应用于高频数字化LLC谐振变换器的变模态调制策略

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

以数字化LLC谐振变换器为研究对象,针对其达到1 MHz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2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。分析了该策略的工作原理和设计要点,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变模态策略的有效性。

A digitally-controlled LLC resonant converter is studied.When it is applied to scenarios with frequency of up to 1 MHz,the frequency resolution will be insufficient,resulting in output voltage fluctuations accordingly.A variable modality modulation strategy is proposed to resolve this issue,which consists of two modalities,i.e.,the conventional frequency modulation modality that only modulates frequency and the complex modulation modality that modulates both frequency and duty ratio.When the switching frequency is detected to be fluctuating by minimum frequency interval in complex modulation modality,the voltage gain of the converter can be elaborately regulated by locking the switching frequency and adjusting the duty ratio.Therefore,the issue of output voltage fluctuations in single frequency modulation can be suppressed.The analysis of the operating principle under this strategy and the key points of design are given.In addition,a comparative experiment was carried out on a 1 MHz prototype,and experimental results verified the effectiveness of the proposed strategy.