Battery equalization control circuit

Abstract

The utility model provides a battery equalization control circuit, which comprises N equalization devices, two input ends of each equalization device are respectively connected with an input voltage positive and an input voltage negative, and the output end of each equalization device is connected to two ends of a single cell; the equalization device comprises a BUCK circuit, a bridge circuit, a transformer and a rectification circuit which are connected in sequence. The input end of the BUCK circuit serves as the input end of the equalization device, and the output end of the rectification circuit serves as the output end of the equalization device. According to the battery equalization control circuit provided by the utility model, one equalization device is connected in parallel at two ends of each cell, so that the requirement of the industry for wider and wider input voltage at present can be met, and the cost can be further reduced.

Description

Technical Field

[0001] This utility model relates to the field of battery voltage equalization technology, and in particular to a battery equalization control circuit. Background Technology

[0002] The battery energy storage industry is developing rapidly and its applications are becoming increasingly widespread. Due to factors such as battery materials and manufacturing processes, the voltage of individual cells in a battery pack may differ after charging or discharging. This can lead to reduced battery pack lifespan or overcharging / discharging, causing safety issues. Since batteries account for over 80% of the total cost, improving battery lifespan is equivalent to significantly reducing costs; therefore, battery balancing technology has become an essential means to improve battery lifespan.

[0003] A common battery balancing scheme in the prior art is as follows: Figure 1 As shown, placing an equalization device between two connected battery cells results in (N-1) equalization devices in a battery pack with N cells. A typical equalization device is a non-isolated buck-boost circuit that determines the direction of current by detecting the voltage difference between the cells, allowing the cell with the higher voltage to charge the cell with the lower voltage. This scheme is simple to control, but it has a significant drawback: energy must be transferred between adjacent cells. If two cells that are far apart need to be equalized, the equalization efficiency will be very low. For example, if the first cell in the battery pack has a higher voltage and the Nth cell has a lower voltage, and energy needs to be transferred for equalization, the first cell must first transfer energy to the second, then to the third, and so on, until finally reaching the Nth cell. In this process, the equalization efficiency is very low, and energy loss is significant during multiple transfers.

[0004] Another common battery balancing scheme in the prior art is as follows: Figure 2 As shown, its circuit structure consists of a flyback topology bidirectional equalization circuit and a matrix switch. The matrix switch selects the two cells to be charged and discharged, allowing the cell with higher voltage to charge the cell with lower voltage, thus solving the problem of... Figure 1 The illustrated technical solution suffers from low efficiency due to the step-by-step energy transfer. In applications with a narrow input voltage range, such as 24V, 48V, and 72V, the flyback topology exhibits better overall performance, higher balancing efficiency, and relatively lower energy transfer losses. However, for balancing control boards, the ideal is for a single product to be compatible with all systems. Therefore, the industry has increasingly demanded an input range of 20V-100V to accommodate most current battery pack voltages. With such a wide range, the flyback topology suffers from poor overall performance, and the transformer's size and cost increase significantly. Figure 2 The technical solution shown requires matrix switches and their isolation drivers, as well as AFEs, to work together, and the overall cost is also relatively high. Utility Model Content

[0005] The purpose of this invention is to provide a battery balancing control circuit that is compatible with the input voltage of most current battery packs.

[0006] The objective of this utility model is achieved through the following technical solution:

[0007] A battery balancing control circuit includes N balancing devices, where N≥1. Each balancing device has two input terminals connected to a positive input voltage and a negative input voltage, respectively, and each balancing device has an output terminal connected to both ends of a single battery cell. The balancing device comprises a BUCK circuit, a bridge circuit, a transformer, and a rectifier circuit connected in sequence. The input terminal of the BUCK circuit serves as the input terminal of the balancing device, and the output terminal of the rectifier circuit serves as the output terminal of the balancing device.

