battery pack, so as to achieve the effect of high-efficiency discharge and charge equalization under the condition of avoiding easy short circuit.

[0007] According to one aspect of the utility model, an active balancing circuit for a battery pack is provided, the active balancing circuit for a battery pack comprising a battery pack, an input switch array, an output switch array, a DC isolation conversion module, a control module and a gating module;

[0008] The battery pack includes a plurality of unit batteries connected in series;

[0009] The input switch array includes a plurality of input group switches, the number of the input group switches is the same as the number of the unit batteries and corresponds one to one, and the input group switches are connected in series between the corresponding unit batteries and the output end of the DC isolation conversion module;

[0010] The output switch array includes a plurality of output group switches, the number of the output group switches is the same as the number of the unit batteries and corresponds one to one, and the output group switches are connected in series between the corresponding unit batteries and the input end of the DC isolation conversion module;

[0011] The DC isolation conversion module is used to convert the input voltage and isolate the input end and output end of the DC isolation conversion module;

[0012] The input end of the control module is electrically connected to the input end of the gating module, and the output end of the gating module is electrically connected to the plurality of input group switches and the plurality of output group switches. The control module is used to output a control signal, and the gating module is used to select one of the plurality of input group switches and select one of the plurality of output group switches based on the control signal.

[0013] In an optional embodiment of the present utility model, the gating module includes an input gating circuit and an output gating circuit;

[0014] The output end of the input gating circuit is electrically connected to the plurality of input group switches, and is used to select one of the plurality of input group switches based on the control signal;

[0015] The output end of the output gating circuit is electrically connected to the plurality of output group switches, and is used to select one of the plurality of output group switches based on the control signal.

[0016] In an optional embodiment of the present invention, the input gating circuit and / or the output gating circuit includes a decoder.

[0017] In an optional embodiment of the present utility model, the input group switch includes an input positive switch and an input negative switch; the input positive switches of the plurality of input group switches are connected in series one by one between the positive pole of the unit battery and the positive output terminal of the DC isolation conversion module; the input negative switches of the plurality of input group switches are connected in series one by one between the negative pole of the unit battery and the negative output terminal of the DC isolation conversion module;

[0018] And / or, the output group switch includes an output positive switch and an output negative switch; the output positive switches of the multiple output group switches are connected in series one by one between the positive pole of the unit battery and the positive input terminal of the DC isolation conversion module; the output negative switches of the multiple output group switches are connected in series one by one between the negative pole of the unit battery and the negative input terminal of the DC isolation conversion module.

[0019] In an optional embodiment of the utility model, the input positive switch, the input negative switch, the output positive switch and the output negative switch include one of a photorelay, a relay, a MOSFET field effect transistor, an IGBT insulated gate bipolar transistor, and a bipolar transistor.

[0020] In an optional embodiment of the present invention, the active balancing circuit further includes an analog-to-digital conversion module, an input end of the analog-to-digital conversion module is electrically connected to the plurality of unit batteries, and a communication end of the analog-to-digital conversion module is communicatively connected to a communication end of the control module.

[0021] In an optional embodiment of the present utility model, the communication end of the analog-to-digital conversion module is connected to the communication end of the control module through one of I2C, SPI, UART serial port and parallel interface.

[0022] In an optional embodiment of the present utility model, the DC isolation conversion module includes a boost circuit, and the boost circuit is used to boost the input voltage and then output it.

[0023] In an optional embodiment of the present utility model, the DC isolation conversion module includes one of a DC-DC DC isolation converter, a Boost switching regulator topology circuit, a flyback converter topology circuit, and a Cuk converter topology circuit.

[0024] In an optional embodiment of the present invention, the current control end of the control module is electrically connected to the PWM control end of the DC isolation conversion module, and the control module is used to output a PWM control signal to the PWM control end of the DC isolation conversion module to control the operating current of the DC isolation conversion module.

[0025] The technical solution of the embodiment of the utility model can select the output group switch corresponding to the unit battery that needs to be discharged through the selection module, and select the input group switch corresponding to the unit battery that needs to be charged. At this time, the discharged unit battery will be electrically connected to the input end of the DC isolation conversion module, and the charged unit battery will be electrically connected to the output end of the DC isolation conversion module. When the corresponding input group switch and output group switch are closed, the balanced charge can continuously flow from the high voltage unit to the low voltage unit battery, that is, the electric energy of one unit battery can be used to charge another unit battery, realizing active balancing. When the corresponding input group switch and output group switch are disconnected, the active balancing can be stopped, so that the present solution achieves the effect of efficient discharge and charge balancing in the case of avoiding easy short circuit.

[0026] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present utility model, nor are they intended to limit the scope of the present utility model. Other features of the present utility model will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1A schematic diagram of the structure of an active equalization circuit for a battery pack provided by an embodiment of the utility model;

[0029] Figure 2 It is a partial circuit structure diagram of another active equalization circuit for a battery pack provided by an embodiment of the utility model.

