Single-Stage Dimmable PFC DCM Flyback Converter without Electrolytic Capacitor for LED Lamps

The attention has been increased about energy problem caused by exhaustion of fossil fuel in the whole world. Under a situation like this, a light-emitting diode (LED) has been applied various industry field and general lighting because of its high efficiency, low power consumption, environment-friendly characteristic and long lifetime. The LED lighting is needed a ac to dc driver when it is applied in ac source because it use the constant current. Among the drivers, the most popular one is the switching converter. Generally, the electrolytic capacitor is used in the switching converter for constant output. However the lifetime of the electrolytic capacitor is shorter than the LED lighting. Therefore the lifetime of entire system is decreased. This paper presents the single-stage flyback converter without the electrolytic capacitor. Instead of the large capacitive electrolytic capacitor, the small capacitive film capacitor is used which has enough lifetime compared with the LED lightings. Because of decreasing the capacitive of capacitor, the large 120[Hz] ripple is shown on the output. To reduce the 120[Hz] ripple, LC resonant filter is applied. The two type of LC resonant filter, one is parallel type, and the other is serial type, is proposed. And the performances of two type of filter are compared and analyzed. Without additional circuit, the power factor is corrected with discontinuous conduction mode design. Also, a dimming control is available with only one switch using the analog dimming control. The proposed converter is verified through the simulation and the experimental works.