Control method of battery charging circuit and battery charging device

Abstract

The invention discloses a control method of a battery charging circuit and a battery charging device, and a preceding-stage converter of the battery charging circuit comprises M paths of buck-boost converters which are connected in parallel; the control method comprises the steps of determining a total current instruction value according to actual parameters of a battery; determining a current instruction value of each buck-boost converter according to the total current instruction value; determining an average current value output by the buck-boost converter of each path in the K work cycles; determining the deviation percentage of the average current value output by each step-up and step-down converter in the K work cycles and the current instruction value of each step-up and step-down converter; according to the deviation percentage, adjusting the current instruction value of each path of working buck-boost converter, and realizing that the average current values output by each path of working buck-boost converter in the L working periods are the same; wherein L is an integer greater than K. According to the invention, the problem of non-uniform load current distribution between the voltage converters is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a control method for a battery charging circuit and a battery charging device. Background Art

[0002] Currently, the load current distribution between parallel-connected voltage converters in battery charging circuits is often uneven due to factors such as manufacturing variations, operating environment, or load characteristics. This can cause one voltage converter to be overloaded, overloaded, or even malfunction, while another converter may be lightly loaded or unloaded. Summary of the Invention

[0003] The present invention provides a control method for a battery charging circuit and a battery charging device to solve the problem of uneven load current distribution among voltage converters.

[0004] In a first aspect, the present invention provides a control method for a battery charging circuit, wherein the battery charging circuit includes a front-stage converter and a rear-stage converter, the front-stage converter including M buck-boost converters connected in parallel; wherein M is an integer greater than or equal to 1;

[0005] Control methods include:

[0006] The total current command value is determined according to the actual parameters of the battery; the total current command value is the total current value required to be output by the N-way buck-boost converter, where N is an integer greater than or equal to 1 and N is less than or equal to M;

[0007] Determining a current command value for each of the N buck-boost converters in operation according to the total current command value;

[0008] Determine an average current value output by each of N working buck-boost converters within K working cycles; where K is an integer greater than or equal to 1;

[0009] Determine the deviation percentage between the average current value output by each buck-boost converter in K working cycles and the current command value of each buck-boost converter;

[0010] The current command value of each working buck-boost converter is adjusted according to the deviation percentage to achieve the same average current value output by each working buck-boost converter within L working cycles; wherein L is an integer greater than K.

[0011] Optionally, the total current command value is determined based on actual battery parameters, including:

[0012] Determine the battery charging mode according to the actual voltage of the battery;

[0013] Determining a battery charging power command value based on the battery charging mode, the battery temperature, and the battery temperature rise curve; the battery charging power command value is a target power value for controlling battery charging;

[0014] Determine the actual charging power of the battery based on the actual voltage of the battery and the actual current flowing into the battery;

[0015] The total current command value is calculated based on the battery charging power command value and the actual charging power of the battery.

[0016] Optionally, a battery charging mode is determined according to the actual voltage of the battery, including:

[0017] When the actual voltage of the battery is less than or equal to the first threshold voltage, the charging mode of the battery is controlled to be the first constant current mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1; when the actual voltage of the battery is greater than the first voltage threshold and less than or equal to the second threshold voltage, the charging mode of the battery is controlled to be the second constant current mode, and the N-way buck-boost converters are controlled to operate, where N is an integer greater than 1 and less than or equal to M; when the actual voltage of the battery is greater than or equal to the second threshold voltage, the charging mode of the battery is controlled to be the constant voltage mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1.

[0018] Optionally, determining a current command value of each of the N buck-boost converters according to the total current command value includes:

[0019] The total current command value is divided by N to obtain the current command value of each of the N buck-boost converters.

[0020] Optionally, determining a deviation percentage between an average current value output by each working buck-boost converter during K working cycles and a current command value of each buck-boost converter includes:

[0021] Subtract the average current value from the current command value, and then divide it by the current command value to get the deviation percentage;

[0022] Adjust the current command value of each buck-boost converter according to the deviation percentage, including:

[0023] When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the sum of the current command value and the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the current command value minus the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

[0024] Optionally, determining a deviation percentage between an average current value output by each working buck-boost converter during K working cycles and a current command value of each buck-boost converter includes:

[0025] Subtract the current command value from the average current value, and then divide it by the current command value to get the deviation percentage;

[0026] Adjust the current command value of each buck-boost converter according to the deviation percentage, including:

[0027] When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the current command value minus the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the sum of the current command value and the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

[0028] Optionally, determining an average current value output by each of the N buck-boost converters within K working cycles includes:

[0029] Obtain the actual current value output by each buck-boost converter in K working cycles in real time;

[0030] Calculate the actual total current value output by each buck-boost converter within K working cycles;

[0031] The actual total current value is divided by K to obtain the average current value output by each buck-boost converter in K working cycles.

[0032] In a second aspect, the present invention provides a battery charging device, wherein the battery charging device includes a plurality of controllers and a battery charging circuit;

[0033] The battery charging circuit includes a front-stage converter and a rear-stage converter, the front-stage converter and the rear-stage converter are connected, and the rear-stage converter is connected to the battery;

[0034] The front-stage converter includes M buck-boost converters connected in parallel; wherein M is an integer greater than or equal to 1; the rear-stage converter includes an LLC resonant converter; the controllers are provided in a one-to-one correspondence with the buck-boost converters, the buck-boost converters are connected to the corresponding controllers, and the multiple controllers are connected to each other;

[0035] The controller corresponding to one of the working buck-boost converters is used to execute the control method of the battery charging circuit according to any one of claims 1 to 7.

