A novel single switch two diode wide conversion ratio step down/up converter is presented. The proposed converter is derived from the conventional single-ended primary inductor converter (SEPIC) topology, and it can operate as a capacitor-diode voltage multiplier, which offers simple structure, reduced electromagnetic interference (EMI), and reduced semiconductor voltage stress. The main advantages of the proposed converter are the continuous input/output current, higher voltage conversion ratio, and near-zero input and output current ripples compared with the conventional SEPIC converter. The absence of both a transformer and an extreme duty cycle permits the proposed converter to operate at high switching frequencies. Hence, the overall advantages will be: higher efficiency, reduced size and weight, simpler structure and control. The theoretical analysis results obtained with the proposed structure are compared with the conventional SEPIC topology. The performance of the proposed converter is verified through computer simulations and experimental results.proposed converter to operate at high switching frequencies. Hence, the overall advantages will be: higher efficiency, reduced size and weight, simpler structure and control.Comparison results with the conventional SEPIC converter show that the proposed modified SEPIC is more suitable for applications that require a high input-to-output voltage conversion ratio. The proposed converter has few extra components compared to the conventional SEPIC converter, and it is regulated by the conventional PWM technique at constant frequency. However, the additional components is outweighed by the significant advantages gained, thus expecting the popularity of this technique to other exiting topologies. The performance of the converter is verified by means of simulation and experimental tests which confirm the operating principles of the proposed converter. 374

SUMMARYThis paper presents a new single-stage single-switch high power factor correction AC/DC converter suitable for low-power applications (< 150 W) with a universal input voltage range (90-265 V rms ). The proposed topology integrates a buck-boost input current shaper followed by a buck and a buck-boost converter, respectively. As a result, the proposed converter can operate with larger duty cycles compared with the existing single-stage singleswitch topologies, hence, making them suitable for extreme step-down voltage conversion applications. Several desirable features are gained when the three integrated converter cells operate in discontinuous conduction mode. These features include low semiconductor voltage stress, zero-current switch at turn-on, and simple control with a fast well-regulated output voltage. A detailed circuit analysis is performed to derive the design equations. The theoretical analysis and effectiveness of the proposed approach are confirmed by experimental results obtained from a 100-W/24-V dc laboratory prototype.

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