A light load LLC resonant converter output voltage precision control method and related device

Abstract

The application discloses a light-load LLC resonant converter output voltage precision control method and related devices, comprising: calculating the cross-period number N of pulse cross-period modulation; in the effective pulse period, constructing a state trajectory plane with the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables, combining the current operating parameters and the cross-period number N to plan the switching tube action time in the effective pulse period, controlling the resonant current in the effective pulse period, and improving the equivalent load current in the pulse retention period; according to the cross-period number N, calculating the corresponding first driving pulse duty ratio and switching frequency, outputting the calculated first driving pulse duty ratio and switching frequency to the switching tube of the LLC resonant converter, and realizing first-period steady-state tracking. The method and related devices can realize precise closed-loop control of the output voltage, ensure zero-voltage turn-on of the switching tube, and improve light-load operation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power electronic conversion technology, and relates to a method and related device for precise control of the output voltage of a light-load LLC resonant converter. Background Technology

[0002] LLC resonant converters, with their advantages of soft-switching characteristics across the entire load range, high conversion efficiency, and high power density, have become one of the mainstream topologies for medium- and high-power DC-DC conversion applications. Traditional LLC resonant converters generally employ pulse frequency modulation (PFM) strategies, adjusting the switching frequency to change the impedance characteristics of the resonant cavity, thereby regulating the voltage gain and achieving output voltage regulation.

[0003] However, under light load conditions, traditional PFM control has insurmountable defects: on the one hand, the voltage gain characteristics of the LLC resonant cavity are determined by the quality factor Q. Under light load, the Q value is extremely low, and the gain curve becomes extremely flat. Large changes in the switching frequency can only bring about a small change in the voltage gain, and the frequency regulation capability is almost ineffective. On the other hand, the output junction capacitance of the switching transistor, the parasitic capacitance of the high-frequency transformer, and the parasitic parameters of the winding will form additional resonant branches with the resonant cavity components under light load high-frequency conditions, resulting in a "gain boost" phenomenon where the voltage gain increases with the increase of the switching frequency, forming a frequency runaway region. Traditional PFM control cannot reduce the gain by increasing the switching frequency, ultimately causing output voltage overshoot, a serious decrease in voltage regulation accuracy, or even failure to regulate voltage normally.

[0004] Therefore, there is an urgent need to develop a control method that can simultaneously solve the problems of light-load gain increase, poor voltage regulation accuracy, and loss of soft-switching characteristics in LLC converters without additional hardware circuits, and only through control algorithm optimization. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and related device for precise control of the output voltage of a light-load LLC resonant converter. This method and related device can solve the problems of gain increase, poor voltage regulation accuracy and loss of soft switching characteristics of LLC converters under light load without additional hardware circuits, realize precise closed-loop control of the output voltage, and at the same time ensure zero-voltage turn-on of the switching transistor, thereby improving the efficiency of light-load operation.

[0006] To achieve the above objectives, this invention discloses a method for precise control of the output voltage of a lightly loaded LLC resonant converter, comprising: 1) Real-time acquisition of input voltage, output voltage and load current of LLC resonant converter, and determination of whether LLC resonant converter is operating under light load condition based on load current of LLC resonant converter; 2) When the LLC resonant converter is operating under light load conditions, the LLC resonant converter is switched to the pulse cross-cycle modulation mode of the fusion state trajectory. Based on the error between the output voltage and the reference voltage of the LLC resonant converter, the number of cross-cycles N of the pulse cross-cycle modulation is calculated by the closed-loop regulator. 3) During the effective pulse period, the resonant current and resonant capacitor voltage of the LLC resonant cavity are used as state variables to construct a state trajectory plane. Combined with the current operating parameters and the number of cycles N, the switching action time of the switching transistor within the effective pulse period is planned, the resonant current within the effective pulse period is controlled, and the equivalent load current within the pulse retention period is increased. 4) Calculate the duty cycle and switching frequency of the first driving pulse according to the number of cycles N, and output the calculated duty cycle and switching frequency of the first driving pulse to the switching transistor of the LLC resonant converter to realize steady-state tracking of the first cycle.

