Output Voltage Sampling Circuit for Discontinuous Conduction Mode Flyback Pulse-Width Modulation Controller

摘要

Primary-side controlled pulse-width modulation (PWM) flyback converter has been widely used in low-power and low-voltage products for its simple structure and low cost. This paper presents a novel output voltage sampling circuit which considers the influence of the rectifier diode current on the output voltage sampling. The output voltage sampling circuit samples the output voltage at 85% of the secondary inductance discharge time T-dis of last cycle, which improves the accuracy of the output voltage sampling circuit. Besides, the circuit can also sample the secondary inductance discharge time T-dis. Finally, a chip has been fabricated in 0.6 mu m complementary metal-oxide semiconductor (CMOS) process, which is used in the presented output voltage sampling circuit in its internal circuit to simple output voltage and achieve constant output voltage.