A comparative study of two DC/DC converter topologies for telecommunications

Contemporary telecommunication systems demand small size power supplies with a high level of electromagnetic capability and low power dissipation. Resonant power conversion topologies meeting these requirements have been available and successfully implemented in practice for a decade. A phase-shifted, pulse-width modulated (PWM) converter topology has been proposed aiming to combine the resonant soft-switching mechanism (featuring low switching losses) with the effectiveness of the PWM-control method (featuring low conduction losses). An extensive comparison between a parallel resonant converter and phase-shifted PWM converter over various operating conditions has been accomplished. Both topologies have been designed to comply with technical specifications typical for telecommunications. The complexities of the comparison mean that one topology cannot be considered more favourable than the other unless a set of operating specifications is defined. In terms of converter efficiency alone, above 70% of full rated output power the performances are very similar. Soft-switched PWM is slightly more efficient in the mid load range, but not at light loads when soft-switching operation is lost. The severe EMI problems and difficulty in manufacturing consistently phase-shifted PWM topology has also been discussed. It has been concluded in summary that the advantages of the parallel resonant converter outweigh those of phase-shifted PWM converter if they are designed to meet typical telecommunication requirements.