Battery active equalization circuit and active equalization battery

Abstract

The utility model belongs to the technical field of battery management, and discloses a battery active equalization circuit and an active equalization battery, comprising a first transformer L1, a second transformer L2, a first switch tube Q1, a second switch tube Q2, a cell switching selection analog switch U1, a first isolation capacitor C3 and a second isolation capacitor C4. Electric energy flowing between the high-voltage battery cell and the low-voltage battery cell is achieved through the first transformer L1, control over the electric energy flowing between the high-voltage battery cell and the low-voltage battery cell is achieved through the first switch tube Q1 and the second switch tube Q2, electric energy can be transmitted to the low-voltage battery cell side from the high-voltage battery cell side through the bidirectional working principle, the difference between the battery cells is reduced, and the reliability of the device is improved. And finally, voltage balance among the battery cells in the battery is realized, so that the overall performance and safety of the battery pack are improved, and the service life of the battery pack is prolonged. A magnetic isolation circuit is formed by arranging a second transformer L2, a first isolation capacitor C3 and a second isolation capacitor C4. The balance circuit is simple in design, low in cost and high in balance speed.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery management, and relates to a battery active balancing circuit and an active balancing battery. Background Art

[0002] In battery packs, voltage imbalances between cells are inevitable. Even if cell consistency is strictly controlled during production, variations between cells will gradually become apparent with increasing charge and discharge cycles and changes in operating environments. Without effective balancing measures, these variations will continue to increase, resulting in reduced battery pack capacity utilization and even dangerous situations such as overcharging or over-discharging. Therefore, voltage balancing technology is essential to improve the overall performance and safety of battery packs. Cell voltage balancing technologies can be categorized into two main types: passive balancing and active balancing.

[0003] The basic process of passive balancing is as follows: By connecting discharge resistors in parallel with the battery pack, the voltage of the higher-voltage cells is reduced to the same level as the lower-voltage cells. This method is simple and easy to implement, but it is inefficient and has low energy utilization. Most of the electrical energy is dissipated as heat, which does not effectively extend the battery pack's service life.

[0004] The basic process of active balancing is as follows: energy is transferred between cells, transferring excess energy from higher-voltage cells to lower-voltage cells to achieve equalization. This method effectively improves energy utilization, reduces unnecessary energy waste, and extends the life of the battery pack. However, existing active balancing circuits are often complex and costly, and their balancing speed is slow when the number of cells is large. Utility Model Content

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a battery active balancing circuit and an active balancing battery.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a battery active balancing circuit, including a first transformer L1, a second transformer L2, a first switch tube Q1, a second switch tube Q2, a cell switching selection analog switch U1, a first isolation capacitor C3 and a second isolation capacitor C4; one end of the primary side of the first transformer L1 is used to connect to the positive end of the high-voltage cell side, the other end of the primary side is connected to the drain of the first switch tube Q1, one end of the secondary side is connected to one end of the cell switching selection analog switch U1, the other end of the secondary side is connected to the drain of the second switch tube Q2, and the other end of the cell switching selection analog switch U1 is used to connect to the low Voltage cell side; one end of the primary side of the second transformer L2 is connected to one end of the first isolation capacitor C3, and the other end of the primary side is connected to the secondary ground plane GND2; one end of the secondary side is connected to the gate of the second switch tube Q2 through the second isolation capacitor C4, and the other end of the secondary side is connected to the secondary ground plane GND2; a primary winding switch tube control terminal P-GATE is provided on the gate of the first switch tube Q1, and a secondary winding switch tube control terminal S-GATE is provided on the other end of the first isolation capacitor C3; the source of the first switch tube Q1 is grounded, and the source of the second switch tube Q2 is connected to the secondary ground plane GND2.

