Self-oscillating series-resonant led driver applied to reduce low-frequency current ripple transmission

This paper presents the analysis and design of an LED driver based on the series-resonant converter (SRC) and on the self-oscillating command circuit (SOCC). The use of SRC provides a reduction of the low frequency (LF) ripple in the LEDs' current, originated by the voltage ripple in the output of the power factor correction (PFC) stage (bus voltage ripple). The attenuation of the ripple transmission from the bus voltage to the LEDs' current achieves some desired goals: (1) reduction of the bulk capacitance used at the output of the PFC stage, enabling the employment of long-life film capacitors, and (2) increasing of the efficiency of the LED driver because of the low switching losses of the series-resonant converter. The SOCC stamps on the LED driver the low-cost, simplicity, and robustness features. In order to avoid any mismatch between the SRC LF current ripple reduction design guidelines and the SOCC design, a design methodology is presented. Experimental results from a self-oscillating series resonant converter to supply a 10 Watts LED lamp are presented, validating the feasibility of the developed methodology and the proposed analysis.