[0030] Among them: 1. battery pack; 11. unit battery; 2. input switch array; 21. input group switch; 211. input positive switch; 212. input negative switch; 21a. light-emitting device; 21b. light-receiving device; 3. output switch array; 31. output group switch; 311. output positive switch; 312. output negative switch; 4. DC isolation conversion module; 5. control module; 6. selection module; 61. input selection circuit; 62. output selection circuit; 7. analog-to-digital conversion module; 8. power supply module. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0032] In this application, the terms "comprises", "includes", "has" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0033] In this application, the term "and / or" is a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects before and after are in an "and / or" relationship.

[0034] In the present application, the terms "connect", "combine", "couple", and "install" may refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, direct connection refers to two parts or components being connected together without the need for an intermediate piece, and indirect connection refers to two parts or components being connected to at least one intermediate piece respectively, and the two parts or components being connected via the intermediate piece. In addition, "connect" and "couple" are not limited to physical or mechanical connections or couplings, and may include electrical connections or couplings.

[0035] In this application, it will be understood by those skilled in the art that the function performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the function performed by a part can also be performed by one part, one component, or a combination of multiple parts.

[0036] In this application, the terms "controller", "processor", "central processing unit", "CPU", and "MCU" are interchangeable. When a unit "controller", "processor", "central processing unit", "CPU", or "MCU" is used to perform a specific function, unless otherwise specified, these functions can be performed by a single unit or multiple units.

[0037] In the present application, the terms “device”, “module” or “unit” may be implemented in the form of hardware or software to achieve specific functions.

[0038] In this application, the terms "calculate", "judge", "control", "determine", "identify", etc. refer to the operations and processes of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

[0039] Figure 1 A schematic diagram of the structure of an active equalization circuit for a battery pack provided by an embodiment of the utility model is shown as follows: Figure 1 As shown, the active balancing circuit for a battery pack includes a battery pack 1 , an input switch array 2 , an output switch array 3 , a DC isolation conversion module 4 , a control module 5 and a gating module 6 .

[0040] The battery pack 1 includes a plurality of unit cells 11 connected in series. The unit cells 11 are batteries that can be charged and discharged independently. The type of the unit cells 11 can be one of a lead-acid battery, a lithium battery, a nickel-metal hydride battery, a nickel-chromium battery, and a supercapacitor. The type of the unit cells 11 is not specifically limited here, as long as the type of the unit cells 11 in the battery pack 1 is kept consistent. The specific number of the unit cells 11 can be selected according to the actual application and the working voltage limit of the circuit.

[0041] The input switch array 2 includes a plurality of input group switches 21, which are switch devices that can control the on and off of the circuit. The number of the input group switches 21 is the same as the number of the unit cells 11 and corresponds one to one, that is, each input group switch 21 is used to control one unit cell 11, and the input group switch 21 is connected in series between the corresponding unit cell 11 and the output end of the DC isolation conversion module 4, that is, each unit cell 11 and the output end of the DC isolation conversion module 4 are connected in series with a corresponding input group switch 21, and the closing of the input group switch 21 can make the corresponding unit cell 11 and the output end of the DC isolation conversion module 4 electrically connected, and the opening of the input group switch 21 can make the corresponding unit cell 11 and the output end of the DC isolation conversion module 4 disconnected.

[0042] The output switch array 3 includes a plurality of output group switches 31, which are switch devices that can control the on and off of the circuit. The number of the output group switches 31 is the same as the number of the unit cells 11 and corresponds one to one, that is, each input group switch 21 is used to control one unit cell 11. The output group switch 31 is connected in series between the corresponding unit cell 11 and the input end of the DC isolation conversion module 4, that is, there is a corresponding output group switch 31 connected in series between each unit cell 11 and the input end of the DC isolation conversion module 4, and the closing of the output group switch 31 can make the corresponding unit cell 11 and the input end of the DC isolation conversion module 4 electrically connected, and the opening of the output group switch 31 can make the corresponding unit cell 11 and the input end of the DC isolation conversion module 4 disconnected.

[0043] The DC isolation conversion module 4 is used to convert the input voltage and isolate the input and output ends of the DC isolation conversion module 4; wherein, the DC isolation conversion module 4 refers to a module that can perform voltage conversion and can isolate its own input and output ends. Since the input end of the DC isolation conversion module 4 is connected to the unit battery 11 through the output group switch 31, when the output group switch 31 is closed, the electric energy of the unit battery 11 corresponding to the output group switch 31 can be output to the DC isolation conversion module 4. When the input group switch 21 is closed, the unit battery 11 corresponding to the input group switch 21 can receive the electric energy output by the DC isolation conversion module 4 for charging. Therefore, the function of the DC isolation conversion module 4 is to connect the unit battery 11 that needs to be discharged and the unit battery 11 that needs to be charged, complete the charge transfer through the DC isolation conversion module 4, and realize the balancing function between the unit batteries 11. The DC isolation conversion module 4 does not require external energy storage equipment, such as capacitors, batteries, transformers, etc., and ensures circuit safety while completing the continuous balanced discharge action, and there will be no short circuit burning and other phenomena.

[0044] Because the discharge unit battery 11 and the charging unit battery 11 are stacked in series, there is a potential difference of 1 to n unit batteries 11 between different unit batteries 11; assuming that the voltage of a unit battery 11 is Vbat, the minimum potential difference between two unit batteries 11 is Vcell, and the maximum potential difference is Vbat*(n-1); therefore, any two unit batteries 11 need to be connected by a DC isolation conversion module 4 in an electrically isolated manner to prevent short circuit burning between the unit batteries 11 and excessive voltage difference from damaging the circuit.

