Closed-loop control method and device of LLC resonant converter

Abstract

The invention discloses a closed-loop control method and device for an LLC resonant converter. The method comprises the following steps: determining a frequency adjustment range; taking a minimum output signal in the output voltage loop, the output current loop and the battery current loop as a minimum loop output signal; generating a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty ratio; the switching frequency is adjusted based on the first fitted curve and the duty cycle is adjusted based on the second fitted curve to control an output voltage, an output current, and a battery current of the LLC resonant converter. According to the LLC resonant converter, closed-loop control of the LLC resonant converter is realized, the gain range can be improved, the output voltage range can be expanded, the output current and the battery current can be accurately limited, the stability and dynamic response of the output voltage can be adjusted according to loop output, and the dynamic nature and robustness of the system are improved.

Description

Technical Field

[0001] The present application relates to the field of LLC resonant converters, and in particular to a closed-loop control method and device for LLC resonant converters. Background Art

[0002] LLC resonant converter is a widely used topology in the field of power electronics, especially in high efficiency and high power density power conversion systems.

[0003] Traditional LLC resonant circuits usually use open-loop control (not relying on feedback signals). The resonant tank design parameters are simple, and the output voltage cannot be controlled stably or the output current can not be accurately limited. In addition, the gain cannot reach greater than 1. Therefore, the output voltage range is narrow and cannot meet the needs of some special power supply requirements. Summary of the invention

[0004] The purpose of the present application is to provide a closed-loop control method, device, electronic device and computer-readable storage medium of an LLC resonant converter, which can improve the gain range, expand the output voltage range, accurately limit the output current and battery current, and regulate the stability of the output voltage.

[0005] In order to achieve the above object, the present application provides a closed-loop control method of an LLC resonant converter, wherein the output of the LLC resonant converter includes an output voltage, an output current and a battery current, and the control loop of the LLC resonant converter includes an output voltage loop, an output current loop and a battery current loop, and the method includes:

[0006] Determine the frequency adjustment range;

[0007] taking the minimum output signal among the output voltage loop, the output current loop and the battery current loop as the minimum loop output signal;

[0008] generating a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle;

[0009] The switching frequency is adjusted based on the first fitting curve and the duty cycle is adjusted based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter.

[0010] Optionally, determining the frequency adjustment range includes:

[0011] determining a first resonant frequency and a second resonant frequency of the resonant converter, the second resonant frequency being less than the first resonant frequency;

[0012] The frequency adjustment range is determined based on the first resonant frequency and the second resonant frequency.

[0013] Optionally, the calculation formula of the first resonant frequency is:

[0014]

[0015] The calculation formula of the second resonant frequency is:

[0016]

[0017] Among them, f r is the first resonant frequency, f m is the second resonant frequency, L r is the resonant inductor, C r is the resonant capacitor, L m is the magnetizing inductance.

[0018] Optionally, based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage and a third stage;

[0019] The first stage is in the drive-off stage and the range of the minimum loop output signal is less than or equal to a first preset value in the first stage. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency of the frequency adjustment range;

[0020] In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage;

[0021] In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the switching frequency is assigned to the maximum frequency, when the minimum loop output signal is equal to the fourth preset value, the switching frequency is assigned to the minimum frequency of the frequency adjustment range, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage;

[0022] The first preset value is smaller than the second preset value, the second preset value is smaller than the third preset value, the third preset value is smaller than the fourth preset value, and the fourth preset value is equal to 1.

[0023] Optionally, the first preset value is between 0.003 and 0.007.

[0024] Optionally, the second preset value is between 0.03 and 0.10, the third preset value is between 0.08 and 0.15, and the difference between the third preset value and the second preset value is between 0.03 and 0.07.

[0025] In order to achieve the above object, the present application also provides a closed-loop control device for an LLC resonant converter, wherein the output of the LLC resonant converter includes an output voltage, an output current and a battery current, and the control loop of the LLC resonant converter includes an output voltage loop, an output current loop and a battery current loop, and the device includes:

[0026] A determination device for determining a frequency adjustment range;

[0027] an acquisition device, used for taking the minimum output signal among the output voltage loop, the output current loop and the battery current loop as a minimum loop output signal;

[0028] A generating device, used to generate a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle;

[0029] A regulating device is used to regulate the switching frequency based on the first fitting curve and to regulate the duty cycle based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter.

