Lithium battery active equalization system and equalization method based on transformer

Abstract

The invention discloses a lithium battery active equalization system and equalization method based on a transformer, and the system comprises a gating switch module which comprises a switching tube array and an output switching assembly, and a plurality of gating switching tubes in the switching tube array are connected with the positive and negative electrodes of a plurality of cells in a battery pack respectively; the voltage sampling module comprises a voltage data output end and a plurality of voltage sampling ends, and the plurality of voltage sampling ends are respectively connected with the positive and negative electrodes of the plurality of battery cells; the input end of the transformer buck-boost module is connected with the output switching assembly, and the output end is connected with the battery pack; the control module is connected with the voltage data output end and is connected with the control ends of the voltage sampling module and the transformer buck-boost module, and the control module can obtain the voltage data of each battery cell based on the voltage sampling module to control the on-off of a switch in the gating switch module. And charging and discharging processing is carried out on the battery cell through a transformer in the transformer buck-boost module, so that the voltage of the battery cell is adjusted, and the energy conversion rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery pack charging and discharging, and in particular to a transformer-based lithium battery active equalization system and an equalization method. Background Art

[0002] As lithium iron phosphate battery technology continues to mature, costs are gradually decreasing. At the same time, due to its higher safety, a large number of applications at home and abroad have begun to switch from ternary systems to lithium iron phosphate batteries. In addition, there is also a large demand for recycling lithium iron phosphate batteries for secondary utilization in the market. However, due to the inherent physical and chemical properties of lithium iron phosphate batteries and differences in production processes, there are large differences in the consistency of single cell voltage or battery pack voltage difference at the beginning and end of the charge and discharge cycle. This difference may cause individual cells in the battery pack to be overcharged or over-discharged during the discharge process, thereby affecting the performance and service life of the entire battery pack. Therefore, it is particularly important to balance the differential batteries.

[0003] At present, the balancing technology solutions used in the industry are mainly divided into passive balancing. Passive balancing consumes battery energy by connecting resistors of corresponding resistance in parallel at both ends of batteries with high single-cell voltage differences, thereby achieving the purpose of balancing. However, the passive balancing method will cause the resistors to generate large heat, and the balancing current is generally small, resulting in low current energy conversion rate and easy energy waste. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a transformer-based lithium battery active balancing system and balancing method, which can charge and discharge the battery cells in the battery pack through the transformer, thereby simply and effectively realizing active balancing of the lithium battery pack to improve energy conversion efficiency and reduce energy waste.

[0005] In a first aspect, an embodiment of the present invention provides a transformer-based lithium battery active balancing system, comprising: a battery pack, comprising a plurality of battery cells connected in series; a gating switch module, comprising a switch tube array and an output switching component, wherein the plurality of gating switch tubes in the switch tube array are respectively connected to the positive and negative electrodes of the plurality of battery cells; a voltage sampling module, comprising a voltage data output terminal and a plurality of voltage sampling terminals, wherein the plurality of voltage sampling terminals are respectively connected to the positive and negative electrodes of the plurality of battery cells; a transformer buck-boost module, wherein the input terminal is connected to the output switching component, and the output terminal is connected to the battery pack; a control module, connected to the voltage data output terminal, and connected to the voltage sampling module and the control terminal of the transformer buck-boost module; wherein the control module is used to obtain the voltage data of each of the battery cells through the voltage sampling module, and control the on and off of the switch in the gating switch module based on the voltage data, so as to connect the selected battery cells in parallel to the input terminal of the transformer buck-boost module, and control the transformer buck-boost module to charge or discharge the battery cells through the transformer, so as to adjust the voltage of the battery cells.

[0006] In some embodiments, the battery pack includes n battery cells connected in series, the switch tube array includes n+1 gate switch tubes, and the output switching component includes multiple output positive and negative switching switches or multiple n-to-1 switching switches; wherein one end of the n+1 gate switch tubes are respectively connected to the positive and negative electrodes of the n battery cells connected in series, and the other end of the n+1 gate switch tubes are respectively connected to the positive and negative input ends of the transformer buck-boost module through the output switching component; the control module is also used to control the on and off of the switches in the output switching component to connect the positive and negative electrodes of a single battery cell selected by the n+1 gate switch tubes to the positive and negative input ends of the transformer buck-boost module, respectively.

[0007] In some embodiments, the control module is also used to obtain the voltage values ​​of the n battery cells according to the voltage data, and determine the maximum voltage value and the minimum voltage value, and when the difference between the maximum voltage value and the minimum voltage value is greater than a preset voltage difference value, calculate the average voltage value of the n battery cells, so as to control the transformer buck-boost module to charge or discharge the selected single battery cell through the transformer based on the average voltage value, so as to adjust the voltage of the battery cell.

[0008] In some embodiments, the transformer buck-boost module includes a single transformer; the control module is also used to control the primary side energy input of the transformer to the secondary side to charge the selected single battery cell when the voltage value of the selected single battery cell is less than the average voltage value; and to control the secondary side energy input of the transformer to the primary side to discharge the selected single battery cell when the voltage value of the selected single battery cell is greater than the average voltage value.