[0036] Optionally, the buck-boost converter includes: a first transistor, a second transistor, a third transistor, a fourth transistor, a first inductor, and a first capacitor;

[0037] A first end of the first transistor is connected to the positive electrode of the DC power supply, a second end of the first transistor is connected to the first end of the second transistor, and a second end of the second transistor is connected to the negative electrode of the DC power supply; a first end of the fourth transistor is connected to the positive bus, a second end of the fourth transistor is connected to the first end of the third transistor, and a second end of the third transistor is connected to the negative bus; a first inductor is connected between the second end of the first transistor and the first end of the third transistor, and a first capacitor is connected between the positive bus and the negative bus;

[0038] The input end of the LLC resonant converter is connected to the positive bus and the negative bus.

[0039] Optionally, the LLC resonant converter includes: a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a twelfth transistor, a resonant capacitor, a resonant inductor, an excitation inductor, a winding coil, and an output capacitor;

[0040] The output end of each buck-boost converter is connected to the positive bus and the negative bus; the first end of the fifth transistor is connected to the positive bus, the second end of the fifth transistor is connected to the first end of the sixth transistor, and the second end of the sixth transistor is connected to the negative bus; the first end of the eighth transistor is connected to the positive bus, the second end of the eighth transistor is connected to the first end of the seventh transistor, and the second end of the seventh transistor is connected to the negative bus;

[0041] The first end of the resonant capacitor is connected to the second end of the fifth transistor, the second end of the resonant capacitor is connected to the first end of the resonant inductor, the second end of the resonant inductor is connected to the first end of the winding coil, and the second end of the winding coil is connected to the first end of the seventh transistor; the excitation inductor is connected between the first end and the second end of the winding coil;

[0042] a first terminal of a ninth transistor connected to the positive electrode of the battery, a second terminal of the ninth transistor connected to the first terminal of the tenth transistor, and a second terminal of the tenth transistor connected to the negative electrode of the battery; a first terminal of a twelfth transistor connected to the positive electrode of the battery, a second terminal of the twelfth transistor connected to the first terminal of the eleventh transistor, and a second terminal of the eleventh transistor connected to the negative electrode of the battery;

[0043] The third end and the fourth end of the winding coil are connected to the second end of the ninth transistor and the first end of the eleventh transistor, and the output capacitor is connected between the positive electrode and the negative electrode of the battery.

[0044] According to the technical solution of the embodiment of the present invention, the controller as the master can perform closed-loop control of the system input power, calculate the total current command value based on the actual parameters of the battery, determine the current command value of each of the N buck-boost converters based on the total current command value, control the corresponding controller as the slave to calculate the average current value output by each buck-boost converter over K working cycles and the deviation percentage of the current command value of each buck-boost converter, and adjust the current command value of each buck-boost converter based on the deviation percentage to achieve the same average current value output by each buck-boost converter over L working cycles, thereby achieving closed-loop control of the system. The technical solution of the embodiment of the present invention can achieve current sharing among multiple buck-boost converters in the battery charging circuit, thereby solving the problem of uneven load current distribution between parallel-connected voltage converters in the current battery charging circuit.

[0045] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0047] Figure 1 1 is a schematic structural diagram of a battery charging device provided by an embodiment of the present invention;

[0048] Figure 2 is a flow chart of a method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0049] Figure 3 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of a structure of a controller provided by an embodiment of the present invention for calculating a total current command value based on a battery charging power command value and an actual charging power of the battery;

[0051] Figure 5 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0052] Figure 6 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0053] Figure 7 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0054] Figure 8 This is a schematic structural diagram of a controller provided by an embodiment of the present invention, which obtains the duty cycle of the buck-boost converter of a corresponding branch based on the current command value and real-time current sampling value of the buck-boost converter of a single branch;

[0055] Figure 9 This is a calculation flow chart of a controller for obtaining a duty cycle of a buck-boost converter provided by an embodiment of the present invention;

[0056] Figure 10 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0057] Figure 11 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention;

[0058] Figure 12 The figure is a structural diagram of a battery charging circuit and battery connection provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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.

[0060] It should be noted that the terms "first", "second", etc. in the description 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.

[0061] Figure 1 is a structural diagram of a battery charging device provided by an embodiment of the present invention. Figure 2FIG. 1 is a flow chart of a method for controlling a battery charging circuit provided by an embodiment of the present invention. Figure 2 As shown, the battery charging device includes multiple controllers 40 and a battery charging circuit 1. The battery charging circuit 1 includes a front-stage converter 10 and a rear-stage converter 20. The front-stage converter 10 is connected to the rear-stage converter 20, and the rear-stage converter 20 is connected to the battery 30. The front-stage converter 10 includes M buck-boost converters 11 connected in parallel, where M is an integer greater than or equal to 1. The controllers 40 are arranged in a one-to-one correspondence with the buck-boost converters 11, and the buck-boost converters 11 are connected to the corresponding controllers 40. The multiple controllers 40 are connected to each other. Figure 2 As shown, the control method of the battery charging circuit 1 includes:

[0062] S100: Determine a total current command value based on actual battery parameters; the total current command value is the total current value required to control N buck-boost converters, where N is an integer greater than or equal to 1 and N is less than or equal to M.

[0063] Specifically, such as Figure 1 As shown, the battery charging device is powered on, the controller 40 is awakened and starts working, and each buck-boost converter 11 has a DC voltage input. The controllers 40 are connected to each other in communication, and each controller 40 can number the buck-boost converter 11 corresponding to it. For example, the buck-boost converters 11 can be numbered in sequence. The controllers 40 communicate with each other and select the controller 40 corresponding to one of the buck-boost converters 11 as the master, and the controllers 40 corresponding to the remaining buck-boost converters 11 as slaves. The master can control the slaves in communication, so that the slaves control the buck-boost converters 11 corresponding to the slaves, and the master can also control the buck-boost converters 11 corresponding to the slaves. For example, the controllers 40 communicate with each other, and the controller 40 corresponding to the buck-boost converter 11 with the smallest number and a DC voltage input can be selected as the master.

