Power efficiency improvement of a multi-oscillated current resonant type DC-DC converter

This paper deals with an improvement of a power efficiency of a multi-oscillated current resonant type DC-DC converter. The current resonant type converter employs generally the pulse frequency modulation and its magnetizing inductance is set relatively low. For this reason, the magnetizing current through the converter causes a power loss under a light load. In order to solve this problem, a multi-oscillated current resonant type DC-DC converter has been proposed, and revealed the advantage of its control method which can reduce power loss under light load and keep low switching noise. In this topology, output power is controlled by duty ratio and operating frequency is determined by resonant condition. In this paper, an analysis of power loss by focusing on switching devices in this converter to improve power efficiency was given. As a result, it was confirmed that the loss of diodes in secondary side occupies main loss. Adopting the synchronous rectifier in the secondary side, the maximum power efficiency is improved to 96.3%, and the average efficiency, which is averaged efficiency at 25%, 50%, 75% and 100% of the rated load, reached 95.5%.