Principles of quasi- and multi-resonant power conversion techniques

Recently developed quasi-resonant and multi-resonant DC-DC power conversion techniques are reviewed. Quasi-resonant converter (QRC) and multi-resonant converter (MRC) topologies are derived from the conventional square-wave, pulse-width modulated (PWM) converters by adding resonant components to achieve zero-current switching (ZCS) or zero-voltage switching (ZVS) of the semiconductor devices. ZCS and ZVS reduce switching losses caused by the parasitic leakage inductance of the power transformer and junction capacitances of semiconductor devices. As a result, QRCs and MRCs can operate at higher switching frequencies and achieve higher power density than PWM converters. Explanations of operations of zero-current-switched and zero-voltage-switched QRCs and MRCs are provided, and their relative advantages and limitations are discussed.<>