Hybrid control soft start method for LLC full-bridge converter

Abstract

The invention relates to the technical field of converter starting, in particular to an LLC full-bridge converter hybrid control soft start method, comprising the following steps: selecting a hybrid soft start strategy combining down-conversion starting and PWM starting, and respectively introducing nonlinear orders of a control switch frequency decline curve in the down-conversion starting process and a duty ratio rise curve in the PWM starting process; defining a mathematical formula of the change of the switching frequency and the duty ratio along with time when two nonlinear orders are different in value; establishing a simulation model, and substituting a mathematical formula that the switching frequency and the duty ratio change along with time when the two nonlinear orders are different in value into the simulation model; performing simulation testing on the nonlinear orders with different values, extracting the maximum resonance current, and determining an order combination with the best maximum resonance current suppression effect; and performing soft start of the LLC full-bridge converter based on the determined order combination. According to the invention, the current in the soft start process can be effectively suppressed, and meanwhile, quick start and device safety are considered.

Description

Technical Field

[0001] This application relates to the technical field of converter startup, and particularly to a hybrid control soft startup method for LLC full-bridge converters. Background Art

[0002] In the process of new energy development and utilization, power electronics technology plays a crucial role. Especially for DC-DC converters, which are the key links of energy conversion, they need to have efficient and stable voltage conversion capabilities, reasonable voltage and current stress control, and excellent conversion efficiency. As a specific topology example of LLC resonant converters, LLC full-bridge converters have become the core devices for realizing bidirectional energy transmission in new energy systems because they can achieve soft-switching characteristics within a wide load range, while also taking into account high efficiency and low electromagnetic interference. However, during the startup process of LLC full-bridge converters, since the energy in the resonant cavity has not been established, the DC bus voltage is directly applied to the resonant network, resulting in extremely large resonant current spikes inside, which may damage power switch devices or magnetic components. Therefore, how to achieve the soft startup process of LLC full-bridge converters has become a key challenge in their design.

[0003] Currently, the main soft startup technologies for LLC full-bridge converters are frequency reduction startup strategies, PWM startup strategies, and phase-shift startup strategies. First, the frequency reduction startup strategy limits the current rise rate during the startup phase by setting the initial switching frequency much higher than the resonant frequency and utilizing the frequency's regulation characteristic of the resonant cavity impedance. As the output voltage gradually builds up, the switching frequency is gradually reduced to the steady-state operating point at a preset slope, thereby suppressing the resonant current peak. Secondly, during the startup phase of the PWM startup strategy, the duty cycle of the driving signals of the inverter bridge switching tubes is linearly increased from the initial value of 0 to the steady-state value (such as 50%), controlling the rate at which the DC bus transmits energy to the resonant cavity. The progressive adjustment of the duty cycle can slow down the voltage mutation of the resonant capacitor, thereby reducing the amplitude of the current spike. Finally, the phase-shift startup strategy controls the phase difference between the driving signals of the upper and lower bridge arms of the inverter bridge, gradually expanding from the initial 0° to 180°, and using the modulation effect of the phase-shift angle on the energy transmission path to inject energy into the resonant cavity in stages. The dynamic adjustment of the phase difference can effectively limit the rising slope of the resonant current, thus avoiding current overshoot.

[0004] Although the above strategies alleviate the problem of inrush current impact to a certain extent, their core still relies on the linear or piecewise regulation of a single control variable. Due to the highly non-linear characteristics of the LLC resonant network during startup, the linear change of a single control parameter is difficult to match the changing trend of the dynamic impedance of the resonant cavity in real time. For example, in the frequency-down startup strategy, the fixed decreasing rate of the switching frequency may cause the frequency adjustment to lag behind the energy accumulation rate of the resonant cavity, resulting in unstable current suppression effect. The PWM startup strategy and the phase-shift startup strategy can only adjust the energy transfer rate and cannot directly intervene in the instantaneous amplitude of the resonant current, resulting in limited ability to suppress the current peak. Therefore, the core problem existing in the prior art is that the linear regulation strategy of a single control dimension mismatches the non-linear dynamic characteristics of the LLC resonant cavity, resulting in insufficient current suppression accuracy during the soft startup process and making it difficult to balance fast startup and device safety. Summary of the Invention