[0045] The input end of the control module 5 is electrically connected to the input end of the gating module 6, and the output end of the gating module 6 is electrically connected to the multiple input group switches 21 and the multiple output group switches 31. The control module 5 is used to output a control signal, and the gating module 6 is used to select one of the multiple input group switches 21 and one of the multiple output group switches 31 based on the control signal. Among them, the control module 5 refers to a functional module for performing logic control. Preferably, the control module 5 includes an MCU microcontroller. The gating module 6 refers to a module that can select one of the input group switches 21 and select one of the output group switches 31.

[0046] When active balancing is required, the output group switch 31 corresponding to the unit battery 11 that needs to be discharged can be selected through the selection module 6, and the input group switch 21 corresponding to the unit battery 11 that needs to be charged can be selected. At this time, the discharged unit battery 11 will be electrically connected to the input end of the DC isolation conversion module 4, and the charged unit battery 11 will be electrically connected to the output end of the DC isolation conversion module 4. When the corresponding input group switch 21 and output group switch 31 are closed, the balanced charge can continuously flow from the high-voltage unit to the low-voltage unit battery 11, that is, the electric energy of a high-voltage unit battery 11 can be used to charge another low-voltage unit battery 11, thereby realizing active balancing. When the corresponding input group switch 21 and output group switch 31 are disconnected, the active balancing can be stopped.

[0047] When an abnormal operation occurs, that is, when the input switch array 2 and the output switch array 3 selected by the input selection circuit 61 and the output selection circuit 62 correspond to the same unit battery 11, the unit battery 11 will produce a self-discharge and self-charge effect, and the unit battery 11 itself and the DC isolation conversion module 4 will not be short-circuited or damaged. It is just an invalid operation. The energy is slightly lost due to the voltage conversion, but it will not cause damage to the system circuit itself. The system circuit is still safe and works normally.

[0048] The above scheme, by setting the input switch array 2, the output switch array 3 and the DC isolation conversion module 4, can connect the unit battery 11 that needs to be discharged and the unit battery 11 that needs to be charged to achieve active balancing. At the same time, during active balancing, the present scheme can select the output group switch 31 corresponding to the unit battery 11 that needs to be discharged and the output group switch 31 corresponding to the unit battery 11 that needs to be charged through the selection module 6. Since the selection module 6 selects one of the output group switch 31 and the input group switch 21, it avoids the situation in the related art where two or more switches are turned on and connected together due to direct control of the closure of multiple switches, causing a short circuit of two or more unit batteries 11, thereby avoiding the risk of combustion and explosion.

[0049] Since this solution is a technical solution in which the unit cell 11 directly discharges or charges the unit cell 11, compared with the prior art method in which the unit cell 11 passes through a transformer to the battery pack 1 and then from the battery pack 1 to the unit cell 11, the time efficiency is doubled at the same power; compared with the two-step balancing method of first charging and then discharging the supercapacitor, the time efficiency is doubled at the same power, so the balancing operation time efficiency of this solution is high and the speed is fast. In addition, this solution realizes the switching of the unit cell 11 through the input switch array 2 and the output switch array 3, and only requires a unidirectional DC isolation conversion module 4. Compared with the method in the related art in which each unit cell 11 requires a transformer, the transformer resource requirements required by the system are greatly reduced, saving a lot of component costs.

[0050] In addition, the balancing of this solution has no restrictions on the working state, and the balancing method has a wide range of application scenarios. It supports balancing of battery pack 1 in any state of idle, charging or discharging, which expands the use scenarios of battery balancing, improves the overall performance of battery pack 1, and extends the service life of the battery. It supports balancing between unit cells 11 in battery pack 1. The same method can be used for balancing between battery packs 1 in a battery stack by selecting different working withstand voltages, rated powers and other parameters. The main difference between balancing battery pack 1 and balancing unit cells 11 is the different working voltages. When balancing battery pack 1, each component and module needs to have higher withstand voltage and power requirements.

[0051] In summary, this solution can achieve high-efficiency discharge and charge balance without prone to short circuit.

[0052] In an optional embodiment of the present utility model, as Figure 1As shown, the gating module 6 includes an input gating circuit 61 and an output gating circuit 62; the output end of the input gating circuit 61 is electrically connected to multiple input group switches 21, and is used to select one of the multiple input group switches 21 based on a control signal; the output end of the output gating circuit 62 is electrically connected to multiple output group switches 31, and is used to select one of the multiple output group switches 31 based on a control signal.

[0053] The input gating circuit 61 refers to a circuit for selectively gating the input group switches 21, which can select a group of input group switches 21 in the input array switch, and control the switch components included in the input group switches 21 to be closed or disconnected at the same time, so that the output end of the DC isolation conversion module 4 is electrically connected or disconnected with the unit battery 11. The output gating circuit 62 refers to a circuit for selectively gating the output group switches 31, which can select a group of output group switches 31 in the output array switch, and control the switch components included in the output group switches 31 to be closed or disconnected at the same time, so that the input end of the DC isolation conversion module 4 is electrically connected or disconnected with the unit battery 11.

