Novel technique for bidirectional series-resonant DC/DC converter in discontinuous mode

This study analyses a novel technique for obtaining a voltage conversion ratio greater than one in a bidirectional seriesresonant DC/DC converter (SRC). The converter works in a discontinuous mode: it transfers energy in packets, but it also accumulates some packets in order to raise the output voltage. This study presents a comprehensive theoretical analysis for the two modes: the step-down mode (common mode) and the novel step-up mode. The converter transfers energy during fixed time intervals (called states), and it is also able to accumulate energy in a novel state called the accumulation state. With this, the circuit can achieve a voltage conversion ratio of up to two. In addition, a design methodology is presented, and it is validated in the design of a high-current bidirectional DC/DC converter for battery applications. The results of the voltage conversion ratio and efficiency measurement are presented along with a comparison with an resonant LLC converter. The converter reaches an efficiency rate of 91% and the voltage conversion ratio varies from 0.8 to 1.22 at maximum power. Using this novel technique, the SRC can now be used in a bidirectional DC/DC converter applied to energy storage devices, such as batteries or supercapacitors.