[0005] The present application provides a hybrid control soft startup method for an LLC full-bridge converter, which can effectively suppress the current during the soft startup process and balance fast startup and device safety at the same time. The present application provides the following technical solutions: In a first aspect, the present application provides a hybrid control soft startup method for an LLC full-bridge converter, and the method includes: Select a hybrid soft startup strategy combining frequency-down startup and PWM startup and set initial parameters, where the initial parameters include the switching frequency and the duty cycle; Respectively introduce the non-linear order of the curve for controlling the decrease of the switching frequency during the frequency-down startup process and the non-linear order of the curve for the increase of the duty cycle during the PWM startup process, set the soft startup time, and define mathematical formulas for the variation of the switching frequency and the duty cycle with time when the two non-linear orders take different values; Establish an LLC full-bridge converter simulation model on a simulation software and set the model parameters, and substitute the mathematical formulas for the variation of the switching frequency and the duty cycle with time when the two non-linear orders take different values into the simulation model; Use the simulation model to perform simulation tests on the two non-linear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect; Based on the order combination with the best maximum resonant current suppression effect, adopt a hybrid soft startup strategy combining frequency-down startup and PWM startup to perform soft startup of the LLC full-bridge converter.

[0006] In a specific feasible implementation, the selection of a hybrid soft startup strategy combining frequency-down startup and PWM startup and setting initial parameters includes: Set the initial switching frequency of the excitation signal to the resonant frequency Triple that, the initial duty cycle of the excitation signal is set to 0%, and the steady-state duty cycle is set to 48%.

[0007] In a specific feasible implementation, the mathematical formulas defining the variation of the switching frequency and duty cycle with time for different values of the two non-linear orders include: Set the soft-start time to , that is, from the start moment to the steady-state establishment moment The time interval. During this time period, when the two non-linear orders take different values, the switching frequency and the duty cycle vary with time as shown by the following mathematical formulas: ; Where, is the resonant frequency, is the total soft-start time, is the steady-state duty cycle, is the non-linear order controlling the decline curve of the switching frequency during the frequency-down start, is the non-linear order of the duty cycle rise curve during the PWM start.

[0008] In a specific feasible implementation, establishing an LLC full-bridge converter simulation model on the simulation software and setting the model parameters include: Establish an LLC full-bridge converter simulation model on the SIMULINK, an extension tool of MATLAB. Set the soft-start duration to 5 ms and the resonant frequency to 60 kHz.

[0009] In a specific feasible implementation, substituting the mathematical formulas for the variation of the switching frequency and duty cycle with time for different values of the two non-linear orders into the simulation model includes: The specific mathematical formulas are as follows: ; Where, is the non-linear order controlling the decline curve of the switching frequency during the frequency-down start, is the non-linear order of the duty cycle rise curve during the PWM start.

[0010] In a specific feasible implementation, using the simulation model to perform simulation tests on different values of the two non-linear orders, extracting the maximum resonant current, and determining the order combination with the best maximum resonant current suppression effect includes: Use the mathematical formulas to set different and The combination simulates the variation of the switching frequency and duty cycle during the startup process. Under each set of parameters, the maximum resonant current data from startup to the steady state stage is extracted, and a three-dimensional relationship diagram of the maximum resonant current between and is plotted; By comparing the simulation results under each combination, it is determined which set of and can minimize the maximum resonant current.

[0011] In a second aspect, the present application provides an LLC full-bridge converter hybrid control soft-start system, adopting the following technical solutions: An LLC full-bridge converter hybrid control soft-start system includes: A strategy selection module for selecting a hybrid soft-start strategy combining frequency reduction startup and PWM startup and setting initial parameters, where the initial parameters include the switching frequency and the duty cycle; A non-linear order introduction module for respectively introducing the non-linear order of the control switching frequency decline curve during frequency reduction startup and the non-linear order of the duty cycle rise curve during PWM startup, setting the soft-start time, and defining mathematical formulas for the variation of the switching frequency and duty cycle with time when the two non-linear orders take different values; A simulation model construction module for building an LLC full-bridge converter simulation model on simulation software and setting model parameters, and substituting the mathematical formulas for the variation of the switching frequency and duty cycle with time when the two non-linear orders take different values into the simulation model; A simulation test module for performing simulation tests on the two non-linear orders with different values using the simulation model, extracting the maximum resonant current, and determining the order combination with the best maximum resonant current suppression effect; A soft-start module for performing soft start of the LLC full-bridge converter based on the order combination with the best maximum resonant current suppression effect, adopting a hybrid soft-start strategy combining frequency reduction startup and PWM startup.