[0008] Furthermore, the BUCK circuit includes a first MOSFET TR1, a first diode D1, an inductor L1, and a first capacitor C1; the drain of the first MOSFET TR1 serves as one input terminal of the equalization device and is connected to the positive input voltage; the anode of the first diode D1 is connected to one end of the first capacitor C1 and serves as the other input terminal of the equalization device and is connected to the negative input voltage; the source of the first MOSFET TR1 is connected to the cathode of the first diode D1 and one end of the inductor L1; the gate of the first MOSFET TR1 is connected to an external first control signal, which controls the first MOSFET TR1 to be turned on or off; the other end of the inductor L1 is connected to the other end of the first capacitor C1 and serves as the output terminal of the BUCK circuit.

[0009] Furthermore, the bridge circuit is a half-bridge circuit, and the primary winding of the transformer has a center tap; the half-bridge circuit includes a second MOSFET TR2-1 and a third MOSFET TR2-2; the drains of the second MOSFET TR2-1 and the third MOSFET TR2-2 are connected to the negative input voltage; the source of the second MOSFET TR2-1 is connected to one end of the primary winding of the transformer, and the source of the third MOSFET TR2-2 is connected to the other end of the primary winding of the transformer; the center tap of the primary winding is connected to the output terminal of the BUCK circuit; the gate of the second MOSFET TR2-1 receives a second control signal, and the gate of the third MOSFET TR2-2 receives a third control signal.

[0010] Furthermore, the bridge circuit is a full-bridge circuit, which includes a second MOSFET TR2-1, a third MOSFET TR2-2, a fourth MOSFET TR2-3, and a fifth MOSFET TR2-4. The source of the second MOSFET TR2-1 and the source of the third MOSFET TR2-2 are connected to the output terminal of the BUCK circuit; the drain of the fourth MOSFET TR2-3 and the drain of the fifth MOSFET TR2-4 are connected to the negative input voltage; the drain of the second MOSFET TR2-1 and the source of the fourth MOSFET TR2-3 are connected to one end of the primary winding of the transformer, and the drain of the third MOSFET TR2-2 and the source of the fifth MOSFET TR2-4 are connected to the other end of the primary winding of the transformer; the gate of the second MOSFET TR2-1 and the gate of the fifth MOSFET TR2-4 input a second control signal; and the gate of the third MOSFET TR2-2 and the gate of the fourth MOSFET TR2-3 input a third control signal.

[0011] Furthermore, the rectifier circuit is a half-bridge rectifier circuit, which includes a second diode D2-1, a third diode D2-2, and a second capacitor C2. The secondary winding of the transformer has a center tap. The anode of the second diode D2-1 is connected to one end of the secondary winding, and the anode of the third diode D2-2 is connected to the other end of the secondary winding. The cathodes of the second diode D2-1 and the third diode D2-2 are connected to one end of the second capacitor C2 and serve as the positive output of the rectifier circuit. The other end of the second capacitor C2 is connected to the center tap of the secondary winding and serves as the negative output of the rectifier circuit. The positive and negative outputs of the rectifier circuit are the output terminals of the equalization device.

[0012] Furthermore, the rectifier circuit is a full-bridge rectifier circuit, which includes a second diode D2-1, a third diode D2-2, a fourth diode D2-3, a fifth diode D2-4, and a second capacitor C2. The anode of the second diode D2-1 and the cathode of the fourth diode D2-3 are connected to one end of the secondary winding, and the anode of the third diode D2-2 and the cathode of the fifth diode D2-4 are connected to the other end of the secondary winding. The cathodes of the second diode D2-1 and the third diode D2-2, and one end of the second capacitor C2 are connected and serve as the positive output of the rectifier circuit. The anodes of the fourth diode D2-3 and the fifth diode D2-4, and the other end of the second capacitor C2 are connected and serve as the negative output of the rectifier circuit. The positive and negative outputs of the rectifier circuit are the output terminals of the equalization device.

[0013] The battery balancing control circuit of this invention connects an balancing device in parallel across each cell, which can meet the industry's growing demand for a wider range of input voltages and further reduce costs. Attached Figure Description

[0014] Figure 1This is one of the existing battery balancing solutions.

[0015] Figure 2 This is the second existing battery balancing solution.

[0016] Figure 3 This is a block diagram of the battery balancing control circuit of this utility model.