[0064] The host controller 40 can detect the actual parameters of the battery 30, which may include the actual voltage of the battery 30, the temperature of the battery 30, the temperature rise curve of the battery 30, and the actual current flowing into the battery 30. The host controller 40 can control the operation of the N-way buck-boost converter 11 based on the actual parameters of the battery 30. For example, when the charging mode of the battery 30 requires low-current charging, the host controller 40 can control the operation of one buck-boost converter 11, that is, the host controller 40 controls the operation of the corresponding buck-boost converter 11. When the charging mode of the battery 30 requires high-current charging, the host controller 40 can control the operation of the N-way buck-boost converter 11.

[0065] The controller 40 as the host can calculate the total current command value based on the actual parameters of the battery 30. The total current command value is the total current value output by the N-way buck-boost converters 11 that need to work when the controller 40 as the host issues the command.

[0066] S110: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0067] Specifically, such as Figure 1 As described above, the controller 40 as the host divides the total current command value by N to obtain the current command value that each working buck-boost converter 11 needs to output. The initial current command value corresponding to each working buck-boost converter 11 is the same.

[0068] S120: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0069] Specifically, the controller 40 serving as the master can detect the actual output current of each working buck-boost converter 11 in real time and calculate the average current value output by each working buck-boost converter 11 within K working cycles. The controller 40 serving as the master can also control the controller 40 serving as the slave to detect the actual output current of the corresponding working buck-boost converter 11 in real time and calculate the average current value output by the corresponding working buck-boost converter 11 within K working cycles.

[0070] S130: Determine a deviation percentage between an average current value output by each buck-boost converter within K working cycles and a current command value of each buck-boost converter.

[0071] Specifically, the controller 40 as the master can calculate the difference between the current command value and the average current value of each working buck-boost converter 11, and divide the difference by the corresponding current command value as the deviation percentage. The controller 40 as the master can also control the controller 40 as the slave to calculate the difference between the current command value and the average current value of the corresponding working buck-boost converter 11, and divide the difference by the corresponding current command value as the deviation percentage. The deviation percentage can reflect the relationship between the current command value and the average current value of each working buck-boost converter 11, as well as the degree of deviation between the current command value and the average current value of each working buck-boost converter 11.

[0072] S140: Adjust the current command value of each buck-boost converter according to the deviation percentage to achieve the same average current value output by each buck-boost converter within L working cycles; where L is an integer greater than K.

[0073] Specifically, such as Figure 1 As shown, the current command value of each buck-boost converter 11 is adjusted according to the deviation percentage. For example, the current command value of each buck-boost converter 11 can be 2A, and the actual average current output of the buck-boost converter 11 can be 2.1A. The controller 40 as the master can control the corresponding controller 40 as the slave to subtract the current average value from the current command value, and then divide it by the current command value to obtain the deviation percentage. In this case, the deviation percentage is a negative value. Then, the current command value is multiplied by the absolute value of the deviation percentage as a correction value. Finally, the current command value is subtracted from the correction value to obtain a new current command value. After obtaining the new current command value, the corresponding controller 40 can adjust the duty cycle of the buck-boost converter 11, thereby adjusting the current actually output by the buck-boost converter 11. In this way, the average current value output by the buck-boost converter 11 within L working cycles is close to the initial current command value, that is, close to 2A. The actual average current output by the buck-boost converter 11 of the other circuit can be 1.8A. The master controller 40 can control the corresponding slave controller 40 to subtract the average current value from the current command value, and then divide it by the current command value to obtain the deviation percentage. In this case, the deviation percentage is a positive value. The current command value is then multiplied by the deviation percentage to obtain a correction value. Finally, the correction value is added to the current command value to obtain a new current command value. After obtaining the new current command value, the corresponding controller 40 can adjust the duty cycle of the buck-boost converter 11, thereby adjusting the actual current output by the buck-boost converter 11. This ensures that the average current value output by the buck-boost converter 11 over L operating cycles is close to the initial current command value, that is, close to 2A. The actual average current output by the buck-boost converter 11 of the other circuit can be 2A, and the corresponding current command value is not adjusted in this case. Through the above adjustment process, the average current value output by each operating buck-boost converter 11 over L operating cycles can be the same.

[0074] According to the technical solution of the embodiment of the present invention, the controller 40, acting as the master, can perform closed-loop control of the system input power. It calculates a total current command value based on the actual parameters of the battery 30, determines the current command value for each of the N buck-boost converters 11 based on the total current command value, and controls the corresponding slave controller 40 to calculate the deviation percentage between the average current value output by each buck-boost converter 11 over K working cycles and the current command value of each buck-boost converter 11. Based on the deviation percentage, the current command value of each buck-boost converter 11 is adjusted to ensure that the average current value output by each buck-boost converter 11 over L working cycles is the same, thereby achieving closed-loop control of the system. The technical solution of the embodiment of the present invention can achieve current sharing among multiple buck-boost converters 11 operating in the battery charging circuit 1, thereby solving the problem of uneven load current distribution between parallel-connected voltage converters in the current battery charging circuit.

[0075] Optionally, based on the above embodiments, Figure 3 FIG. 1 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention. Figure 3 The control method of the battery charging circuit includes:

[0076] S200: Determine a battery charging mode according to the actual voltage of the battery.

[0077] Specifically, such as Figure 1 As shown, the controller 40 as the host can detect the actual voltage of the battery 30, and determine the charging mode of the battery 30 according to the current actual voltage of the battery 30, and then control the number of operations of the buck-boost converter 11 according to the charging mode of the battery 30.

[0078] S210: Determine a charging power command value for the battery according to the battery charging mode, the battery temperature, and the battery temperature rise curve; the charging power command value for the battery is a target power value for controlling charging of the battery.

[0079] Specifically, such as Figure 1 As shown, the controller 40, acting as the host, can sample the current temperature of the battery 30 in the current charging mode of the battery 30 and calculate the charging power command value of the battery 30 based on the temperature sample and the temperature rise curve of the battery 30. The charging power command value is a command issued by the controller 40, acting as the host, requiring the battery charging circuit 1 to provide the target charging power to the battery 30.

