Step-by-Step Threshold Design Methodology of Switching Frequency Regulation for a Generalized Resonant DC-DC Converter

The frequency threshold (FTH) is vital for the switching frequency regulation (SFR) of resonant dc-dc converters to restrain the fluctuation range of the output dc voltage and eliminate the low-voltage and overvoltage issues. Therefore, a step-by-step FTH design method is proposed in this article for a generalized resonant dc-dc converter. The mathematical model of the normalized voltage gain is established to reveal the function of the FTH in the SFR scheme. After then, combining the resonant circuit feature and the permitted fluctuation range of the output dc voltage, the specific upper and lower values of the FTH are derived within three steps. A design example is also detailedly presented to facilitate the proposed design. Experimental results verify the performance of the proposed step-by-step FTH design using a resonant converter prototype.