A 10MHz Forward-Flyback Resonant DC/DC Converter

Flyback converter is widely used for low-power DC/DC conversion with the simple circuit structure. However, it suffers high switching loss caused by its hard switching operation when the switching frequency is enhanced. This paper proposes a high-frequency resonant DC/DC converter based on the traditional flyback converter. The converter employs a resonant inductor and two resonant capacitors, which achieves soft switching of the switch and the diode. It can also absorb the parasitic parameters of the circuit. Therefore, the converter can enhance the switching frequency to improve the power density without increasing the loss obviously. Furthermore, the circuit performance gets further improved by reversing the connection of the dotted terminals of the transformer. The operation principles are presented in detail. And the ON-OFF hysteresis control is applied to adjust the output voltage. Finally, a 10MHz prototype with 12V input and 5V/10W output was built to verify the theoretical analysis.