[0030] Optionally, based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage and a third stage;

[0031] The first stage is in the drive-off stage and the range of the minimum loop output signal is less than or equal to a first preset value in the first stage. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency of the frequency adjustment range;

[0032] In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage;

[0033] In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the switching frequency is assigned to the maximum frequency, when the minimum loop output signal is equal to the fourth preset value, the switching frequency is assigned to the minimum frequency of the frequency adjustment range, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage;

[0034] The first preset value is smaller than the second preset value, the second preset value is smaller than the third preset value, the third preset value is smaller than the fourth preset value, and the fourth preset value is equal to 1.

[0035] In order to achieve the above object, the present application also provides an electronic device, including:

[0036] processor;

[0037] a memory storing executable instructions of the processor;

[0038] The processor is configured to execute the closed-loop control method of the LLC resonant converter as described above by executing the executable instructions.

[0039] In order to achieve the above-mentioned purpose, the present application also provides a computer-readable storage medium, on which a program is stored, and when the program is executed by a processor, the closed-loop control method of the LLC resonant converter as described above is implemented.

[0040] In the embodiment of the present application, the minimum output signal in the output voltage loop, the output current loop and the battery current loop is taken as the minimum loop output signal, and then the first fitting curve of the minimum loop output signal and the switching frequency and the second fitting curve of the minimum loop output signal and the duty cycle are generated, and then the switching frequency is adjusted based on the first fitting curve and the duty cycle is adjusted based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter. It can be seen that the present application realizes the closed-loop control of the LLC resonant converter, which can improve the gain range, expand the output voltage range, accurately limit the output current and battery current, and can adjust the stability and dynamic response of the output voltage according to the loop output, thereby improving the dynamics and robustness of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Flow chart of a closed-loop control method of an LLC resonant converter in an embodiment of the present application.

[0042] Figure 2 4 is a structural block diagram of a closed-loop control device of an LLC resonant converter in an embodiment of the present application.

[0043] Figure 3 is a block diagram of an LLC control loop in an embodiment of the present application.

[0044] Figure 4 4 is a topology diagram of the LLC resonant converter in an embodiment of the present application.

[0045] Figure 5 It is a schematic block diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0047] The embodiments of the present application disclose a closed-loop control method and device for an LLC resonant converter.

[0048] like Figure 4 As shown, the LLC resonant converter includes an input voltage source V in , inverter circuit I, resonant cavity II, transformer T and secondary side rectifier circuit III, resonant cavity II includes resonant capacitor C r , resonant inductor L r and the magnetizing inductance L m The output of LLC resonant converter includes output voltage, output current and battery current. Figure 3 As shown, the control loop of the LLC resonant converter involved therein includes an output voltage loop 100 , an output current loop 200 and a battery current loop 300 .

[0049] In a specific example of this application, the LLC resonant converter is as follows:

[0050] Input voltage source V in There is an input capacitor C in parallel in The inverter circuit I is a full-bridge inverter circuit I, including four switch tubes Q1, Q2, Q3 and Q4. The input end of the full-bridge inverter circuit I is connected to the input voltage V in The full-bridge inverter circuit I is used to convert the input DC voltage into an AC square wave voltage. The output end of the full-bridge inverter circuit I is connected in series with the resonant cavity II, where the excitation inductance L mExisting in transformer T, resonant cavity II exhibits different impedance characteristics at different switching frequencies, so the LLC resonant converter can adjust the voltage by changing the switching frequency. The output end of resonant cavity II is connected to the input end of transformer Tr, and transformer T is used to adjust the AC voltage. The secondary rectifier circuit III includes diodes D1, D2, D3, and D4, which together form a full-bridge diode rectifier circuit. The input end of the secondary rectifier circuit III is connected to the output end of transformer T, which is used to convert the AC voltage output by transformer T into a DC voltage. The output end of the secondary rectifier circuit III is connected to the output capacitor C o and diode D5, output capacitor C o Used to filter and maintain the stability of the output voltage.

[0051] The output voltage loop 100 is used to control the stability of the output voltage. Ref and the output voltage feedback value V dc The output obtained after the difference is processed by PI is the output voltage signal. The output current loop 200 is used to limit the maximum output current. dcRef With the output current I dc The output obtained after the difference is processed by PI is the output current signal. The battery current loop 300 is used to limit the battery current to stably charge the set external components. batref and the battery current feedback value I bat The output obtained after the difference is processed by PI is the battery current signal. In the control method of the embodiment of the present application, the output voltage signal, the output current signal and the battery current signal are compared, and the minimum value of the three is taken as the minimum loop output signal.