[0054] Since there is always only one and only one input group switch 21 and output group switch 31 that are enabled, the only input group switch 21 only electrically connects one unit battery 11 to the output end of the DC isolation conversion module 4, and the only output group switch 31 only electrically connects one unit battery 11 to the input end of the DC isolation conversion module 4, thereby avoiding the absence of input enabling circuit 61 and output enabling circuit 62. The control module 5 directly controls multiple switch devices to close, causing multiple switch devices to be turned on and connected together, causing a short circuit between two or more unit batteries 11, thereby avoiding the risk of combustion and explosion.

[0055] Since the input switch array 2 and the output switch array 3 are enabled and maintained simultaneously without a triggering relationship, the process from the output current of the discharged unit battery 11 to the input current of the charged unit battery 11 is continuous, and no time-sharing switch is required to realize the temporary storage exchange of the external energy storage container, and the balancing efficiency is high.

[0056] Finally, since the input switch array 2 and the output switch array 3 both select to open any unique input group switch 21 and output group switch 31, the charge is continuously discharged from one unit cell 11 to another unit cell 11, and the input switch array 2 and the output switch array 3 select the input group switch 21 and the output group switch 31 of the same unit cell 11 to be closed, there is no risk of short circuit.

[0057] Based on the above embodiment, the input gating circuit 61 and / or the output gating circuit 62 includes a decoder.

[0058] Among them, decoding is the reverse process of encoding. During encoding, each binary code is given a specific meaning, that is, it represents a certain signal or object. The process of "translating" the specific meaning of the code state is called decoding, and the circuit that implements the decoding operation is called a decoder. In other words, a decoder is a circuit that can translate the state of the input binary code into an output signal to represent its original meaning.

[0059] The decoder usually includes multiple selection channels and logic circuits, so the decoder can select a selection channel according to the code output by the control module 5 after logic circuit calculation processing, to select an input group switch 21 or an output group switch 31, and simultaneously open or close the input group switch 21 and the output group switch 31 to achieve electrical connection or disconnection between the DC isolation conversion module 4 and the unit battery 11. When the input group switch 21 and the output group switch 31 are closed, the balanced charge can continuously flow from the high voltage unit to the low voltage unit battery 11, and when the input group switch 21 and the output group switch 31 are disconnected, the balancing stops.

[0060] The decoder usually includes a driving circuit with m-bit coding input and n-bit selection channel output, where n is equal to 2 to the power of m. In this way, the IO pin resources of the control module 5 can be saved. For example, if 16 unit cells 11 require 16 input group switches 21 and 16 output group switches 31, then only 4 IO pins of the control module 5 are needed. At the same time, it can also avoid the control module 5 directly controlling the input group switch 21 and the output group switch 31 through the IO pin, resulting in the simultaneous selection of two input group switches 21 and / or two output group switches 31, thereby causing a short circuit between the two unit cells 11, thereby avoiding the danger of misoperation. Therefore, the present solution has high safety and completely avoids the risk of short circuit. No matter what code the control module 5 outputs to select the input array switch and the output array switch, it will not cause a short circuit between the unit cells 11, thereby avoiding the unit cells 11 from catching fire and exploding, thereby ensuring the safety of the active balancing circuit.

[0061] Since the unit cell 11 generally has a positive electrode and a negative electrode, preferably, Figure 1 As shown, the input group switch 21 includes an input positive switch 211 and an input negative switch 212; the input positive switches 211 of the multiple input group switches 21 are connected in series one by one between the positive pole of the unit battery 11 and the positive output end of the DC isolation conversion module 4, that is, the input positive switch 211 is used to control the connection between the positive pole of the corresponding unit battery 11 and the positive output end of the DC isolation conversion module 4; the input negative switches 212 of the multiple input group switches 21 are connected in series one by one between the negative pole of the unit battery 11 and the negative output end of the DC isolation conversion module 4, that is, the input negative switch 212 is used to control the connection between the negative pole of the corresponding unit battery 11 and the negative output end of the DC isolation conversion module 4.

[0062] Specifically, the input group switches 21 and the unit cells 11 can be numbered, and the input positive switch 211 and the input negative switch 212 of the input group switch 21 are respectively connected to the positive and negative electrodes of the unit cells 11 corresponding to the serial numbers. For example, the input group switches 21 are numbered SI1 to SIn, and the unit cells 11 are numbered BAT1 to BATn, where 1 to n are serial numbers, so the input positive switch 211 of the input group switch 21 numbered SI1 will be electrically connected to the positive electrode of the unit cell 11 numbered BAT1, and the input negative switch 212 of the input group switch 21 numbered SI1 will be electrically connected to the negative electrode of the unit cell 11 numbered BAT1, and so on, the input positive switches 211 and the input negative switches 212 of the multiple input group switches 21 will be connected to the positive and negative electrodes of the multiple unit cells 11 in a one-to-one correspondence. In addition, the ends of all the input group switches 21 away from the unit cells 11 can be aggregated and then connected to the output end of the DC isolation conversion module 4. That is, the ends of the multiple input positive switches 211 away from the unit battery 11 are aggregated and electrically connected to the positive output end of the DC isolation conversion module 4, and the ends of the multiple input negative switches 212 away from the unit battery 11 are aggregated and electrically connected to the negative output end of the DC isolation conversion module 4.

