A digital controller IC for the flyback converter with primary-side feedback is proposed. The controller is used for adapter charger or LED driver applications. To obtain high accuracy for the primary-side feedback, a digital primary-side sensing technology is adopted, which can auto-track the knee point of the primary auxiliary winding voltage. Furthermore, an internal digital compensator eliminates the need for external loop compensation components while achieving excellent line and load regulation. The controller could output both constant voltage and constant current depending on the load current. Pulse width modulation and pulse frequency modulation are used in constant voltage mode while quasi-resonant control is used in constant current mode. The digital controller is validated by using FPGA. A digital controller IC for the flyback converter with primary-side feedback is proposed. The controller is used for adapter charger or LED driver applications. Which achieves high accuracy for the primary-side feedback, a digital primary-side sensing technology is which The internal voltage compensator eliminates the need for external loop compensation components while achieving excellent line and load regulation. The controller could output both constant voltage and constant current depending on the load current. Pulse width modulation and pulse frequency modulation are used in constant voltage mode while quasi-resonant control is used in constant current mode. The digital controller is validated by using FPGA.