[0017] Figure 4 This is a circuit block diagram of the equalization device of this utility model.

[0018] Figure 5 This is one of the circuit diagrams of the equalization device of this utility model.

[0019] Figure 6 This is the second circuit diagram of the equalization device of this utility model. Detailed Implementation

[0020] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0021] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0022] This utility model provides a battery balancing control circuit, such as... Figures 3 to 6 As shown, the system includes N equalization devices, where N ≥ 1. Each equalization device has its input terminals connected to a positive input voltage VIN+ and a negative input voltage VIN-, and its output terminal connected to both ends of a single battery cell. The equalization device comprises a BUCK circuit, a bridge circuit, a transformer, and a rectifier circuit connected in sequence. The input terminal of the BUCK circuit serves as the input terminal of the equalization device, and the output terminal of the rectifier circuit serves as the output terminal of the equalization device.

[0023] The equalization device of this invention is a unidirectional equalization circuit. All input terminals of the equalization device are connected together. Its input terminals (VIN+, VIN-) can be connected to an external power supply or to both ends of a battery string. This invention does not restrict the source of the input voltage for the equalization device. The output terminal of the equalization device is connected to both ends of an individual battery cell. If a specific battery cell has a low voltage and needs charging, the detection method and algorithm require external circuitry. This invention does not involve the detection of individual battery cell voltages, therefore it will not be described in detail.

[0024] Figure 3 The working principle is as follows: An external detection circuit detects that a certain battery cell has a low voltage and needs charging. It then controls the BUCK circuit of that circuit to conduct. After the input voltage is stepped down by the BUCK circuit, the output becomes a stable voltage, making subsequent circuitry easier to handle. The subsequent circuitry can use a constant voltage circuit for isolation, which includes a bridge circuit, a transformer, and a rectifier circuit. This two-stage structure separates the wide input range and isolation processing. The stable voltage output from the BUCK circuit is rectified by the bridge circuit on the primary side of the transformer, transformed to a standard battery voltage by the transformer, and then rectified and filtered by the rectifier circuit on the secondary side of the transformer to charge the low-voltage battery cell. Compared to existing technologies, this invention has a simpler circuit design, uses lower-cost materials, and achieves lower balancing efficiency and energy transfer losses. Figure 2 The existing technologies shown are not significantly different. That is, they achieve essentially the same technical effect using simple, low-cost circuits.

[0025] Furthermore, as an embodiment of the BUCK circuit in this utility model, such as Figure 4 As shown, the circuit includes a first MOSFET TR1, a first diode D1, an inductor L1, and a first capacitor C1. The drain of the first MOSFET TR1 serves as one input terminal of the equalization device, connected to the positive input voltage VIN+. The anode of the first diode D1 is connected to one end of the first capacitor C1 and serves as the other input terminal of the equalization device, connected to the negative input voltage VIN-. The source of the first MOSFET TR1 is connected to the cathode of the first diode D1 and one end of the inductor L1. The gate of the first MOSFET TR1 is connected to an external first control signal, which controls the first MOSFET TR1 to turn on or off. The other end of the inductor L1 is connected to the other end of the first capacitor C1 and serves as the output terminal of the BUCK circuit. When a battery cell has a low voltage and needs charging, the first control signal controls the first MOSFET TR1 in the equalization device connected to that battery cell to turn on, and the BUCK circuit in that equalization device operates, stepping down the input voltage.

[0026] Furthermore, as one embodiment of the bridge circuit in this utility model, such as Figure 5The diagram shows a half-bridge circuit, comprising a second MOSFET TR2-1 and a third MOSFET TR2-2. The drains of both MOSFETs TR2-1 and TR2-2 are connected to the negative input voltage VIN-, and their sources are connected to a transformer. The gate of MOSFET TR2-1 receives an external second control signal, and the gate of MOSFET TR2-2 receives an external third control signal.

[0027] When the bridge circuit is a half-bridge circuit, transformer T1 is as follows: Figure 5 As shown, the circuit includes a primary winding and a secondary winding, with the primary winding having a center tap. The source of the second MOSFET TR2-1 is connected to one end of the primary winding, and the source of the third MOSFET TR2-2 is connected to the other end of the primary winding. The center tap of the primary winding is connected to the output of the BUCK circuit. The two ends of the secondary winding are connected to the rectifier circuit.

