Simplified Analysis and Optimal Design Method for LLC Resonant Converter Based Focusing Magnet DC Power Supply in High Power LINAC Applications

ABSTRACT Soft switching of primary‐side semiconductor switches across the full operational range, high‐frequency transformer nonidealities, and the high reactive energy in the resonant tank circuit is key challenges in the design of focusing magnet DC power supplies (FMDPS). To address these issues, this paper presents a simplified and optimized design method for an LLC resonant converter (LLC‐RC)‐based FMDPS in high‐power linear accelerators (LINACs). The proposed LLC‐RC power converter, with its optimal design approach, effectively resolves these challenges, achieving zero voltage switching (ZVS) at turn‐ON across the entire operational range. Additionally, transformer nonidealities such as leakage inductance and magnetizing inductance are absorbed within the resonant tank and utilized to advantage. The proposed converter is designed with an optimal quality factor (Q), minimizing the total reactive energy in the circuit. The work also presents a steady‐state analysis of the proposed topology, along with derived expressions for voltage gain, input impedance, and resonant frequencies. To validate the concept, a 600‐W experimental prototype (input: 250 V; output: 30 V/20A) featuring soft switching throughout the full operating range was developed, achieving a maximum efficiency of 95.99%. The experimental results closely align with the theoretical design and simulation outcomes.