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A high step-up PWM non-isolated dc-dc converter with soft switching is proposed in this paper. The converter has minimum auxiliary elements to achieve high power density and high voltage gain. The ZVS operation of the main power switch results in negligible capacitive turn-on losses. Since the duty cycle of the auxiliary switch is narrow and its operation is under ZCS condition, the losses that the auxiliary circuit imposes are not significant. Also, all the diodes are operated under soft-switching conditions solving the reverse recovery problem. All the inductors are coupled on only one magnetic core, reducing size and conduction losses. Compared to the hard switched counterpart, the electromagnetic interference of the proposed converter is reduced. Furthermore, the output voltage of the proposed converter is controlled by an integral sliding mode control strategy during the load variations. Also, the proposed integral sliding mode control strategy has been compared with the PI control strategy, improving the transient response and the robustness under load variations while the switching frequency is constant. The effectiveness and accuracy of the proposed converter are verified by practical laboratory results which are obtained from a 250W prototype.

In this study, a new family of soft-switching pulse-width-modulated (PWM) converters with a lossless passive snubber is introduced. The switch is turned on under zero-current switching and turned off under zero-voltage switching and all diodes turn on and off under soft switching conditions. The proposed snubber consists of two resonant inductors a resonant capacitor and three diodes which can be applied to all non-isolated DC-DC converters. A buck converter with the proposed snubber is analysed and to verify theoretical analysis, a 100 W prototype is implemented and efficiency of converter compared with hard switching counterpart. Also to confirm the effectiveness of the proposed snubber to reduce conducted electromagnetic interference (EMI), the conducted EMI of a buck converter with proposed snubber cell is compared with conventional buck converter.

A new bidirectional flyback converter is introduced in this study. To provide soft-switching condition, two identical auxiliary circuits are applied to both sides of the converter, without using any extra switches. These circuits do not impose high voltage or current stresses on the converter. To transfer the power in each direction, only one switch is gated through pulse-width modulation technique. So, the control circuit of this converter is very simple. Regardless of the power flow direction, the switch of the converter is turned on under zero-current condition and is almost turned off under zero-voltage condition. The experimental results of the proposed bidirectional converter are presented to verify the theoretical analysis.

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