English title

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Considering simplicity of the practical implementation, application of the sliding mode control in power electronics converters has increased in recent years. Equivalent control approach can be used to stabilize the converter switching frequency in sliding mode control of the converters. In this approach, controller gains are tuned by trial and error and hence, stability of the controller cannot be guaranteed in a wide range of operation. To cope with this problem, a novel approach for sliding mode controller design as well as gains selection in flyback switch mode power supplies is developed in this paper. Also, adaptive backstepping and sliding mode nonlinear controllers are compared considering different criteria according to experimental tests in a wide operating range.

Evaluation criteria are steady-state error, converter dynamic response during start-up, robustness of the controller against load and line changes and finally, ease of practical implementation. Using Texas instruments digital signal processor (DSP-TMS320F2810), practical responses of the developed controllers are presented. Also, simulations are accomplished using MATLAB/Simulink software.

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A reciprocal dual-band BALUN is designed by the series connection of a multi-stage Wilkinson power divider and a 180° phase shifter. The use of the word “reciprocal” is due to the fact that if the unbalanced input and balanced outputs are replaced, it also has a proper performance. As a proof of concept, a prototype model is fabricated and measured. The return loss is less than 10dB in the frequency bands 2.5 to 5.5 GHz and 10.1 to 13 GHz. The isolation between the balanced ports is better than -15dB. Simultaneously, the unbalance between the amplitudes and phases of balanced ports is less than 0.6 dB and , respectively. This BALUN is designed appropriately for TV satellite downlink.