串联谐振型DC/DC变换器定宽调频策略

A Fixed-width Frequency Modulation Strategy for Series Resonant DC/DC Converter

串联谐振型高频隔离DC/DC变换器具有增益范围宽、效率高、功率密度大等优点,但现有控制方法经常出现功率开关器件无法实现软开关的情况。针对此问题,这里提出一种定宽调频控制策略,将谐振周期作为固定的脉宽,并通过引入断续时间以实现开关管的零电流开通;同时通过调整开关频率实现对输出电压的调节。以其在LLC电路中的应用为例,为实现定宽调频控制,在变换器中增加了直流母线侧二极管,以阻止电流的反向流通。研究励磁电流对电压增益的影响,分析了不同工况的增益曲线。搭建了LLC电路实验装置,验证了所提定宽调频控制策略理论分析的正确性和实现软开关与输出电压调节的有效性。

High-frequency isolated series resonant DC/DC converters have the advantages of wide gain range,high ef-ficiency and high power density,nevertheless the existing control methods often fail to achieve soft switching of the power devices.Regarding this problem,a fixed-width frequency modulation control strategy is proposed,in which the resonant period is taken as a fixed pulse width and zero current switching is achieved by the introduction of intermit-tent period.Meanwhile,the output voltage can be regulated by adjusting the switching frequency.Taking its application in the LLC circuit as an example,in order to realize the fixed-width frequency modulation control,a DC bus-side diode is added in the converter to block the reverse current.The influence of excitation current on voltage gain is studied,and the gain curves under different working conditions are analyzed.An LLC circuit experimental prototype is built to verify the correctness of the theoretical analysis of the proposed fixed-width frequency modulation control strategy and the effectiveness of realizing soft switching and output voltage regulation.