Performance characteristics of a half-bridge type series resonant dc-dc converter with auxiliary switches

Series resonant dc-dc converters possess the advantage of high efficiency for a relatively wide load range because their circulating energy is small. However, it is often observed that the switching frequency varies greatly when the input voltage and load current change, and in particular that the switching frequency enters the audible frequency range when the load current decreases. A half-bridge type series resonant dc-dc converter with auxiliary switches has been designed in order to prevent this lowering of the switching frequency under light load conditions. This paper analyses the performance characteristics of a half-bridge type series resonant de-de converter with auxiliary switches, including operation of the control circuit. The relationship among the circuit parameters, the operation modes, and output characteristics is clarified, and the regulation mechanism of the output voltage is defined. (C) 1998 Scripta Technica, Electron Comm Jpn Pt 1, 82(2): 74-81, 1999.