Topology Morphing Control Strategies for Full-bridge LLC Converter

Abstract

Wide soft switching operation range, high frequency operation, and simple control strategy are the main characteristics for LLC converter. Thus, it has been widely used in industry. In particular, renewable energy systems, like photovoltaic (PV) and fuel cell, require wide voltage gain range application, which is challenging for traditional LLC converters since wide switching frequency variation range is necessary. To narrow down the switching frequency operation range, in this paper, the topology morphing control strategies for full-bridge LLC converter are investigated. The traditional full-bridge LLC converter can operate as half-bridge mode or frequency doubler operation mode by simply modifying the gate signals. Then, the converter voltage gain is doubled when compared with traditional full-bridge converter, and only half of the switching frequency operation range is required to cover the same voltage gain range. Operational principles, comparative analysis, and experimental validation are presented.