[0063] Since the unit cells 11 are connected in series, the input negative pole switch 212 of two adjacent input group switches 21 of the stacked unit cells 11 is connected together with the input positive pole switch 211 of the next level, that is, one end of the input positive pole switch 211 of an input group switch 21 will be connected to the input negative pole switch 212 of the next input group switch 21, the positive pole of the corresponding unit cell 11 and the negative pole of the unit cell 11 adjacent to the corresponding unit cell 11, that is, the right side of the input positive pole switch 211 of the input group switch 21 numbered SI1 will be connected to the right side of the input negative pole switch 212 of the input group switch 21 numbered SI2, the positive pole of the unit cell 11 numbered BAT1 and the negative pole of the unit cell 11 numbered BAT2, and the other input group switches 21 are connected to the unit cells 11 in a similar manner.

[0064] In an optional embodiment of the present utility model, as Figure 1As shown, the output group switch 31 includes an output positive switch 311 and an output negative switch 312; the output positive switches 311 of the plurality of output group switches 31 are connected in series one by one between the positive pole of the unit battery 11 and the positive input terminal of the DC isolation conversion module 4, that is, the output positive switch 311 is used to control the connection between the positive pole of the corresponding unit battery 11 and the positive input terminal of the DC isolation conversion module 4. The output negative switches 312 of the plurality of output group switches 31 are connected in series one by one between the negative pole of the unit battery 11 and the negative input terminal of the DC isolation conversion module 4, that is, the output negative switch 312 is used to control the connection between the negative pole of the corresponding unit battery 11 and the negative input terminal of the DC isolation conversion module 4.

[0065] Specifically, the output group switches 31 and the unit cells 11 can be numbered, and the output positive switch 311 and the output negative switch 312 of the output group switch 31 are respectively connected to the positive and negative electrodes of the unit cells 11 corresponding to the serial numbers. For example, the output group switches 31 are numbered SO1 to SOn, and the unit cells 11 are numbered BAT1 to BATn, where 1 to n are serial numbers. Therefore, the output positive switch 311 of the output group switch 31 numbered SO1 will be electrically connected to the positive electrode of the unit cell 11 numbered BAT1, and the output negative switch 312 of the output group switch 31 numbered SO1 will be electrically connected to the negative electrode of the unit cell 11 numbered BAT1. Similarly, the output positive switches 311 and the output negative switches 312 of the output group switches 31 will be connected to the positive and negative electrodes of the multiple unit cells 11 in a one-to-one correspondence. In addition, the ends of all the output group switches 31 away from the unit cells 11 can be aggregated and then connected to the input end of the DC isolation conversion module 4. That is, the ends of the multiple output positive switches 311 away from the unit battery 11 are gathered together and electrically connected to the positive input end of the DC isolation conversion module 4, and the ends of the multiple output negative switches 312 away from the unit battery 11 are gathered together and electrically connected to the negative input end of the DC isolation conversion module 4.

[0066] Since the unit cells 11 are connected in series, the output negative pole switch 312 of two adjacent output group switches 31 of the stacked unit cells 11 is located at the upper level and the output positive pole switch 311 of the lower level is connected together, that is, one end of the output positive pole switch 311 of one output group switch 31 will be connected to the input negative pole switch 212 of the next output group switch 31, the positive pole of the corresponding unit cell 11 and the negative pole of the unit cell 11 adjacent to the corresponding unit cell 11, the left end of the output positive pole switch 311 of the output group switch 31 numbered SO1 will be connected to the left end of the output negative pole switch 312 of the output group switch 31 numbered SO2, the positive pole of the unit cell 11 numbered BAT1 and the negative pole of the unit cell 11 numbered BAT2, and the other output group switches 31 are connected to the unit cells 11 in a similar manner.

[0067] In an optional embodiment of the utility model, the input positive switch 211, the input negative switch 212, the output positive switch 311 and the output negative switch 312 include one of a photorelay, a relay, a MOSFET field effect transistor, an IGBT insulated gate bipolar transistor, and a bipolar transistor. Since the photorelay, the relay, the MOSFET field effect transistor, the IGBT insulated gate bipolar transistor, and the bipolar transistor all have a switch function of controlling the on and off of the circuit, they can all be used as one of the input positive switch 211, the input negative switch 212, the output positive switch 311 and the output negative switch 312 to realize the functions of the input switch array 2 and the output switch array 3.

[0068] In this embodiment, photorelays can be used as the input positive switch 211, the input negative switch 212, the output positive switch 311 and the output negative switch 312. Figure 2 As shown, Figure 2 In the example, the photo relay is used as the input positive switch 211 and the input negative switch 212. The photo relay includes a light emitting device 21a and a light receiving device 21b. The light emitting device 21a includes a light emitting diode, and the light receiving device 21b includes two MOSFET tubes connected in series. The light emitting diode is connected in series between the power supply and the input selection circuit 61. The MOSFET tube of the input positive switch 211 is connected in series between the positive electrode of the battery and the positive output terminal of the DC isolation conversion module 4. The MOSFET tube of the input negative switch 212 is connected in series between the negative electrode of the battery and the negative output terminal of the DC isolation conversion module 4. For the case where the photo relay is used as the output positive switch 311 and the output negative switch 312, it is only necessary to replace the input selection circuit 61 in the above text with the output selection circuit 62, replace the positive output terminal of the DC isolation conversion module 4 with the positive input terminal of the DC isolation conversion module 4, and replace the negative output terminal of the DC isolation conversion module 4 with the negative input terminal of the DC isolation conversion module 4. No further description is given again.