[0080] S220: Determine the actual charging power of the battery according to the actual voltage of the battery and the actual current flowing into the battery.

[0081] Specifically, such as Figure 1As shown, the controller 40 as the host can detect the current actual voltage of the battery 30 and the actual current flowing into the battery 30, and calculate the actual charging power of the battery 30. The calculation formula is as follows:

[0082] P S =V bat *I bat

[0083] Among them, P s is the actual charging power of the battery 30, V bat is the actual current voltage of the battery 30, I bat is the actual current flowing into the battery 30 .

[0084] S230: Calculate a total current command value based on the battery charging power command value and the actual charging power of the battery. The total current command value is the total current value required to control the output of N buck-boost converters, where N is an integer greater than or equal to 1 and less than or equal to M.

[0085] Specifically, Figure 4 FIG. 1 is a schematic diagram showing a structure of a controller according to an embodiment of the present invention for calculating a total current command value based on a battery charging power command value and an actual charging power of the battery. Figure 1 and Figure 4 As shown, the controller 40 may include a battery input power controller 41, which sets the battery charging power command value P ref and the actual charging power P of the battery 30 s Input to the battery input power controller 41, the battery input power controller 41 may include a proportional integral regulator, the battery input power controller 41 may be based on the battery charging power command value P ref and the actual charging power P of the battery 30 s Calculate the total current command value I t_ref .

[0086] S240: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0087] S250: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0088] S260: Determine a deviation percentage between an average current value output by each buck-boost converter in K working cycles and a current command value of each buck-boost converter.

[0089] S270: Adjust the current command value of each buck-boost converter according to the deviation percentage to achieve the same average current value output by each buck-boost converter within L working cycles; where L is an integer greater than K.

[0090] Optionally, based on the above embodiments, Figure 5 FIG. 1 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention. Figure 5 As shown, the control method of the battery charging circuit includes:

[0091] S300: When the actual voltage of the battery is less than or equal to the first threshold voltage, the battery charging mode is controlled to be the first constant current mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1; when the actual voltage of the battery is greater than the first voltage threshold and less than or equal to the second threshold voltage, the battery charging mode is controlled to be the second constant current mode, and the N-way buck-boost converters are controlled to operate, where N is an integer greater than 1 and less than or equal to M; when the actual voltage of the battery is greater than or equal to the second threshold voltage, the battery charging mode is controlled to be the constant voltage mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1.

[0092] Specifically, such as Figure 1 As shown, the controller 40 as the host can detect the actual voltage of the battery 30, and determine the charging mode of the battery 30 according to the current actual voltage of the battery 30, and then control the number of working buck-boost converters 11 according to the charging mode of the battery 30. If the controller 40 as the host detects that the voltage of the battery 30 is less than or equal to the first threshold voltage, the controller 40 as the host needs to control the charging mode of the battery 30 to be the first constant current mode. In the first constant current mode, the charging current of the battery 30 is constant and small, and the voltage of the battery 30 increases. At this time, the controller 40 as the host communicates with other controllers as slaves to control the corresponding buck-boost converters 11 of the other slaves to not work. The number of working buck-boost converters 11 is one, and the controller 40 as the host determines the power allocation number to be 1. The controller 40 as the host divides the total current command value by the power allocation number to obtain the current command value that each working buck-boost converter 11 needs to output.

[0093] If the controller 40 acting as the host detects that the voltage of the battery 30 is greater than the first threshold voltage and less than or equal to the second threshold voltage, the controller 40 acting as the host needs to control the charging mode of the battery 30 to the second constant current mode. In the second constant current mode, the charging current of the battery 30 is constant and large, and the voltage of the battery 30 increases significantly. At this time, the controller 40 acting as the host communicates with other controllers acting as slaves to set the number of working buck-boost converters 11 to N, where N is greater than 1 and less than or equal to M. The controller 40 acting as the host dynamically detects the driving input status of each buck-boost converter 11, counts the number of buck-boost converter branches 11 that have received external inputs and completed the communication handshake, and determines the power allocation number N. The controller 40 acting as the host divides the total current command value by the power allocation number to obtain the current command value that each working buck-boost converter 11 needs to output.

[0094] If the host controller 40 detects that the voltage of the battery 30 is greater than the second threshold voltage, the host controller 40 needs to control the charging mode of the battery 30 to a constant voltage mode. In this constant voltage mode, the output voltage of the battery charging circuit 1 is constant, and the charging current of the battery 30 is low. At this time, the host controller 40 communicates with the other slave controllers 40 to control the corresponding buck-boost converters 11 to be non-operating, so that only one buck-boost converter 11 is in operation. The host controller 40 also determines that the power allocation number is 1. The host controller 40 divides the total current command value by the power allocation number to obtain the current command value required to be output by each active buck-boost converter 11.

[0095] S310: Determine a charging power command value for the battery according to the battery charging mode, the battery temperature, and the battery temperature rise curve; the charging power command value for the battery is a target power value for controlling charging of the battery.

[0096] S320: Determine the actual charging power of the battery according to the actual voltage of the battery and the actual current flowing into the battery.

[0097] S330: Calculate a total current command value based on the battery charging power command value and the actual charging power of the battery. The total current command value is the total current value required to control the output of N buck-boost converters, where N is an integer greater than or equal to 1 and less than or equal to M.

[0098] S340: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0099] S350: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0100] S360: Determine a deviation percentage between an average current value output by each buck-boost converter within K working cycles and a current command value of each buck-boost converter.

[0101] S370: Adjust the current command value of each buck-boost converter according to the deviation percentage to achieve the same average current value output by each buck-boost converter within L working cycles; where L is an integer greater than K.

