A ZV-ZCS electrolytic capacitor-LessAC/DC isolated LED driver with continous energy regulation

Abstract

Conventional AC/DC LED drivers require a large energy storage capacitor at the output to provide a constant current to the LEDs. In order to minimize the size and cost of the driver circuit, electrolytic capacitors are conventionally used due to its high energy density and low cost. However, electrolytic capacitors are sensitive to operating temperature and have much shorter lifetime than the LED semiconductor devices, which significantly reduces the overall life time of the LED system. Another drawback with the current LED drivers is that the presence of the switching power losses restricts the use of high frequency operation, which results in using bulky passive circuit components in the drivers and significantly reduces the circuit power efficiency. This paper proposes a single-stage high power factor LED driver with almost zero switching losses and without the electrolytic capacitor. In the proposed circuit, discontinuous conduction mode (DCM) boost converter was utilized as a power factor correction (PFC) circuit, where it was integrated with an asymmetrical pulse width modulated (APWM) series resonant converter to form a single stage power conversion unit to drive the LEDs. The proposed circuit is able to achieve zero turn-on and turn-off switching operation and is able to eliminate the conventionally needed electrolytic capacitors by continuously regulating the DC-link voltage. The proposed LED driver was simulated and tested on a 12W design example to confirm that an almost unity power factor and an efficiency of 95% can be achieved.