[0008] Optionally, the battery cell switching selection analog switch U1 includes several switch units; the switch unit includes a first switch group and a second switch group; one end of the first switch group is connected to one end of the secondary side of the first transformer L1, and one end of the second switch group is connected to the secondary side ground plane GND2, and the other end of the first switch group and the other end of the second switch group are both used to connect the connection lines of two adjacent battery cells set on the low-voltage battery cell side.

[0009] Optionally, it also includes a voltage-stabilizing capacitor C2; the battery cell switching selection analog switch U1 also includes a third switch group; one end of the voltage-stabilizing capacitor C2 is connected to one end of the secondary side of the first transformer L1, and the other end is connected to one end of the third switch group, and the other end of the third switch group is used to connect to the negative end of the low-voltage battery cell side.

[0010] Optionally, the first switch group, the second switch group and the third switch group each include two MOS transistors connected back to back.

[0011] Optionally, it also includes a duty cycle adjustment circuit; the duty cycle adjustment circuit includes a first resistor R1, a first operational amplifier OPA1, a second resistor R2, a second operational amplifier OPA2, an OR gate U2 and a PI regulator; one end of the first resistor R1 is connected to the source of the first switch tube Q1 and the positive input terminal of the first operational amplifier OPA1, and the other end is connected to the negative input terminal of the first operational amplifier OPA1 and the secondary ground plane GND2; one end of the second resistor R2 is connected to the source of the second switch tube Q2 and the negative input terminal of the second operational amplifier OPA2, and the other end is connected to the positive input terminal of the second operational amplifier OPA2 and the secondary ground plane GND2; the OR gate U2 One input end is connected to the output end of the first operational amplifier OPA1, the second input end is connected to the output end of the second operational amplifier OPA2, the output end is connected to the first input end of the PI regulator, the second input end of the PI regulator is used to input the theoretical output voltage of the secondary side of the first transformer L1, and the output end is connected to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE; the PI regulator is used to generate a primary winding switch tube control signal and a secondary winding switch tube control signal according to the output signal of the OR gate U2, and send them to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE respectively.

[0012] Optionally, the primary winding switch tube control signal and the secondary winding switch tube control signal are both PWM signals.

[0013] Optionally, the pulses of the primary winding switch tube control signal and the secondary winding switch tube control signal are complementary.

[0014] Optionally, a filter capacitor C1 is further included; one end of the filter capacitor C1 is connected to one end of the primary side of the first transformer L1, and the other end is used to connect to the negative end of the high-voltage battery cell.

[0015] Optionally, a comparator OPA3 is further included; the negative input end of the comparator OPA3 is connected to one end of the secondary side of the first transformer L1, the positive input end is provided with a reference voltage terminal REF for inputting a reference voltage signal, and the output end is provided with an undervoltage detection terminal ULVO.

[0016] In a second aspect, the present invention provides an active balancing battery, wherein the active balancing battery is provided with the above-mentioned active balancing circuit.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This utility model's active battery balancing circuit achieves electrical energy flow between high-voltage and low-voltage cells by providing a first transformer L1. This energy flow is controlled by first and second switching tubes Q1 and Q2. Through its bidirectional operating principle, it can transfer electrical energy from the high-voltage cell side to the low-voltage cell side, reducing voltage differences between the cells and ultimately achieving voltage balance between the cells within the battery, thereby improving the overall performance and safety of the battery pack and extending its service life. Furthermore, because the primary and secondary circuits of the transformer in a high-voltage battery require isolation, a magnetic isolation circuit is formed by providing a second transformer L2, a first isolation capacitor C3, and a second isolation capacitor C4. This circuit transmits the secondary gate drive signal received by the secondary winding switch tube control terminal S-GATE to the gate of the second switching tube Q2 to drive the second switching tube Q2. This utility model features a simple design, low cost, and rapid balancing speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a topological diagram of the battery active balancing circuit in use state of the present utility model. DETAILED DESCRIPTION

[0020] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0022] The present invention is described in further detail below with reference to the accompanying drawings:

[0023] See also Figure 1In one embodiment of the present invention, a battery active balancing circuit is provided, including a first transformer L1, a second transformer L2, a first switch tube Q1, a second switch tube Q2, a cell switching selection analog switch U1, a first isolation capacitor C3, and a second isolation capacitor C4.

