开发、推广和利用新能源是应对当前能源危机和环保问题的有力举措，而新能源发电系统受气候、地理位置、传输容量等诸多因素制约，当外部环境条件变化时发电单元输出电压范围变宽。为给后级逆变电路输出稳定的直流电压，需要在新能源发电单元与后级电路之间设计一个单向DC/DC变换器。传统的DC/DC变换器输入电压范围不够宽、电路结构复杂并且开关损耗大，本文研究在宽输入电压范围内高效工作的DC/DC变换器。

  全桥LLC谐振变换器不仅适用于中大功率应用场合，还能够在整个负载范围内实现软开关而达到较高的工作效率。变频模式下，变换器动态响应好、转换效率高，但在宽输入电压条件下磁性元件设计困难。移相模式下，变换器的控制电路结构简单易于实现，但占空比变化范围较大可能会导致占空比丢失，电路效率降低。本文在芯片UCC3895移相控制的功能上引入变频控制，将两种控制策略的优点相结合，使变换器在低压输入时工作在变频模式，在高压输入时工作在移相模式，解决宽范围输入电压条件下变换器工作效率降低的问题。论文给出了具体的电路实现，基于PSIM仿真平台，搭建仿真模型测试混合控制下宽范围输入电压全桥LLC谐振变换器的工作特性。仿真结果表明混合控制变换器能够在较宽的输入电压条件下高效工作。

  最后，在实验室搭建一台2kW的样机，并进行相关实验对论文的设计进行验证。所得实验结果表明采用混合控制策略的全桥LLC谐振变换器在较宽的输入电压范围内具有较高的工作效率，验证了本文所采用的混合控制策略的可行性。

  The development, promotion and utilization of new energy is a powerful measure to deal with the current Energy crisis and environmental protection problems. However, the new energy power generation system is restricted by many factors such as climate, geographical location, transmission capacity, etc. When the external environmental conditions change, the output voltage range of the power generation unit becomes wider. To output stable DC voltage to the subsequent inverter circuit, it is necessary to design a unidirectional DC/DC converter between the new energy generation unit and the subsequent circuit. Traditional DC/DC converters have insufficient input voltage range, complex circuit structure, and high switching losses. This paper studies DC/DC converters that operate efficiently within a wide input voltage range.

  The full bridge LLC resonant converter is not only suitable for medium to high power applications, but also can achieve high work efficiency by achieving soft switching throughout the entire load range. In variable frequency mode, the converter has good dynamic response and high conversion efficiency, but it is difficult to design magnetic components under wide input voltage conditions. In phase-shifting mode, the control circuit structure of the converter is simple and easy to implement, but a large range of duty cycle changes may lead to loss of duty cycle and reduced circuit efficiency. This article introduces variable frequency control on the chip UCC3895 phase-shifting control function, combining the advantages of the two control strategies to make the converter work in variable frequency mode at low voltage input and phase shift mode at high voltage input, solving the problem of reduced efficiency of the converter under wide range input voltage conditions. The paper provides a specific circuit implementation. Based on the PSIM simulation platform, a simulation model is built to test the operating characteristics of a wide range input voltage full bridge LLC resonant converter under hybrid control. The simulation results show that the hybrid control converter can work efficiently under a wide input voltage range.

   Finally, a 2kW prototype was built in the laboratory and relevant experiments were conducted to verify the design of the paper. The experimental results obtained indicate that the full bridge LLC resonant converter using a hybrid control strategy has high operating efficiency over a wide input voltage range, verifying the feasibility of the hybrid control strategy used in this paper

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