A Single-chip PFM-controlled LED driver with 0.5% illuminance variation

A high-efficiency LED driver with the pulse frequency modulation (PFM) control method to generate nearly consistent illuminance is demonstrated in this investigation. The illuminance consistency is achieved by sensing the feedback voltage and the temperature to modulate the on time of power devices such that automatic illuminance regulation is carried out. The recommended LED driver using the PFM control method is featured with an up-and-coming illuminance equalizer. Thus, it does not need any compensation circuit. Utilizing a 0.5-μm High Voltage CMOS process, the prototype has successfully fabricated, occupying 3.2 mm2 of chip area. The measurement outcomes of the chip demonstrate that the current error remains within 1% when the LED output current set at 20 mA. Moreover, the variation in illuminance is exceptionally low, measuring a mere 0.5%. Furthermore, the efficiency reaches 91% verified by the measurement results.