Electrolytic Capacitorless AC/DC LED Driver

This paper presents electrolytic capacitorless AC/DC LED driver. It adopts Boost–Buck topology, through modulation of the conduction time Ton and the change of input current reference, to reduce the instantaneous input and output power difference, so a smaller film capacitor can be used instead of the electrolytic capacitor. Therefore, LED driver power life has been effectively improved. The Buck converter operates in the inductor current discontinuous conduction mode to achieve constant output current by controlling the peak current. The control IC is fabricated in TSMC 0.35-μm 5-V/650-V CMOS/LDMOS process, and verified in a 72-V/150-mA circuit prototype. The test results show that when the range of input voltage is 175–264 Vac, the efficiency of the system is 83%, the voltage linear regulation is ±1%, the load regulation is ±0.5%, and the electrolytic capacitor is replaced by 470-nF CBB capacitor under the condition that the power factor is above 0.7. Therefore, the design of the control chip in the LED...