Flying capacitor topology active equalization circuit and method using charge pump

Abstract

The invention discloses a flying capacitor topology active equalization circuit and method using a charge pump, in the circuit, a bidirectional input and output selection module is electrically connected with a battery module, a first switch module and a second switch module, and a boost module is electrically connected with the first switch module and a charge storage and release module. The charge storage and release module is electrically connected with the second switch module; the bidirectional input / output selection circuit is used for selecting at least one battery module needing charge equalization, and the battery module needing charge equalization is a battery module providing charge or needing charge input; the boosting module is used for boosting the voltage transmitted by at least one battery module providing charges by k times and then transmitting the voltage to the charge storage and release module for storage; the charge storage and release module is used for transmitting charges stored in the charge storage and release module to at least one battery module needing charge input. According to the invention, the cost is lower, the size is smaller, the weight is lighter, the structure is simpler, the control strategy is simple, and the balancing efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic circuits, and particularly relates to a flying capacitor topology active balancing circuit and method using a charge pump. BACKGROUND

[0002] Through battery balancing, each cell in the battery pack is effectively monitored and maintained in a healthy state of charge. This not only increases the number of battery cycles, but also provides additional protection against damage to the battery cells due to overcharging / deep discharging.

[0003] Passive balancing dissipates excess charge through a bleeder resistor, allowing all battery cells to have roughly equivalent SoC, but it does not extend the system runtime. Balancing that dissipates energy using resistors is generally referred to as passive balancing. Active balancing is a more complex balancing technique that increases the total available charge in the battery pack by redistributing charge within the cells during charging and discharging cycles, thus extending the system runtime. Compared with passive balancing, active balancing can shorten the charging time and reduce the heat generated during balancing. Balancing that is achieved through capacity transfer is generally referred to as active balancing.

[0004] Traditional passive balancing usually uses a resistor bypass to achieve balancing by dissipating the energy of the battery with a higher voltage in the form of heat. This method is simple and low in cost, but the energy utilization efficiency is extremely low. For high-energy-density battery packs (such as electric vehicles and energy storage systems), this energy waste not only reduces the overall efficiency of the system, but also generates unnecessary heat at the resistor, increasing the burden of thermal management. The advantage of active balancing lies in its energy transfer rather than energy dissipation. It aims to "move" energy from high-SOC monomers to low-SOC monomers, or to the entire battery pack (or from the battery pack), thereby significantly reducing energy loss and improving the overall efficiency of the system.

[0005] Currently, existing active balancing schemes based on transformers / inductors and DC-DC converters have high efficiency, but usually have high cost (i.e., a large number of transformers, inductors, and other magnetic components, a large number of power switches, and complex control circuits are required), complex control strategies (e.g., precise control of multi-path switch timing, avoidance of magnetic saturation, and handling of electromagnetic interference EMI), difficult design and debugging, large size / weight (i.e., magnetic components are usually large in size and heavy in weight, which is not conducive to system miniaturization and lightweight, especially in space-limited applications such as consumer electronics and drones), and other shortcomings. The existing active balancing method based on the capacitor topology has a low balancing speed and can only balance the charge to a single cell, but cannot balance the charge to multiple cells. SUMMARY

[0006] In order to solve the above problems existing in the prior art, the application provides a flying capacitor topology active balancing circuit and method using a charge pump. The technical problem to be solved by the application is achieved by the following technical scheme: The application provides a flying capacitor topology active balancing circuit using a charge pump, comprising: A bidirectional input-output selection module, a voltage boosting module, a charge storage and release module, a first switch module, a second switch module and N battery modules connected in series, wherein N is a positive integer greater than or equal to 2. The bidirectional input-output selection module is electrically connected with each battery module, the first switch module and the second switch module respectively, the voltage boosting module is electrically connected with the first switch module and the charge storage and release module respectively, and the charge storage and release module is electrically connected with the second switch module. The bidirectional input-output selection circuit is used for selecting at least one battery module that needs to be balanced in charge, wherein the at least one battery module that needs to be balanced in charge is at least one battery module that provides charge or at least one battery module that needs to input charge. The voltage boosting module is used for boosting the voltage transmitted by the at least one battery module that provides charge by k times and then transmitting the voltage to the charge storage and release module, wherein k is a positive integer greater than 1. The charge storage and release module is used for storing the charge transmitted by the voltage boosting module or transmitting the charge stored by itself to the at least one battery module that needs to input charge.