[0009] In some embodiments, the transformer buck-boost module also includes an optocoupler component, a primary-side controlled buck IC and a secondary-side controlled boost IC, the optocoupler component and the primary-side controlled buck IC are connected to the primary side of the transformer, the secondary-side controlled boost IC is connected to the secondary side of the transformer, the two ends of the primary side of the transformer are connected to the positive and negative poles of the battery pack, and the two ends of the secondary side of the transformer are connected to the positive and negative poles of the selected single battery cell.

[0010] In some embodiments, the control module is used to send a high-level signal to the optocoupler component so that the optocoupler component enables the primary-side controlled buck IC to perform a buck mode, and is used to send a first PWM signal to the primary-side controlled buck IC so that the primary-side controlled buck IC controls the duty cycle corresponding to the primary side of the transformer based on the voltage of the battery pack input by the first PWM signal and the inductance of the transformer, so that the primary side energy of the transformer is input to the secondary side, and after adjustment, synchronous rectification and filtering by the secondary-side controlled boost IC, is input to the positive and negative poles of the selected single battery cell to charge the selected single battery cell.

[0011] In some embodiments, the control module is used to send a high-level signal to the secondary side so that the secondary side controls the boost IC to perform a boost mode, and is used to send a second PWM signal to the secondary side control boost IC so that the secondary side control boost IC controls the duty cycle corresponding to the secondary side of the transformer based on the voltage of the battery pack input by the second PWM signal and the inductance of the transformer, so that the secondary side energy of the transformer is input to the primary side, and after adjustment, synchronous rectification and filtering by the primary side control buck IC, it is input to the positive and negative poles of the battery pack to discharge the selected single battery cell.

[0012] In some embodiments, a current detection module is also arranged between the selection switch module and the negative pole of the transformer buck-boost module, the signal detection end of the current detection module is connected to the control module, the resistor in the current detection module is connected in series with the negative pole of the secondary transformer and the negative pole of the selected battery cell, and the control module is also used for the current signal corresponding to the resistor to adjust the duty cycle corresponding to the first PWM signal and the second PWM signal according to the current signal.

[0013] In some embodiments, the current detection module also includes an operational amplifier IC, which is used to obtain the current signal corresponding to the resistor, amplify the signal through the same-direction amplifier input positive pin and the same-direction amplifier input negative pin, and then output the filtered and amplified current signal to the control module through the first pin.

[0014] In a second aspect, an embodiment of the present invention provides a transformer-based active balancing method for lithium batteries, which is applied to a transformer-based active balancing system for lithium batteries as described in any one of the embodiments in the first aspect, and the method includes: acquiring voltage data of each of the battery cells through the voltage sampling module; controlling the on and off of the switch in the selection switch module based on the voltage data to connect the selected battery cells in parallel to the input end of the transformer buck-boost module; and controlling the transformer buck-boost module to charge or discharge the battery cells through the transformer to adjust the voltage of the battery cells.

[0015] According to an embodiment of the present invention, a transformer-based lithium battery active balancing system and balancing method are provided, which have at least the following beneficial effects: in the present application, the battery pack includes a plurality of cells connected in series, the selection switch module includes a switch tube array and an output switching component, a plurality of selection switch tubes in the switch tube array are respectively connected to the positive and negative electrodes of the plurality of cells, and are used to select specific cells, and the output switching component is used to switch the positive and negative electrodes of the selected cells and connect them separately in parallel to the input end of the transformer buck-boost module; the voltage sampling module includes a voltage data output end and a plurality of voltage sampling ends, and the plurality of voltage sampling ends are respectively connected to the positive and negative electrodes of the plurality of cells. The negative pole is connected to collect the voltage data of each battery cell, and the voltage data output end transmits the collected voltage data to the control module; the transformer buck-boost module, the input end is connected to the output switching component of the selection switch module, and the output end is connected to the positive and negative poles of the battery pack. The module realizes the buck-boost conversion of electric energy through the transformer, and charges or discharges the selected battery cell; the control module is connected to the voltage data output end, receives the voltage data collected by the voltage sampling module, and is connected to the control end of the voltage sampling module and the transformer buck-boost module, and is used to control the on and off of the switch in the selection switch module and the working state of the transformer buck-boost module. Among them, it can be understood that the control module obtains the voltage data of each battery cell through the voltage sampling module, calculates and compares the voltage of each battery cell based on the voltage data, determines the battery cell that needs to be balanced, and then can control the on and off of the switch in the selection switch module, selects the battery cell that needs to be balanced in parallel to the input end of the transformer buck-boost module, and controls the transformer buck-boost module to charge or discharge the selected battery cell through the transformer to adjust the voltage of the battery cell. Through the above process, the transformer-based lithium battery active balancing system provided by the present invention can efficiently and reliably achieve voltage balancing of each battery cell in the battery pack, so as to improve energy conversion efficiency and reduce energy waste, thereby improving the overall performance and service life of the battery pack.