[0069] Through the photoelectric isolation function of the photorelay, the control module 5 and the input gating circuit 61 can conveniently control the input switch array 2. This method is very convenient for the control module 5 and the gating module 6 to implement, and there is no need to consider the high voltage problem of the battery cells connected in series, because the control end and the output end of the photorelay have been isolated by the photoelectric signal.

[0070] In other embodiments, a relay may be selected to replace the photorelay. The input control end of the relay is a coil, the output is a spring contact connection, and the input is isolated from the output. The advantages of the relay are that the output impedance is very small, the input and output isolation impedance is high, the contact current and power are large, but the control speed is low compared to the electronic switch, and the service life is short. Therefore, it is suitable for applications where the battery pack 1 has a large capacity and requires high power balancing and low balancing frequency.

[0071] In other embodiments, the input positive switch 211, the input negative switch 212, the output positive switch 311 and the output negative switch 312 can also select different types of transistors such as MOSFET field effect transistors, IGBT insulated gate bipolar transistors, bipolar transistors, etc. to realize the functions of electronic switches and switch arrays. No specific limitation is made here, only examples are given.

[0072] In an optional embodiment of the present utility model, as Figure 1 As shown, the active balancing circuit further includes an analog-to-digital conversion module 7 , an input end of the analog-to-digital conversion module 7 is electrically connected to the plurality of unit batteries 11 , and a communication end of the analog-to-digital conversion module 7 is communicatively connected to a communication end of the control module 5 .

[0073] The analog-to-digital conversion module 7 refers to a module that can convert analog signals into digital signals. Since the analog-to-digital conversion module 7 is electrically connected to multiple unit cells 11, the voltage value of the unit cell 11 can be obtained. Specifically, the analog-to-digital conversion module 7 converts the differential analog voltage into a digital signal through ADC, and the converted value is stored in the analog-to-digital conversion module 7, waiting for the control module 5 to read it through the communication terminal. The control module 5 controls the analog channel of the analog-to-digital conversion module 7 to complete the analog-to-digital conversion of each unit cell 11 in turn, and reads the converted value of each unit cell 11, and obtains the voltage value of the unit cell 11 through calculation.

[0074] On the basis of the above embodiment, the communication end of the analog-to-digital conversion module 7 is connected to the communication end of the control module 5 through one of I2C, SPI, UART serial port and parallel interface. Therefore, the control module 5 can control the switching of the ADC analog channel of the analog-to-digital conversion module 7 by communicating with the analog-to-digital conversion module 7, and complete the ADC analog-to-digital conversion and voltage data collection of each unit battery 11 in turn.

[0075] In an optional embodiment of the present utility model, the DC isolation conversion module 4 includes a boost circuit, and the boost circuit is used to boost the input voltage and then output it.

[0076] Among them, the boost circuit refers to a circuit that can boost the voltage input to the input end. The input voltage range and output voltage value of the boost circuit can be determined according to the actual selection of the switching circuit and different types of unit batteries 11, so as to ensure that the output voltage of the boost circuit after boosting is higher than the voltage value of the unit battery 11 being charged plus the sum of the voltage drop values ​​of each switch and other components in the circuit, so that the output of the boost circuit can charge the unit battery 11; at the same time, ensure that the output voltage is lower than the maximum charging voltage limit of the unit battery 11 plus the sum of the voltage drop values ​​of each switch and other components in the circuit, so that the unit battery 11 does not exceed its maximum protection charging voltage limit when charging, so as to prevent battery damage.

[0077] In an optional embodiment of the present utility model, the DC isolation conversion module 4 includes one of a DC-DC DC isolation converter, a Boost switching regulator topology circuit, a flyback converter topology circuit, and a Cuk converter topology circuit.

[0078] Among them, the DC-DC direct current isolation converter, the Boost switching regulator topology circuit, the flyback converter topology circuit, and the Cuk converter topology circuit all have the function of voltage conversion and can also realize isolation of the input and output ends, so one of the DC-DC direct current isolation converter, the Boost switching regulator topology circuit, the flyback converter topology circuit, and the Cuk converter topology circuit can be selected as the DC isolation conversion module 4.

[0079] In addition, in a specific embodiment, the DC-DC direct current isolation converter, the Boost switching regulator topology circuit, the flyback converter topology circuit, and the Cuk converter topology circuit can be operated in a boost mode. At this time, the DC-DC direct current isolation converter, the Boost switching regulator topology circuit, the flyback converter topology circuit, and the Cuk converter topology circuit are boost circuits that can realize the boost function to ensure that the unit battery 11 can be charged normally.

