A Resonant Converter with a Novel PCB-made High-Frequency Toroidal Coreless Transformer

In this research, a resonant converter has been designed for a pulsed current low-voltage automotive application. The key element of the converter is a PCB-made high-frequency toroidal coreless transformer. The transformer has been designed to transfer 1 kW absorption peaks through bursts of a 6.78 MHz sine wave. At this frequency, the efficiency of magnetic components decreases mainly due to winding and core losses. The specific geometry of the coreless transformer allows the zeroing of the core losses and maximizes the coupling factor between the primary and secondary sides of the transformer. SPICE and Finite Element Method (FEM) simulations have been used to determine the PCB layers and geometrical characteristics. Then, a prototype has been developed and experimental tests have been carried out at different working frequencies by tuning the resonant capacitance.