Energy-efficient residential lighting such as household Light-Emitting Diode (LED) lamps with AC input require an AC/DC converter (or driver) with large output capacitance to minimize the low frequency LED current ripple. The energy storage capacitor used in the conventional AC/DC LED driver is usually an electrolytic capacitor due to its low cost and high energy density. However, the average lifetime of an electrolytic capacitor is at least 2 to 3 times less than that of a LED device. Hence, the potential lifetime of the LED lamp is significantly affected by the presence of the electrolytic capacitor in the driver circuit. In this article, 2 novel isolated single-switch AC/DC high power factor LED drivers without using any electrolytic capacitors are proposed. In the proposed circuits, the energy storage capacitor is moved to the rectifier side, with a three-winding transformer used to provide isolation; input power factor correction as well as to store and provide the required energy to the output. As a result, the energy storage capacitance is significantly reduced, which allows film capacitor to be used to replace the conventionally used electrolytic capacitors.
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