[0052] See also Figure 1 as well as Figure 3 and Figure 4 , the closed-loop control method of the LLC resonant converter in the embodiment of the present application includes:

[0053] S1, determine the frequency adjustment range Min_F ~ Max_F.

[0054] In some implementations, determining the frequency adjustment range Min_F to Max_F includes:

[0055] Determining a first resonant frequency and a second resonant frequency (peak frequency) of the resonant converter, the second resonant frequency being less than the first resonant frequency;

[0056] A frequency adjustment range Min_F to Max_F is determined based on the first resonant frequency and the second resonant frequency.

[0057] When the switching frequency is at the first resonant frequency, the gain of the LLC resonant converter is 1, and when the switching frequency is at the second resonant frequency, the gain of the LLC resonant converter is greater than 1. For the frequency adjustment range of Min_F to Max_F, the gain is maximum when the switching frequency is Min_F, and the gain is minimum when the switching frequency is Max_F.

[0058] Specifically, the calculation formula of the first resonant frequency is:

[0059]

[0060] The calculation formula for the second resonant frequency is:

[0061]

[0062] Among them, f r is the first resonant frequency, f m is the second resonant frequency, L r is the resonant inductor, C r is the resonant capacitor, L m is the magnetizing inductance.

[0063] It should be understood that the gain can be adjusted by adjusting the switching frequency within the frequency adjustment range Min_F ~ Max_F. When determining the frequency adjustment range Min_F ~ Max_F, Min_F should be selected near the second resonant frequency fm to ensure that the required gain can still be obtained at the lowest input voltage. Max_F should be selected near the first resonant frequency fr to avoid increased switching losses and reduced efficiency caused by excessive switching frequency. LLC resonant converters may exhibit unstable behavior in certain frequency ranges, especially when approaching the resonant frequency point. Therefore, when determining Min_F and Max_F, these unstable areas need to be avoided. In addition, the stable operating frequency range can be determined by experiment or simulation, and Min_F and Max_F can be selected accordingly. According to the simulation and experimental results, the most appropriate Min_F and Max_F values ​​are selected by comprehensively considering factors such as gain range, stability and efficiency.

[0064] S2, taking the minimum output signal among the output voltage loop, the output current loop and the battery current loop as the minimum loop output signal.

[0065] S3, generating a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle.

[0066] In some implementations, based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage (PWM duty cycle adjustment stage) and a third stage (PFM frequency adjustment stage). The three stages of the first fitting curve and the second fitting curve are consistent, and are divided in the same way based on the range of the minimum loop output signal.

[0067] The first stage is in the drive-off stage and the range of the minimum loop output signal in the first stage is less than or equal to the first preset value. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency Max_F of the frequency adjustment range Min_F to Max_F.

[0068] In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency Max_F, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage (the two endpoints are connected).

[0069] In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the assigned switching frequency is the maximum frequency Max_F, when the minimum loop output signal is equal to the fourth preset value, the assigned switching frequency is the minimum frequency Min_F in the frequency adjustment range Min_F to Max_F, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage (the two endpoints are connected).

[0070] The first preset value is less than the second preset value, the second preset value is less than the third preset value, the third preset value is less than the fourth preset value, and the fourth preset value is equal to 1.

[0071] Specifically, in the first stage, Pwm_Prd=Max_F_PRD, D_Dead=Pwm_Prd-1, wherein Pwm_Prd is the PRD value corresponding to the frequency, Max_F_PRD is the PRD value of the maximum frequency Max_F, and D_Dead is the dead zone corresponding to the duty cycle.

[0072] In the second stage, Pwm_Prd=Max_F_PRD, D_Dead=D_K*LoopOut+D_B, where D_K is the duty cycle fitting coefficient, LoopOut is the minimum loop output signal, and D_B is the duty cycle fitting bias.

[0073] In the third stage, Pwm_Prd=F_K*LoopOut+F_B, D_Dead=Min_Dead, where F_K is the frequency fitting coefficient, F_B is the frequency fitting bias, and Min_Dead is the dead zone corresponding to the maximum duty cycle.

[0074] Specifically, the first preset value is between 0.003 and 0.007.

[0075] Specifically, the second preset value is between 0.03 and 0.10, the third preset value is between 0.08 and 0.15, and the difference between the third preset value and the second preset value is between 0.03 and 0.07.

[0076] In a specific example, the first preset value is 0.005, the second preset value is 0.05, and the third preset value is 0.10.

