Abstract

Telecommunication and computer systems require power supply topologies that offer high efficiency and high power density at ever-increasing switching frequencies. There are many resonant topologies that can offer this, but the asymmetrical pulse-width modulated (APWM) resonant DC/DC converter is a simple topology that operates at a constant frequency and with near-zero voltage switching losses. However, the range of input voltage where high efficiency is maintained is narrow. After a certain limit, zero voltage switching is lost and the voltage stress on the resonant inductor becomes too high. A modified APWM resonant DC/DC converter topology is proposed that employs an auxiliary network. Steady-state analysis and computer simulations are performed and show how this simple auxiliary network compensates the original topology by improving the efficiency and reducing the resonant inductor voltage stress. A prototype of the modified topology is constructed and experimental analysis supports the theoretical results. Operating curves and a design example help to realize optimum values of the major components. To further improve the performance, the use of MOSFETs as synchronous rectifiers in place of diode rectifiers is proposed. Two examples of synchronous rectifier topologies that are applicable to the converter under study are investigated. Computer simulation shows the feasibility of employing synchronous rectification with the modified APWM series resonant DC/DC converter.