To increase the power conversion density, decrease switching losses and electromagnetic interference (EMI) and provide safe operating area (SOA) for switch, applying snubber circuits which provide soft switching conditions is inevitable. Among different types of snubber circuits, passive snubbers due to their simplicity and robustness are preferred. These snubber circuits can obtain soft switching conditions without any additional switch. Thus, gate drive and control circuits remain simple. In this paper, a simple lossless passive snubber circuit which can be applied on isolated and non-isolated converters is introduced. The proposed snubber circuit provides ZCS and ZVS conditions at turning on and off instants, respectively. The proposed snubber is applied on a boost converter and analyzed. Also, in order to prove the effectiveness of the proposed snubber circuit from the converter efficiency and EMI viewpoints, a 200W prototype boost converter is implemented and experimental results are presented. Also, the simulation results of a soft switched flyback converter with the proposed snubber cell are presented.

Power electronic systems such as switching power supplies are accounted as noise sources for other sensitive circuits. EMI caused by power converters can disturb the normal operation of the converter and other adjacent systems. Major research is concentrated on EMI mitigation for power converters in which the main concern is compliance with EMC standards to ensure proper operation of converters and nearby systems. This paper reviews EMI reduction techniques related to switching power converters with emphasis on the conducted EMI. A comprehensive review of significant research works is performed and various methods are thoroughly discussed and compared. Also, a classification of methods is presented. Moreover, converter prototypes are realized which contain several EMI mitigation techniques and their effects are presented via experimental results.

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In this paper, a non-isolated dual-input DC-DC converter with zero-voltage transition (ZVT) is proposed for renewable energy systems. The proposed converter has high step-up conversion gain without using any transformer or coupled inductors. The proposed structure consists of two boost cells, one diode-capacitor multiplier cell, and one ZVT auxiliary circuit. The main switches turn on and off under zero voltage condition and the auxiliary switch turns on under zero current condition and turns off under zero current and zero voltage conditions. Soft switching conditions, high efficiency, continuous current of input sources, low-voltage stress on switches, and returning the energy of the auxiliary circuit to the boost cell connected to the lower-voltage input are the main advantages of the proposed converter. The steady-state analysis of the converter and operation intervals are discussed. A 160-W prototype of the proposed converter is designed and implemented. Experimental results confirm the theoretical analysis. The efficiency reaches 96.7% at the nominal load by providing soft-switching for all switches. The proposed topology can be extended for multi-input applications by expanding the number of diode-capacitor multiplier and input boost cells. KEYWORDS high step-up converter, multi-input converter, soft switching, zero-voltage transition Int J Circ Theor Appl. 2020;48:762-776. wileyonlinelibrary.com/journal/cta

Forward converter is popular for isolated switching power supply. Generally, power switching converters are the sources of electromagnetic interference (EMI) because of their high transient voltage and current. In this study, reduction of conducted EMI in the single-switch forward converter is examined using a symmetric topology. At this end, the forward converter topology is modified to achieve a symmetric topology. EMI model of the conventional forward converter and symmetric forward converter are derived taking into account the main parasitic of components and printed circuit tracks. Accuracy of the predicted EMI is verified by the measured EMI for two converters. In addition to the symmetric approach evaluation from the EMI viewpoint, the effect of this approach on the output voltage noise is examined. Finally, the combination of a passive EMI filtering with the symmetric method is utilised for EMC compliance.