A New High Step-Down Buck Converter With a Series Capacitor

DC–DC converters are increasingly necessary in alternative energy, industrial automation, electric vehicles, and telecommunications. Variable switching frequency dc–dc converters offer flexibility, high performance, and efficiency across a wide range of loads, with better electromagnetic interference/electromagnetic compatibility (EMI)/(EMC) performance and dynamic response than converters with fixed switching frequency and variable duty cycle. They can also be smaller and less expensive, especially for high-frequency applications. This article presents a new high step-down buck converter with a series capacitor for variable frequency applications. The special topology of the switches in the proposed converter results in doubling the frequency of the current and voltage ripple of the output filter. This has a significant impact on reducing the size and weight of output filter elements. The proposed converter provides zero voltage zero current switching (ZVZCS) turn-off and ZCS turn-on condition for all the main switches and ZVZCS turn-on condition and ZCS turn-off condition for synchronous rectifier switch without using the antiparallel diode and enables common ground and continuous output current. In this converter, the coupled-inductor and snubber circuits are not utilized so it leads to high efficiency and simplifies the converter topology. Finally, a 310V/24V/600W prototype is implemented to validate the theoretical analysis and benefits.