Investigation of the Active Ripple Compensation Technique to Reduce Bulk Capacitance in Offline Flyback-Based LED Drivers

Abstract

This paper presents the study of an offline flyback-based light-emitting diode (LED) driver with reduced storage capacitance. An approach called active ripple compensation was used for minimizing the converter bulk capacitance. This technique is oriented to voltage-controlled pulse width modulation converters and is based on the modulation of the duty cycle, which allows for the reduction of the filtering capacitance by increasing the harmonic content of the input current up to the limits established by the standards. By means of the design procedure presented in this paper, the amount of capacitance reduction and input current distortion can be fully controlled and theoretically predicted. In addition, no extra sensors are required to implement the proposed technique, apart from the LED current sensor already available in most LED drivers. Experimental results from a 50-W laboratory prototype supplied from a 220-V 60-Hz grid were carried out. The results were compared with the conventional approach, attesting the superior performance of the proposed methodology.