[0007] Furthermore, a light load threshold K is preset, where K is a preset percentage of the rated load current. When the real-time collected load current is less than or equal to K times the rated load current, the LLC resonant converter is determined to be operating under light load conditions; when the real-time collected load current is greater than K times the rated load current, the LLC resonant converter is determined to be using the traditional pulse frequency modulation mode.

[0008] Furthermore, the value range of the light load threshold K varies with the voltage gain, and the value of K is different under different voltage gains.

[0009] Furthermore, the number of cycles N is a non-negative integer, and the value of N is 0≤N≤Nmax, where Nmax is the preset maximum number of cycles. The larger the absolute value of the error between the output voltage and the reference voltage of the LLC resonant converter, the larger the value of the number of cycles N, the larger the equivalent load current, and the smaller the voltage gain at the same switching frequency.

[0010] Furthermore, the specific process of step 3) is as follows: The resonant capacitor voltage value at the end of the pulse skipping phase before the start of the effective pulse period is taken as the starting point of the state trajectory of this effective pulse period. The state trajectories of the upper and lower bridge arm conduction segments within the effective pulse period are planned sequentially, so that the LLC resonant converter can track the steady-state trajectory in the first driving pulse. Closed-loop control ensures that the switching transistor achieves zero-voltage turn-on during subsequent steady-state cycles.

[0011] Furthermore, in step 4), the generation rule of the drive pulse sequence is as follows: in every Nmax switching cycles, the drive pulse obtained by the state trajectory planning is output only in the first cycle, and the subsequent (Nmax-N-1) cycles work in steady state, and the drive pulses of all switching transistors are blocked from (Nmax-N) to Nmax.

[0012] Furthermore, the LLC resonant converter is a half-bridge LLC resonant topology or a full-bridge LLC resonant topology, and the secondary side of the LLC resonant converter adopts a diode rectification or synchronous rectification structure; The closed-loop controller is a PI controller, a PID controller, or a sliding mode controller.

[0013] This invention discloses a precise control system for the output voltage of a lightly loaded LLC resonant converter, comprising: The judgment module is used to collect the input voltage, output voltage and load current of the LLC resonant converter in real time, and to determine whether the LLC resonant converter is operating under light load conditions based on the load current of the LLC resonant converter. The calculation module is used to switch the LLC resonant converter to the pulse cross-cycle modulation mode of the fusion state trajectory when the LLC resonant converter is operating under light load conditions. Based on the error between the output voltage and the reference voltage of the LLC resonant converter, the number of cross-cycles N of the pulse cross-cycle modulation is calculated by the closed-loop regulator. The planning module is used to construct a state trajectory plane with the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables during the effective pulse period. It combines the current operating parameters and the number of cycles N to plan the switching action time of the switching transistors within the effective pulse period, control the resonant current within the effective pulse period, and increase the equivalent load current within the pulse retention period. The control module is used to calculate the duty cycle and switching frequency of the first driving pulse according to the number of cycles N, and output the calculated duty cycle and switching frequency of the first driving pulse to the switching transistor of the LLC resonant converter to realize steady-state tracking of the first cycle.

[0014] The present invention discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for generating and sending trusted status alarm information.

[0015] The present invention discloses a computer-readable storage medium storing a computer program, characterized in that the computer program, when executed by a processor, implements the steps of the method for generating and uploading trusted status alarm information.

[0016] The present invention has the following beneficial effects: The method and related device for precise output voltage control of a light-load LLC resonant converter described in this invention, during operation, collects the operating parameters of the LLC resonant converter in real time and determines the light-load condition. Under the light-load condition, it switches to the target modulation mode. Based on the output voltage error, it calculates the number of pulse cycles and simultaneously plans the state trajectory for the retained effective pulse period, precisely controlling the switching timing to increase the equivalent load current within the effective pulse period. This causes the LLC resonant cavity gain characteristic to return to a monotonically decreasing pattern, effectively suppressing the gain rise under light load. It should be noted that this invention requires no additional hardware circuitry; precise closed-loop control of the output voltage under light load can be achieved solely through control algorithm optimization, while ensuring zero-voltage turn-on of the switching transistor, significantly improving the voltage regulation accuracy and operating efficiency of the LLC converter under light load conditions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is the main circuit topology of the full-bridge LLC resonant converter to which this invention applies; Figure 2 This is an overall flowchart of the control method described in this invention; Figure 3 A comparison diagram of voltage gain characteristics between traditional PFM control and the control method of this invention under light load conditions; Figure 4 This is a schematic diagram of the resonant cavity state trajectory planning within the effective pulse period of the present invention; Figure 5 This is a key operating waveform diagram under the control method of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0021] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0023] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0024] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0027] Example 1 refer to Figures 1 to 5 The method for precise control of the output voltage of a lightly loaded LLC resonant converter described in this embodiment includes the following steps: 1) Signal acquisition and operating condition judgment.