[0080] In this embodiment, the DC isolation conversion module 4 uses a DC-DC isolation converter. The DC-DC isolation converter adopts a boosting method. The values ​​of the input voltage and the output voltage can be determined according to the actual selection of the switching circuit and different types of unit batteries 11, so as to ensure that the output voltage of the DC-DC isolation converter after boosting is higher than the sum of the voltage value of the charged unit battery 11 plus the voltage drop values ​​of each switch and other components in the circuit, so that the output of the DC-DC isolation converter can charge the unit battery 11; at the same time, ensure that the output voltage is lower than the maximum charging voltage limit of the unit battery 11 plus the sum of the voltage drop values ​​of each switch and other components in the circuit, so that the unit battery 11 does not exceed the maximum protection charging voltage when charging, so as to prevent battery damage.

[0081] Specifically, if we choose the unit cell 11 to be a ternary lithium battery, the maximum charging voltage is 4.2V. The input switch array 2 and the output switch array 3 are implemented by selecting a photorelay (optically coupled LED driving MOSFET field effect tube output), and the input voltage of the DC-DC direct current isolation converter can be selected in the range of 3V to 4.2V, and the output is selected to be 4.2V. For other types of batteries, such as lithium iron phosphate, because the operating voltage range is different from that of ternary lithium, the input voltage of the DC-DC direct current isolation converter can be selected and adjusted according to the actual range.

[0082] When the above method is used for balancing, the charge migration efficiency is high and the loss is small during balancing. Each time the balancing is performed, the unit cell 11 with the highest voltage and the unit cell 11 with the lowest voltage are selected to achieve high charge to compensate low charge, and complete discharge and charging at one time, avoiding the charge cycle migration through the unit cells 11 one by one, or through the intermediate capacitor, or the charge migration of the intermediate battery group twice in the existing technical solution, which greatly improves the efficiency; its efficiency is basically equivalent to the working efficiency of the DC-DC direct current isolation converter, and the industry level of the DC-DC direct current isolation converter is about 88%. It avoids the problem that 1 / N (N is the number of unit cells 11) of the current is offset when the battery group 1 is charged or discharged when the transformer solution is used for balancing. The DC-DC conversion efficiency of 88% is higher than the DC-DC conversion efficiency of 88%×88%=77% of the supercapacitor twice, and at the same time reduces energy waste.

[0083] In an optional embodiment of the present utility model, the current control end of the control module 5 is electrically connected to the PWM control end of the DC isolation conversion module 4, and the control module 5 is used to output a PWM control signal to the PWM control end of the DC isolation conversion module 4 to control the working current of the DC isolation conversion module 4. Among them, by controlling the working current of the DC isolation conversion module 4 through the control module 5, the balanced current can be adjusted to control the time, power and heat dissipation effect of the balance. In addition, the enable control end of the control module 5 is electrically connected to the enable end of the DC isolation conversion module 4, and the enable end of the DC isolation conversion module 4 can be turned off when it is necessary to stop the balance.

[0084] In other embodiments, the DC isolation conversion module 4 may also be selected to have a function that does not require PWM to control the current size, and a DC isolation conversion module 4 with a suitable fixed current may be directly used. The enable control pin of the DC isolation conversion module 4 may also not be used, that is, the voltage conversion work can be performed as soon as it is powered on. The input voltage and output voltage of the DC isolation conversion module 4 can be selected as fixed input and fixed output voltages according to actual requirements, or can be configured by adjustment to match different types of battery voltages.

[0085] In an optional embodiment of the present utility model, as Figure 1As shown, the active balancing circuit includes a power supply module 8, the power input terminal of the power supply module 8 is electrically connected to the positive pole of the battery pack 1, and the power supply terminal of the power supply module 8 is electrically connected to the selection module 6, the analog-to-digital conversion module 7 and the control module 5, and is used to supply power to the selection module 6, the analog-to-digital conversion module 7 and the control module 5, so that the selection module 6, the analog-to-digital conversion module 7 and the control module 5 can work normally.

[0086] The specific balancing method of the present solution is described below with a specific embodiment. The control module 5 controls the analog-to-digital conversion module 7 through the control end to collect the voltage data of each unit cell 11 and read the voltage value of the unit cell 11. By finding the unit cell 11 with the highest voltage and the lowest voltage, the voltage difference between the unit cell 11 with the highest voltage and the lowest voltage is calculated, and it is determined whether the voltage difference is greater than a preset voltage difference threshold. The preset voltage difference threshold is the threshold that the voltage difference will be greater than when starting balancing. If the voltage difference is greater than the preset voltage difference threshold, balancing is started, otherwise balancing is not started.

[0087] In this embodiment, the number n of the unit cells 11 is set to be 8. When balancing is required, the control module 5 outputs a 3-bit code through the IO pin, the code range is from 0 to 7, and the corresponding binary value is 000B-111B. The decoder output of the output selection circuit 62 selects the channel corresponding to the code, and controls one of the output group switches 31 in the output switch array 3. The output group switch 31 is used to control the output of the unit cell 11 with the highest voltage. Similarly, the control module 5 outputs a 3-bit code through another group of IO pins, and the decoder output of the input selection circuit 61 selects the channel corresponding to the code to control one of the input group switches 21 in the input switch array 2. The input group switch 21 is used to control the input of the unit cell 11 with the lowest voltage. At this time, the unit cells 11 with the highest voltage and the lowest voltage have established a current balancing loop through the output switch array 3, the DC isolation conversion module 4, and the input switch array 2.

