Soft Switched Flyback Converter Using Active Lossless Snubber

In this paper, a new active lossless snubber circuit is proposed, which provides a soft-switching condition for the traditional Pulse Width Modulation (PWM) fly-back converter. This active lossless snubber circuit creates Zero Voltage Switching (ZVS) condition for the main switch, while Zero Current Switching (ZCS) condition is achieved for the auxiliary switch. Moreover, based on the soft-switching condition, diode reverse recovery problem is omitted and leads to reduction of switching losses and increased efficiency. Additionally, the voltage stress of the auxiliary switch is clamped to the input voltage level which leads to its low capacitive turn ON loss. Furthermore, the presented active lossless snubber circuit provides soft-switching condition independent from load condition. The main and auxiliary switches do not need an isolated gate driver, since their source pins are connected to the input ground. In this manuscript, the different operating modes are explained in detail, and a comprehensive design procedure is presented. Furthermore, loss breakdown for converter elements is offered at full load. The simulation results of the proposed converter using PSPICE software are shown for 155V input, 24 V, 120 W output, and 100 kHz switching frequency to justify the theoretical analysis. The proposed converter has high efficiency of 94.08% at full load.