Single-Switch ZVZCS Quasi-Resonant CLL Isolated DC-DC Converter for 32” LCD TV

In this paper, a single-switch ZVZCS quasi-resonant CLL isolated DC-DC converter for driving a low-ower (less than 100 W) 32” LED backlighting liquid crystal display television (LCD TV) is proposed. The proposed converter exhibits both forward and flyback operational characteristics. All semiconductors are activated and deactivated under the soft switching conditions during the switching transition without additional active devices. The switching frequency varies less than about 10 kHz for load variations, leading to minimizing the efficiency reduction under light load. Furthermore, the low di/dt and dv/dt by soft switching enhance the electromagnetic interference (EMI) performance above 1 MHz. A theoretical analysis is described in detail, and a 72-W prototype converter verifies the validity of the analysis.