Hybrid Control Soft-Start Method for LLC Full-Bridge Converter

Abstract

The present application relates to the technical field of converter startup, and in particular to a hybrid control soft-start method for an LLC full-bridge converter. The method adopts a hybrid soft-start strategy combining frequency reduction startup and PWM startup, introduces nonlinear orders for controlling the switching frequency decrease curve during frequency reduction startup and the duty cycle increase curve during PWM startup, defines mathematical formulas for the change of switching frequency and duty cycle over time when the two nonlinear orders have different values, establishes a simulation model, and introduces the mathematical formulas for the change of switching frequency and duty cycle over time when the two nonlinear orders have different values ​​into the simulation model; performs simulation tests on the nonlinear orders with different values, extracts the maximum resonant current, and determines the order combination with the best maximum resonant current suppression effect; and performs soft-start of the LLC full-bridge converter based on the determined order combination. The present application can effectively suppress the current during the soft-start process while taking into account both fast startup and device safety.

Description

Technical Field

[0001] The present application relates to the technical field of converter startup, and in particular to a hybrid control soft-start method for an LLC full-bridge converter. Background Art

[0002] Power electronics technology plays a vital role in the development and utilization of renewable energy. In particular, DC-DC converters, a key link in energy conversion, must possess efficient and stable voltage conversion capabilities, reasonable voltage and current stress control, and excellent conversion efficiency. The LLC full-bridge converter, a specific topology of the LLC resonant converter, has become a core device for achieving bidirectional energy transmission in renewable energy systems due to its ability to achieve soft switching characteristics over a wide load range while balancing high efficiency and low electromagnetic interference. However, during the startup process of the LLC full-bridge converter, because the resonant cavity energy has not yet been established, the DC bus voltage is directly applied to the resonant network, resulting in extremely large resonant current spikes within the converter, which can damage power switching devices or magnetic components. Therefore, achieving a soft-start process for the LLC full-bridge converter becomes a key challenge in its design.

[0003] Currently, the main soft-start technologies for LLC full-bridge converters include frequency-reduction, PWM, and phase-shift strategies. First, the frequency-reduction strategy sets the initial switching frequency well above the resonant frequency, leveraging the frequency's ability to modulate the resonant cavity impedance to limit the current rise rate during the startup phase. As the output voltage gradually builds, the switching frequency is gradually reduced to the steady-state operating point at a preset slope, thereby suppressing the resonant current peak. Second, the PWM strategy controls the rate of energy transfer from the DC bus to the resonant cavity during the startup phase by linearly increasing the duty cycle of the inverter bridge switch drive signal from an initial value of 0 to a steady-state value (e.g., 50%). This gradual duty cycle adjustment mitigates sudden voltage changes on the resonant capacitor, thereby reducing the current spike amplitude. Finally, the phase-shift strategy gradually increases the phase difference between the drive signals of the upper and lower arms of the inverter bridge from an initial 0° to 180°. This phase-shift angle modulates the energy transfer path, injecting energy into the resonant cavity in stages. Dynamic adjustment of the phase difference effectively limits the resonant current rise rate, thereby preventing current overshoot.

[0004] Although the above strategies have alleviated the problem of starting current shock to a certain extent, their core still relies on the linear or segmented adjustment of a single control variable. Since the LLC resonant network exhibits highly nonlinear characteristics during the startup process, 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, the fixed reduction rate of the switching frequency in the frequency reduction startup strategy 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 only adjust the energy transfer rate and cannot directly intervene in the instantaneous amplitude of the resonant current, resulting in their limited ability to suppress the current peak. Therefore, the core problem of the existing technology is that the linear adjustment strategy of a single control dimension is mismatched with the nonlinear dynamic characteristics of the LLC resonant cavity, resulting in insufficient current suppression accuracy during the soft start process, making it difficult to take into account both fast startup and device safety. Summary of the Invention

[0005] This application provides a hybrid control soft-start method for an LLC full-bridge converter, which can effectively suppress the current during the soft-start process while taking into account both fast startup and device safety. This application provides the following technical solutions:

[0006] In a first aspect, the present application provides a hybrid control soft-start method for an LLC full-bridge converter, the method comprising:

[0007] Select a hybrid soft-start strategy that combines frequency reduction and PWM start-up and set the initial parameters, including switching frequency and duty cycle;

[0008] The nonlinear order of the switching frequency decrease curve during the frequency reduction startup process and the nonlinear order of the duty cycle increase curve during the PWM startup process are introduced respectively. The soft start time is set, and the mathematical formulas for the change of switching frequency and duty cycle with time are defined for different values ​​of the two nonlinear orders.

