Circuit Design Considerations for Reducing Parasitic Effects on GaN-Based 1-MHz High-Power-Density High-Step-Up/Down Isolated Resonant Converters

With the availability of wide bandgap devices, the power converters can now potentially operate at megahertz (MHz) or higher frequencies while achieving ultrahigh efficiency. Such a high-frequency switching is particularly important for isolated converters to reduce the size of the passive components, achieve high power-density, and reduce costs. However, unlike the conventional kilohertz switching, in MHz switching, the parasitic components will significantly affect the circuit operation. These effects are compounded by high-ratio step-up or step-down isolated converters because the parasitic capacitances/inductances are squared times the turns’ ratio of the transformer when reflecting from high-voltage (HV) to low-voltage (LV) side to LV/HV side. In this paper, a high-step-up series resonant converter is used as a design example to explore the effects of parasitic inductances induced from the LV side and parasitic capacitances induced from the HV side on the circuit operation under MHz switching conditions. Afterward, the printed circuit board (PCB) layout and the planar transformer are optimized through the finite-element method to minimize the parasitic effects. Finally, a 1-MHz, 38-V/380-V, 300-W resonant converter prototypes are built and compared to verify the design optimization.