[0012] In a third aspect, the present application provides an electronic device, where the device includes a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement an LLC full-bridge converter hybrid control soft-start method as described in the first aspect.

[0013] In a fourth aspect, the present application provides a computer-readable storage medium, where a program is stored in the storage medium, and the program is used to implement an LLC full-bridge converter hybrid control soft-start method as described in the first aspect when executed by a processor.

[0014] In summary, the beneficial effects of the present application at least include: (1) By adopting a hybrid soft-start strategy that combines frequency reduction start-up and PWM start-up, and introducing non-linear control parameters, the changes in the switching frequency and duty cycle can be precisely regulated during the start-up process, enabling the system to smoothly transition to the steady state within the predetermined soft-start time. This can significantly reduce the resonant current spikes caused by sudden energy changes in the resonant cavity, prevent current surges from damaging power devices and magnetic components, thereby improving the safety and reliability of the system.

[0015] (2) By adopting a high-frequency and zero-duty-cycle state at the initial stage of soft start, and then gradually reducing the switching frequency and increasing the duty cycle according to the non-linear model, the phased control of energy injection is realized. This can not only quickly establish the system energy in a short time, but also avoid unstable phenomena caused by sudden energy increase during start-up, thus ensuring that the system can smoothly reach the steady-state operating state in a relatively short time.

[0016] (3) Through the optimization of the non-linear order parameters, the dynamic adjustment of the switching frequency and duty cycle during the soft-start process can precisely match the non-linear impedance characteristics of the resonant cavity, thereby achieving double optimization of energy transmission and current suppression. This optimization not only reduces the switching losses and electromagnetic interference of the system, but also improves the conversion efficiency and dynamic response performance, providing reliable technical support for efficient energy conversion in new energy systems.

[0017] By combining the two strategies of frequency reduction start-up and PWM start-up, setting reasonable initial parameters, establishing a mathematical model describing the changes of the switching frequency and duty cycle with time during the start-up process using the introduced non-linear order parameters, and obtaining the optimal parameter combination through simulation tests in MATLAB / SimulINK, the system can be smoothly transitioned to the steady state within the predetermined soft-start time, effectively suppressing the resonant current spikes generated during the start-up process, solving the problem that it is difficult for traditional single control strategies to balance fast start-up and current suppression, and ensuring the safe and stable operation of power electronic devices.

[0018] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly and implement it in accordance with the content of the specification, the following provides a detailed description with reference to the preferred embodiments of this application and the accompanying drawings. Brief Description of the Drawings

[0019] Figure 1 It is a schematic flow chart of the hybrid control soft-start method for the LLC full-bridge converter in the embodiment of this application.

[0020] Figure 2 It is a graph showing the relationship between the switching frequency and duty cycle with time when m and n take different values in the embodiment of this application.

[0021] Figure 3In the embodiments of the present application, the startup process for different values of m and n is simulated, and the maximum resonant current from startup to the steady state stage is extracted, from which a three-dimensional relationship diagram of the maximum resonant current versus m and n is made.

[0022] Figure 4 In the embodiments of the present application, the resonant current waveforms during the startup process obtained by simulation are compared between direct startup, linear frequency reduction startup, linear PWM startup, and the hybrid control soft startup method of the LLC full-bridge converter.

[0023] Figure 5 In the embodiments of the present application, the resonant capacitor voltage waveforms during the startup process obtained by simulation are compared between direct startup, linear frequency reduction startup, linear PWM startup, and the hybrid control soft startup method of the LLC full-bridge converter.

[0024] Figure 6 In the embodiments of the present application, it is the structural block diagram of the hybrid control soft startup system of the LLC full-bridge converter.

[0025] Figure 7 In the embodiments of the present application, it is the block diagram of the electronic device for hybrid control soft startup of the LLC full-bridge converter. Specific Embodiments

[0026] The following combines the accompanying drawings and embodiments to further describe in detail the specific embodiments of the present application. The following embodiments are used to illustrate the present application, but are not used to limit the scope of the present application.