[0009] Establish an LLC full-bridge converter simulation model on the simulation software and set the model parameters. In addition, introduce the mathematical formulas of the change of switching frequency and duty cycle with time when the two nonlinear orders have different values ​​into the simulation model.

[0010] The simulation model is used to simulate and test two nonlinear orders with different values, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect;

[0011] Based on the order combination with the best maximum resonant current suppression effect, a hybrid soft-start strategy combining frequency reduction start-up and PWM start-up is adopted to soft-start the LLC full-bridge converter.

[0012] In a specific implementation scheme, the hybrid soft start strategy combining frequency reduction start and PWM start and setting initial parameters includes:

[0013] Set the initial switching frequency of the excitation signal to Set as resonant frequency The initial duty cycle of the excitation signal is set to 0%, and the steady-state duty cycle is set to 48%.

[0014] In a specific implementation scheme, the mathematical formulas defining the changes of the switching frequency and the duty cycle over time when the two nonlinear orders have different values ​​include:

[0015] 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:

[0016] ;

[0017] 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. is the nonlinear order of the duty cycle rising curve during PWM startup.

[0018] In a specific implementation scheme, establishing an LLC full-bridge converter simulation model on the simulation software and setting model parameters includes:

[0019] A simulation model of the LLC full-bridge converter is established on SIMULINK, an extension tool of MATLAB. The soft-start duration is set to 5ms and the resonant frequency is set to 60kHz.

[0020] In a specific implementation scheme, introducing 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 includes:

[0021] The specific mathematical formula is as follows:

[0022] ;

[0023] in, is the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process. is the nonlinear order of the duty cycle rising curve during PWM startup.

[0024] In a specific possible implementation scheme, 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:

[0025] 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 them;

[0026] By comparing the simulation results under each combination, we can determine which group and It can minimize the maximum resonant current.

[0027] In a second aspect, the present application provides an LLC full-bridge converter hybrid control soft start system, which adopts the following technical solutions:

[0028] An LLC full-bridge converter hybrid control soft-start system, comprising:

[0029] Strategy selection module, 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;

[0030] The nonlinear order introduction module is used to 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 switching frequency and duty cycle over time when the two nonlinear orders have different values;

[0031] A simulation model building module is used to build a simulation model of the LLC full-bridge converter on the simulation software and set the model parameters, and to introduce the mathematical formulas for the changes of the switching frequency and duty cycle over time when the two nonlinear orders have different values ​​into the simulation model;

[0032] A simulation test module is used to perform simulation tests on two nonlinear orders with different values ​​using a simulation model, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect;

[0033] The soft start module is used to soft start the LLC full-bridge converter based on the order combination with the best maximum resonant current suppression effect, using a hybrid soft start strategy that combines frequency reduction start and PWM start.

[0034] In a third aspect, the present application provides an electronic device comprising 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 the first aspect.

[0035] In a fourth aspect, the present application provides a computer-readable storage medium, wherein the storage medium stores a program, and when the program is executed by a processor, it is used to implement a hybrid control soft start method of an LLC full-bridge converter as described in the first aspect.

[0036] In summary, the beneficial effects of this application include at least:

[0037] (1) By adopting a hybrid soft-start strategy that combines frequency reduction and PWM start-up and introduces nonlinear control parameters, the switching frequency and duty cycle can be precisely controlled during the startup process, allowing the system to smoothly transition to a steady state within the predetermined soft-start time. This significantly reduces the resonant current spike caused by energy mutations in the resonant cavity, preventing current shocks from damaging power devices and magnetic components, thereby improving system safety and reliability.

[0038] (2) By using a high frequency and zero duty cycle state at the beginning of the soft start, and then gradually reducing the switching frequency and increasing the duty cycle according to the nonlinear model, the energy injection is controlled in stages. This can not only quickly build up the system energy in a short period of time, but also avoid the instability caused by the sudden increase in energy at startup, thus ensuring that the system can smoothly reach a steady-state working state in a short period of time.

