Digital Closed-Loop Control Strategy to Maintain the Phase Shift of a Multi-Channel BCM Boost Converter for PFC Applications

This paper presents a novel closed-loop digital control scheme to maintain proper interleaving operation of a multi-channel boundary-conduction-mode boost converter used in power-factor-correction applications. The proposed control scheme is suitable for implementation on a low-cost microcontroller. This is made possible by executing the control scheme at a constant sampling rate that is much slower than the maximum switching frequency of the converter. The performance of the control scheme is further improved by using an adaptive gain that scales with the on-time of the converter, which provides optimal phase-shift control and stability under all operating conditions. The digital closed-loop control scheme is validated experimentally on a three-channel 1-kW prototype ac-dc converter. The converter has an output voltage of 400 V and a universal input voltage range of 85-265 V. The prototype converter uses a low-cost microcontroller while demonstrating correct interleaving operation.