[0028] The second and third control signals are two alternating square wave signals. With the first MOSFET TR1 turned on, when the second control signal is high, the second MOSFET TR2-1 is turned on, and when the third control signal is low, the third MOSFET TR2-2 is turned off. At this time, a voltage with negative at the top and positive at the bottom is formed on the primary winding of transformer T1, the primary winding is energized, and a square wave signal is output from the secondary winding. When the third control signal is high, the third MOSFET TR2-2 is turned on, and when the second control signal is low, the second MOSFET TR2-1 is turned off. At this time, a voltage with positive at the top and negative at the bottom is formed on the primary winding of transformer T1, the primary winding is energized, and a square wave signal is output from the secondary winding.

[0029] Furthermore, as another embodiment of the bridge circuit in this utility model, such as Figure 6 The diagram shows a full-bridge circuit, which includes a second MOSFET TR2-1, a third MOSFET TR2-2, a fourth MOSFET TR2-3, and a fifth MOSFET TR2-4. Transformer T1 is shown below. Figure 6As shown, the circuit includes a primary winding and a secondary winding. The source of the second MOSFET TR2-1 and the source of the third MOSFET TR2-2 are connected to the output of the BUCK circuit. The drain of the fourth MOSFET TR2-3 and the drain of the fifth MOSFET TR2-4 are connected to the negative input voltage VIN-. The drain of the second MOSFET TR2-1 and the source of the fourth MOSFET TR2-3 are connected to one end of the primary winding of transformer T1, and the drain of the third MOSFET TR2-2 and the source of the fifth MOSFET TR2-4 are connected to the other end of the primary winding of transformer T1. The two ends of the secondary winding are connected to a rectifier circuit. The gate of the second MOSFET TR2-1 and the gate of the fifth MOSFET TR2-4 receive an external second control signal. The gate of the third MOSFET TR2-2 and the gate of the fourth MOSFET TR2-3 receive an external third control signal.

[0030] The second and third control signals are two alternating square wave signals. With the first MOSFET TR1 turned on, when the second control signal is high, the second MOSFET TR2-1 and the fifth MOSFET TR2-4 are turned on. At this time, the third control signal is low, and the third MOSFET TR2-2 and the fourth MOSFET TR2-3 are turned off. At this point, a voltage with the top positive and the bottom negative is formed on the primary winding of transformer T1, the primary winding is energized, and a square wave signal is output from the secondary winding. When the third control signal is high, the third MOSFET TR2-2 and the fourth MOSFET TR2-3 are turned on. At this time, the second control signal is low, and the second MOSFET TR2-1 and the fifth MOSFET TR2-4 are turned off. At this point, a voltage with the top negative and the bottom positive is formed on the primary winding of transformer T1, the primary winding is energized, and a square wave signal is output from the secondary winding.

[0031] Furthermore, as one embodiment of the rectifier circuit in this utility model, such as Figure 5 The diagram shows a half-bridge rectifier circuit, comprising a second diode D2-1, a third diode D2-2, and a second capacitor C2. The secondary winding of transformer T1 includes a center tap. The anode of the second diode D2-1 is connected to one end of the secondary winding, and the anode of the third diode D2-2 is connected to the other end. The cathodes of the second diode D2-1 and the third diode D2-2, along with one end of the second capacitor C2, are connected and serve as the positive output VO+ of the rectifier circuit. The other end of the second capacitor C2 is connected to the center tap of the secondary winding and serves as the negative output VO- of the rectifier circuit. The positive and negative outputs VO+ and VO- of the rectifier circuit are the two output terminals of the equalization device. The positive output VO+ is connected to the positive terminal of the battery cell, and the negative output VO- is connected to the negative terminal of the battery cell.

[0032] When the primary voltage of transformer T1 is positive at the top and negative at the bottom, the secondary side outputs a square wave signal, forming an output voltage between the cathode of the second diode D2-1 and the center tap of the transformer. When the primary voltage of transformer T1 is negative at the top and positive at the bottom, the secondary side outputs a square wave signal, forming an output voltage between the cathode of the third diode D2-2 and the center tap of the transformer.