[0028] The input DC voltage Vin, output voltage Vo, and load current Io of the converter are collected in real time through voltage and current sampling circuits; a light load threshold K is preset; when the real-time collected load current Io ≤ K... When Io > K, the converter is determined to be operating under light load conditions, and proceeds to step 2); when Io > K When Irated, the converter adopts the traditional PFM control mode to ensure operating efficiency and control performance under medium and heavy load conditions.

[0029] 2) Control mode switching and cycle count calculation; When the operating condition is determined to be light load, the control mode is smoothly switched through the digital controller to avoid output voltage fluctuations during the mode switching process. The digital controller switches to the pulse cross-cycle modulation mode of the fused state trajectory, and then compares the real-time acquired output voltage Vo with the preset reference voltage Vref to calculate the voltage error signal ΔV = Vo - Vref. ΔV is input to the closed-loop regulator to obtain the number of pulse cross-cycles N. In this embodiment, the preset maximum number of cross-cycles Nmax = 10 is used to avoid excessive output voltage ripple due to an excessive number of cross-cycles. Specifically, when the output voltage Vo is higher than the reference voltage, ΔV is positive, the output of the closed-loop regulator increases, the number of pulse cross-cycles N increases, the output energy decreases, and the output voltage decreases. When the output voltage Vo is lower than the reference voltage, ΔV is negative, the output of the closed-loop regulator decreases, the number of pulse cross-cycles N decreases, the output energy increases, and the output voltage increases.

[0030] 3) Planning the state trajectory of the first pulse; For each retained valid pulse cycle, a two-dimensional state trajectory plane is constructed using the resonant current iLr of the LLC resonant cavity and the resonant capacitor voltage vCr as state variables. Combining the current input voltage Vin, output voltage Vo, and the number of cycles N, the state trajectory within the first pulse cycle is segmented and planned. The specific process is as follows: 31) Determine the starting point of the trajectory: Before the start of the effective pulse period, the converter is in the pulse skipping phase of N cycles. At this time, the resonant cavity current is 0 and the resonant capacitor voltage is maintained at the voltage value at the end of the previous effective period. This is taken as the starting point of the state trajectory of the current effective pulse period. 32) Segmented trajectory planning: The state trajectories of the upper and lower bridge arm conduction segments within the first pulse cycle are planned sequentially, enabling the converter to track the steady-state trajectory on the first drive pulse. Subsequent pulses operate in steady state, increasing the equivalent load current and raising the resonant cavity quality factor Q to several times that of traditional PFM control. The gain characteristics return to a monotonically decreasing law, effectively reducing voltage gain and suppressing gain rise. 33) Soft switching constraint: Through closed-loop control, it is ensured that the resonant current is not zero when the switch is turned off during the steady-state cycle, so as to provide energy for the charging and discharging of the junction capacitance of the switch and ensure that the switch achieves zero-voltage turn-on in the next effective pulse cycle, thus avoiding hard switching losses.

[0031] 4) Pulse sequence generation and drive output. Based on the calculated number of cycles N, the corresponding drive pulse sequence is generated. For example, when N=3, in every Nmax switching cycles, drive pulses S1-S4 are output only in the first to (Nmax-3)th cycles, and the drive pulses of all switching transistors are blocked in the subsequent 3 cycles. The generated drive pulse signal is output to the MOSFET drive circuit to control the switching on and off of the transistors.

[0032] 5) Cyclic control. In this embodiment, the digital controller uses a control cycle to repeatedly execute steps 1) to 4), thereby achieving real-time closed-loop precise control of the output voltage under light load conditions.