[0016] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0019] Figure 11 is a schematic diagram of a module of a transformer-based lithium battery active balancing system provided in an embodiment of the present invention;

[0020] Figure 2 This is another optional module schematic diagram of a transformer-based lithium battery active balancing system provided in an embodiment of the present invention;

[0021] Figure 3 It is a circuit diagram of a transformer buck-boost module in a transformer-based lithium battery active balancing system provided by an embodiment of the present invention;

[0022] Figure 4 The present invention is a schematic circuit diagram of a current detection module in a transformer-based lithium battery active balancing system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0024] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, "above", "below", "within", etc. are understood to include the number itself, "any one" means one or more, "at least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. If there is a description of the first and the second, it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0025] It should be noted that the terms such as setting, installing, and connecting in the embodiments of the present invention should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the embodiments of the present invention in combination with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected or indirectly connected through an intermediate medium.

[0026] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] As lithium iron phosphate battery technology continues to mature, costs are gradually decreasing. At the same time, due to its higher safety, a large number of domestic and foreign companies have begun to switch from ternary systems to lithium iron phosphate batteries. In addition, there is also a large demand for recycling lithium iron phosphate batteries in the market. However, due to the inherent physical and chemical properties of lithium iron phosphate batteries and differences in production processes, there are large differences in the consistency of single cell voltage or battery pack voltage difference at the beginning and end of the charge and discharge cycle. This difference may cause individual cells in the battery pack to be overcharged or over-discharged during the discharge process, thereby affecting the performance and service life of the entire battery pack. Therefore, it is particularly important to balance the difference batteries. At present, the current balancing technology solutions used in the industry are mainly divided into passive balancing. Passive balancing consumes battery energy by connecting resistors of corresponding resistance in parallel at both ends of the battery with a higher single cell voltage difference, thereby achieving the purpose of balancing. However, the passive balancing method will cause the resistor to generate large heat and the balancing current is generally small, resulting in low current energy conversion rate and easy energy waste.

[0028] Based on this, the purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a transformer-based lithium battery active balancing system and balancing method, which can charge and discharge the cells in the battery pack through the transformer, thereby simply and effectively realizing active balancing of the lithium battery pack to improve energy conversion efficiency and reduce energy waste.

[0029] The present application scheme is further described below with reference to the accompanying drawings.

[0030] refer to Figure 1 , Figure 1 It is a module schematic diagram of a transformer-based lithium battery active equalization system provided by an embodiment of the present invention; in a first aspect, an embodiment of the present invention provides a transformer-based lithium battery active equalization system, including: a battery pack, including multiple battery cells connected in series; a gating switch module, including a switch tube array and an output switching component, and multiple gating switch tubes in the switch tube array are respectively connected to the positive and negative electrodes of the multiple battery cells; a voltage sampling module, including a voltage data output end and multiple voltage sampling ends, and the multiple voltage sampling ends are respectively connected to the positive and negative electrodes of the multiple battery cells; a transformer buck-boost module, the input end of which is connected to the output switching component, and the output end is connected to the battery pack; a control module, which is connected to the voltage data output end, and is connected to the voltage sampling module and the control end of the transformer buck-boost module; wherein the control module is used to obtain voltage data of each battery cell through the voltage sampling module, and control the on and off of the switch in the gating switch module based on the voltage data, so as to connect the gating battery cell in parallel to the input end of the transformer buck-boost module, and control the transformer buck-boost module to charge or discharge the battery cell through the transformer to adjust the voltage of the battery cell.

[0031] Among them, the battery pack in the present application includes multiple cells connected in series, the selection switch module includes a switch tube array and an output switching component, the multiple selection switch tubes in the switch tube array are respectively connected to the positive and negative poles of the multiple cells, used to select specific cells, and the output switching component is used to switch the positive and negative poles of the selected cells and connect them in parallel to the input end of the transformer buck-boost module; the voltage sampling module includes a voltage data output end and multiple voltage sampling ends, the multiple voltage sampling ends are respectively connected to the positive and negative poles of the multiple cells, used to collect voltage data of each cell, and the voltage data output end transmits the collected voltage data to the control module; the transformer buck-boost module, the input end is connected to the output switching component of the selection switch module, and the output end is connected to the positive and negative poles of the battery pack. The module realizes the buck-boost conversion of electric energy through a transformer, and charges or discharges the selected cells; the control module is connected to the voltage data output end, receives the voltage data collected by the voltage sampling module, and is connected to the control end of the voltage sampling module and the transformer buck-boost module, and is used to control the on and off of the switch in the selection switch module and the working state of the transformer buck-boost module. Among them, it can be understood that the control module obtains the voltage data of each battery cell through the voltage sampling module, calculates and compares the voltage of each battery cell based on the voltage data, determines the battery cell that needs to be balanced, and then can control the on and off of the switch in the selection switch module, selects the battery cell that needs to be balanced in parallel to the input end of the transformer buck-boost module, and controls the transformer buck-boost module to charge or discharge the selected battery cell through the transformer to adjust the voltage of the battery cell. Through the above process, the transformer-based lithium battery active equalization system provided by the present invention can efficiently and reliably realize the voltage balance of each battery cell in the battery pack, so as to improve the energy conversion rate and reduce energy waste, thereby improving the overall performance and service life of the battery pack.

