Research On Reducing Electromagnetic Interference Of Switching Mode Power Supply With Chaotic Methods

Switching mode power supply is widely employed in aerospace industry, computer, communication, military field and energy because of its advantages in small size, high efficiency in electrical energy conversion, light weight, high speed and control accuracy. But improvement in the working frequency of the switching mode power supply can reduce size and weight of the supply while increase the switching loss, lower the working efficiency and focalize electromagnetic interference.Electromagnetic interference is the decrease in capability of apparatus and transmission path and system caused by electromagnetic disturbance. Because the electronic devices of the switching mode power supply are in the switch state instead of the linear state, by the instant that they are turned on and off, especially when high-powered apparatuses are used, there will be a considerable change rate in voltage and current, hence strong electromagnetic disturbance may appear. Still, the switching mode power supply works in a high frequency (20KHz-1MHz), which is just in the range (9KHz-30KHz) that EMI is transmitted, so the whole switching mode power supply will become an interfering source, which brings serious problems of EMI and makes it difficult for the peripheral electron device to work properly. There are some traditional means to solve the problem of EMI of switching mode, power supply such as filtering, grounding, by passing, decoupling and shielding, which all aim at intercepting the path of the electromagnetic propagation and are inactive methods in the intention.The chaos is a kind of common nonlinear phenomenon, it refers to a certain but unpredictable motions. From the working principle of the Switching mode power supply, it is known that the topological structure of a Switching mode power supply is different because of the adjustment's condition is different, that is, the structure of the Switching mode power supply working normally is always changes between two or three different topological structure, therefore, Switching mode power supply is a complex nonlinear time-varying systems. With the rapid development of electronic technology, electronicians have got a further understanding of the switching mode power supply. They have discovered abundant non-linear phenomena such as splitting, quasi-periodic motion and chaos included in the switching mode power supply. The way usually used is to eliminate the non-linear phenomena, but is there the possibility to make use of them?The traditional switching mode power supply works in the periodic state, on the integral frequency point of its working frequency and fundamental frequency. Electromagnetic radiation of the switching mode power supply is very strong, especially when it is working in the HF state. It can be learned from the chaotic dynamics theory that the power spectrum of the chaotic signals is successive, and compared to Periodic signals and quasi-periodic signal, the energy in frequency domain of chaotic signal is relatively uniform and it's spectral peak is lower, while They have the same amount of energy. This inspires the people to reduce the electromagnetic disturbance with the chaos phenomenon.The paper verifies in the way of theoretical analyzing and emulating by Matlab that the bifurcation and chaos phenomena exist in the switching mode power supply by taking boost direct-current transformer controlled by peak current as the example, and analyzes the current power spectrum of the inductance working in the cycle state and chaos state, verifies that electromagnetic disturbance can be reduced with chaotic methods through the qualitative and quantitative comparison. The way by the simulation experiment can judge chaos and its parameters simply and effectively, and provides the basis for the next circuit test.The simulation experiment method adopted hybrid modeling simulation by model and program. The main circuit use the power electronics model of matlab while we establishing the simulation model, the model simplifies the main circuit and representatives of the real power supply at the same time; The control circuit uses programming method for accuracy controlling the switching device of the main circuit, verifying that the chaos phenomena exist and electromagnetic disturbance can be reduced with chaotic methods in the switching mode power supply.In the first chapter, this paper introduces the non-linear phenomena and some thoughts of reducing electromagnetic disturbance with the chaotic methods. Present status and significance of the research on this subject are also introduced in this chapter. Elementary knowledge of chaology are introduced in the second chapter. In Chapter Three, methods to recognize and control chaos are introduced. The next, simulation software and methods are introduced in the fourth chapter. In Chapter Five, the paper verifies in the emulating way that electromagnetic disturbance can be reduced with chaotic methods by taking Boost direct-current transformer controlled by peak current as the example. Chapter Six is a summary of the main content of the paper, which also points out difficulties in reducing electromagnetic interference with chaotic methods and meanwhile predicts the outlook of its application in the future.