A LLC-Based Hybrid PWM and Charge Control Scheme for MEA/AEA Systems Under Light Load Condition
摘要
The evolution of More/All-Electric Aircraft (MEA/AEA) has driven the demand for efficient and reliable power conversion systems, particularly DC/DC converters. LLC resonant converter is widely adopted due to its high efficiency and low EMI; however, its performance degrades significantly under light-load conditions—common in standby or partial-power flight modes. Various studies have been proposed to address this issue, such as switchable magnetizing inductance, zero-crossing-point detection, or adaptive phase-shift control. While effective, these methods often add system complexity. Simpler strategies like burst mode and pulse skipping modulation (PSM) improve light-load efficiency by reducing switching losses but tend to result in large output ripple and unstable dynamic response. To overcome these limitations, this paper presents a hybrid PWM and charge control scheme for LLC converters in MEA/AEA systems under light loads. The scheme features adjustable duty ratio and burst pulse quantity, enabling improved control flexibility. The methodology of calculating PWM and burst pulse quantity will be elaborated via time-domain analysis. To prove, a 1-kW (540 VDC / 28 VDC) PLECS models implementing both the conventional HHC and the proposed scheme are developed. Simulation results demonstrate the proposed control strategy achieves superior transient response (200 μs from 100%–1% load) and reduced output voltage ripple (80 mV under 1% load).