[0102] Optional, Figure 6 FIG. 1 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention. Figure 6 As shown, the control method of the battery charging circuit includes:

[0103] S400: When the actual voltage of the battery is less than or equal to the first threshold voltage, the battery charging mode is controlled to be the first constant current mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1; when the actual voltage of the battery is greater than the first voltage threshold and less than or equal to the second threshold voltage, the battery charging mode is controlled to be the second constant current mode, and the N-way buck-boost converters are controlled to operate, where N is an integer greater than 1 and less than or equal to M; when the actual voltage of the battery is greater than or equal to the second threshold voltage, the battery charging mode is controlled to be the constant voltage mode, and the N-way buck-boost converters are controlled to operate, where N is equal to 1.

[0104] S410: Determine a charging power command value for the battery according to the battery charging mode, the battery temperature, and the battery temperature rise curve; the charging power command value for the battery is a target power value for controlling charging of the battery.

[0105] S420: Determine the actual charging power of the battery according to the actual voltage of the battery and the actual current flowing into the battery.

[0106] S430: Calculate a total current command value based on the battery charging power command value and the actual charging power of the battery. The total current command value is the total current value required to control the output of N buck-boost converters, where N is an integer greater than or equal to 1 and less than or equal to M.

[0107] S440: Divide the total current command value by N to obtain a current command value for each of the N buck-boost converters.

[0108] Specifically, such as Figure 1As shown, the controller 40 as the host determines that the number of working buck-boost converters 11 is N, where N is an integer greater than or equal to 1 and less than or equal to M. That is, the controller 40 as the host determines that the power distribution number is N, and the controller 40 as the host divides the total current command value by N to calculate the current command value of each of the N working buck-boost converters 11. The calculation formula is as follows:

[0109]

[0110] Among them, I s_ref is the current command value of each buck-boost converter 11, I t_ref is the total current command value, and N is the number of working buck-boost converters 11.

[0111] S450: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0112] S460: Determine a deviation percentage between an average current value output by each buck-boost converter in K working cycles and a current command value of each buck-boost converter.

[0113] S470: Adjust the current command value of each buck-boost converter according to the deviation percentage to achieve the same average current value output by each buck-boost converter within L working cycles; where L is an integer greater than K.

[0114] Optionally, based on the above embodiments, Figure 7 FIG. 1 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention. Figure 7 As shown, the control method of the battery charging circuit includes:

[0115] S500: Determine a total current command value based on actual battery parameters; the total current command value is the total current value required to output by controlling N buck-boost converters, where N is an integer greater than or equal to 1 and N is less than or equal to M.

[0116] S510: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0117] S520: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0118] S530: Subtract the average current value from the current command value, and then divide the result by the current command value to obtain a deviation percentage.

[0119] Specifically, the controller 40 acting as the host obtains the current sampling value of the corresponding buck-boost converter 11 in real time, and calculates the total current value of K working cycles, thereby calculating the average current value of K working cycles. The controller 40 acting as the host subtracts the average current value from the current command value, and then divides it by the current command value to obtain the deviation percentage.

[0120] The controller 40 as the host controls the other N-1 controllers 40 as slaves to obtain the current sampling values ​​of the corresponding buck-boost converters 11 in real time, and calculates the total current value of K working cycles, thereby calculating the average current value of K working cycles. The controller 40 as the host controls the other N-1 controllers 40 as slaves to subtract the average current value from the current command value, and then divide it by the current command value to obtain the deviation percentage.

[0121] S540: When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the sum of the current command value and the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the current command value minus the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

[0122] Specifically, Figure 8 1 is a schematic structural diagram of a controller according to an embodiment of the present invention, which obtains the duty cycle of the buck-boost converter of a corresponding branch based on the current command value and real-time current sampling value of the buck-boost converter of a single branch. Figure 9 FIG. 1 is a flow chart showing a controller for obtaining a duty cycle of a buck-boost converter according to an embodiment of the present invention. Figure 1 、 Figure 8 and Figure 9 As shown, I s_ref1 , I s_ref2 ...I s_refN I1, I2, ..., I represents the current command value of the first working branch buck-boost converter 11, the current command value of the second working branch buck-boost converter 11, ..., the current command value of the N-th working branch buck-boost converter 11. N represents the current sampling value of the first working branch buck-boost converter 11, the current sampling value of the second working branch buck-boost converter 11, ... the current sampling value of the N-th working branch buck-boost converter 11, I 1_avg , I 2_avg ...I N_avgrepresents the average current value within K working cycles of the buck-boost converter 11 of the first working branch, the average current value within K working cycles of the buck-boost converter 11 of the second working branch, ..., the average current value within K working cycles of the buck-boost converter 11 of the Nth working branch, A1, A2, ..., AN represent the deviation percentage corresponding to the buck-boost converter 11 of the first working branch, the deviation percentage corresponding to the buck-boost converter 11 of the second working branch, ..., the deviation percentage corresponding to the buck-boost converter 11 of the Nth working branch, D1, D2, ..., D N It represents the duty cycle of the first working branch's buck-boost converter 11, the duty cycle of the second working branch's buck-boost converter 11, and so on, the duty cycle of the N-th working branch's buck-boost converter 11.

[0123] The controller 40 corresponding to the N active branches of the buck-boost converter 11 calculates the average current value for K working cycles based on the real-time current sampling values ​​over K working cycles. It then subtracts the average current value from the current command value, and divides the result by the current command value to obtain the deviation percentage for the corresponding branch. The deviation percentage can be negative or positive. When the deviation percentage is positive, the product of the current command value and the deviation percentage is used as the first correction value, and the sum of the current command value and the first correction value is used as the new current command value. When the deviation percentage is negative, the product of the current command value and the deviation percentage is used as the second correction value, and the sum of the current command value and the second correction value is used as the new current command value. When the deviation percentage is zero, the current command value remains unchanged. The controller 40 may include a branch current controller 42, which can calculate the duty cycle of the buck-boost converter 11 for the corresponding branch based on the new current command value and the current sampling values, thereby adjusting the actual output current of the buck-boost converter 11. This ensures that the average current value output by the buck-boost converter 11 over L working cycles is close to the initial current command value.