[0033] Example 2 The light-load LLC resonant converter output voltage precision control system of the present invention includes: The judgment module is used to collect the input voltage, output voltage and load current of the LLC resonant converter in real time, and to determine whether the LLC resonant converter is operating under light load conditions based on the load current of the LLC resonant converter. The calculation module is used to switch the LLC resonant converter to the pulse cross-cycle modulation mode of the fusion state trajectory when the LLC resonant converter is operating under light load conditions. Based on the error between the output voltage and the reference voltage of the LLC resonant converter, the number of cross-cycles N of the pulse cross-cycle modulation is calculated by the closed-loop regulator. The planning module is used to construct a state trajectory plane with the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables during the effective pulse period. It combines the current operating parameters and the number of cycles N to plan the switching action time of the switching transistors within the effective pulse period, control the resonant current within the effective pulse period, and increase the equivalent load current within the pulse retention period. The control module is used to calculate the duty cycle and switching frequency of the first driving pulse according to the number of cycles N, and output the calculated duty cycle and switching frequency of the first driving pulse to the switching transistor of the LLC resonant converter to realize steady-state tracking of the first cycle.

[0034] The module division in this embodiment is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in each embodiment of this application can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0035] Example 3 A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of a method for precise control of the output voltage of a light-load LLC resonant converter. For example, this includes: real-time acquisition of the input voltage, output voltage, and load current of the LLC resonant converter; determining whether the LLC resonant converter is operating under light-load conditions based on the load current; when the LLC resonant converter is operating under light-load conditions, switching the LLC resonant converter to a pulse-cross-cycle modulation mode with a fused state trajectory; and based on the LLC resonant converter... The error between the output voltage and the reference voltage is calculated by the closed-loop regulator to obtain the number of cycles N for pulse cross-cycle modulation. During the effective pulse period, a state trajectory plane is constructed using the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables. The switching timing within the effective pulse period is planned by combining the current operating parameters and the number of cycles N, controlling the resonant current within the effective pulse period, and increasing the equivalent load current within the pulse retention period. The duty cycle and switching frequency of the corresponding first-drive pulse are calculated based on the number of cycles N, and the calculated duty cycle and switching frequency are output to the switching transistor of the LLC resonant converter to achieve steady-state tracking in the first cycle. The memory may include main memory, such as high-speed random access memory, or it may also include non-volatile memory, such as at least one disk storage device. The processor, network interface, and memory are interconnected via an internal bus, which can be an industry standard architecture bus, a peripheral component interconnection standard bus, an extended industry standard architecture bus, etc. The bus can be divided into address bus, data bus, control bus, etc. The memory is used to store programs; specifically, the program may include program code, which includes computer operation instructions. Memory can include main memory and non-volatile memory, and provides instructions and data to the processor.

[0036] Example 4 A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for precise control of the output voltage of a light-load LLC resonant converter. For example, the method includes: real-time acquisition of the input voltage, output voltage, and load current of the LLC resonant converter; determining whether the LLC resonant converter is operating under light-load conditions based on the load current; when the LLC resonant converter is operating under light-load conditions, switching the LLC resonant converter to a pulse-cross-cycle modulation mode with a fused state trajectory; and controlling the output voltage of the LLC resonant converter relative to a reference voltage. The voltage error is calculated using a closed-loop regulator to obtain the number of cycles N for pulse cross-cycle modulation. During the effective pulse period, a state trajectory plane is constructed using the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables. The switching timing within the effective pulse period is planned by combining the current operating parameters with the number of cycles N, controlling the resonant current within the effective pulse period, and increasing the equivalent load current within the pulse retention period. The duty cycle and switching frequency of the corresponding first-drive pulse are calculated based on the number of cycles N, and the calculated duty cycle and switching frequency are output to the switching transistor of the LLC resonant converter to achieve steady-state tracking in the first cycle. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0037] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0038] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0039] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0040] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0041] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0042] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0043] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for precise control of the output voltage of a lightly loaded LLC resonant converter, characterized in that, include: 1) Real-time acquisition of input voltage, output voltage and load current of LLC resonant converter, and determination of whether LLC resonant converter is operating under light load condition based on load current of LLC resonant converter; 2) When the LLC resonant converter is operating under light load conditions, the LLC resonant converter is switched to the pulse cross-cycle modulation mode of the fusion state trajectory. Based on the error between the output voltage and the reference voltage of the LLC resonant converter, the number of cross-cycles N of the pulse cross-cycle modulation is calculated by the closed-loop regulator. 3) During the effective pulse period, the resonant current and resonant capacitor voltage of the LLC resonant cavity are used as state variables to construct a state trajectory plane. Combined with the current operating parameters and the number of cycles N, the switching action time of the switching transistor within the effective pulse period is planned, the resonant current within the effective pulse period is controlled, and the equivalent load current within the pulse retention period is increased. 4) Calculate the duty cycle and switching frequency of the first driving pulse according to the number of cycles N, and output the calculated duty cycle and switching frequency of the first driving pulse to the switching transistor of the LLC resonant converter to realize steady-state tracking of the first cycle.

2. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 1, characterized in that, A preset light load threshold K is set, where K is a preset percentage of the rated load current. When the real-time collected load current is less than or equal to K times the rated load current, the LLC resonant converter is determined to be operating under light load conditions. When the real-time collected load current is greater than K times the rated load current, the LLC resonant converter is determined to be using the traditional pulse frequency modulation mode.

3. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 2, characterized in that, The value range of the light load threshold K varies with the voltage gain, and the value of K is different under different voltage gains.

4. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 1, characterized in that, The number of cycles N is a non-negative integer, and the value of N is 0≤N≤Nmax, where Nmax is the preset maximum number of cycles. The larger the absolute value of the error between the output voltage and the reference voltage of the LLC resonant converter, the larger the value of the number of cycles N, the larger the equivalent load current, and the smaller the voltage gain at the same switching frequency.

5. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 1, characterized in that, The specific process of step 3) is as follows: The resonant capacitor voltage value at the end of the pulse skipping phase before the start of the effective pulse period is taken as the starting point of the state trajectory of this effective pulse period. The state trajectories of the upper and lower bridge arm conduction segments within the effective pulse period are planned sequentially, so that the LLC resonant converter can track the steady-state trajectory in the first driving pulse. Closed-loop control ensures that the switching transistor achieves zero-voltage turn-on during subsequent steady-state cycles.

6. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 1, characterized in that, In step 4), the generation rule of the drive pulse sequence is as follows: in every Nmax switching cycles, the drive pulse obtained by the state trajectory planning is output only in the first cycle, and the subsequent (Nmax-N-1) cycles work in steady state. From (Nmax-N) to Nmax, the drive pulses of all switching transistors are blocked.

7. The method for precise control of the output voltage of a lightly loaded LLC resonant converter according to claim 1, characterized in that, The LLC resonant converter is a half-bridge LLC resonant topology or a full-bridge LLC resonant topology, and the secondary side of the LLC resonant converter adopts a diode rectification or synchronous rectification structure. The closed-loop controller is a PI controller, a PID controller, or a sliding mode controller.

8. A precise control system for the output voltage of a lightly loaded LLC resonant converter, characterized in that, include: The judgment module is used to collect the input voltage, output voltage and load current of the LLC resonant converter in real time, and to determine whether the LLC resonant converter is operating under light load conditions based on the load current of the LLC resonant converter. The calculation module is used to switch the LLC resonant converter to the pulse cross-cycle modulation mode of the fusion state trajectory when the LLC resonant converter is operating under light load conditions. Based on the error between the output voltage and the reference voltage of the LLC resonant converter, the number of cross-cycles N of the pulse cross-cycle modulation is calculated by the closed-loop regulator. The planning module is used to construct a state trajectory plane with the resonant current and resonant capacitor voltage of the LLC resonant cavity as state variables during the effective pulse period. It combines the current operating parameters and the number of cycles N to plan the switching action time of the switching transistors within the effective pulse period, control the resonant current within the effective pulse period, and increase the equivalent load current within the pulse retention period. The control module is used to calculate the duty cycle and switching frequency of the first driving pulse according to the number of cycles N, and output the calculated duty cycle and switching frequency of the first driving pulse to the switching transistor of the LLC resonant converter to realize steady-state tracking of the first cycle.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for generating and sending trusted status alarm information as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for generating and sending trusted status alarm information as described in any one of claims 1-7.

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