[0039] (3) By optimizing the nonlinear order parameters, the dynamic adjustment of the switching frequency and duty cycle during the soft-start process can accurately match the nonlinear impedance characteristics of the resonant cavity, thereby achieving dual optimization of energy transmission and current suppression. This optimization not only reduces system switching losses and electromagnetic interference, but also improves conversion efficiency and dynamic response performance, providing reliable technical support for efficient energy conversion in new energy systems.

[0040] By combining the frequency reduction startup and PWM startup strategies and setting reasonable initial parameters, a mathematical model describing the time-varying switching frequency and duty cycle during the startup process is established using the introduced nonlinear order parameters. The optimal parameter combination is obtained through simulation testing in MATLAB / SimulINK, thereby achieving a smooth transition of the system to a steady-state state within the predetermined soft-start time, effectively suppressing the resonant current spikes generated during the startup process, and solving the problem that traditional single control strategies are difficult to balance fast startup and current suppression, thus ensuring the safe and stable operation of power electronic devices.

[0041] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application and to implement it in accordance with the contents of the specification, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 1 is a flow chart of a hybrid control soft start method for an LLC full-bridge converter in an embodiment of the present application.

[0043] Figure 2 3 is a graph showing the relationship between switching frequency and duty cycle over time when m and n take different values ​​in an embodiment of the present application.

[0044] Figure 3 In the embodiment of the present application, the startup process under different values ​​of m and n is simulated, and the maximum resonant current from the startup to the steady state stage is extracted, thereby making a three-dimensional relationship diagram between the maximum resonant current and m and n.

[0045] Figure 4 This is a resonant current waveform diagram obtained by simulation during the startup process by comparing direct startup, linear frequency reduction startup, linear PWM startup, and the LLC full-bridge converter hybrid control soft start method in the embodiments of the present application.

[0046] Figure 5 This is a diagram of the resonant capacitor voltage waveform obtained by simulation during the startup process by comparing direct startup, linear frequency reduction startup, linear PWM startup, and the LLC full-bridge converter hybrid control soft start method in the embodiments of the present application.

[0047] Figure 6 This is a structural block diagram of the LLC full-bridge converter hybrid control soft start system in an embodiment of the present application.

[0048] Figure 7 4 is a block diagram of an electronic device for hybrid control soft start of an LLC full-bridge converter in an embodiment of the present application. DETAILED DESCRIPTION

[0049] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0050] Optionally, the present application uses the LLC full-bridge converter hybrid control soft start method provided in each embodiment as an example for explanation in an electronic device, where the electronic device is a terminal or a server. The terminal can be a mobile phone, a computer, a tablet computer, etc. This embodiment does not limit the type of electronic device.

[0051] Reference Figure 1, is a flow chart of a hybrid control soft-start method for an LLC full-bridge converter provided by an embodiment of the present application, the method comprising at least the following steps:

[0052] Step S101 : selecting a hybrid soft start strategy combining frequency reduction start and PWM start and setting initial parameters, the initial parameters including switching frequency and duty cycle.

[0053] In step S101, a hybrid soft-start strategy combining frequency reduction and PWM start-up is first selected. The frequency reduction start-up strategy controls the impedance of the resonant cavity by adjusting the switching frequency, which can effectively suppress the current shock in the initial stage of startup. However, its single frequency adjustment has insufficient control over the energy transfer rate. The PWM start-up strategy adjusts the energy injection rate through a linear increase in the duty cycle, but has limitations in suppressing the instantaneous peak of the resonant current. After the two are combined, the frequency reduction start-up strategy can dynamically adjust the impedance of the resonant cavity through nonlinear changes in frequency, while the PWM start-up strategy accurately controls the acceleration of energy injection through nonlinear changes in the duty cycle. The two complement each other in the time domain: the high impedance characteristics in the initial stage of frequency reduction provide a buffer for the gradual increase in the duty cycle, while the accelerated increase in the duty cycle makes up for the insufficient energy transfer efficiency in the later stage of frequency reduction, thereby achieving nonlinear cooperative suppression of the resonant current and avoiding the dynamic mismatch problem under a single control dimension.

