LLC谐振变换器结构简单且效率高，已在基站、服务器电源和新能源等众多领域得到广泛应用。但采用DSP（Digital Signal Processor）等数字控制器不利于LLC谐振变换器控制系统的小型化、集成化。为此，设计基于FPGA（Field Programmable Gate Array）的LLC谐振变换器数字控制器具有理论研究意义和工程应用价值。

本文首先分析LLC谐振变换器的拓扑结构和工作原理，建立了LLC谐振变换器的基波等效模型，推导了增益表达式。接着，针对LLC谐振变换器在启动时存在较大冲击电流的问题，通过分析研究变占空比软启动和变频软启动控制方法的优缺点，提出改进型混合控制启动策略，该策略能更好的抑制冲击电流。针对在低压大电流应用中LLC效率低的问题，提出数字控制同步整流策略来提高变换器效率。为提高控制器的控制精度，设计了对称N阶结构的有限长单位冲激响应滤波算法，采用流水线电路结构及复用思想，大大减少了硬件资源消耗。同时，提出PWM/PFM调制方案和闭环稳压方案，变换器开环软启动时先变占空比后变频，闭环时调节频率使输出电压稳定。在实现对LLC谐振变换器的基本控制和驱动后，添加上位机通信和电路保护等必要的辅助模块对其进行优化控制，来保证系统的高灵活性和高可靠性。最后，根据LLC谐振变换器数字控制器的设计方案，在Simulink中验证方案可行后，进行控制器Verilog代码设计，并采用QuestaSim仿真初步验证代码的正确性。

本文研制了一台12V/10A的全桥LLC谐振变换器样机，并搭建控制器验证平台，以测试实际控制效果，实验结果表明，系统在输入电压和负载的动态范围内均可稳定输出，其它电气性能均符合指标，验证了控制器方案的可行性及各模块功能的正确性。

With a simple structure and high efficiency, LLC resonant converters have been widely used in various fields such as base stations, server power supplies and new energy sources. However, the use of digital controllers, such as DSP (Digital Signal Processor), is not conducive to the miniaturization and integration of the control system of the LLC resonant converter. Therefore, the design of the digital controller for the LLC resonant converter based on FPGA (Field Programmable Gate Array) has theoretical research significance and engineering application value.

Firstly, the topology and working principle of the LLC resonant converter are analyzed. The fundamental equivalent model of the LLC resonant converter is established, and the gain expression is derived. Then, aiming at the problem that the LLC resonant converter has a large inrush current when starting, by analyzing the advantages and disadvantages of variable duty cycle soft start and variable frequency soft start control methods, an improved hybrid control start strategy is proposed, which can better suppress the inrush current. Aiming at the problem of low efficiency of LLC in low voltage and high current applications, a digital control synchronous rectification strategy is proposed to improve the efficiency of the converter. To improve the control accuracy of the controller, a symmetrical N-order Finite Impulse Response filtering algorithm is designed. The pipeline circuit structure and multiplexing ideas are used to greatly reduce hardware resource consumption. At the same time, a PWM/PFM modulation scheme and a closed-loop voltage stabilization scheme are proposed. When the converter is open-loop soft-started, the duty cycle is first changed and then the frequency is changed. When the closed loop is adjusted, the frequency is adjusted to make the output voltage stable. After realizing the basic control and drive of the LLC resonant converter, the necessary auxiliary modules such as upper computer communication and circuit protection are added to optimize the control to ensure the high flexibility and high reliability of the system. According to the design scheme of the LLC resonant converter digital controller, after verifying the feasibility of the scheme in Simulink, the Verilog code of the controller is designed, and the correctness of the code is preliminarily verified by QuestaSim simulation.

In this dissertation, a 12V/10A full-bridge LLC resonant converter prototype is designed, and a controller verification platform is built to test the actual control effect. The experimental results show that the system can stabilize the output within the dynamic range of input voltage and load, and other electrical performances are in line with the index, which verifies the feasibility of the controller scheme and the correctness of the functions of each module.

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