[0024] Among them, one end of the primary side of the first transformer L1 is used to connect to the positive terminal of the high-voltage battery cell side, the other end of the primary side is connected to the drain of the first switch tube Q1, one end of the secondary side is connected to one end of the battery cell switching selection analog switch U1, and the other end of the secondary side is connected to the drain of the second switch tube Q2. The other end of the battery cell switching selection analog switch U1 is used to connect to the low-voltage battery cell side; one end of the primary side of the second transformer L2 is connected to one end of the first isolation capacitor C3, and the other end of the primary side is connected to the secondary ground plane GND2; one end of the secondary side is connected to the gate of the second switch tube Q2 through the second isolation capacitor C4, and the other end of the secondary side is connected to the secondary ground plane GND2; a primary winding switch tube control terminal P-GATE is provided on the gate of the first switch tube Q1, and a secondary winding switch tube control terminal S-GATE is provided on the other end of the first isolation capacitor C3; the source of the first switch tube Q1 is grounded, and the source of the second switch tube Q2 is connected to the secondary ground plane GND2.

[0025] This utility model's active battery balancing circuit achieves electrical energy flow between high-voltage and low-voltage cells by providing a first transformer L1. This energy flow is controlled by first and second switching tubes Q1 and Q2. Through its bidirectional operating principle, it can transfer electrical energy from the high-voltage cell side to the low-voltage cell side, reducing voltage differences between the cells and ultimately achieving voltage balance between the cells within the battery, thereby improving the overall performance and safety of the battery pack and extending its service life. Furthermore, because the primary and secondary circuits of the transformer in a high-voltage battery require isolation, a magnetic isolation circuit is formed by providing a second transformer L2, a first isolation capacitor C3, and a second isolation capacitor C4. This circuit transmits the secondary gate drive signal received by the secondary winding switch tube control terminal S-GATE to the gate of the second switching tube Q2 to drive the second switching tube Q2. This utility model features a simple design, low cost, and rapid balancing speed.

[0026] In one possible embodiment, the cell switching selection analog switch U1 includes a plurality of switch units; the switch unit includes a first switch group and a second switch group; one end of the first switch group is connected to one end of the secondary side of the first transformer L1, and one end of the second switch group is connected to the secondary side ground plane GND2, and the other end of the first switch group and the other end of the second switch group are both used to connect the connection lines of two adjacent cells set on the low-voltage cell side.

[0027] Specifically, the control terminal MUX1-16 is set on the cell switching selection analog switch U1. By controlling these switch units through the control terminal MUX1-16, it is possible to efficiently select and connect to a specific low-voltage cell side, thereby optimizing the power transfer path and reducing energy loss.

[0028] In a possible implementation, it further includes a voltage-stabilizing capacitor C2; the battery cell switching selection analog switch U1 also includes a third switch group; one end of the voltage-stabilizing capacitor C2 is connected to one end of the secondary side of the first transformer L1, and the other end is connected to one end of the third switch group, and the other end of the third switch group is used to connect to the negative end of the low-voltage battery cell side.

[0029] Specifically, the voltage stabilizing capacitor C2 is set as the output voltage stabilizing capacitor of the secondary winding of the first transformer L1, which stabilizes the output voltage of the secondary winding of the first transformer L1 and reduces the influence of voltage fluctuation on the battery balancing process.

[0030] In a possible implementation manner, each of the first switch group, the second switch group, and the third switch group includes two MOS transistors connected back to back.

[0031] Specifically, each battery cell controls the switch through back-to-back MOS tubes to ensure efficient energy transfer.

