Optimal Zero-Voltage Switching Tracking Approach for Wide-Range Boost Converters Operating in the Boundary Conduction Mode

This article introduces a timing optimization approach for wide input voltage range boost converters operating in the Boundary Conduction Mode (BCM). Based on a time-domain analysis of the transient converter waveforms during the deadtime, this work describes the required timing scheme to achieve the optimal Zero Voltage Switching (ZVS) turn on condition for the low-side transistor, in which the driving voltage toggles exactly when the switching node voltage becomes null. The proposed approach consists in optimizing simultaneously the duration of the negative inductor current extension time and the deadtime, so as to achieve optimal ZVS with minimal inductor current ripple. The approach only requires input and output voltage sensors and a Zero-Current Detection (ZCD) circuit, already present in ordinary BCM converters, and is proven to accurately predict the optimal timing parameters. The optimization approach is implemented on a microcontroller, and experimental results on a synchronous boost reveal that the on-line timing adjustment enhances the converter efficiency by up to 1.1%, and preserves the optimal ZVS operation also in transient conditions. Its simple implementation and performance improvement make this approach suitable for wide-range step-up applications.