Ring-free zero-voltage switching technique for use in switching power converters

Abstract

A ring-free zero-voltage switching technique for use in a switching power converter having a zero-voltage switching circuit to achieve high-performance and high-density zero-voltage switching and a transformer to produce an oscillatory L-C circuit at the primary side thereof during zero-voltage switching of the switching power converter, the technique includes the step of short-circuiting the current at inductance means of the L-C circuit upon the occurrence of ringing, and to suppress the voltage at capacitor means of the L-C circuit, so as to eliminate parasitic ringing produced by the zero-voltage switching circuit, to effectively reduce power loss and lower the reverse voltage rating requirement to the secondary side rectification component, to greatly increase the working frequency and power density, to eliminate EMI noises, to minimize the size of the heat sink required for dissipating heat energy from the power MOSFETS, and to let the switching power converters meet the requirements of international EMI regulations and be applicable to the designs of mini electronic products.