$90^\circ$-Valley Unified Controller for Zero-Voltage-Switching Quasi-Square-Wave (ZVS-QSW) Boost Converter
Branko Majmunović, Brent McDonald, Sheng-Yang Yu, Johan Strydom
Abstract
This paper presents a novel control strategy for Zero-Voltage-Switching Quasi-Square-Wave (ZVS-QSW) Boost converter. The controller is based on an exact, closed-form analytical solution of the converter, that is obtained under the assumption that the duration of the valley resonant transition corresponds to a 90° angle. A Zero-Voltage-Detection (ZVD) circuit is used to tune the switching frequency to a value that results in the 90° valley resonant transition. The controller is implemented digitally, and it's not affected by the propagation delay of the ZVD signal. Zero-voltage-switching (ZVS) of the main device is guaranteed by the closed-loop ZVD frequency tuning, and accurate current control is achieved with the exact analytical solution of the converter. Contrary to commonly used approaches that rely on high-frequency current measurement, this current control is realized without measuring the current. The controller is implemented in a Power Factor Correction (PFC) circuit, in conjunction with an outer voltage loop. The approach is validated experimentally on a 5 kW prototype, using GaN devices, and featuring a power density of 120 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , peak efficiency greater than 99%, and a Total Harmonic Distortion (THD) well below the specified requirements, across the entire load range.