[0077] In a specific example, the first duty cycle value is 20% (ignoring the dead zone), and the second duty cycle value is 50% (ignoring the dead zone).

[0078] S4, adjusting the switching frequency based on the first fitting curve and adjusting the duty cycle based on the second fitting curve to control the output of the LLC resonant converter, the output of the LLC resonant converter including the output voltage, the output current and the battery current. That is, when in the corresponding stage, the switching frequency and the duty cycle are adjusted based on the corresponding fitting curve to control the output voltage, the output current and the battery current of the LLC resonant converter.

[0079] In an embodiment of the present application, the minimum output signal in the output voltage loop, the output current loop and the battery current loop is taken as the minimum loop output signal, and then a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle are generated, and then the switching frequency is adjusted based on the first fitting curve and the duty cycle is adjusted based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter. It can be seen that the present application realizes the closed-loop control of the LLC resonant converter, which can improve the gain range, expand the output voltage range, accurately limit the output current and battery current, and can adjust the stability and dynamic response of the output voltage according to the loop output, thereby improving the dynamics and robustness of the system. In addition, the embodiment of the present application can achieve a one-to-one correspondence between the size of the loop output and the system gain in the aforementioned three stages, that is, a smooth transition of the full power range is achieved.

[0080] Please combine Figures 2 to 4 The embodiment of the present application discloses a closed-loop control device for an LLC resonant converter. The device comprises:

[0081] Determining means 201, for determining a frequency adjustment range Min_F to Max_F;

[0082] The acquisition device 202 is used to obtain the minimum output signal among the output voltage loop, the output current loop and the battery current loop as the minimum loop output signal;

[0083] A generating device 203, used to generate a first fitting curve of a minimum loop output signal and a switching frequency and a second fitting curve of a minimum loop output signal and a duty cycle;

[0084] The regulating device 204 is used to regulate the switching frequency based on the first fitting curve and to regulate the duty cycle based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter.

[0085] In some implementations, based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage (PWM duty cycle adjustment stage) and a third stage (PFM frequency adjustment stage).

[0086] The first stage is in the drive-off stage and the range of the minimum loop output signal in the first stage is less than or equal to the first preset value. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency Max_F of the frequency adjustment range Min_F to Max_F.

[0087] In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency Max_F, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage (the two endpoints are connected).

[0088] In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the assigned switching frequency is the maximum frequency Max_F, when the minimum loop output signal is equal to the fourth preset value, the assigned switching frequency is the minimum frequency Min_F in the frequency adjustment range Min_F to Max_F, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage (the two endpoints are connected).

[0089] The first preset value is less than the second preset value, the second preset value is less than the third preset value, the third preset value is less than the fourth preset value, and the fourth preset value is equal to 1.

[0090] In an embodiment of the present application, the minimum output signal in the output voltage loop, the output current loop and the battery current loop is taken as the minimum loop output signal, and then a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle are generated, and then the switching frequency is adjusted based on the first fitting curve and the duty cycle is adjusted based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter. It can be seen that the present application realizes the closed-loop control of the LLC resonant converter, which can improve the gain range, expand the output voltage range, accurately limit the output current and battery current, and can adjust the stability and dynamic response of the output voltage according to the loop output, thereby improving the dynamics and robustness of the system. In addition, the embodiment of the present application can achieve a one-to-one correspondence between the size of the loop output and the system gain in the aforementioned three stages, that is, a smooth transition of the full power range is achieved.

[0091] Please combine Figure 5 , the embodiment of the present application further provides an electronic device, including:

[0092] Processor 30;

[0093] a memory 40 in which executable instructions of the processor 30 are stored;

[0094] The processor 30 is configured to execute the closed-loop control method of the LLC resonant converter as described above by executing executable instructions.

[0095] In order to achieve the above-mentioned purpose, the present application also provides a computer-readable storage medium, on which a program is stored, and when the program is executed by a processor, the closed-loop control method of the LLC resonant converter as described above is implemented.

[0096] It should be understood that in the embodiments of the present application, the processor referred to may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0097] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by hardware related to computer program instructions, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0098] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0099] The above disclosure is only a preferred example of the present application and cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are all within the scope covered by the present application.

Claims

1. A closed-loop control method for an LLC resonant converter, wherein the output of the LLC resonant converter includes an output voltage, an output current and a battery current, and the control loop of the LLC resonant converter includes an output voltage loop, an output current loop and a battery current loop, wherein: The method comprises: Determine the frequency adjustment range; taking the minimum output signal among the output voltage loop, the output current loop and the battery current loop as the minimum loop output signal; generating a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle; The switching frequency is adjusted based on the first fitting curve and the duty cycle is adjusted based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter.