[0054] Then set the initial parameters, including: the initial switching frequency of the excitation signal Set as resonant frequency The initial switching frequency is three times of the original switching frequency, the initial duty cycle of the excitation signal 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 3x, the resonant cavity exhibits high impedance, significantly limiting the current rise rate. In engineering, a frequency of 3x balances switching losses with current suppression requirements. Below 3x, the suppression effect is insufficient, while above 3x, switching losses increase dramatically. Setting the initial duty cycle to 0 completely blocks energy injection at startup, preventing current spikes. The steady-state duty cycle is set to 48% instead of 50% to allow for a safety margin for the switch dead time. Therefore, the duty cycle is slightly lower than 50%, a commonly used value in engineering.

[0055] In practice, the frequency reduction strategy maintains a high frequency during the initial startup phase to limit current rise. Simultaneously, the PWM startup strategy maintains a nonlinear duty cycle decrease to reduce impedance, while a nonlinear duty cycle increase allows for phased energy injection. The frequency decrease rate and duty cycle increase rate form a nonlinear coupling, ensuring that impedance changes and energy transfer rates are matched in real time, minimizing sudden energy changes in the resonant cavity.

[0056] Step S102: introducing a nonlinear order for controlling the switching frequency decrease curve during the frequency reduction startup process and a nonlinear order for controlling the duty cycle increase curve during the PWM startup process, setting the soft start time, and defining a mathematical formula for how the switching frequency and duty cycle change with time when the two nonlinear orders have different values.

[0057] In step S102, in order to accurately control the change of switching frequency and duty cycle during soft start, the nonlinear order of the switching frequency reduction curve is introduced during the frequency reduction start process. and the nonlinear order of the duty cycle rising curve during PWM startup , where the parameter It is used to adjust the rate at which the switching frequency decreases from the initial value to the steady-state resonant frequency, and the parameter Used to control the rate at which the duty cycle increases from zero to the steady-state duty cycle. Different values ​​of these two parameters will directly affect the smoothness of 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.

[0058] To establish the mathematical formula, first set the soft start time to , that is, from the start time To the time of steady state establishment time interval, during which time period, when and Switching frequency at different values and duty cycle The mathematical formula for this change over time is as follows:

[0059] ;

[0060] in, is the resonant frequency, is the total soft start time, is the steady-state duty cycle, which is 0.48 in this application. When the switching frequency is three times the resonant frequency, the duty cycle is set to zero to ensure that there is no energy injection at the start-up moment. When the startup is completed, the switching frequency drops to the resonant frequency and the duty cycle increases to the set steady-state value of 48%.

[0061] Step S103: Establish an LLC full-bridge converter simulation model on the simulation software and set the model parameters, and introduce the mathematical formulas of the change of the switching frequency and the duty cycle with time when the two nonlinear orders have different values ​​into the simulation model.

[0062] In step S103, a simulation model of the LLC full-bridge converter is established in SIMULINK, an extension tool of MATLAB, and key model parameters are clearly set. The soft start duration is set to 5ms, and the resonant frequency is set to 60kHz. These parameters were selected based on engineering practice and experimental data: 5ms is sufficient to achieve a fast and smooth startup transition, while the resonant frequency of 60kHz is a value that has been widely verified and has good results in current designs. Next, the mathematical model derived in step S102 is substituted into the simulation model. The specific mathematical formula is as follows:

[0063] ;

[0064] It can be seen from this that when and When taking different values, the switching frequency and duty cycle Over time The relationship between the changes is shown in the attached Figure 2 Shown as nonlinear.

[0065] Step S104: using a simulation model to perform simulation tests on two nonlinear orders with different values, extracting the maximum resonant current, and determining an order combination with the best maximum resonant current suppression effect.

[0066] In step S104, based on the simulation model established on the simulation software, the nonlinear order with different values ​​is and Specifically, using the above mathematical formula, 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. After arranging these data, the maximum resonant current and and The three-dimensional relationship diagram between Figure 3 As shown in the figure, the startup effect under each parameter combination is intuitively demonstrated. By comparing the simulation results under each combination, we can determine which group and The maximum resonant current can be minimized, thereby achieving optimal suppression of the resonant current.

[0067] In practice, the order combination with better resonant current suppression effect is shown in Table 1:

[0068]

[0069] It can be concluded that the order combination with the best current suppression effect is m=2, n=8.

[0070] Step S105 : 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 perform soft start of the LLC full-bridge converter.

[0071] In step S105, based on the order combination that best suppresses the maximum resonant current, a hybrid soft-start strategy combining frequency reduction and PWM startup is used to soft-start the LLC full-bridge converter. This strategy uses optimal parameters to adjust the excitation signal in real time, ensuring a smooth transition to steady-state within the predetermined soft-start duration. This effectively suppresses the resonant current and ensures safe and stable system operation.