[0007] The application further provides a flying capacitor topology active balancing method using a charge pump, which is realized by the flying capacitor topology active balancing circuit using a charge pump, and the method comprises the following steps: In the charging phase, the battery module with the highest charge among the N battery modules connected in series is selected as a battery module that provides charge, and the voltage provided by the battery module that provides charge is boosted by k times and then stored. In the discharging phase, a target battery module among the N battery modules connected in series is selected as a battery module that needs to input charge, and the target battery module is at least one battery module with the lowest charge among the N battery modules connected in series, and charge is input to the target battery module.

[0008] Compared with the prior art, the application has the following beneficial effects: The application uses a capacitor topology scheme, uses a charge storage and release module as an energy transfer medium, connects the bidirectional input and output selection module with different single batteries, and uses a boost module to generate a higher voltage difference when a high SOC single battery charges the charge storage and release module, so that the charge can be quickly transferred, thereby improving the balancing speed. In addition, through the design of the boost module, the active balancing is no longer limited by the highest voltage of the capacitor, so that multiple single batteries can be balanced at one time, thereby improving the balancing efficiency. In addition, compared with the magnetic element scheme, the capacitor generally has lower cost, smaller size, lighter weight, simpler structure, and simple control strategy.

[0009] The application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a structural schematic diagram of an active equalization circuit using a flying capacitor topology of a charge pump provided by an embodiment of the application; Figure 2 is another structural schematic diagram of an active equalization circuit using a flying capacitor topology of a charge pump provided by an embodiment of the application; Figure 3 is a charging path schematic diagram of a flying capacitor provided by an embodiment of the application; Figure 4 is a discharging path schematic diagram of a flying capacitor provided by an embodiment of the application; Figure 5 is another discharging path schematic diagram of a flying capacitor provided by an embodiment of the application. DETAILED DESCRIPTION

[0011] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0012] The application provides an active equalization circuit using a flying capacitor topology of a charge pump, as shown in Figure 1As shown, the circuit comprises: a bidirectional input-output selection module, a voltage boosting module, a charge storage and release module, a first switch module, a second switch module, and N battery modules connected in series, wherein N is a positive integer greater than or equal to 2. The bidirectional input-output selection module is electrically connected with each battery module, the first switch module, and the second switch module respectively, the voltage boosting module is electrically connected with the first switch module and the charge storage and release module respectively, and the charge storage and release module is electrically connected with the second switch module. The bidirectional input-output selection circuit is used for selecting at least one battery module that needs to be charge balanced, wherein the at least one battery module that needs to be charge balanced is at least one battery module that provides charge or at least one battery module that needs to input charge; the voltage boosting module is used for increasing the voltage transmitted by the at least one battery module that provides charge by k times and then transmitting the voltage to the charge storage and release module, wherein k is a positive integer greater than 1; and the charge storage and release module is used for storing the charge transmitted by the voltage boosting module or transmitting the stored charge to the at least one battery module that needs to input charge.

[0013] In the present application, the positive and negative electrodes of each battery module are electrically connected with one input / output end of the bidirectional input-output selection module respectively, the first and second ends of the first switch module are electrically connected with one output end of the bidirectional input-output selection module respectively, and the third and fourth ends of the first switch module are electrically connected with one input end of the voltage boosting module respectively. The first and second ends of the second switch module are electrically connected with one input end of the bidirectional input-output selection module respectively, and the third and fourth ends of the second switch module are electrically connected with one output end of the charge storage and release module respectively; and the control end of the bidirectional input-output selection module is used for inputting a selection control signal, wherein the selection control signal is used for controlling the gating of the input end and the output end of the bidirectional input-output selection module.

[0014] Specifically, when the bidirectional input-output selection module gates the two input ends connected with the positive and negative electrodes of the battery module with the highest charge among the N battery modules connected in series, the first switch module is in a conductive state, and the second switch module is in a closed state, the circuit is in a charging stage, and the voltage boosting module increases the voltage transmitted by the battery module with the highest charge by k times and then transmits the voltage to the charge storage and release module for storage. When the bidirectional input-output selection module gates the input ends connected with the positive and negative electrodes of at least one battery module with the lowest charge among the N battery modules connected in series, the first switch module is in a closed state, and the second switch module is in a conductive state, the circuit is in a discharging stage, and the charge storage and release module transmits the balanced charge stored therein to the at least one battery module with the lowest charge.

[0015] Exemplarily, the first switch module is composed of switch SW1 and switch SW2, and the second switch module is composed of switch SW3 and switch SW4. One end of switch SW1 is the first end of the first switch module, the other end of switch SW1 is the third end of the first switch module, one end of switch SW2 is the second end of the first switch module, the other end of switch SW2 is the fourth end of the first switch module, and the control ends of switch SW1 and switch SW2 are both used for connecting the first switch control signal, which is used for controlling the conduction and closing of switch SW1 and switch SW2. One end of switch SW3 is the first end of the second switch module, the other end of switch SW3 is the third end of the second switch module, one end of switch SW4 is the second end of the second switch module, the other end of switch SW4 is the fourth end of the second switch module, and the control ends of switch SW3 and switch SW4 are both used for connecting the second switch control signal, which is used for controlling the conduction and closing of switch SW3 and switch SW4.

