J.-F. Chen

Current-fed full-bridge boost converter with zero current switching for high voltage applications

This paper presents a current-fed full-bridge boost converter with zero current switching (ZCS) based on constant on-time control for high voltage applications. The proposed converter utilizes the leakage inductor and the winding parasitic capacitor resonant tank to achieve ZCS. In order to achieve ZCS under wide load range, the turn-on time of the full-bridge boost converter is kept constant and the output voltage is regulated via frequency modulation. Finally, a laboratory prototype converter with 1 kV/600 W is implemented to verify the ZCS performance of the proposed converter. The highest efficiency of the proposed converter is 92%.

Study and implementation of a novel bidirectional DC-DC converter with high conversion ratio

A novel bidirectional DC-DC converter with high conversion ratio is proposed in this paper. The proposed converter uses the coupled-inductor to achieve high voltage conversion ratio. In the boost mode, the proposed converter is cascaded by boost converter and flyback converter with voltage double to increase the voltage gain. The switch voltage stress is reduced by a voltage clamping circuit, and the leakage-inductor energy is recycled. In the buck mode, the circuit consists of asymmetrical half-bridge flyback converter and buck converter. The leakage-inductor energy is recycled by a clamping circuit, and all of the switches achieve zero-voltage-switching turn on. This paper first analyzes the proposed converter operating principles and steady-state circuit characteristics. Eventually, a prototype circuit with conversion voltage 24 V/400 V and output power 500 W is implemented to verify the feasibility of the proposed converter.

Single DC/AC CCFL Inverter for Large Size LCD TV with Burst Control

Currently, dual AC voltage sources are used in the large size LCDTV to drive long and straight CCFLs. These dual AC voltage sources are out-off phase and are applied to the two sides of CCFL to overcome non-uniformity problem. But, higher cost is the penalty of this solution. This paper presents a novel CCFL inverter driver technology for large size LCDTV. The proposed burst control technology is capable to driving 950mm length or even longer CCFL by single voltage source. The luminance of lamp output is above 80% uniformity. Due to the negative incremental resistance of the CCFL, the leakage current flowing through the parasitic capacitor can be efficiently reduced with the proposed control scheme. Finally, a 42-inch LCD TV CCFL inverter is implemented experimentally to demonstrate the high efficacy and uniform luminance of the backlight system

Single-stage CCM PFC electronic ballast

This paper presents a single-stage electronic ballast with continuous-current-mode (CCM) power factor correction (PFC), which is a combination of a boost-type PFC network and a DC/AC inverter to allow CCM operation for the PFC inductor in the boost-type PFC network. Among the PFC techniques proposed in recent years, in general, the discontinuous-current-mode single-stage PFC electronic ballasts have such drawbacks as high electromagnetic interference, high current stress, and high switching and conduction losses. The PFC capacitor of the developed boost-type PFC network can help the PFC inductor to achieve CCM, thus shaping the input current of the proposed electronic ballast to achieve high power factor (PF). Finally, a 36 W rated power electronic ballast prototype circuit is designed and implemented. Experimental results verify the advantages of the proposed ballast; these include the following: the input current harmonics meet the IEC 61000-3-2 Class C Standard, and the ballast offers lower conducted EMI and lower current stress on switches and diodes.