Analysis of the noise and efficiency characteristics in a quasi-resonant converter

A quasi-resonant converter using flyback topology can realize soft switching with relatively simple circuit. However, a switching device with high withstand voltage is necessary to achieve complete zero voltage switching when the input voltage is high and it causes decrease of efficiency because a switching device with high withstand voltage has relatively high on voltage. Therefore, we analyzed efficiency and noise of a quasi-resonant converter with a low breakdown voltage and low on voltage switching device under the condition of non-zero voltage switching. As a result of the analysis, it is found that high efficiency and low noise are achieved with non-zero voltage switching.