This paper proposes a single-phase high-powerfactor ac/dc converter with soft-switching characteristic. The circuit topology is derived by integrating a boost converter and a buck converter. The boost converter performs the function of power-factor correction (PFC) to obtain high power factor and low current harmonics at the input line. The buck converter further regulates the dc-link voltage to provide a stable dc output voltage. Without using any active-clamp circuit or snubber circuit, the active switches of the proposed converter can achieve zero-voltage switching-on (ZVS) transition together with high power factor that satisfies the IEC 61000-3-2 standards over a wide load range from 30% to 100% rated power. The steady-state analysis is developed and a design example is provided. A prototype circuit of 60 W was built and tested. Experimental results verify the feasibility of the proposed circuit with satisfactory performance.
This paper presents a single-stage driver with soft-switching and interleaved power-factor correction (PFC) features suitable for light-emitting diode (LED) energy-saving streetlight applications. The proposed LED streetlight driver integrates an interleaved buck-boost PFC converter with coupled inductors and a half-bridge LLC resonant converter into a single-stage power-conversion circuit with reduced voltage stress on the DC-linked capacitor and power switches, and it is suitable for operating at high utility-line voltages. Furthermore, coupled inductors in the interleaved buck-boost PFC converter are operated in discontinuous-conduction mode (DCM) for accomplishing PFC, and the half-bridge LLC resonant converter features zero-voltage switching (ZVS) to reduce switching losses of power switches, and zero-current switching (ZCS) to decrease conduction losses of power diodes. Operational modes and design considerations for the proposed LED streetlight driver are introduced. Finally, a 144 W (36V/4A)-rated LED prototype driver is successfully developed and implemented for supplying a streetlight module and operating with a utility-line input voltage of 220 V. High power factor, low output-voltage ripple factor, low output-current ripple factor, and high efficiency are achieved in the proposed LED streetlight driver.
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