A primary-side output current estimator with process compensator for the flyback control circuits is designed and analyzed in this investigation. Flyback control circuits play a key role of smart lighting systems, where LED drivers require a compensator to keep the system stable. The process sensor is in charge of the detection of the chip process corner. Then, the process compensator correspondingly selects a comparator according to the output of the process sensor. Detailed analysis, including the method of the process sensor and the selection procedure of the process compensator, is reported. All-PVT-corner post-layout simulations of the proposed current estimator demonstrate 89.84 % efficiency, and 15.53 W power consumption given 5 V power supply and 50 kHz system clock rate.