Offline application of the fixed-frequency clamped-mode series resonant converter

The performance of the clamped-mode series resonant converters (CMSRC) is studied for an offline application. The CMSRC has the advantage of fixed-frequency operation, resulting in an easier design of magnetic components for resonant tank and filtering. Two prototypes were designed and tested experimentally, one to operate below resonant frequency (mode B) and the other to operate above resonant frequency (mode A). The efficiency is mainly determined by the rectifier losses and the switching losses. Where mode-B operation is implemented (below resonant frequency), the recovery of the diodes greatly increases the turn-on losses of the devices. The operation mode with four switches turned on at zero voltage, mode A´ at above resonant frequency, shows better efficiency. Therefore, if higher frequencies of operation are desired, mode A´ is the better choice among the four modes of operation discussed