Adaptive Frequency Modulation Design of BUCK Converter

Traditional methods for achieving soft switching typically involve adding passive components to the topology, such as in LLC converters. However, these methods can only achieve ZVS (Zero Voltage Switching) turn-on at specific duty cycles and fail to do so across the full duty cycle range. This paper introduces a digital adaptive control method based on a synchronous Buck converter, capable of achieving ZVS turn-on for all switches under any duty cycle condition. To meet the conditions for zero-voltage switching, the method employs a sampling circuit to collect input and output voltages and inductor currents in real time. These values are then used in digital calculations to determine appropriate delay-off times, dead times, and switching frequencies. The soft-switching technology is realized by dynamically adjusting the switching frequency. Finally, simulations and experiments validate the effectiveness of the proposed ZVS turn-on scheme across the entire duty cycle range.