ABSTRACT
Generally, a switched-mode power converter is often required to meet all or most of the following specifications:
• High switching frequency • High power density for reduction of size and weight • High conversion efficiency • Low total harmonic distortion (THD) • Controlled power factor if the source is an AC voltage • Low electromagnetic interference (EMI)
A review of the commonly used pulse-width-modulating (PWM) converter and new generated resonant converter is presented in order to fully understand the two major branches of the high frequency switching converter. Although PWM technique is widely used in power electronic applications, it encounters serious problems when the switching converter operates at
high frequencies. Due to the hard-switching transitions caused by PWM technique, switching losses possess large proportion in total power dissipations. In other words, when the switch is turned on, the current through it rises very fast, while the voltage across it cannot descend immediately due to the parasitic output capacitance. Similarly, when the switch is turned off, the voltage across it rises rapidly while the current through it cannot drop at once because of the recombination of carriers.
