Analysis and Efficiency Improvement of Quasi-Resonant Flyback Converter with Adaptive Valley Detection and Variable Frequency Control

QR-Flyback converters exhibit poor efficiency performance under high input voltage and light load conditions. This paper investigates the control of Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) in quasi-resonant flyback converters across varying input voltages $(V_{in})$, output voltages $(V_{o})$, and load conditions $(P_{o})$. An adaptive frequency control method is proposed, enabling the QR-Flyback converter to operate at an appropriate frequency, thereby improving efficiency. Additionally, this paper presents an adaptive valley detection scheme for QR-Flyback converters, applicable to wide input/output voltage ranges and various load conditions. The proposed control architecture is validated through simulations.