[0124] Optionally, based on the above embodiments, Figure 10 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention, characterized in that: Figure 10 As shown, the control method of the battery charging circuit includes:

[0125] S600: Determine a total current command value based on actual battery parameters; the total current command value is the total current value required to control N buck-boost converters, where N is an integer greater than or equal to 1 and N is less than or equal to M.

[0126] S610: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0127] S520: Determine an average current value output by each of the N buck-boost converters within K working cycles; wherein K is an integer greater than or equal to 1.

[0128] S630: Subtract the current command value from the average current value, and then divide the result by the current command value to obtain a deviation percentage.

[0129] Specifically, such as Figure 1 As shown, the controller 40 as the host obtains the current sampling value of the corresponding buck-boost converter 11 in real time, and calculates the total current value of K working cycles, thereby calculating the average current value of K working cycles. The controller 40 as the host subtracts the current command value from the average current value, and then divides it by the current command value to obtain the deviation percentage.

[0130] The controller 40 as the host controls the other N-1 controllers 40 as slaves to obtain the current sampling values ​​of the corresponding buck-boost converter 11 in real time, and calculates the total current value of K working cycles, thereby calculating the average current value of K working cycles. The controller 40 as the host controls the other N-1 controllers 40 as slaves to subtract the current command value from the average current value, and then divide it by the current command value to obtain the deviation percentage.

[0131] S640: When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the current command value minus the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the sum of the current command value and the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

[0132] Specifically, the controller 40 corresponding to the buck-boost converter 11 of each of the N active branches calculates the average current value for K working cycles based on the real-time current sampling values ​​over K working cycles. The controller 40 then subtracts the current command value from the average current value, and divides the result by the current command value to obtain the deviation percentage for the corresponding branch. The deviation percentage can be negative or positive. When the deviation percentage is positive, the product of the current command value and the deviation percentage is used as the first correction value, and the new current command value is obtained by subtracting the first correction value from the current command value. When the deviation percentage is negative, the product of the current command value and the deviation percentage is used as the second correction value, and the new current command value is obtained by subtracting the second correction value from the current command value. When the deviation percentage is zero, the current command value remains unchanged. The controller 40 can calculate the duty cycle of the buck-boost converter 11 of the corresponding branch based on the new current command value and the current sampling values, thereby adjusting the actual output current of the buck-boost converter 11. This ensures that the average current value output by the buck-boost converter 11 over L working cycles is close to the initial current command value.

[0133] Optionally, based on the above embodiments, Figure 11 is a flow chart of another method for controlling a battery charging circuit provided by an embodiment of the present invention, characterized in that: Figure 11 As shown, the control method of the battery charging circuit includes:

[0134] S700: Determine a total current command value based on actual battery parameters; the total current command value is the total current value required to control the output of N buck-boost converters, where N is an integer greater than or equal to 1 and N is less than or equal to M.

[0135] S710: Determine a current command value for each of the N buck-boost converters according to the total current command value.

[0136] S720: Acquire in real time the actual current value output by each buck-boost converter within K working cycles.

[0137] Specifically, such as Figure 1 As shown, the controller 40 as the host obtains the current sampling value output by the corresponding buck-boost converter 11 within K working cycles in real time, and the controller 40 as the host controls the other N-1 controllers 40 as slaves to obtain the current sampling value output by the corresponding buck-boost converter 11 within K working cycles in real time.

[0138] S730: Calculate the actual total current value output by each buck-boost converter within K working cycles.

[0139] Specifically, such as Figure 1 As shown, the controller 40 serving as the host calculates the total current value of K working cycles, and the controller 40 serving as the host controls the other N-1 controllers 40 serving as slaves to calculate the total current value of K working cycles.

[0140] S740: Divide the actual total current value by K to obtain the average current value output by each buck-boost converter in K working cycles.

[0141] Specifically, such as Figure 1 As shown, the controller 40 as the master divides the actual total current value by K to obtain the average current value output by the buck-boost converter 11 of the corresponding branch within K working cycles. The controller 40 as the master controls the controllers 40 of the other N-1 slaves to divide the actual total current value by K to obtain the average current value output by the buck-boost converter 11 of the corresponding branch within K working cycles.

[0142] S750: Determine a deviation percentage between an average current value output by each buck-boost converter within K working cycles and a current command value of each buck-boost converter.

[0143] S760: Adjust the current command value of each buck-boost converter according to the deviation percentage to ensure that the average current value output by each buck-boost converter within L working cycles is the same; where L is an integer greater than K.

[0144] Optionally, based on the above embodiments, continue to refer to Figure 1 The battery charging device includes multiple controllers 40 and a battery charging circuit 1. The battery charging circuit 1 includes a front-stage converter 10 and a rear-stage converter 20. The front-stage converter 10 is connected to the rear-stage converter 20, and the rear-stage converter 20 is connected to the battery 30. The front-stage converter 10 includes M buck-boost converters 11 connected in parallel; wherein M is an integer greater than or equal to 1. The rear-stage converter 20 includes an LLC resonant converter. The controllers 40 are arranged in a one-to-one correspondence with the buck-boost converters 11, and the buck-boost converters 11 are connected to the corresponding controllers 40, and the multiple controllers 40 are connected to each other. The controller 40 corresponding to one of the working buck-boost converters 11 is used to execute the control method of the battery charging circuit provided by any of the above embodiments of the present invention, and has the beneficial effects of the control method of the charging circuit provided by any of the above embodiments of the present invention.

