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A new zero-voltage-switching (ZVS) push-pull pulse-width modulation (PWM) converter is proposed in this paper. The wide ZVS condition for all of the switches is obtained by utilizing the energy stored in the output inductor and magnetizing inductance. As a result, the switching losses can be dramatically reduced. A simple auxiliary circuit including two small diodes and one capacitor is added at the secondary side of a high frequency (HF) transformer to reset the primary current during the circulating stage and to clamp the voltage spike across the rectifier diodes, which enables the use of low-voltage and low-cost diodes to reduce the conducting and reverse recovery losses. In addition, there are no active devices or resistors in the auxiliary circuit, which can be realized easily. A detailed steady operation analysis, characteristics, design considerations, experimental results and a loss breakdown are presented for the proposed converter. A 500 W prototype has been constructed to verify the effectiveness of the proposed concept. [ABSTRACT FROM AUTHOR]

For evolutionary algorithms with the ability to self-adapt, linking the algorithmic operators and the problem features is one of the most interesting topics. One of the best ways to begin a study of this topic is to explore the relationship between the optimization hardness and the problem features. This paper attempts to interpret the relationship between optimization hardness and frequency features of real-parameter problems through a qualitative analysis based on an idealized model. Based on the results of a theoretically qualitative analysis, the effective high-frequency ratio (EHFR) is subsequently proposed to measure the optimization hardness of real-parameter problems. Finally, three aspects to the performance of EHFR are evaluated: stability, precision and ability to distinguish. Test results show that the EHFR is relevant not only for the results of theoretical analysis, but also for the other features related to the optimization hardness. [ABSTRACT FROM AUTHOR]