[0027] Optionally, the present application takes the hybrid control soft startup method of the LLC full-bridge converter provided in each embodiment as an example for illustration in an electronic device. The electronic device is a terminal or a server. The terminal can be a mobile phone, a computer, a tablet computer, etc. The type of the electronic device is not limited in this embodiment.

[0028] Refer to Figure 1 , which is a schematic flow diagram of the hybrid control soft startup method of the LLC full-bridge converter provided by an embodiment of the present application. The method at least includes the following steps: Step S101: Select a hybrid soft startup strategy combining frequency reduction startup and PWM startup and set initial parameters, where the initial parameters include the switching frequency and the duty cycle.

[0029] In step S101, a hybrid soft start strategy combining frequency reduction start and PWM start is first selected. The frequency reduction start strategy controls the impedance of the resonant cavity by adjusting the switching frequency, which can effectively suppress the current impact at the initial start-up, but its single frequency regulation is insufficient to control the energy transfer rate. The PWM start strategy adjusts the energy injection rate through the linear increase of the duty cycle, but there are limitations in suppressing the instantaneous peak of the resonant current. After the two are combined, the frequency reduction start strategy can dynamically adjust the impedance of the resonant cavity through the nonlinear change of the frequency, while the PWM start strategy can accurately control the acceleration of energy injection through the nonlinear change of the duty cycle. The two complement each other in the time domain: the high impedance characteristics at the initial stage of frequency reduction provide a buffer for the gradual increase of the duty cycle, and the accelerated increase of the duty cycle makes up for the lack of energy transmission efficiency in the later stage of frequency reduction, thereby achieving nonlinear collaborative suppression of the resonant current and avoiding the dynamic mismatch problem under a single control dimension.

[0030] Then set the initial parameters, including: the initial switching frequency of the excitation signal The resonant frequency The initial switching frequency is three times of that of the excitation signal, the initial duty cycle is set to 0%, and the steady-state duty cycle is set to 48%. Set to 3 times the resonant frequency The reason is that when the switching frequency Much larger than the resonant frequency When the frequency is 3 times, the resonant cavity presents high impedance characteristics, which can significantly limit the current rise rate. The 3 times frequency can balance the switching loss and current suppression requirements in engineering. If it is lower than 3 times, the suppression effect is insufficient, and if it is higher than 3 times, the switching loss increases dramatically. The initial duty cycle is set to 0 to completely block the energy injection at the moment of startup and avoid current spikes. The steady-state duty cycle is set to 48% instead of 50% to reserve a safety margin for the dead time of the switch tube, so the duty cycle is slightly lower than 50%, and 48% is a commonly used value in engineering.

[0031] In practice, the frequency reduction strategy maintains high frequency in the initial startup period to limit the current rise, while the PWM startup strategy keeps the duty cycle nonlinearly decreasing to reduce impedance, while the duty cycle nonlinearly increases to inject energy in stages. The frequency reduction rate and the duty cycle increase rate form a nonlinear coupling to ensure that the impedance change matches the energy transfer rate in real time, thereby avoiding sudden changes in the energy of the resonant cavity as much as possible.

[0032] Step S102, respectively introduce the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process and the nonlinear order of the duty cycle increase curve during the PWM startup process, set the soft start time, and define the mathematical formula for the change of the switching frequency and the duty cycle with time when the two nonlinear orders have different values.

[0033] In step S102, in order to precisely control the variation rules of the switching frequency and duty cycle during the soft start process, the non-linear order of the curve controlling the decrease of the switching frequency during the frequency reduction start process and the non-linear order of the curve of the duty cycle increase during the PWM start process are respectively introduced. Among them, the parameter is used to adjust the rate at which the switching frequency decreases from the initial value to the steady-state resonance frequency, while the parameter is used to control the rate at which the duty cycle rises from zero to the steady-state duty cycle. Different values of these two parameters will directly affect the smoothness of the energy injection into the resonant cavity during the soft start process, thus having a key impact on the suppression effect of the maximum resonant current.

[0034] To establish a mathematical formula, first set the soft start time as , that is, the time interval from the start moment to the steady-state establishment moment . During this time period, when and take different values, the mathematical formulas for the variation of the switching frequency and the duty cycle with time are as follows: ; Among them, is the resonance frequency, is the total soft start time, is the steady-state duty cycle, which is 0.48 in this application. At the start moment , the switching frequency is three times the resonance frequency, and the duty cycle is set to zero to ensure no energy injection at the start instant. At the steady-state establishment moment , after startup, the switching frequency drops to the resonance frequency, and the duty cycle rises to the set steady-state value of 48%.