[0145] According to the technical solution of the embodiment of the present invention, the battery charging circuit 1 includes a two-stage battery charging control circuit with multiple parallel inputs and series outputs, a front-stage converter 10 composed of multiple buck-boost converters 11 connected in parallel, and a rear-stage converter 20 composed of an LLC resonant converter. Compared with the existing single-stage battery charging circuit, the two-stage conversion topology can reduce circuit pressure on the one hand and improve system efficiency on the other hand. By adjusting the duty cycle of the multiple buck-boost converters 11 connected in parallel and the voltage gain of the LLC resonant converter, it can adapt to application scenarios with a wide range of voltage outputs. At the same time, the two-stage battery charging circuit with multiple parallel inputs and then series outputs can comprehensively optimize the device selection cost and improve charging efficiency.

[0146] Optionally, based on the above embodiments, Figure 12 FIG. 1 is a structural diagram of a battery charging circuit and a battery connection provided by an embodiment of the present invention. Figure 1 and Figure 12As shown, the buck-boost converter 11 includes a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a first inductor L1, and a first capacitor C1. The first end of the first transistor T1 is connected to the positive electrode of the DC power supply Uin, the second end of the first transistor T1 is connected to the first end of the second transistor T2, and the second end of the second transistor T2 is connected to the negative electrode of the DC power supply Uin. The first end of the fourth transistor T4 is connected to the positive bus L+, the second end of the fourth transistor T4 is connected to the first end of the third transistor T3, and the second end of the third transistor T3 is connected to the negative bus L-. The first inductor L1 is connected between the second end of the first transistor T1 and the first end of the third transistor T3, and the first capacitor C1 is connected between the positive bus L+ and the negative bus L-. The input of the LLC resonant converter is connected to the positive bus L+ and the negative bus L-.

[0147] Specifically, the buck-boost converter 11 may include a four-switch buck-boost converter, wherein the control terminals of the first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 may be connected to a corresponding controller 40. The controller 40, acting as the master, may control the on-time and off-time of the corresponding first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 according to the latest current command value, thereby controlling the duty cycle of the corresponding buck-boost converter 11, thereby achieving an average current value output by the buck-boost converter 11 within L working cycles close to the initial current command value. The controller 40, acting as the master, may control the controller 40, acting as the slave, to control the on-time and off-time of the corresponding first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 according to the latest current command value, thereby controlling the duty cycle of the corresponding buck-boost converter 11, thereby achieving an average current value output by the buck-boost converter 11 within L working cycles close to the initial current command value. Ultimately, the average current value output by each working buck-boost converter 11 within L working cycles is the same.

[0148] Optionally, based on the above embodiments, continue to refer to Figure 12The LLC resonant converter includes: a fifth transistor T5, a sixth transistor T6, a seventh transistor T7, an eighth transistor T8, a ninth transistor T9, a tenth transistor T10, an eleventh transistor T11, a twelfth transistor T12, a resonant capacitor Cr, a resonant inductor Lr, an excitation inductor Lm, a winding Ln, and an output capacitor Co. The output end of each buck-boost converter 11 is connected to the positive bus L+ and the negative bus L-. The first end of the fifth transistor T5 is connected to the positive bus L+, the second end of the fifth transistor T5 is connected to the first end of the sixth transistor T6, and the second end of the sixth transistor T6 is connected to the negative bus L-. The first end of the eighth transistor T8 is connected to the positive bus L+, the second end of the eighth transistor T8 is connected to the first end of the seventh transistor T7, and the second end of the seventh transistor T7 is connected to the negative bus L-. The first end of the resonant capacitor Cr is connected to the second end of the fifth transistor T5. The second end of the resonant capacitor Cr is connected to the first end of the resonant inductor Lr. The second end of the resonant inductor Lr is connected to the first end of the winding coil Ln. The second end of the winding coil Ln is connected to the first end of the seventh transistor T7. The excitation inductor Lm is connected between the first and second ends of the winding coil Ln. The first end of the ninth transistor T9 is connected to the positive electrode of the battery 30. The second end of the ninth transistor T9 is connected to the first end of the tenth transistor T10. The second end of the tenth transistor T10 is connected to the negative electrode of the battery 30. The first end of the twelfth transistor T12 is connected to the positive electrode of the battery 30. The second end of the twelfth transistor T12 is connected to the first end of the eleventh transistor T11. The second end of the eleventh transistor T11 is connected to the negative electrode of the battery 30. The third and fourth ends of the winding coil Ln are connected to the second end of the ninth transistor T9 and the first end of the eleventh transistor T11. The output capacitor Co is connected between the positive and negative electrodes of the battery 30.

[0149] Specifically, as the operating current of each buck-boost converter 11 increases, the input voltage of the subsequent cascaded LLC resonant converter reaches the operating threshold and starts generating power. The LLC resonant converter uses open-loop control, with an operating frequency at the resonant point fr and a gain of 1. Based on the LLC resonant converter's transformation ratio, the bus voltage of the multiple parallel buck-boost converters 11 is clamped to the product of the battery 30 voltage and the LLC resonant converter's transformation ratio.

[0150] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0151] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for controlling a battery charging circuit, characterized in that: The battery charging circuit includes a front-stage converter and a rear-stage converter, wherein the front-stage converter includes M buck-boost converters connected in parallel; wherein M is an integer greater than or equal to 1; The control method includes: Determine a total current command value based on actual parameters of the battery; the total current command value is the total current value required to be output by the buck-boost converters for controlling N circuits, where N is an integer greater than or equal to 1 and less than or equal to M; Determining a current command value of each of the N buck-boost converters according to the total current command value; Determine an average current value output by each of the N buck-boost converters in K working cycles; wherein K is an integer greater than or equal to 1; Determine a deviation percentage between an average current value output by each buck-boost converter in K working cycles and a current command value of each buck-boost converter; The current command value of each buck-boost converter in operation is adjusted according to the deviation percentage to achieve the same average current value output by each buck-boost converter in operation within L working cycles; wherein L is an integer greater than K.

