Light Load Efficiency Enhancement Strategy for Single-Stage AC-DC by Using Adaptive Switching Frequency

This paper presents a modulation scheme that utilizes adaptive switching frequency (f
sw
) to enhance light load efficiency performance for a single-stage stage AC to DC converter. Single-stage converters operate with hard switching during light load operations, leading to significant switching losses and Electro Magnetic Interference (EMI). This situation is severe with low voltage gain or low battery voltage. In addition, a single-stage converter experiences low total harmonic distortion (THD) at light load operation. The proposed modulation scheme improved the light-load efficiency, and power quality of the conversion. Experiment results from a 3.7 kW single-stage OBC prototype are provided to verify the theoretical claims at various load levels. The proposed method is good for Battery Energy Storage Systems (BESS) and photovoltaic (PV) applications where various levels of load conversion may be involved.