[0032] In one possible implementation, the system further includes a duty cycle adjustment circuit; the duty cycle adjustment circuit includes a first resistor R1, a first operational amplifier OPA1, a second resistor R2, a second operational amplifier OPA2, an OR gate U2, and a PI regulator; one end of the first resistor R1 is connected to the source of the first switch tube Q1 and the positive input terminal of the first operational amplifier OPA1, and the other end is connected to the negative input terminal of the first operational amplifier OPA1 and the secondary ground plane GND2; one end of the second resistor R2 is connected to the source of the second switch tube Q2 and the negative input terminal of the second operational amplifier OPA2, and the other end is connected to the positive input terminal of the second operational amplifier OPA2 and the secondary ground plane GND2; or The first input end of the gate U2 is connected to the output end of the first operational amplifier OPA1, the second input end is connected to the output end of the second operational amplifier OPA2, the output end is connected to the first input end of the PI regulator, the second input end of the PI regulator is used to input the theoretical output voltage of the secondary side of the first transformer L1, and the output end is connected to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE; the PI regulator is used to generate a primary winding switch tube control signal and a secondary winding switch tube control signal according to the output signal of the OR gate U2, and send them to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE respectively.

[0033] Optionally, the primary winding switch tube control signal and the secondary winding switch tube control signal are both PWM signals, and the pulses of the primary winding switch tube control signal and the secondary winding switch tube control signal are complementary.

[0034] Specifically, to ensure that there is no short circuit in the primary voltage input and the first switch tube Q1 fails, a first resistor R1 is added to the primary power supply circuit. When current flows through the first resistor R1, a voltage is generated. The first operational amplifier OPA1 is used to form a voltage monitoring circuit. When the voltage is higher than the set threshold, it is determined that the primary circuit is overcurrent. Similarly, to avoid overcurrent in the secondary circuit, a second resistor R2 is added to the secondary power supply circuit to transmit the voltage signal to the second operational amplifier OPA2. The signals of the first operational amplifier OPA1 and the second operational amplifier OPA2 are sent to the OR gate U2 together. If there is abnormal current, the OR gate U2 will output a high level to prompt, and can stop outputting the gate drive signals of the first switch tube Q1 and the second switch tube Q2 according to the situation.

[0035] At the same time, the battery cell requires cross-current constant voltage charging. To achieve a stable voltage output, voltage closed-loop control can be used. By detecting the output voltage in real time and comparing it with the given output voltage, the error between the two values ​​is input into the PI regulator. The PI proportional integral calculation within the PI regulator determines the duty cycle of the switch Q1. Furthermore, through PWM control, the pulse signals for the first and second switches Q1 and Q2 are generated, i.e., the primary and secondary winding switch control signals.

[0036] In a balanced system, both the input and output voltages are voltage sources with a very small, essentially fixed voltage range. The primary control objective is the transformer's output current. Given a constant transformation ratio (N1:N2) between the first transformer L1 and the second transformer L2, and constant input and output voltages, the duty cycle of the switch is uniquely determined. With a uniquely determined duty cycle, the output current has a unique relationship with the transformer current. Therefore, in a bidirectional DC-DC converter, the output current of the circuit can also be controlled by controlling the transformer current. The current can be obtained by detecting the voltage across the second resistor R2, while simultaneously detecting the secondary output voltage to form voltage and current feedback to maintain a constant voltage and current output.

[0037] In a possible implementation, a filter capacitor C1 is further included; one end of the filter capacitor C1 is connected to one end of the primary side of the first transformer L1 , and the other end is used to connect to the negative end of the high-voltage battery cell.

[0038] Specifically, setting the filter capacitor C1 as the primary input filter capacitor of the first transformer L1 significantly reduces the high-frequency noise and harmonic interference when the high-voltage battery core transmits electric energy to the first transformer L1, effectively purifies the input current, and ensures the smoothness and efficiency of electric energy transmission.