2. The control method of the battery charging circuit according to claim 1, characterized in that: The total current command value is determined based on the actual parameters of the battery, including: determining a charging mode of the battery according to an actual voltage of the battery; determining a charging power command value for the battery according to a charging mode of the battery, a temperature of the battery, and a temperature rise curve of the battery; the charging power command value for the battery is a target power value for controlling charging of the battery; determining an actual charging power of the battery according to an actual voltage of the battery and an actual current flowing into the battery; The total current command value is calculated according to the charging power command value of the battery and the actual charging power of the battery.

3. The control method of the battery charging circuit according to claim 2, characterized in that: Determining a charging mode of the battery according to an actual voltage of the battery includes: When the actual voltage of the battery is less than or equal to the first threshold voltage, the charging mode of the battery is controlled to be a first constant current mode, and the N-way buck-boost converter is controlled to operate, where N is equal to 1; when the actual voltage of the battery is greater than the first voltage threshold and less than or equal to the second threshold voltage, the charging mode of the battery is controlled to be a second constant current mode, and the N-way buck-boost converter is controlled to operate, where N is an integer greater than 1 and less than or equal to M; when the actual voltage of the battery is greater than or equal to the second threshold voltage, the charging mode of the battery is controlled to be a constant voltage mode, and the N-way buck-boost converter is controlled to operate, where N is equal to 1.

4. The control method of the battery charging circuit according to claim 1, characterized in that: Determining a current command value of each of the N buck-boost converters according to the total current command value includes: The total current command value is divided by N to obtain the current command value of each of the N buck-boost converters.

5. The control method of the battery charging circuit according to claim 1, characterized in that: Determining a deviation percentage between an average current value output by each working buck-boost converter in K working cycles and a current command value of each working buck-boost converter includes: Subtracting the average current value from the current command value and dividing the result by the current command value to obtain the deviation percentage; Adjusting the current command value of each buck-boost converter according to the deviation percentage includes: When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the sum of the current command value and the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the current command value minus the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

6. The control method of the battery charging circuit according to claim 1, characterized in that: Determining a deviation percentage between an average current value output by each working buck-boost converter in K working cycles and a current command value of each working buck-boost converter includes: Subtracting the current command value from the average current value and dividing the result by the current command value to obtain the deviation percentage; Adjusting the current command value of each buck-boost converter according to the deviation percentage includes: When the deviation percentage is a positive number, the product of the current command value and the deviation percentage is used as the first correction value, and the current command value minus the first correction value is used as the new current command value; when the deviation percentage is a negative number, the product of the current command value and the absolute value of the deviation percentage is used as the second correction value, and the sum of the current command value and the second correction value is used as the new current command value; when the deviation percentage is zero, the current command value remains unchanged.

7. The control method of the battery charging circuit according to claim 1, characterized in that: Determining an average current value output by each of the N buck-boost converters within K working cycles includes: Real-time acquisition of the actual current value output by each buck-boost converter within K working cycles; Calculating the actual total current value output by the buck-boost converter of each path within K working cycles; The actual total current value is divided by K to obtain the average current value output by each buck-boost converter in K working cycles.

8. A battery charging device, characterized in that: The battery charging device includes a plurality of controllers and a battery charging circuit; The battery charging circuit includes a front-stage converter and a rear-stage converter, the front-stage converter is connected to the rear-stage converter, and the rear-stage converter is connected to the battery; The front-stage converter includes M buck-boost converters connected in parallel; wherein M is an integer greater than or equal to 1; the rear-stage converter includes an LLC resonant converter; the controllers are provided in a one-to-one correspondence with the buck-boost converters, the buck-boost converters are connected to the corresponding controllers, and the multiple controllers are connected to each other; The controller corresponding to one of the working buck-boost converters is used to execute the control method of the battery charging circuit according to any one of claims 1 to 7.

9. The battery charging device according to claim 8, characterized in that The buck-boost converter includes: a first transistor, a second transistor, a third transistor, a fourth transistor, a first inductor and a first capacitor; A first end of the first transistor is connected to the positive electrode of a DC power supply, a second end of the first transistor is connected to the first end of the second transistor, and a second end of the second transistor is connected to the negative electrode of the DC power supply; a first end of the fourth transistor is connected to the positive bus, a second end of the fourth transistor is connected to the first end of the third transistor, and a second end of the third transistor is connected to the negative bus; the first inductor is connected between the second end of the first transistor and the first end of the third transistor, and the first capacitor is connected between the positive bus and the negative bus; The input end of the LLC resonant converter is connected to the positive bus and the negative bus.

10. The battery charging device according to claim 8, characterized in that The LLC resonant converter includes: a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, an eleventh transistor, a twelfth transistor, a resonant capacitor, a resonant inductor, an excitation inductor, a winding coil and an output capacitor; The output end of each buck-boost converter is connected to a positive bus and a negative bus; the first end of the fifth transistor is connected to the positive bus, the second end of the fifth transistor is connected to the first end of the sixth transistor, and the second end of the sixth transistor is connected to the negative bus; the first end of the eighth transistor is connected to the positive bus, the second end of the eighth transistor is connected to the first end of the seventh transistor, and the second end of the seventh transistor is connected to the negative bus; The first end of the resonant capacitor is connected to the second end of the fifth transistor, the second end of the resonant capacitor is connected to the first end of the resonant inductor, the second end of the resonant inductor is connected to the first end of the winding coil, and the second end of the winding coil is connected to the first end of the seventh transistor; the excitation inductor is connected between the first end and the second end of the winding coil; a first end of the ninth transistor connected to the positive electrode of the battery, a second end of the ninth transistor connected to the first end of the tenth transistor, and a second end of the tenth transistor connected to the negative electrode of the battery; a first end of the twelfth transistor connected to the positive electrode of the battery, a second end of the twelfth transistor connected to the first end of the eleventh transistor, and a second end of the eleventh transistor connected to the negative electrode of the battery; The third end and the fourth end of the winding coil are connected to the second end of the ninth transistor and the first end of the eleventh transistor, and the output capacitor is connected between the positive electrode and the negative electrode of the battery.

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