[0035] Step S103: Establish an LLC full-bridge converter simulation model on the simulation software and set the model parameters, and substitute the mathematical formulas for the variation of the switching frequency and duty cycle with time when the two non-linear orders take different values into the simulation model.

[0036] In step S103, establish a simulation model of the LLC full-bridge converter on the SIMULINK, an extended tool of MATLAB, and clearly set the key model parameters. Among them, the soft start duration is set to 5 ms, and the resonance frequency is set to 60 kHz. The selection of the above parameters is based on engineering practice and experimental data: 5 ms is sufficient to achieve a fast and smooth startup transition, and the resonance frequency of 60 kHz is a value that has been verified more and has good effects in the current design. Then, substitute the mathematical model derived in step S102 into the simulation model, and the specific mathematical formulas are as follows: ; It can be seen that when and take different values, the switching frequency and the duty cycle vary with time as shown in the appendix Figure 2 and the relationship is non-linear.

[0037] Step S104: Use the simulation model to perform simulation tests on two non-linear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect.

[0038] In step S104, based on the simulation model established on the simulation software, perform simulation tests on the non-linear orders and with different values. Specifically, using the aforementioned mathematical formulas, set different and combinations respectively to simulate the changes in the switching frequency and duty cycle during the startup process. Under each set of parameters, extract the maximum resonant current data from the startup to the steady-state stage. After organizing these data, plot the three-dimensional relationship diagram between the maximum resonant current and and as shown in Figure 3 , which visually shows the startup effect under each parameter combination. By comparing the simulation results under each combination, determine which group of and can make the maximum resonant current reach the minimum value, thereby achieving the best suppression of the resonant current.

[0039] In implementation, the order combinations with better resonant current suppression effects are shown in Table 1:

[0040] It can be concluded that the order combination with the best current suppression effect is m = 2 and n = 8.

[0041] Step S105: Based on the order combination with the best maximum resonant current suppression effect, adopt a hybrid soft-start strategy combining frequency reduction startup and PWM startup to perform soft startup on the LLC full-bridge converter.

[0042] In step S105, based on the order combination with the best maximum resonant current suppression effect, adopt a hybrid soft-start strategy combining frequency reduction startup and PWM startup to perform soft startup on the LLC full-bridge converter. This strategy uses the optimal parameters to adjust the excitation signal in real time, enabling the system to smoothly transition to the steady-state within the predetermined soft-start duration, thereby effectively suppressing the resonant current and ensuring the safe and stable operation of the system.

[0043] In summary, by combining the frequency - reduction start - up and PWM start - up strategies, setting reasonable initial parameters, establishing a mathematical model that describes the variation of the switching frequency and duty cycle with time during the start - up process using the introduced non - linear order parameter, and obtaining the optimal parameter combination through simulation tests in MATLAB / SimulINK, the system can smoothly transition to the steady - state within the predetermined soft - start time, effectively suppressing the resonant current spikes generated during the start - up process, solving the problem that traditional single - control strategies are difficult to balance fast start - up and current suppression, and ensuring the safe and stable operation of power electronic devices.

[0044] In addition, preferably, to verify the suppression effect of the hybrid soft - start strategy on the resonant current and resonant capacitor voltage, common soft - start schemes are selected for comparison, such as linear frequency - reduction start - up (m = 1), linear PWM start - up (n = 1), and direct start - up. Substituting these combinations into the simulation model of the simulation software, the waveforms of the resonant current and resonant capacitor voltage during the start - up process are respectively as shown in Figure 4 and Figure 5 shown. It can be seen from the attached figures that the start - up time required for direct start - up is extremely short, and the current and voltage peaks both appear in the middle of the start - up. Under the frequency - reduction start - up strategy, the voltage and current at the initial stage of the converter start - up show a slightly decreasing trend and then slowly increase. When the switching frequency equals the resonant frequency, that is, when t = 5 ms, the voltage and current reach the peak, and then continuously decrease until the steady - state. Under the PWM start - up strategy, the voltage and current of the converter first rise slowly, remain unchanged for a period of time after reaching the peak, and have a small - amplitude fluctuation when the start - up is about to be completed, and then return to the steady - state; while under the hybrid soft - start strategy of the present application, the voltage and current of the converter increase slowly, reach the peak in the middle and late stages of the start - up, and then slightly decrease to the steady - state.

