Research on a primary-side regulation quasi-resonant flyback converter

To achieve low power consumption and miniaturization design goals, this paper focuses on the research of a primary-side regulation quasi-resonant flyback converter structure. The converter operates in boundary conduction mode under heavy load, reducing the complexity of system control and avoiding excessive peak currents; it switches to discontinuous conduction mode under light load to improve conversion efficiency. The converter uses a clamp circuit to sample the output voltage and convert it into a current signal. The sampling is completed by a sample and hold circuit at the knee point, simplifying the output voltage sampling and eliminating the need for auxiliary windings. Circuit design and layout implementation were completed based on a standard 0.18μm BCD process. Simulation results show that the converter achieves a peak conversion efficiency of 88.27% under input voltage of 3-32V and output voltage of 5V, and it also has a conversion efficiency of over 70% under light load. The chip area is 1.48mm × 2.5mm.