[0033] Furthermore, as another embodiment of the rectifier circuit in this utility model, such as Figure 6 The diagram shows a full-bridge rectifier circuit, comprising a second diode D2-1, a third diode D2-2, a fourth diode D2-3, a fifth diode D2-4, and a second capacitor C2. The secondary winding of transformer T1 has no center tap. The anode of the second diode D2-1 and the cathode of the fourth diode D2-3 are connected to one end of the secondary winding, while the anode of the third diode D2-2 and the cathode of the fifth diode D2-4 are connected to the other end. The cathodes of the second diode D2-1 and the third diode D2-2, along with one end of the second capacitor C2, are connected and serve as the positive output VO+ of the rectifier circuit. The anodes of the fourth diode D2-3 and the fifth diode D2-4, along with the other end of the second capacitor C2, are connected and serve as the negative output VO- of the rectifier circuit. The positive and negative outputs VO+ and VO- of the rectifier circuit are the two output terminals of the equalization device. The positive output VO+ is connected to the positive terminal of the battery cell, and the negative output VO- is connected to the negative terminal of the battery cell.

[0034] When the primary voltage of transformer T1 is positive at the top and negative at the bottom, the secondary side outputs a square wave signal. Current flows out from the upper end of the secondary winding, charges the second capacitor C2 through the third diode D2-2, and then returns to the upper end of the secondary winding through the fourth diode D2-3. An output voltage is formed across the second capacitor C2. When the primary voltage of transformer T1 is negative at the top and positive at the bottom, the secondary side outputs a square wave signal. Current flows out from the lower end of the secondary winding, charges the second capacitor C2 through the second diode D2-1, and then returns to the upper end of the secondary winding through the fifth diode D2-4. An output voltage is formed across the second capacitor C2.

[0035] Despite the seemingly numerous components, the actual manufacturing cost of this equalization device circuit is relatively low. The inductor L1 in the BUCK circuit can be a commercially available I-type inductor, costing no more than 0.4 yuan. The first MOSFET TR1, the first diode D1, the second MOSFET TR2-1, the third MOSFET TR2-2, the fourth MOSFET TR2-3, and the fifth MOSFET TR2-4 can be integrated into a single chip, with an estimated cost of 0.8 yuan. The transformer T1 can be implemented using a magnetic ring transformer, costing approximately 0.5 yuan per transformer. Therefore, the total cost of the equalization device is approximately 2 yuan. This is the biggest advantage of the circuit structure of this invention. It also meets the industry's increasing demand for wider input voltage ranges. The above component selection is only to illustrate the low cost of the equalization device circuit of this invention and does not imply that the component selection is limited to these.

[0036] The two implementations of the bridge circuit and the two implementations of the rectifier circuit of this utility model can be combined in any way without any difference in technical effect. The half-bridge circuit and the half-bridge rectifier circuit require a center tap in the transformer winding. The full-bridge circuit and the full-bridge rectifier circuit do not require a center tap in the transformer winding, making the transformer manufacturing relatively simple.

[0037] The above description is merely illustrative of the embodiments of this utility model and is not intended to limit the scope of this utility model. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model without creative labor should be included within the protection scope of this utility model.

Claims

1. A battery balancing control circuit, comprising N balancing devices, N≥1, wherein the two input terminals of each balancing device are respectively connected to a positive input voltage and a negative input voltage, and the output terminal of each balancing device is connected to both ends of a single battery cell; characterized in that, The equalization device includes a BUCK circuit, a bridge circuit, a transformer, and a rectifier circuit connected in sequence; the input terminal of the BUCK circuit serves as the input terminal of the equalization device, and the output terminal of the rectifier circuit serves as the output terminal of the equalization device.