[0045]

[0046] It can be seen from the data in Table 2 that the hybrid - control soft - start method of the LLC full - bridge converter of the present application not only has a faster start - up speed but also has a better suppression effect on the resonant voltage and current.

[0047] Figure 6 FIG. is the structural block diagram of the hybrid - control soft - start system of the LLC full - bridge converter provided by an embodiment of the present application. The system at least includes the following modules: A strategy selection module, which is used to select a hybrid soft - start strategy that combines frequency - reduction start - up and PWM start - up and set the initial parameters. The initial parameters include the switching frequency and the duty cycle; A non - linear order introduction module is used to introduce the non - linear order of the control switch frequency decline curve during the frequency - down startup process and the non - linear order of the duty - cycle rise curve during the PWM startup process respectively, set the soft - start time, and define the mathematical formulas for the variation of the switch frequency and the duty - cycle with time when the two non - linear orders take different values; A simulation model construction module is used to establish an LLC full - bridge converter simulation model on simulation software and set the model parameters, and substitute the mathematical formulas for the variation of the switch frequency and the duty - cycle with time when the two non - linear orders take different values into the simulation model; A simulation test module is used to perform simulation tests on the two non - linear orders with different values by using the simulation model, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect; A soft - start module is used to perform soft - start of the LLC full - bridge converter based on the order combination with the best maximum resonant current suppression effect, adopting a hybrid soft - start strategy combining frequency - down startup and PWM startup.

[0048] For related details, refer to the method embodiment above.

[0049] Figure 7 It is a block diagram of an electronic device provided by an embodiment of the present application. The device at least includes a processor 401 and a memory 402.

[0050] The processor 401 may include one or more processing cores, such as a 4 - core processor, an 8 - core processor, etc. The processor 401 may be implemented in at least one of the hardware forms of DSP (Digital Signal Processing), FPGA (Field - Programmable Gate Array), and PLA (Programmable Logic Array). The processor 401 may also include a main processor and a coprocessor. The main processor is a processor used to process data in the wake - up state, also known as the CPU (Central Processing Unit); the coprocessor is a low - power processor used to process data in the standby state. In some embodiments, the processor 401 may be integrated with a GPU (Graphics Processing Unit), and the GPU is responsible for rendering and drawing the content required to be displayed on the display screen. In some embodiments, the processor 401 may also include an AI (Artificial Intelligence) processor, and the AI processor is used to process computational operations related to machine learning.

[0051] The memory 402 may include one or more computer-readable storage media, which may be non-transitory. The memory 402 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices and flash storage devices. In some embodiments, the non-transitory computer-readable storage media in the memory 402 is used to store at least one instruction for being executed by the processor 401 to implement the LLC full-bridge converter hybrid control soft start method provided in the method embodiments of the present application.

[0052] In some embodiments, the electronic device may further optionally include: a peripheral device interface and at least one peripheral device. The processor 401, the memory 402, and the peripheral device interface may be connected through a bus or signal lines. Each peripheral device may be connected to the peripheral device interface through a bus, signal lines, or a circuit board. Schematically, the peripheral devices include but are not limited to: a radio frequency circuit, a touch display screen, an audio circuit, and a power supply, etc.

[0053] Of course, the electronic device may also include fewer or more components, and this embodiment does not limit this.

[0054] Optionally, the present application also provides a computer-readable storage medium, in which a program is stored, and the program is loaded and executed by a processor to implement the LLC full-bridge converter hybrid control soft start method in the above method embodiments.

[0055] Optionally, the present application also provides a computer product, which includes a computer-readable storage medium, in which a program is stored, and the program is loaded and executed by a processor to implement the LLC full-bridge converter hybrid control soft start method in the above method embodiments.

