应用于高频数字化LLC谐振变换器的变模态调制策略

以数字化LLC谐振变换器为研究对象，针对其达到1MHz应用时出现的频率分辨率不足及其导致的输出电压脉动问题，提出了一种抑制该问题的变模态调制策略。该策略包含两个模态：传统的仅调节频率的频率调制模态和频率及占空比同时调节的复合调制模态。在复合调制模态下，当检测到开关频率以最小频率间隔来回跳动时，锁定开关频率并通过调节占空比以实现对变换器电压增益的精细调节，从而抑制单一频率调制下出现的输出电压脉动问题。文中给出了该策略的工作原理分析、设计要点分析，并在一台1 MHz的样机上完成了对比实验，实验结果验证了所提出变模态策略的有效性。

Variable Modality Modulation Strategy Applied to High-frequency Digitally-controlled LLC Resonant Converter

Digitally-controlled LLC resonant was studied, especially focusing on the issue that the frequency resolution was insufficient and hence resulting in output voltage fluctuation when applying in 1 MHz frequency or above, and a variable modality modulation strategy was proposed in order to throttle this issue. The proposed strategy contained two modalities, conventional frequency modulation modality which only frequency was modulated and complex modulation modality which both frequency and duty ration were both modulated. The voltage gain could be elaborately regulated by locking switching frequency and adjusting duty ratio when the switching frequency was detected to be fluctuating by minimum interval in complex modulation modality, therefore, the output voltage fluctuation issue coming from single frequency modulation could be throttled. Analysis on operation theory, key points of design were presented and comparison results was done on a 1 MHz prototype, and the effectiveness of the proposed strategy was verified by the experimental results.