2. The battery balancing control circuit according to claim 1, characterized in that, The BUCK circuit includes a first MOSFET (TR1), a first diode (D1), an inductor (L1), and a first capacitor (C1). The drain of the first MOSFET (TR1) is connected to the positive input voltage as one input terminal of the equalization device, and the anode of the first diode (D1) is connected to one end of the first capacitor (C1) and serves as the other input terminal of the equalization device, connected to the negative input voltage. The source of the first MOSFET (TR1) is connected to the cathode of the first diode (D1) and one end of the inductor (L1), respectively. The gate of the first MOSFET (TR1) is connected to an external first control signal, which controls the first MOSFET (TR1) to be turned on or off. The other end of the inductor (L1) is connected to the other end of the first capacitor (C1) and serves as the output terminal of the BUCK circuit.

3. The battery balancing control circuit according to claim 1, characterized in that, The bridge circuit is a half-bridge circuit, and the primary winding of the transformer has a center tap. The half-bridge circuit includes a second MOSFET (TR2-1) and a third MOSFET (TR2-2). The drains of the second MOSFET (TR2-1) and the third MOSFET (TR2-2) are connected to the negative input voltage. The source of the second MOSFET (TR2-1) is connected to one end of the primary winding of the transformer, and the source of the third MOSFET (TR2-2) is connected to the other end of the primary winding of the transformer. The center tap of the primary winding is connected to the output terminal of the BUCK circuit. The gate of the second MOSFET (TR2-1) receives a second control signal, and the gate of the third MOSFET (TR2-2) receives a third control signal.

4. The battery balancing control circuit according to claim 1, characterized in that, The bridge circuit is a full-bridge circuit, which includes a second MOSFET (TR2-1), a third MOSFET (TR2-2), a fourth MOSFET (TR2-3), and a fifth MOSFET (TR2-4). The source of the second MOSFET (TR2-1) and the source of the third MOSFET (TR2-2) are connected to the output terminal of the BUCK circuit. The drain of the fourth MOSFET (TR2-3) and the drain of the fifth MOSFET (TR2-4) are connected to the negative input voltage. The drain of the second MOSFET (TR2-1) and the source of the fourth MOSFET (TR2-3) are connected to one end of the primary winding of the transformer, and the drain of the third MOSFET (TR2-2) and the source of the fifth MOSFET (TR2-4) are connected to the other end of the primary winding of the transformer. The gate of the second MOSFET (TR2-1) and the gate of the fifth MOSFET (TR2-4) receive a second control signal. The gate of the third MOSFET (TR2-2) and the gate of the fourth MOSFET (TR2-3) receive a third control signal.

5. The battery balancing control circuit according to claim 3 or 4, characterized in that, The rectifier circuit is a half-bridge rectifier circuit, which includes a second diode (D2-1), a third diode (D2-2), and a second capacitor (C2). The secondary winding of the transformer has a center tap. The anode of the second diode (D2-1) is connected to one end of the secondary winding, and the anode of the third diode (D2-2) is connected to the other end of the secondary winding. The cathodes of the second diode (D2-1), the third diode (D2-2), and one end of the second capacitor (C2) are connected and serve as the positive output of the rectifier circuit. The other end of the second capacitor (C2) is connected to the center tap of the secondary winding and serves as the negative output of the rectifier circuit. The positive and negative outputs of the rectifier circuit are the output terminals of the equalization device.

6. The battery balancing control circuit according to claim 3 or 4, characterized in that, The rectifier circuit is a full-bridge rectifier circuit, which includes a second diode (D2-1), a third diode (D2-2), a fourth diode (D2-3), a fifth diode (D2-4), and a second capacitor (C2). The anode of the second diode (D2-1) and the cathode of the fourth diode (D2-3) are connected to one end of the secondary winding, and the anode of the third diode (D2-2) and the cathode of the fifth diode (D2-4) are connected to the other end of the secondary winding. The cathodes of the second diode (D2-1), the third diode (D2-2), and one end of the second capacitor (C2) are connected and serve as the positive output of the rectifier circuit. The anodes of the fourth diode (D2-3), the fifth diode (D2-4), and the other end of the second capacitor (C2) are connected and serve as the negative output of the rectifier circuit. The positive and negative outputs of the rectifier circuit are the output terminals of the equalization device.

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