[0056] The technical features of the above embodiments may be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0057] The above embodiments only represent several implementation manners of the present application, and the description thereof is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A hybrid control soft start method for LLC full-bridge converter, characterized in that: The method comprises: Select a hybrid soft start strategy that combines frequency reduction start and PWM start and set the initial parameters, including switching frequency and duty cycle; The nonlinear order of the switching frequency reduction curve during the frequency reduction start-up process and the nonlinear order of the duty cycle increase curve during the PWM start-up process are introduced respectively, the soft start time is set, and the mathematical formulas of the switching frequency and duty cycle changes with time when the two nonlinear orders have different values ​​are defined; Establish the LLC full-bridge converter simulation model on the simulation software and set the model parameters, and bring the mathematical formulas of the switching frequency and duty cycle changing with time when the two nonlinear orders have different values ​​into the simulation model; The simulation model is used to conduct simulation tests on two nonlinear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect; Based on the order combination with the best maximum resonant current suppression effect, a hybrid soft-start strategy combining frequency reduction start and PWM start is adopted to soft-start the LLC full-bridge converter.

2. The LLC full-bridge converter hybrid control soft-start method according to claim 1, characterized in that: The hybrid soft start strategy combining frequency reduction start and PWM start and setting initial parameters includes: Set the initial switching frequency of the excitation signal to The resonant frequency The initial duty cycle of the excitation signal is set to 0% and the steady-state duty cycle is set to 48%.

3. The LLC full-bridge converter hybrid control soft-start method according to claim 2, characterized in that: The mathematical formulas for defining the change of the switching frequency and the duty cycle over time when the two nonlinear orders have different values ​​include: Set the soft start time to , that is, from the start time To the time of steady state establishment The time interval during which the switching frequency is and duty cycle The mathematical formula for this change over time is as follows: ； in, is the resonant frequency, is the total soft start time, is the steady-state duty cycle, is the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process. It is the nonlinear order of the duty cycle rising curve during PWM startup.

4. The LLC full-bridge converter hybrid control soft-start method according to claim 3, characterized in that: The step of establishing a LLC full-bridge converter simulation model on the simulation software and setting model parameters includes: A simulation model of LLC full-bridge converter is established on SIMULINK, an extended tool of MATLAB. The soft-start duration is set to 5ms and the resonant frequency is set to 60kHz.

5. The LLC full-bridge converter hybrid control soft-start method according to claim 4, characterized in that: The mathematical formulas for changing the switching frequency and duty cycle over time when the two nonlinear orders have different values ​​are introduced into the simulation model include: The specific mathematical formula is as follows: ； in, is the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process. It is the nonlinear order of the duty cycle rising curve during PWM startup.

6. The LLC full-bridge converter hybrid control soft-start method according to claim 5, characterized in that: The simulation model is used to perform simulation tests on two nonlinear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect, including: Use mathematical formulas to set different and The combination of the switching frequency and duty cycle during the startup process is simulated. Under each set of parameters, the maximum resonant current data from the startup to the steady state stage is extracted, and the maximum resonant current and the maximum resonant current are plotted based on the maximum resonant current data. and Three-dimensional relationship diagram between By comparing the simulation results under each combination, determine which group and It can minimize the maximum resonant current.

7. An LLC full-bridge converter hybrid control soft start system, characterized in that: include: The strategy selection module is used to select a hybrid soft start strategy combining frequency reduction start and PWM start and set initial parameters, including switching frequency and duty cycle; The nonlinear order introduction module is used to introduce the nonlinear order of the switching frequency reduction curve during the frequency reduction start-up process and the nonlinear order of the duty cycle increase curve during the PWM start-up process, set the soft start time, and define the mathematical formulas of the switching frequency and duty cycle changes with time when the two nonlinear orders have different values; A simulation model building module is used to build a simulation model of the LLC full-bridge converter on the simulation software and set model parameters, and to bring the mathematical formulas of the change of the switching frequency and the duty cycle over time when the two nonlinear orders have different values ​​into the simulation model; A simulation test module is used to use a simulation model to perform simulation tests on two nonlinear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect; The soft start module is used to perform soft start of the LLC full-bridge converter by adopting a hybrid soft start strategy combining frequency reduction start and PWM start based on the order combination with the best maximum resonant current suppression effect.

8. An electronic device, characterized in that: The device includes a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement a hybrid control soft start method for an LLC full-bridge converter as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: The storage medium stores a program, and when the program is executed by the processor, it is used to implement the LLC full-bridge converter hybrid control soft start method as described in any one of claims 1 to 6.

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