[0032] refer to Figure 2 , Figure 2 It is another optional module schematic diagram of a transformer-based lithium battery active balancing system provided by an embodiment of the present invention; in some embodiments, the battery pack includes n battery cells connected in series, the switch tube array includes n+1 gate switch tubes, and the output switching component includes multiple output positive and negative switching switches or multiple n-to-1 switching switches; wherein, one end of the n+1 gate switch tubes is respectively connected to the positive and negative electrodes of the n battery cells connected in series, and the other end of the n+1 gate switch tubes is respectively connected to the positive and negative input ends of the transformer buck-boost module through the output switching component; the control module is also used to control the on and off of the switch in the output switching component to connect the positive and negative electrodes of a single battery cell selected by the n+1 gate switch tubes to the positive and negative input ends of the transformer buck-boost module.

[0033] Specifically, Figure 2 As shown, Figure 2In the figure, corresponding to the switch tube array in the above embodiment, S0-Sn are matrix switch channels composed of MOS tubes, and the control module MCU sends CS1, CS2, CS3 selection signals to the first n-to-1 switch or the second n-to-1 switch or the third n-to-1 switch to switch the MOS switch channels of S0-Sn, select the corresponding battery cells, and switch the positive and negative polarities.

[0034] Among them, it is understandable that Figure 2 Not directly drawn in Figure 1 The voltage sampling module appears in the Figure 2 The circuit structure does not include Figure 1 Corresponding to the voltage sampling module (AFE) in the embodiment, in all embodiments of the present application, the control module needs to be connected to the positive and negative poles of multiple battery cells through multiple voltage sampling terminals of the voltage sampling module, so as to obtain the voltage data of each battery cell through the voltage sampling module, and then perform subsequent active voltage balancing.

[0035] In some embodiments, the control module monitors the voltage of each battery cell in real time through the voltage sampling module, determines the battery cell that needs to be balanced based on the voltage data, and selects the battery cell that needs to be balanced by controlling the switch in the selection switch module, and controls the output switching component to connect the positive and negative electrodes of the selected battery cell to the positive and negative input terminals of the transformer buck-boost module, respectively. For example, when the kth battery cell is selected, the corresponding switch in the output switching component will be closed, connecting the positive electrode of the kth battery cell to the positive input terminal of the transformer buck-boost module, and connecting the negative electrode of the kth battery cell to the negative input terminal of the transformer buck-boost module.

[0036] In some embodiments, the control module is also used to obtain voltage values ​​of n battery cells based on voltage data, and determine the maximum voltage value and the minimum voltage value, and when the difference between the maximum voltage value and the minimum voltage value is greater than a preset voltage difference value, calculate the average voltage value of the n battery cells, so as to control the transformer buck-boost module to charge or discharge the selected single battery cell through the transformer based on the average voltage value, so as to adjust the voltage of the battery cell.

[0037] Among them, it can be understood that when the transformer-based lithium battery active balancing system is started, the control module controls the voltage sampling module to scan the voltage of each battery cell in the battery pack once, collects and reads these voltage data; further, the voltage data is transmitted to the control module, and the control module can calculate and compare the voltage of each battery cell, determine the maximum battery cell voltage value and the minimum battery cell voltage value, if the voltage difference between the maximum battery cell voltage value and the minimum battery cell voltage value is greater than the set value, further calculate the average voltage of the battery pack ((total battery cell voltages-maximum battery cell voltage-minimum battery cell voltage) / (total number of battery cells-2)); further, the control module determines the battery cells that need to be balanced based on the calculation results, and controls the switch tube array in the selection switch module to select the battery cells that need to be balanced, and switches their positive and negative poles and connects them in parallel to the input end of the transformer buck-boost module separately. Through the above detailed control process, the control module of the present invention can calculate the average voltage, and then based on the average voltage, efficiently and accurately realize the voltage balance of each battery cell in the battery pack, thereby improving the overall performance and service life of the battery pack.

[0038] In some embodiments, Figure 1 BAT+ and BAT- correspond to the positive and negative terminals of the battery pack respectively. Figure 3 Cell+ and Cell- correspond to the positive input terminal and negative input terminal of the transformer buck-boost module respectively. In addition, the ENB, PWM1, ENC, PWM2 and other pins of the control module are connected to the transformer buck-boost module, corresponding to the subsequent Figure 3 From the related content, it can be known that ENB is the pin for the control module to send a high-level signal to the optocoupler component, PWM1 is the pin for the control module to send the first PWM signal to the primary side control buck IC, ENC is the pin for sending a high-level signal to the secondary side, and PWM2 is the pin for the control module to send the second PWM signal to the secondary side control buck IC.

[0039] refer to Figure 2 In some embodiments, a current detection module is further provided between the gate switch module and the negative electrode of the transformer buck-boost module, and the signal detection end of the current detection module is connected to the control module. Specifically, Figure 2 As shown, the current detection module is located between the negative output terminal of the output switching component composed of multiple n-to-1 switches and the negative input terminal of the transformer buck-boost module, and the signal detection terminal CA-CU of the current detection module is connected to the control module to monitor and feedback the balanced current in real time.

