A Switching Converter With Superior EMC Property Based On Soft-Switching Technology And Chaotic Spread-Spectrum Technology

With the strictness of Electromagnetic Compatible(EMC) statue, it has important theory and application value to study on switching converters with high efficiency. This paper aims to combine the advantages of chaotic spread spectrum technology and soft-switching technology, and it proposes a new and effective way to improve electromagnetic compatible performance of the switching converters.The main research work includes the following aspects:1) To design a chaotic spread spectrum soft-switching converter. In the chaos spreading pattern, the frequency of switch control signal is changing with the chaotic signal, therefore, it’s necessary to design new soft switching circuit. This new soft switching circuit must be able to work within a certain frequency range. The paper analyzes the working principle of the soft switching circuit after the introduction of Chua chaotic signals. And this paper gives the condions to achieve soft switching of chaotic spreading pattern so that the soft switching circuit can work in a certain frequency range.2) To demonstrate the effectiveness that the soft-switching technology can suppress Electromagnetic Interference(EMI) from a theoretical mathematical derivation. In this paper, the power spectral density function of switch’s drain-source voltage is the starting point, this paper derives the power spectral density function of switch’s drain-source voltage in the hard-switching and soft-switching states, and then observes changes of the power spectral density function in the both states to verify the effectiveness of soft-switching technology to improve EMC performance of the switching converters. At last, this paper verities the correctness of theoretical analysis by circuit simulation with the Saber software.3) To demonstrate the effectiveness that the chaotic spread spectrum soft-switching technology can suppress EMI more effectively from a theoretical mathematical derivation. First, this paper derives the spectral density function of switch’s drain current in chaotic spread spectrum soft switching. It proves theoretically that chaotic spread spectrum soft-switching technology compared to soft-switching technology and single chaos spread spectrum technology can suppress the peak of the spectral density function much better, and thus improve EMC performance of the power converters effectively.Then, this paper studies on the hard switching, soft switching, chaotic spread spectrum hard switching and chaotic spread spectrum soft switching with the Saber software. The simulation results show that chaotic spread spectrum soft-switching converter has better EMC performance.4) To study the influence of chaotic spread spectrum soft-switching technology for the electrical properties of the switching converter. Through analyzing the mechanism of the chaotic spread spectrum soft-switching converter output voltage ripple, this paper derives the mathematical expression of this switching converter output voltage ripple in a switching cycle. And then, this paper analyzes the mathematical expression. The results show that the output voltage ripple will increase with the increase of the chaotic signal. At last, this paper studies further the effect of chaotic spread spectrum soft-switching technology for the switching converter output voltage ripple and other electrical properties by circuit simulation.