[0016] Exemplarily, the bidirectional input and output selection circuit can adopt a bidirectional multipath selection switch module. It should be noted that the bidirectional input and output selection circuit can also adopt other circuit modules with equivalent functions, and the present application does not limit this.

[0017] Exemplarily, the boost module is a charge pump module. It should be noted that the boost module can be a single-stage charge pump, or a two-stage or more cascade-connected charge pump. The specific value of k is determined according to the type of the selected charge pump and the number of cascade-connected charge pumps, and the present application does not limit this. In addition, the boost module can also adopt other circuit modules with equivalent functions, and the present application does not limit this.

[0018] Exemplarily, the charge storage and release module is a flying capacitor. It should be noted that the charge storage and release module can be one flying capacitor, or two or more flying capacitors connected with each other. The specific value of k is determined according to the type of the selected charge pump and the number of cascade-connected charge pumps, and the present application does not limit this.

[0019] Exemplarily, Figure 2 is a circuit structure schematic diagram of the flying capacitor topology active equalization circuit provided by the present application using a charge pump. As shown in Figure 2 BT1~BT5 are five battery cells, SW1~SW4 are four switches, FlyCap represents a flying capacitor, CP module represents a charge pump module, and MUX module represents a bidirectional multipath selection switch module, the input and output of which can be interchanged. The following exemplarily illustrates the working principle of the active equalization circuit of the present application by using the strategy of charging the flying capacitor from a single highest SOC battery cell and then transferring the charge to the lowest SOC battery cell.

[0020] In the charging phase of the flying capacitor, the highest charged single cell in BT1~BT5 is selected by the MUX module, for example, BT4 is selected to provide equalization charge, its positive and negative electrodes are taken as the input of the MUX module, and the two outputs of the MUX module are selected to be connected to one end of the left side of switches SW1 and SW2 respectively, when the switches SW1 and SW2 are closed, and the switches SW3 and SW4 are opened, thereby the voltage V H The input of the incoming charge pump module is double-ended, and after being pumped by the charge pump module, k times V H The flying capacitor is charged. The charging example is shown in FIG. 1, wherein, Figure 3 The red line in FIG. 1 is the charging path. Figure 3

[0021] After the end of the charging process, the flying capacitor voltage is kV H At this time, the switches SW1 and SW2 are opened, the input of the MUX module is selected to be connected to one end of the left side of the switches SW3 and SW4, and the output port of the MUX module is selected to be the single cell with the worst state of charge in the battery pack, for example, BT3, and the voltage kV H stored in the flying capacitor is used to charge this battery single cell, so that the goal of equalizing the high SOC single cell charge to the low SOC single cell is achieved. The discharging example is shown in FIG. 2, wherein, Figure 4 The green line in FIG. 2 is the capacitor discharging path. The present application can improve the equalization speed by using the charge pump module to increase the voltage difference between the single cell and the flying capacitor during charge equalization. Figure 4

[0022] In addition, after the end of the charging process, the flying capacitor voltage is kV H At this time, the switches SW1 and SW2 are opened, the input of the MUX module is selected to be connected to one end of the left side of the switches SW3 and SW4, and the output port of the MUX module is selected to be the two or more single cells with the worst state of charge in the battery pack, for example, BT2 and BT3, and the voltage kV H stored in the flying capacitor is used to charge these two battery single cells simultaneously, so that the goal of simultaneously equalizing the high SOC single cell charge to multiple low SOC single cells is achieved. The discharging example is shown in FIG. 3, wherein, Figure 5 The green line in FIG. 3 is the capacitor discharging path. The structure proposed in the present application has a charge pump module, which can pump up the voltage of the high SOC single cell to 2 times or even higher and store it in the flying capacitor, so that the capacitor can simultaneously perform charge equalization for multiple low SOC single cells. Compared with the case where only one single cell voltage is stored in the flying capacitor, so that it is impossible to achieve reasonable equalization for two or more single cells, the equalization efficiency is greatly improved. Figure 5

[0023] ​​​The application also provides an active equalization method of the flying capacitor topology using the charge pump, which is realized by the active equalization circuit of the flying capacitor topology using the charge pump. S101, in the charging phase, selecting the battery module with the highest charge among the N battery modules connected in series as a battery module for providing charge, and storing the voltage provided by the battery module for providing charge after being raised by k times.