[0040] In some embodiments, the transformer buck-boost module includes a single transformer; the control module is also used to control the primary side energy input of the transformer to the secondary side to charge the selected single battery cell when the voltage value of the selected single battery cell is less than the average voltage value; and to control the secondary side energy input of the transformer to the primary side to discharge the selected single battery cell when the voltage value of the selected single battery cell is greater than the average voltage value.

[0041] refer to Figure 3 , Figure 3 It is a circuit diagram of a transformer buck-boost module in a transformer-based lithium battery active balancing system provided by an embodiment of the present invention; in some embodiments, the transformer buck-boost module also includes an optocoupler component, a primary-side control buck IC and a secondary-side control boost IC, the optocoupler component and the primary-side control buck IC are connected to the primary side of the transformer, the secondary-side control boost IC is connected to the secondary side of the transformer, the two ends of the primary side of the transformer are connected to the positive and negative poles of the battery pack, and the two ends of the secondary side of the transformer are connected to the positive and negative poles of a selected single battery cell.

[0042] In some embodiments, Figure 3 As shown, the current detection module in this application can be divided into the following Figure 3 The multiple modules shown, specifically, the current detection module may include an interconnected battery cell input module, a primary side control buck IC, a transformer, a secondary side control boost IC and a battery pack output module leader, the primary side control buck IC is also connected to an EN-B high level signal input and a PWM1 input module, and the secondary side control boost IC is also connected to an EN-C high level signal input and a PWM2 input module.

[0043] Among them, D1 and D2 in the battery input module are Schottky diodes for reverse connection protection; C1 and C2 are electrolytic capacitors for filtering and smoothing voltage, R1 and R2 are current limiting resistors for limiting current, BAT+ and BAT- are the positive and negative input terminals of the battery pack. T1 is a transformer for isolation and voltage conversion. D3 is a rectifier diode that converts AC to DC, C3 is a filter capacitor for filtering ripple, and R3 and R4 are resistors for setting the operating point.

[0044] In the primary side control buck IC module, U2 is the primary side control buck IC, which is used to control the primary side of the transformer. EN-B is the enable signal input terminal, which is used to enable or disable the IC. SS is the soft start pin, which is used to slowly increase the output voltage. COM is the common ground terminal, GND is the analog ground, DR is the drive output terminal, which is used to drive MOSFET. FB is the feedback pin, which is used for closed-loop control. VDD is the power input terminal.

[0045] In the secondary side control boost IC module, U3 is the secondary side control boost IC, which is used to control the secondary side of the transformer, EN-C is the enable signal input terminal, which is used to enable or disable the IC, SS is the soft start pin, which is used to slowly increase the output voltage, COM is the common ground terminal, GND is the analog ground, DR is the drive output terminal, which is used to drive MOSFET, FB is the feedback pin, which is used for closed-loop control, and VDD is the power input terminal.

[0046] In the battery pack output module, CELL+ and CELL are the positive and negative output terminals of the battery cell, DZ1 is a Zener diode for overvoltage protection, R5 and R6 are current limiting resistors for limiting current, C4 and C5 are electrolytic capacitors for filtering and smoothing voltage, and R10 is a current detection resistor for detecting current.

[0047] In the PWM1 input module and the PWM2 input module, PWM1 and PWM2 are pulse width modulation signal input terminals for controlling the working cycle of the IC, Q1 is a MOSFET for switch control, R7 to R14 are resistors for setting the operating point and bias, in addition, C6 to C15 are capacitors for filtering and decoupling, and R15 to R28 are resistors for setting the operating point and bias.

[0048] Above Figure 3 The key components of the battery management system and their interrelationships are demonstrated, and efficient management and protection of the battery pack are achieved through reasonable layout and component configuration.

[0049] In some embodiments, the control module is used to send a high-level signal to the optocoupler component so that the optocoupler component enables the primary-side controlled buck IC to perform the buck mode, and is used to send a first PWM signal to the primary-side controlled buck IC so that the primary-side controlled buck IC controls the duty cycle corresponding to the primary side of the transformer based on the voltage of the battery pack input by the first PWM signal and the inductance of the transformer, so that the primary side energy of the transformer is input to the secondary side, and after adjustment, synchronous rectification and filtering by the secondary-side controlled boost IC, it is input to the positive and negative poles of the selected single battery cell to charge the selected single battery cell.

[0050] In some embodiments, the control module is used to send a high-level signal to the secondary side so that the secondary side controls the boost IC to perform a boost mode, and is used to send a second PWM signal to the secondary side control boost IC so that the secondary side control boost IC controls the duty cycle corresponding to the secondary side of the transformer based on the voltage of the battery pack input by the second PWM signal and the inductance of the transformer, so that the secondary side energy of the transformer is input to the primary side, and after adjustment, synchronous rectification and filtering by the primary side control buck IC, it is input to the positive and negative poles of the battery pack to discharge the selected single battery cell.

[0051] In some embodiments, Figure 3As shown, if the voltage of the selected cell is lower than the average voltage of the battery pack, the control module sends a high-level signal to the first pin of the optocoupler component U1 through the EN-B pin, so that the primary-side control buck IC U2 enters the buck mode. At the same time, the control module sends a PWM signal to the primary-side control buck IC U2 through the PWM1 pin to control its operating frequency and duty cycle, so that the transformer T1 starts to excite and store energy. The primary energy of the transformer T1 is input to the secondary side, and after the secondary side control ICU3 adjusts the synchronous rectification and filtering, it is input to the positive and negative terminals of the selected cell to charge the cell.

