Design and Control of a High-Power Wide-Gain-Range LLC Resonant Converter

A design and control method are introduced in this paper to improve the overall efficiency of an LLC converter for railway applications, with high power and wide gain range requirements. Multi operation modes are combined together. Magnetizing inductance is designed to minimize device loss under unity gain operation. Boost mode operation provides an ability to boost gain much higher than frequency modulation could, and release the constrain of resonant tank design with respect to the peak gain requirement. The 30kW prototype circuit verifies the proposed design and control method.