[0039] In a possible implementation, a comparator OPA3 is further included; the negative input terminal of the comparator OPA3 is connected to one end of the secondary side of the first transformer L1, the positive input terminal is provided with a reference voltage terminal for inputting a reference voltage signal, and the output terminal is provided with an undervoltage detection terminal.

[0040] Specifically, considering that there may be an undervoltage on the secondary side of the first transformer L1, the comparator OPA3 is used to detect the output voltage of the secondary side of the first transformer L1 to perform undervoltage detection.

[0041] The working process and principle of this utility model are as follows:

[0042] The first switch Q1 serves as the primary switch, and the second switch Q2 serves as the secondary switch. During operation, the circuit controls the switches according to the direction of energy flow. When energy flows from the input to the output, the first switch Q1 is controlled to switch at high frequency, while the second switch Q2 remains in an uncontrolled state. The body diode of the second switch Q2 rectifies during the off period of the second switch Q2. Similarly, when energy flows back from the output to the input, the second switch Q2 is controlled to switch at high frequency, while the first switch Q1 remains in an uncontrolled state. The body diode of the first switch Q1 rectifies during the off period of the first switch Q1. The pulse control signal of the first switch Q1 is complementary to the pulse control signal of the second switch Q2. In this embodiment, the first transformer L1 adopts a single-winding flyback energy transfer transformer that supports a wide voltage input range.

[0043] The voltage difference between each cell can be monitored in real time. When the voltage difference exceeds a preset threshold, the balancing circuit is activated to control the DC-DC charging and discharging operations. Voltage monitoring can be performed using a sampling resistor and an operational amplifier. The high-voltage cell drives the first switching transistor Q1 via the primary winding switching transistor control terminal P-GATE, controlling the flow of power to the low-voltage cell. The low-voltage cell receives energy via the secondary winding switching transistor control terminal S-GATE, achieving bidirectional energy transfer. A PACK module involves multiple cells. The active balancing circuit has only one first transformer L1, which requires cell selection. When balancing the energy storage medium BT1 on the high-voltage cell side, the cell selection analog switch U1 selects whether the secondary side energy is delivered to the low-voltage cell (Cell x), the low-voltage cell (Cell X+1), or the low-voltage cell (Cell X+n), achieving demand balancing.

[0044] BT1 in the circuit can be replaced with a capacitor. The flyback transformer can withstand a voltage input range of 12V to 100V while maintaining stable circuit operation. The capacitor enables rapid charging or discharging of the circuit. The cell selection analog switch, U1, uses a MUX (multiplexer) analog switch, enabling one-to-one fast charging. Compared to the mainstream isolated parallel balancing method on the market, it provides higher balancing current and faster balancing speed.

[0045] Multiple protection mechanisms, including overvoltage, undervoltage, and overcurrent protection, ensure system safety under high loads and extreme conditions. Balancing current is adjusted in real time based on voltage differences, optimizing energy loss during the balancing process. Duty cycle adjustment ensures the optimal balance between efficiency and accuracy.

[0046] In another embodiment of the present invention, an active balancing battery is provided. The active balancing battery has the above-mentioned active balancing circuit installed therein.

[0047] Specifically, based on the setting of the battery active balancing circuit, the active balancing battery can reduce the voltage gap between different internal battery cells and ensure a longer service life.

[0048] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A battery active balancing circuit, characterized in that: It includes a first transformer L1, a second transformer L2, a first switch tube Q1, a second switch tube Q2, a cell switching selection analog switch U1, a first isolation capacitor C3 and a second isolation capacitor C4; One primary end of the first transformer L1 is connected to the positive terminal of the high-voltage cell side, the other end of the primary end is connected to the drain of the first switching tube Q1, one end of the secondary side is connected to one end of the cell switching selection analog switch U1, and the other end of the secondary side is connected to the drain of the second switching tube Q2. The other end of the cell switching selection analog switch U1 is used to connect to the low-voltage cell side. One primary end of the second transformer L2 is connected to one end of the first isolation capacitor C3, and the other end of the primary side is connected to the secondary ground plane GND2. One secondary end is connected to the gate of the second switching tube Q2 through the second isolation capacitor C4, and the other end of the secondary side is connected to the secondary ground plane GND2. A primary winding switching tube control terminal P-GATE is provided on the gate of the first switching tube Q1, and a secondary winding switching tube control terminal S-GATE is provided on the other end of the first isolation capacitor C3. The source of the first switching tube Q1 is grounded, and the source of the second switching tube Q2 is connected to the secondary ground plane GND2.