[0052] In some embodiments, Figure 3 As shown, if the voltage of the selected cell is higher than the average voltage of the battery pack, the control module sends a high-level signal to the second pin of the secondary-side control boost IC U3 through the EN-C pin, so that the secondary-side control boost ICU3 enters the boost mode. At the same time, the control module sends a PWM signal to the secondary-side control boost IC U3 through the PWM2 pin to control its operating frequency and duty cycle, so that the transformer T1 starts to excite and store energy. The secondary-side energy of the transformer T1 is input to the primary side, and after the primary-side control IC U2 adjusts the synchronous rectification and filtering, it is input to the positive and negative terminals of the battery pack to discharge the cell.

[0053] refer to Figure 4 , Figure 4 It is a circuit diagram of a current detection module in a transformer-based lithium battery active balancing system provided by an embodiment of the present invention; in some embodiments, a current detection module is also arranged between the negative pole of the selection switch module and the transformer buck-boost module, the signal detection end of the current detection module is connected to the control module, the resistor in the current detection module is connected in series with the negative pole of the secondary transformer and the negative pole of the selected battery cell, and the control module is also used for the current signal corresponding to the resistor to adjust the duty ratio corresponding to the first PWM signal and the second PWM signal according to the current signal.

[0054] Among them, R10 is a detection resistor, which is used to detect the current of the battery cell. When current flows through R10, a voltage drop will be generated at both ends of it, which is proportional to the current; CAGND is one of the ground reference points of the circuit, which is used to distinguish different ground planes; CELL- is connected to the negative pole of the battery cell; R33, R34, R35, R36, R37 and other resistors form a proportional amplifier network, which is used to amplify the small voltage change on R10 to a larger range, among which R33 and R34 form a voltage divider, and R35, R36 and R37 are used as feedback resistors to determine the gain of the amplifier; C18 is an input capacitor, which is used to filter out high-frequency noise and ensure that only low-frequency signals are amplified, and C19 is a ground capacitor; U7 is an operational amplifier, which is used to The voltage change on R10 is amplified; the gain of the operational amplifier is determined by the external resistor network; REG5V is a 5 volt regulated power supply, which provides a stable power supply for the circuit; C20 is an output capacitor, which is used to filter out the high-frequency components in the amplified signal to make it more stable; CA-CU is the output end, which transmits the amplified current signal to the subsequent control system or other processing circuits. R38, R39, R40, and R41 form another proportional amplifier network for these resistors, which may be used to further amplify or adjust the signal; U8 is used to further process and amplify the signal, C21 is an input capacitor, which is also used to filter out high-frequency noise, and LGND is the ground reference point, which is used to distinguish different ground planes.

[0055] In some embodiments, Figure 2 As shown, the resistor R10 is connected in series between the negative electrode of the secondary transformer and the negative electrode of the selected cell, and a voltage drop is generated according to the current to generate a corresponding current signal; further, as shown Figure 4 As shown, the current signal is amplified through the same-direction amplification input positive pin 3 and the same-direction amplification input negative pin 4 of the operational amplifier IC U7, and then the filtered and amplified current signal is output to the CA-CU port of the control module through the first pin of the operational amplifier IC U7. The control module dynamically adjusts the duty cycle of PWM1 according to the current balancing current to ensure that the balancing current is within a suitable range, for example, the duty cycle is controlled to be 1%-50% during charging, and the duty cycle is controlled to be 1%-90% during discharging, thereby achieving the control of the on-off of the switch in the gating switch module based on the voltage data of each battery cell obtained by the voltage sampling module, and then the battery cell is charged and discharged through the transformer in the transformer step-up / step-down module to adjust the voltage of the battery cell and improve the energy conversion rate.

[0056] In some embodiments, the current detection module also includes an operational amplifier IC, which is used to obtain the current signal corresponding to the resistor, amplify the signal through the positive input pin and the negative input pin of the same-direction amplifier, and then output the filtered and amplified current signal to the control module through the first pin.

