Intermittent Sinusoidal Modulation of Bidirectional Series Resonant Converter With Zero Current Switching, Linear Current Controllability, and Load-Independent Efficiency

Sinusoidal modulation can keep the resonant current in phase with the terminal voltage, and, thus, it is feasible to achieve both zero current switching (ZCS)
on/off
and eliminate backflow power in a series resonant converter. However, it makes the transfer characteristics inherently dependent on the resonant tank and, thus, challenges power regulation. In this article, a novel intermittent sinusoidal modulation is proposed for a bidirectional series resonant converter (BSRC). Each switching cycle incorporates a sinusoidally modulated resonant period and an intermittent period for the current controllability, while fully ZCS as well as null backflow power can be maintained for high efficiency regardless of load conditions. The BSRC operates as a current source, with the normalized voltage gain being either stepped up or down, to achieve a wide range of output power. Moreover, the output power together with the power loss is proportional to the switching frequency, making the high power efficiency independent of the load. Therefore, fully ZCS, linear current controllability, and load-independent high efficiency can be simultaneously realized throughout a wide load range. A 1-kVA BSRC prototype that interfaces a high-voltage bus ranging from 240 to 480 V and a low-voltage bus of 48 V validates the proposed modulation scheme.