Bridgeless electrolytic capacitor-less valley fill AC/DC converter for twin-bus type LED lighting applications

In order to match the main features of LED lighting source and further save power, the power supply for LEDs also requires long life while maintaining high efficiency, high power factor, PWM dimming and low cost. However, a typical power supply for LEDs exist the following drawbacks: (1) utilize bulky electrolytic capacitor as storage capacitor with short lifetime; (2) employ a low frequency diode bridge as the rectifier cell; (3) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, a novel LED lighting driver is proposed in this paper. In this design, the non-cascade Twin-Bus configuration and bridgeless technology are utilized to increase the efficiency of LED power supply, while special DCM operation mode and valley fill circuit are introduced to eliminate electrolytic capacitors and reduce capacitor size. A 50-W prototype has been designed and tested in the laboratory, and the experimental results under universal input voltage operation show the effectiveness and advantages of the proposed circuit.