[0024] S102, in the discharging phase, selecting a target battery module among the N battery modules connected in series as a battery module needing to input charge, and inputting charge to the target battery module, wherein the target battery module is at least one battery module with the lowest charge among the N battery modules connected in series.

[0025] It should be noted that the terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0026] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present description.

[0027] In the description, the word "comprising" does not exclude other components or steps, and "one" or "a" does not exclude a plurality. Some measures are described in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0028] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the scope of protection of the present application.

Claims

1. An active balancing circuit using a charge pump in a flying capacitor topology, characterized in that, include: The system includes a bidirectional input / output selection module, a boost module, a charge storage and release module, a first switch module, a second switch module, and N battery modules connected in series, where N is a positive integer greater than or equal to 2. The bidirectional input / output selection module is electrically connected to each battery module, the first switch module, and the second switch module, respectively. The boost module is electrically connected to the first switch module and the charge storage and release module, respectively. The charge storage and release module is also electrically connected to the second switch module. The bidirectional input / output selection circuit is used to select at least one battery module that needs to be charged, wherein the at least one battery module that needs to be charged is either a battery module that provides charge or a battery module that needs to input charge. The boost module is used to increase the voltage input from at least one battery module that provides charge by a factor of k before inputting it to the charge storage and release module, where k is a positive integer greater than 1. The charge storage and release module is used to store the charge transmitted from the boost module, or to transfer the charge stored therein to at least one battery module that needs to input charge.

2. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 1, characterized in that, The positive and negative terminals of each battery module are electrically connected to one input / output terminal of the bidirectional input / output selection module, the first and second terminals of the first switch module are electrically connected to one output terminal of the bidirectional input / output selection module, and the third and fourth terminals of the first switch module are electrically connected to one input terminal of the boost module.

3. The active balancing circuit using a charge pump with a fly-through capacitor topology according to claim 2, characterized in that, The first and second terminals of the second switch module are electrically connected to one input terminal of the bidirectional input / output selection module, respectively, and the third and fourth terminals of the second switch module are electrically connected to one output terminal of the charge storage and release module, respectively. The control terminal of the bidirectional input / output selection module is used to receive a selection control signal, wherein the selection control signal is used to control the selection of the input and output terminals of the bidirectional input / output selection module.

4. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 2, characterized in that, The first switch module includes a switch SW1 and a switch SW2. One end of the switch SW1 serves as the first end of the first switch module, and the other end of the switch SW1 serves as the third end of the first switch module. One end of the switch SW2 serves as the second end of the first switch module, and the other end of the switch SW2 serves as the fourth end of the first switch module. Furthermore, the control terminals of both the switch SW1 and the switch SW2 are used to receive a first switch control signal, which is used to control the on and off states of the switch SW1 and the switch SW2.

5. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 3, characterized in that, The second switch module includes switch SW3 and switch SW4. One end of switch SW3 serves as the first end of the second switch module, and the other end of switch SW3 serves as the third end of the second switch module. One end of switch SW4 serves as the second end of the second switch module, and the other end of switch SW4 serves as the fourth end of the second switch module. The control terminals of both switches SW3 and SW4 are used to receive a second switch control signal, which is used to control the on and off states of switches SW3 and SW4.

6. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 1, characterized in that, The boost module is a charge pump module.

7. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 1, characterized in that, The charge storage and release module is a Fit capacitor.

8. The active balancing circuit using a charge pump with a fly-through capacitor topology according to claim 3, characterized in that, When the bidirectional input / output selection module selects the two input terminals connected to the positive and negative terminals of the battery module with the highest charge among the N battery modules connected in series, and the first switch module is in the on state and the second switch module is in the off state, the circuit is in the charging stage. The boost module increases the voltage input from the battery module with the highest charge by k times and then inputs it to the charge storage and release module for storage.

9. The active balancing circuit using a charge pump with a flying capacitor topology according to claim 3, characterized in that, When the bidirectional input / output selection module selects the input terminal connected to the positive and negative terminals of at least one of the N battery modules connected in series with the lowest charge, the first switch module is in the off state and the second switch module is in the on state, the circuit is in the discharge stage, and the charge storage and release module transfers the balanced charge stored therein to the at least one battery module with the lowest charge.

10. A method for active balancing of a flying capacitor topology using a charge pump, characterized in that, The active balancing circuit using a charge pump with a fly-through capacitor topology, as described in any one of claims 1 to 9, comprises the following methods: During the charging phase, the battery module with the highest charge among the N battery modules connected in series is selected as the battery module that provides charge, and the voltage provided by the battery module that provides charge is increased by k times before storage; During the discharge phase, a target battery module is selected from the N battery modules connected in series as the battery module that needs to be charged, and a charge is input to the target battery module. The target battery module is at least one battery module with the lowest charge among the N battery modules connected in series.

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