Frequency-adapted hybrid modulation strategy of resonant converter with narrow frequency range

Resonant converters have been widely applied in many fields, such as electric vehicles, renewable energy sources, and switch-mode power supply. Conventional resonant converters generally adopt pulse frequency modulation (PFM), which would cause an extremely wide frequency variation range under wide output applications. However, it would lead to high electromagnetic interference (EMI), low utilization of magnetic components, and loss of soft switching features. For catering to wide output range applications, this paper proposes a self-adaptive narrow frequency range PFM and asymmetrical voltage-cancelation hybrid modulation strategy to solve the above problem. The advantages of the proposed strategy include (1) narrow frequency variation range; (2) self-adaptive shift frequency; and (3) full process achievement of zero voltage switch. The modulation strategy and operational principle and performance analysis of the proposed method are given. Eventually, a series resonant converters-based experimental platform was implemented to verify the proposed strategy.