A Hybrid Modulation Strategy for Asymmetric Half-Bridge Flyback Converters with Wide-Output Voltage Range

This paper proposes a hybrid modulation strategy for asymmetric half-bridge (AHB) flyback converters with wide output voltage range. Traditionally, the pulse-widthmodulation (PWM) technique with duty cycle modulation is adopted for the AHB converter. However, under the PD3.1 specification with the wide output voltage range feature, conventional PWM control methods might fail. Therefore, a hybrid modulation strategy for AHB flyback converters is proposed in this paper. The pulse-wide-modulation (PWM), the pulse-frequency-modulation (PFM) and the burst mode control are integrated and developed for the hybrid control. With the proposed approach, the AHB converter with wide output voltage range can easily be realized without complex control mechanisms. Besides, the soft-switching feature can be achieved under different control modes to ensure the high circuit efficiency. The developed control strategy can be realized by microcontrollers without adding extra circuit or components. Finally, a 240 W prototype circuit with hardware experiments that demonstrate the performance and feasibility of the proposed strategy.