[0072] In summary, by combining the frequency reduction start-up and PWM start-up strategies and setting reasonable initial parameters, a mathematical model describing the time variation of switching frequency and duty cycle during the startup process was established using the introduced nonlinear order parameters. The optimal parameter combination was obtained through simulation testing in MATLAB / SimulINK, thereby achieving a smooth transition of the system to a steady-state state within the predetermined soft-start time, effectively suppressing the resonant current spike generated during the startup process, and solving the problem that traditional single control strategies are difficult to balance fast startup and current suppression, thus ensuring the safe and stable operation of power electronic devices.

[0073] In addition, as a preferred method, in order to test the suppression effect of the hybrid soft start strategy on the resonant current and the resonant capacitor voltage, common soft start schemes such as linear frequency reduction start (m=1) and linear PWM start (n=1) are selected for comparison with direct start. These combinations are substituted into the simulation model of the simulation software to obtain the resonant current and resonant capacitor voltage waveforms during the startup process as shown in the attached figure. Figure 4 and attached Figure 5 As shown in the figure, it can be seen that the startup time required for direct startup is extremely short, and the current and voltage peaks both appear in the middle of the startup. Under the frequency reduction startup strategy, the voltage and current of the converter show a slight decrease in the initial startup period, and then slowly increase. At the resonant frequency, or t = 5ms, the voltage and current reach their peak values, then continue to decline until they reach steady state. Under the PWM startup strategy, the converter's voltage and current first rise slowly, then remain constant for a period after reaching their peak values. Near the end of startup, there is a slight fluctuation before returning to steady state. Under the hybrid soft-start strategy of this application, the converter's voltage and current increase slowly, reaching their peak values ​​in the middle and late stages of startup, and then decrease slightly to reach steady state.

[0074]

[0075] From the data in Table 2, it can be seen that the LLC full-bridge converter hybrid control soft start method of the present application not only has a faster start-up speed, but also has a better resonant voltage and current suppression effect.

[0076] Figure 6 This is a block diagram of a hybrid control soft start system for an LLC full-bridge converter provided by an embodiment of the present application. The system includes at least the following modules:

[0077] Strategy selection module, 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;

[0078] The nonlinear order introduction module is used to 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 switching frequency and duty cycle over time when the two nonlinear orders have different values;

[0079] A simulation model building module is used to build a simulation model of the LLC full-bridge converter on the simulation software and set the model parameters, and to introduce the mathematical formulas for the changes of the switching frequency and duty cycle over time when the two nonlinear orders have different values ​​into the simulation model;

[0080] A simulation test module is used to perform simulation tests on two nonlinear orders with different values ​​using a simulation model, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect;

[0081] The soft start module is used to soft start the LLC full-bridge converter based on the order combination with the best maximum resonant current suppression effect, using a hybrid soft start strategy that combines frequency reduction start and PWM start.

[0082] For relevant details, please refer to the above method embodiment.

[0083] Figure 7 4 is a block diagram of an electronic device provided in one embodiment of the present application. The device includes at least a processor 401 and a memory 402.

[0084] Processor 401 may include one or more processing cores, such as a quad-core processor or an octa-core processor. Processor 401 may be implemented in hardware using at least one of the following: a DSP (Digital Signal Processing), an FPGA (Field-Programmable Gate Array), or a PLA (Programmable Logic Array). Processor 401 may also include a main processor and a coprocessor. The main processor is used to process data in the awake state, also known as a CPU (Central Processing Unit); the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, processor 401 may be integrated with a GPU (Graphics Processing Unit), which is responsible for rendering and drawing content displayed on the display screen. In some embodiments, processor 401 may also include an AI (Artificial Intelligence) processor, which is used to handle computational operations related to machine learning.

[0085] Memory 402 may include one or more computer-readable storage media, which may be non-transitory. Memory 402 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices and flash memory storage devices. In some embodiments, the non-transitory computer-readable storage medium in memory 402 is used to store at least one instruction, which is executed by processor 401 to implement the LLC full-bridge converter hybrid control soft start method provided in the method embodiment of the present application.

