High-Efficiency LLC Resonant Converter with Optimized Frequency Modulation for Wide-Input-Voltage EV Battery ChargingPages 116-135
Abstract:
The LLC resonant converter is widely favored for electric vehicle (EV) onboard charging due to its soft-switching capability. However, conventional frequency modulation (FM) control often forces operation away from resonance at input voltage extremes, degrading efficiency and zero-voltage switching (ZVS) performance. This paper presents an optimized FM-controlled full-bridge LLC resonant converter designed for a wide input voltage range of 35–55 V, delivering 600 W at 360 V output for EV battery charging applications. Employing Fundamental Harmonic Approximation (FHA) modeling and validated through PSIM time-domain simulation, the design achieves a peak efficiency of 98.1% at nominal input while maintaining robust ZVS and zero-current switching (ZCS) across the operational range. The converter demonstrates stable output regulation with voltage ripple below 1 V. Detailed loss analysis and component stress evaluation confirm the design's reliability and thermal margin. The results establish that a strategically optimized FM-controlled LLC topology offers a compelling balance of high performance, simplicity, and cost-effectiveness for next-generation EV onboard chargers.
Keywords: LLC resonant converter, Frequency modulation (FM), Zero-voltage switching (ZVS), EV battery charging, DC/DC converter, Wide input voltage,
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