[0088] When the selected input group switch 21 and output group switch 31 are closed, the unit cell 11 with the highest voltage begins to discharge continuously to the unit cell 11 with the lowest voltage, the voltage of the unit cell 11 with the highest voltage slowly decreases, and the voltage of the unit cell 11 with the lowest voltage slowly increases. When the balancing time exceeds the balancing time setting value, the balancing is stopped, and the collection and calculation of the unit cells 11 are performed again to determine whether the voltage difference between the unit cells 11 with the highest voltage and the lowest voltage is less than the preset voltage difference threshold. If it is less, the balancing is stopped, and the voltage of the unit cells 11 is detected periodically and cyclically, and the unit cells 11 with the highest voltage and the lowest voltage are found, and the voltage difference between the unit cells 11 with the highest voltage and the lowest voltage is calculated, and the next balancing judgment operation is performed; if the voltage difference after balancing is still greater than the preset voltage difference threshold, the balancing of the unit cells 11 with the highest voltage and the lowest voltage in the same group is continued. Repeat the above operation until the condition for the end of balancing is met, and the balancing is ended.

[0089] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0090] The above specific implementations do not constitute a limitation on the protection scope of the present utility model. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. An active balancing circuit for a battery pack, characterized in that: It includes a battery pack, an input switch array, an output switch array, a DC isolation conversion module, a control module and a gating module; The battery pack includes a plurality of unit batteries connected in series; The input switch array includes a plurality of input group switches, the number of the input group switches is the same as the number of the unit batteries and corresponds one to one, and the input group switches are connected in series between the corresponding unit batteries and the output end of the DC isolation conversion module; The output switch array includes a plurality of output group switches, the number of the output group switches is the same as the number of the unit batteries and corresponds one to one, and the output group switches are connected in series between the corresponding unit batteries and the input end of the DC isolation conversion module; The DC isolation conversion module is used to convert the input voltage and isolate the input end and output end of the DC isolation conversion module; The input end of the control module is electrically connected to the input end of the gating module, and the output end of the gating module is electrically connected to the plurality of input group switches and the plurality of output group switches. The control module is used to output a control signal, and the gating module is used to select one of the plurality of input group switches and select one of the plurality of output group switches based on the control signal.

2. The active equalization circuit for a battery pack according to claim 1, characterized in that: The gating module includes an input gating circuit and an output gating circuit; The output end of the input gating circuit is electrically connected to the plurality of input group switches, and is used to select one of the plurality of input group switches based on the control signal; The output end of the output gating circuit is electrically connected to the plurality of output group switches, and is used to select one of the plurality of output group switches based on the control signal.

3. The active equalization circuit for a battery pack according to claim 2, characterized in that: The input gating circuit and / or the output gating circuit comprises a decoder.

4. The active balancing circuit for a battery pack according to any one of claims 1 to 3, characterized in that: The input group switch includes an input positive switch and an input negative switch; the input positive switches of the plurality of input group switches are connected in series one by one between the positive pole of the unit battery and the positive output terminal of the DC isolation conversion module; the input negative switches of the plurality of input group switches are connected in series one by one between the negative pole of the unit battery and the negative output terminal of the DC isolation conversion module; And / or, the output group switch includes an output positive switch and an output negative switch; the output positive switches of the multiple output group switches are connected in series one by one between the positive pole of the unit battery and the positive input terminal of the DC isolation conversion module; the output negative switches of the multiple output group switches are connected in series one by one between the negative pole of the unit battery and the negative input terminal of the DC isolation conversion module.

5. The active balancing circuit for a battery pack according to claim 4, characterized in that: The input positive switch, the input negative switch, the output positive switch and the output negative switch include one of a photorelay, a relay, a MOSFET field effect transistor, an IGBT insulated gate bipolar transistor, and a bipolar transistor.

6. The active balancing circuit for a battery pack according to any one of claims 1 to 3, characterized in that: The active balancing circuit further includes an analog-to-digital conversion module, an input end of the analog-to-digital conversion module is electrically connected to the plurality of unit batteries, and a communication end of the analog-to-digital conversion module is communicatively connected to a communication end of the control module.

7. The active balancing circuit for a battery pack according to claim 6, characterized in that: The communication end of the analog-to-digital conversion module is connected to the communication end of the control module through one of I2C, SPI, UART serial port and parallel interface.

8. The active balancing circuit for a battery pack according to any one of claims 1 to 3, characterized in that: The DC isolation conversion module includes a boost circuit, and the boost circuit is used to boost the input voltage and then output it.

9. The active equalization circuit for a battery pack according to any one of claims 1 to 3, characterized in that: The DC isolation conversion module includes one of a DC-DC DC isolation converter, a Boost switch regulator topology circuit, a flyback converter topology circuit, and a Cuk converter topology circuit.

10. The active balancing circuit for a battery pack according to any one of claims 1 to 3, characterized in that: The current control end of the control module is electrically connected to the PWM control end of the DC isolation conversion module, and the control module is used to output a PWM control signal to the PWM control end of the DC isolation conversion module to control the working current of the DC isolation conversion module.

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