[0086] In some embodiments, the electronic device may optionally include a peripheral device interface and at least one peripheral device. The processor 401, memory 402, and peripheral device interface may be connected via a bus or signal lines. Each peripheral device may be connected to the peripheral device interface via a bus, signal lines, or circuit boards. Illustratively, the peripheral devices include, but are not limited to, a radio frequency circuit, a touchscreen display, an audio circuit, and a power supply.

[0087] Of course, the electronic device may also include fewer or more components, which is not limited in this embodiment.

[0088] Optionally, the present application also provides a computer-readable storage medium, in which a program is stored. The program is loaded and executed by a processor to implement the LLC full-bridge converter hybrid control soft start method of the above method embodiment.

[0089] Optionally, the present application also provides a computer product, which includes a computer-readable storage medium, in which a program is stored. The program is loaded and executed by a processor to implement the LLC full-bridge converter hybrid control soft start method of the above method embodiment.

[0090] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0091] The above embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A hybrid control soft start method for an 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. The initial parameters include switching frequency and duty cycle. Set as resonant frequency The initial duty cycle of the excitation signal is set to 0%, and the steady-state duty cycle is set to 48%; The nonlinear order of the switching frequency decrease curve during the frequency reduction startup process and the nonlinear order of the duty cycle increase curve during the PWM startup process are introduced respectively. The soft start time is set, and the mathematical formulas for the change of switching frequency and duty cycle with time are defined for different values ​​of the two nonlinear orders. The mathematical formulas 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, It is used to control the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process, and is used to adjust the rate at which the switching frequency drops from the initial value to the steady-state resonant frequency. It is the nonlinear order of the duty cycle rising curve during the PWM startup process, which is used to control the rate at which the duty cycle rises from zero to the steady-state duty cycle; Establish an LLC full-bridge converter simulation model on the simulation software and set the model parameters. In addition, introduce the mathematical formulas of the change of switching frequency and duty cycle with time when the two nonlinear orders have different values ​​into the simulation model. Use the simulation model to simulate and test 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: using 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 By comparing the simulation results under each combination, determine which group and Able to minimize the maximum resonant current; Based on the order combination with the best maximum resonant current suppression effect, a hybrid soft-start strategy combining frequency reduction start-up and PWM start-up 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 step of establishing an LLC full-bridge converter simulation model on the simulation software and setting model parameters includes: A simulation model of the LLC full-bridge converter is established on SIMULINK, an extension tool of MATLAB. The soft-start duration is set to 5ms and the resonant frequency is set to 60kHz.

3. The LLC full-bridge converter hybrid control soft-start method according to claim 2, 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. is the nonlinear order of the duty cycle rising curve during PWM startup.

4. 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 that combines frequency reduction start and PWM start and set the initial parameters. The initial parameters include switching frequency and duty cycle. Set as resonant frequency The initial duty cycle of the excitation signal is set to 0%, and the steady-state duty cycle is set to 48%; The nonlinear order introduction module is used to 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 switching frequency and duty cycle over time when the two nonlinear orders have different values; The mathematical formulas 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, It is used to control the nonlinear order of the switching frequency reduction curve during the frequency reduction startup process, and is used to adjust the rate at which the switching frequency drops from the initial value to the steady-state resonant frequency. It is the nonlinear order of the duty cycle rising curve during the PWM startup process, which is used to control the rate at which the duty cycle rises from zero to the steady-state duty cycle; A simulation model building module is used to build a simulation model of the LLC full-bridge converter on the simulation software and set the model parameters, and to introduce the mathematical formulas for the changes of the switching frequency and duty cycle over time when the two nonlinear orders have different values ​​into the simulation model; The simulation test module is used to simulate and test two nonlinear orders with different values ​​using the simulation model, extract the maximum resonant current, and determine the order combination with the best maximum resonant current suppression effect, including: using 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 By comparing the simulation results under each combination, determine which group and Able to minimize the maximum resonant current; The soft start module is used to soft start the LLC full-bridge converter based on the order combination with the best maximum resonant current suppression effect, using a hybrid soft start strategy that combines frequency reduction start and PWM start.

5. 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 the LLC full-bridge converter hybrid control soft start method according to any one of claims 1 to 3.

6. A computer-readable storage medium, characterized in that The storage medium stores a program, which, when executed by a processor, is used to implement a hybrid control soft-start method for an LLC full-bridge converter according to any one of claims 1 to 3.

Images