Sensor-Less Current Sharing over Wide Operating Range for Extended-Duty-Ratio Boost Converter

An extended-duty-ratio (EDR) boost converter is studied extensively in this paper for high voltage gain applications with a wide input (and/or output) voltage range. The EDR is a unique combination of an interleaved, multiphase boost converter and switched capacitor configuration that achieves high voltage gain with significantly lower switch voltage stress and switching losses compared to conventional high-gain solutions. Most of the switches in the multiphase EDR experience only a fixed fraction of the output voltage (1/M, 2/M , etc., where M is the number of phases). Through extensive analysis over a wide operating range, it is shown here that the EDR boost converter has inherent current sharing among the phases only in a limited range of duty ratio - (M-1)/M ≤ D ≤ 1. As the duty ratio reduces beyond this range as required in wide input voltage applications, inherent current sharing property is lost. In this paper, techniques to ensure current sharing under all operating zones without requiring current sensors are presented. Instead of having equal duty ratio for each phase, it is adjusted for each phase according to the operating region of the converter. Extensive analysis is presented to derive the required duty ratio changes for the different phases. The proposed concept is validated with experimental results from a 250 W, 3-phase EDR boost, and GaN-based hardware prototype.