High Efficiency LC Resonant Boost Topology: Analysis and Design

Boost type converters are commonly used as pre-regulators in applications such as photovoltaics, battery storage, and power factor correction. Normally, non-isolated step-up conversion is done using traditional hard-switching boost topologies, but these suffer from low efficiency due to hard switching transitions. Soft-switching boost topologies present an opportunity to increase switching frequency while reducing the size of the converter. In this paper, a new set of equations and an analysis is proposed for a resonant structure with boost capabilities. This LC Boost topology features soft switching at all of the semiconductors, including MOSFETs at both turn-on and turn-off, and at the diodes at turn-off, even in light load. The circuit also has low RMS ripple in the input and output current, which has twice the switching frequency of the converter and lower amplitude. This helps to reduce the input and output capacitance. The characteristic behavior of LC boost is analyzed, including performance and design equations. Simulation and the experimental results are provided for a 400W prototype and are compared to a benchmark traditional boost. Substantial efficiency improvements are achieved.