This paper presents a high-efficiency AC-DC switch-mode power supply (SMPS) using the full-bridge converter circuits. The proposed converter utilizes three full-bridge converter circuits: two full-bridge diode converter circuits and one full-bridge MOSFET converter circuit. The two full-bridge converters are utilized at the primary AC input and the secondary DC output, respectively, and the full-bridge MOSFET converter is used to convert a DC voltage to a high-frequency AC voltage that is converted to another DC voltage with the transformer and the secondary full-bridge diode converter, which is simply referred to as the full-bridge DC-DC converter. However the conventional full-bridge converter has a limit in its operating duty ratio in normal operation, because it results in more conduction loss in light load operation. Therefore, the proposed converter resolves the drawbacks of the conventional full-bridge converter using a modified full-bridge circuit with a DC blocking capacitor in the primary. Thus, the proposed converter has improved total efficiency and performance. The operation principle of the proposed converter is described in detail, and a design example of a prototype is shown. The good performance of the proposed converter is demonstrated through experimental results of the implemented prototype based on the design example.

-This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

-This paper presents a simple high efficiency full-bridge DC-DC converter using a series resonant capacitor. The proposed converter achieves the zero voltage switching of the primary switches under a wide range of load conditions and reduces the high circulating current in the freewheeling mode using the leakage resonant inductance and the series resonant capacitor. Thus, the proposed converter overcomes the drawbacks of the conventional full-bridge DC-DC converter and improves its overall system efficiency. Its structure is simplified by using the leakage inductance of the transformer as the resonant inductance and omitting the DC output filter inductance. Also it can operate over a wide range of input voltages. In this paper, the operational principle, analysis and design example are described in detail. Finally, the experimental results from a 650W (24V/27A) prototype are demonstrated to confirm the operation, validity and features of the proposed converter.

Abstract.This paper presents a high efficiency AC-DC power converter using a modified full-bridge circuit. The proposed converter resolves a drawback of the conventional power converter using a modified full-bridge circuit by inserting the DC blocking capacitor in the converter primary. Thus, the proposed converter can improve total efficiency and its performance.

No abstract