2. The closed-loop control method of the LLC resonant converter according to claim 1, characterized in that: Determining the frequency adjustment range includes: determining a first resonant frequency and a second resonant frequency of the resonant converter, the second resonant frequency being less than the first resonant frequency; The frequency adjustment range is determined based on the first resonant frequency and the second resonant frequency.

3. The closed-loop control method of LLC resonant converter according to claim 2, characterized in that: The calculation formula of the first resonant frequency is: The calculation formula of the second resonant frequency is: Among them, f r is the first resonant frequency, f m is the second resonant frequency, L r is the resonant inductor, C r is the resonant capacitor, L m is the magnetizing inductance.

4. The closed-loop control method of the LLC resonant converter according to claim 1, characterized in that: Based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage and a third stage; The first stage is in the drive-off stage and the range of the minimum loop output signal is less than or equal to a first preset value in the first stage. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency of the frequency adjustment range; In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage; In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the switching frequency is assigned to the maximum frequency, when the minimum loop output signal is equal to the fourth preset value, the switching frequency is assigned to the minimum frequency of the frequency adjustment range, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage; The first preset value is smaller than the second preset value, the second preset value is smaller than the third preset value, the third preset value is smaller than the fourth preset value, and the fourth preset value is equal to 1.

5. The closed-loop control method of LLC resonant converter according to claim 4, characterized in that: The first preset value is between 0.003 and 0.

007.

6. The closed-loop control method of the LLC resonant converter according to claim 4 or 5, characterized in that: The second preset value is between 0.03 and 0.10, the third preset value is between 0.08 and 0.15, and the difference between the third preset value and the second preset value is between 0.03 and 0.

07.

7. A closed-loop control device for an LLC resonant converter, wherein the output of the LLC resonant converter includes an output voltage, an output current and a battery current, and the control loop of the LLC resonant converter includes an output voltage loop, an output current loop and a battery current loop, wherein: The device comprises: A determination device for determining a frequency adjustment range; an acquisition device, used for taking the minimum output signal among the output voltage loop, the output current loop and the battery current loop as a minimum loop output signal; A generating device, used to generate a first fitting curve of the minimum loop output signal and the switching frequency and a second fitting curve of the minimum loop output signal and the duty cycle; A regulating device is used to regulate the switching frequency based on the first fitting curve and to regulate the duty cycle based on the second fitting curve to control the output voltage, output current and battery current of the LLC resonant converter.

8. The closed-loop control device of the LLC resonant converter according to claim 7, characterized in that: Based on the range of the minimum loop output signal, the first fitting curve and the second fitting curve are divided into a first stage, a second stage and a third stage; The first stage is in the drive-off stage and the range of the minimum loop output signal is less than or equal to a first preset value in the first stage. In the first stage, the duty cycle is 0, and the switching frequency takes the maximum frequency of the frequency adjustment range; In the second stage, the range of the minimum loop output signal is between the second preset value and the third preset value, the switching frequency maintains the maximum frequency, when the minimum loop output signal is equal to the second preset value, the initial duty cycle is assigned to the first duty cycle value, when the minimum loop output signal is equal to the third preset value, the duty cycle is assigned to the second duty cycle value, the second duty cycle value is the maximum duty cycle value, and the second fitting curve is obtained by linearization processing between the two endpoints of the second stage; In the third stage, the range of the minimum loop output signal is between the third preset value and the fourth preset value, the duty cycle maintains the second duty cycle value, when the minimum loop output signal is equal to the third preset value, the switching frequency is assigned to the maximum frequency, when the minimum loop output signal is equal to the fourth preset value, the switching frequency is assigned to the minimum frequency of the frequency adjustment range, and the first fitting curve is obtained by linearization processing between the two endpoints of the third stage; The first preset value is smaller than the second preset value, the second preset value is smaller than the third preset value, the third preset value is smaller than the fourth preset value, and the fourth preset value is equal to 1.

9. An electronic device, characterized in that: include: processor; a memory storing executable instructions of the processor; The processor is configured to execute the closed-loop control method of the LLC resonant converter according to any one of claims 1 to 6 by executing the executable instructions.

10. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the closed-loop control method of the LLC resonant converter according to any one of claims 1 to 6 is implemented.

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