[0057] In some embodiments, reference Figures 2 to 4 , the complete process of charging in this application is as follows: when the voltage of the selected battery cell is lower than the average voltage of the battery pack, such as Figure 2 In the figure, S0-Sn are matrix switch channels composed of MOS tubes. The control module MCU sends CS1, CS2, CS3 selection signals to the first n-to-1 switch, the second n-to-1 switch, or the third n-to-1 switch to switch the MOS switch channels of S0-Sn, select the corresponding battery cells, and switch the positive and negative polarities. Figure 3 In the process, the control module MCU sends a high-level signal to the first pin of the optocoupler component U1 through the EN-B pin. The fourth pin of the optocoupler component U1 pulls down the second pin of the primary-side control buck IC U2, enabling the primary-side control buck IC U2 to enter the buck mode. At the same time, the control module MCU sends a PWM signal to the primary-side control buck IC U2 through the PWM1 pin. The first pin of the control buck IC U2 selects the operating frequency according to the voltage of the battery pack input by the PWM signal and the inductance of the transformer, and then sends the duty cycle corresponding to the set balancing current value. At this time, the transformer T1 starts to excite and store energy, and the primary energy of the transformer T1 is input to the secondary side. After being adjusted by the secondary-side control IC U3 for synchronous rectification and filtering, it is input to the positive and negative ends of the battery cell. Charge the battery cell. At the same time, Figure 4 In the current detection circuit, the resistor R10 is connected in series with the negative electrode of the secondary transformer and the negative electrode of the selected battery cell. According to the current at this time, a voltage drop is generated on the resistor R10, and a corresponding current signal is generated. The signal is appropriately amplified through the same-direction amplifier input positive pin 3 and the same-direction amplifier input negative pin 4 of the operational amplifier IC U7, and then the filtered and amplified current signal is output through the first pin of the operational amplifier IC U7 to the CA-CU port of the control module MCU. After calculating the current balanced current size, the appropriate duty cycle of PWM1 is dynamically adjusted. Under normal circumstances, the duty cycle is controlled between 1% and 50%.

[0058] In some embodiments, reference Figures 2 to 4 , the complete process of the discharge action in this application is as follows: when the voltage of the selected cell is higher than the average voltage of the battery pack, such as Figure 2 In the figure, S0-Sn are matrix switch channels composed of MOS tubes. The control module MCU sends CS1, CS2, CS3 selection signals to the first n-to-1 switch, the second n-to-1 switch, or the third n-to-1 switch to switch the MOS switch channels of S0-Sn, select the corresponding battery cells, and switch the positive and negative polarities. Figure 3In the process, the control module MCU sends a high-level signal to the second pin of the secondary-side control boost IC U3 through the EN-C pin, enabling the secondary-side control boost IC U3 to perform the boost mode. At the same time, the control module MCU sends a PWM signal to the secondary-side control boost IC U3 through the PWM2 pin. The first pin of the control boost IC U3 selects the operating frequency according to the voltage of the battery pack input by the PWM signal and the inductance of the transformer, and then sends the duty cycle corresponding to the set balancing current value. At this time, the transformer T1 starts to excite and store energy, and the secondary-side energy of the transformer T1 is input to the primary side. After being adjusted by the primary-side control IC U2 for synchronous rectification and filtering, it is input to the positive and negative terminals of the battery pack to discharge the battery cell. At the same time, Figure 4 In the current detection circuit, the resistor R10 is connected in series with the negative electrode of the secondary transformer and the negative electrode of the selected battery cell. According to the current at this time, a voltage drop is generated on the resistor R10, and a corresponding reverse current signal is generated. The signal is appropriately amplified through the same-direction amplifier input positive pin 3 and the same-direction amplifier input negative pin 4 of the operational amplifier IC U7, and then the filtered and amplified current signal is output through the first pin of the operational amplifier IC U7 to the CA-CU port of the control module MCU. After calculating the current balanced current size, the appropriate duty cycle of PWM1 is dynamically adjusted. Under normal circumstances, the duty cycle is controlled between 1% and 90%.

[0059] In some embodiments, the transformer buck-boost module in the present application includes only one transformer, and active balancing control of the battery cell is achieved through a transformer and a battery selection switch array to achieve the function of charging or discharging the battery cell. The structure is simple and the energy transfer function is performed in a transformer manner, and the conversion efficiency is achieved by cooperating with the transformer control chip to reach more than 85%. It can be understood that the present application adopts a combination of a MOS tube matrix switch channel and an n-to-1 switcher to make the original n transformers required become only one transformer. Compared with the existing traditional passive balancing technology, the advantages are low heat generation, large balancing current, high efficiency, and the corresponding high-voltage battery cell energy can be transferred to the low-voltage battery cell. The battery balancing purpose can be achieved in a shorter time, thereby improving the performance and life of the entire lithium iron phosphate battery pack.

[0060] In a second aspect, an embodiment of the present invention provides a transformer-based active balancing method for lithium batteries, which is applied to a transformer-based active balancing system for lithium batteries such as any one of the embodiments in the first aspect, and the method includes: acquiring voltage data of each battery cell through a voltage sampling module; controlling the on and off of a switch in a selection switch module based on the voltage data to connect the selected battery cell in parallel to the input end of a transformer buck-boost module; and controlling the transformer buck-boost module to charge or discharge the battery cell through a transformer to adjust the voltage of the battery cell.

[0061] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A transformer-based lithium battery active balancing system, characterized in that: include: A battery pack, comprising a plurality of cells connected in series; A gate switch module, comprising a switch tube array and an output switching component, wherein a plurality of gate switch tubes in the switch tube array are respectively connected to the positive and negative electrodes of the plurality of battery cells; A voltage sampling module, comprising a voltage data output terminal and a plurality of voltage sampling terminals, wherein the plurality of voltage sampling terminals are respectively connected to the positive and negative electrodes of the plurality of battery cells; A transformer step-up / step-down module, the input end of which is connected to the output switching component, and the output end of which is connected to the battery pack; A control module connected to the voltage data output terminal, and connected to the voltage sampling module and the control terminal of the transformer buck-boost module; Among them, the control module is used to obtain the voltage data of each battery cell through the voltage sampling module, and control the on and off of the switch in the selection switch module based on the voltage data, so as to connect the selected battery cell in parallel to the input end of the transformer buck-boost module, and control the transformer buck-boost module to charge or discharge the battery cell through the transformer to adjust the voltage of the battery cell.

