Constant Switching Frequency Controlled Class E DC-DC Converter with Wide Input Voltage Range

Very high frequency Class E dc-dc converter has been widely investigated for its simple structure and easy realization of soft switching. Constant switching frequency (CSF) ON-OFF control is usually employed to regulate the converter output voltage for the advantage of excellent dynamic performance and easy parameter optimization. However, it is found that with CSF ON-OFF control, the input power of the Class E dc-dc converter during ON mode increases with the increase of the input voltage, leading to increased modulation frequency and thus diminishing the conversion efficiency. In this paper, a switch-controlled capacitor (SCC) modulated Class E dc-dc converter is presented to solve the efficiency depletion problem under high input voltage. With SCC, the resonant branch impedance of the Class E dc-dc converter is increased to reduce the input power under high input voltages, which helps reduce the modulation frequency and improve the conversion efficiency. A 10-W, 20-MHz Class E dc-dc converter is simulated to verify the feasibility and the advantages of the proposed control scheme.