ANALYSIS AND IMPLEMENTATION OF A QUASI-RESONANT BUCK CONVERTER

A comprehensive analysis of the zero-current-switched (ZCS) buck converter is presented for the lossless case and for the case with parasitic losses in the resonant tank. Since the switching losses are reduced by using a ZCS scheme, the parasitic losses in the resonant tank become an important factor as regards efficiency. Approximate expressions for the efficiency of ZCS, buck quasi-resonant converter (QRC) in both the half-wave and full-wave modes are derived. A multi-loop scheme is used for the ZCS, buck QRC. This control scheme eliminates the need for a voltage-controlled oscillator (VCO), which can be difficult to implement at higher frequencies. Finally, a complete ZCS, buck QRC in both the half-wave and full-wave modes using the multi-loop control is implemented.