2. The battery active balancing circuit according to claim 1, wherein: The cell switching selection analog switch U1 includes several switch units; The switch unit includes a first switch group and a second switch group; one end of the first switch group is connected to one end of the secondary side of the first transformer L1, one end of the second switch group is connected to the secondary ground plane GND2, and the other end of the first switch group and the other end of the second switch group are both used to connect the connection lines of two adjacent battery cells set on the low-voltage battery cell side.

3. The battery active balancing circuit according to claim 2, wherein: It also includes a voltage stabilizing capacitor C2; the cell switching selection analog switch U1 also includes a third switch group; One end of the voltage stabilizing capacitor C2 is connected to one end of the secondary side of the first transformer L1, and the other end is connected to one end of the third switch group. The other end of the third switch group is used to connect to the negative end of the low-voltage battery cell side.

4. The battery active balancing circuit according to claim 3, wherein: The first switch group, the second switch group and the third switch group each include two MOS transistors connected back to back.

5. The battery active balancing circuit according to claim 1, wherein: Also included is a duty cycle adjustment circuit; the duty cycle adjustment circuit includes a first resistor R1, a first operational amplifier OPA1, a second resistor R2, a second operational amplifier OPA2, an OR gate U2 and a PI regulator; One end of the first resistor R1 is connected to the source of the first switch Q1 and the positive input terminal of the first operational amplifier OPA1, and the other end is connected to the negative input terminal of the first operational amplifier OPA1 and the secondary ground plane GND2; One end of the second resistor R2 is connected to the source of the second switch Q2 and the negative input terminal of the second operational amplifier OPA2, and the other end is connected to the positive input terminal of the second operational amplifier OPA2 and the secondary ground plane GND2; The first input end of the OR gate U2 is connected to the output end of the first operational amplifier OPA1, the second input end is connected to the output end of the second operational amplifier OPA2, and the output end is connected to the first input end of the PI regulator. The second input end of the PI regulator is used to input the theoretical output voltage of the secondary side of the first transformer L1, and the output end is connected to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE; the PI regulator is used to generate a primary winding switch tube control signal and a secondary winding switch tube control signal according to the output signal of the OR gate U2, and send them to the primary winding switch tube control terminal P-GATE and the secondary winding switch tube control terminal S-GATE respectively.

6. The battery active balancing circuit according to claim 5, characterized in that: The primary winding switch tube control signal and the secondary winding switch tube control signal are both PWM signals.

7. The battery active balancing circuit according to claim 6, wherein: The pulses of the primary winding switch tube control signal and the secondary winding switch tube control signal are complementary.

8. The battery active balancing circuit according to claim 1, wherein: It also includes a filter capacitor C1; one end of the filter capacitor C1 is connected to one end of the primary side of the first transformer L1, and the other end is used to connect to the negative end of the high-voltage battery cell.

9. The battery active balancing circuit according to claim 1, wherein: It also includes a comparator OPA3; the negative input end of the comparator OPA3 is connected to one end of the secondary side of the first transformer L1, the positive input end is provided with a reference voltage terminal REF for inputting a reference voltage signal, and the output end is provided with an undervoltage detection terminal ULVO.

10. An active balancing battery, characterized in that: The active balancing battery is internally provided with the battery active balancing circuit according to any one of claims 1 to 9.

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