Means of Eliminating Electrolytic Capacitor in AC/DC Power Supplies for LED Lightings

This paper proposes two methods of reducing the storage capacitance in the ac/dc power supplies for light emitting diode (LED) lighting. In doing so, film capacitors can be adopted instead of electrolytic capacitors to achieve a long power supplies' lifetime. The voltage ripple of the storage capacitor is intentionally increased to reduce the storage capacitance. The method of determining the storage capacitance for ensuring that the boost power factor correction converter operates normally in the whole input voltage range is also discussed. For the purpose of further reducing the storage capacitance, a method of injecting the third harmonic current into the input current How is proposed. While ensuring that the input power factor is always higher than 0.9 to comply with regulation standards such as ENERGY STAR, the storage capacitance can be reduced to 65.6% of that with an input power factor of 1. A 60-W experimental prototype is built to verify the proposed methods.