2. The transformer-based lithium battery active balancing system according to claim 1, characterized in that: The battery pack includes n battery cells connected in series, the switch tube array includes n+1 gate switch tubes, and the output switching component includes a plurality of output positive and negative switching switches or a plurality of n-to-1 switching switches; Among them, one end of the n+1 selection switch tubes is respectively connected to the positive and negative electrodes of the n series-connected battery cells, and the other end of the n+1 selection switch tubes is respectively connected to the positive and negative input ends of the transformer buck-boost module through the output switching component; the control module is also used to control the on and off of the switches in the output switching component to connect the positive and negative electrodes of a single battery cell selected by the n+1 selection switch tubes to the positive and negative input ends of the transformer buck-boost module.

3. The transformer-based lithium battery active equalization system according to claim 2, characterized in that: The control module is also used to obtain the voltage values ​​of the n battery cells according to the voltage data, and determine the maximum voltage value and the minimum voltage value, and when the difference between the maximum voltage value and the minimum voltage value is greater than a preset voltage difference value, calculate the average voltage value of the n battery cells, so as to control the transformer step-up / step-down module to charge or discharge the selected single battery cell through the transformer based on the average voltage value, so as to adjust the voltage of the battery cell.

4. The transformer-based lithium battery active equalization system according to claim 3, characterized in that: The transformer buck-boost module includes a single transformer; the control module is also used to control the primary side energy of the transformer to be input to the secondary side when the voltage value of the selected single battery cell is less than the average voltage value, so as to charge the selected single battery cell; and to control the secondary side energy of the transformer to be input to the primary side when the voltage value of the selected single battery cell is greater than the average voltage value, so as to discharge the selected single battery cell.

5. The transformer-based lithium battery active equalization system according to claim 4, characterized in that: The transformer buck-boost module also includes an optocoupler component, a primary-side control buck IC and a secondary-side control boost IC. The optocoupler component and the primary-side control buck IC are connected to the primary side of the transformer, the secondary-side control boost IC is connected to the secondary side of the transformer, the two ends of the primary side of the transformer are connected to the positive and negative poles of the battery pack, and the two ends of the secondary side of the transformer are connected to the positive and negative poles of the selected single battery cell.

6. The transformer-based lithium battery active equalization system according to claim 5, characterized in that: The control module is used to send a high-level signal to the optocoupler component so that the optocoupler component enables the primary-side controlled buck IC to perform a buck mode, and is used to send a first PWM signal to the primary-side controlled buck IC so that the primary-side controlled buck IC controls the duty cycle corresponding to the primary side of the transformer based on the voltage of the battery pack input by the first PWM signal and the inductance of the transformer, so that the primary side energy of the transformer is input to the secondary side, and after adjustment, synchronous rectification and filtering by the secondary-side controlled boost IC, it is input to the positive and negative electrodes of the selected single battery cell to charge the selected single battery cell.

7. The transformer-based lithium battery active equalization system according to claim 6, characterized in that: The control module is used to send a high-level signal to the secondary side so that the secondary side controls the boost IC to perform a boost mode, and is used to send a second PWM signal to the secondary side control boost IC so that the secondary side control boost IC controls the duty cycle corresponding to the secondary side of the transformer based on the voltage of the battery pack input by the second PWM signal and the inductance of the transformer, so that the secondary side energy of the transformer is input to the primary side, and after adjustment, synchronous rectification and filtering by the primary side control buck IC, it is input to the positive and negative electrodes of the battery pack to discharge the selected single battery cell.

8. The transformer-based lithium battery active equalization system according to claim 7, characterized in that: A current detection module is also arranged between the selection switch module and the negative pole of the transformer buck-boost module. The signal detection end of the current detection module is connected to the control module. The resistor in the current detection module is connected in series with the negative pole of the secondary transformer and the negative pole of the selected battery cell. The control module is also used for the current signal corresponding to the resistor to adjust the duty ratio corresponding to the first PWM signal and the second PWM signal according to the current signal.

9. The transformer-based lithium battery active equalization system according to claim 8, characterized in that: The current detection module also includes an operational amplifier IC, which is used to obtain the current signal corresponding to the resistor, amplify the signal through the same-direction amplifier input positive pin and the same-direction amplifier input negative pin, and then output the filtered and amplified current signal to the control module through the first pin.

10. A transformer-based lithium battery active balancing method, characterized in that: The method is applied to the transformer-based lithium battery active balancing system according to any one of claims 1 to 9, and the method comprises: Acquiring voltage data of each of the battery cells through the voltage sampling module; Controlling the on and off of the switch in the gating switch module based on the voltage data, so as to connect the gating cell in parallel to the input end of the transformer buck-boost module; The transformer step-up / step-down module is controlled to charge or discharge the battery cell through the transformer to adjust the voltage of the battery cell.

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