An Improved Mode Transition Technique for a Non-Isolated Bidirectional DC-DC Converter

This brief presents the design and analysis of improved mode transition and startup techniques for a DC-DC bidirectional converter (BDC) for battery charging/discharging applications. The BDC inductor current is controlled in such a way that the current reaches its steady state value naturally without any control effort during the transient operation of the converter. The improved mode transition method ensures suppression of large transient currents in either direction by adopting simple control methodology simultaneously reducing the time of mode transition significantly, to the order of time constant of the inductor employed in the converter. This technique is implemented by sensing the direction of inductor current and generating appropriate PWM switching to the bidirectional switches. The startup technique is essential to suppress the current transient during initial response of the BDC for either modes of operation. The start-up and mode transition logic are very effective and easy to implement. A 400 W BDC is designed, analyzed, simulated and experimentally verified for improved mode transition and smooth startup techniques.