Study On Electromagnetic Compatibility Of Switching Power Supply

In the 21st century, as science and technology develop, especially communication technology, the quality of life of people is raising. And our electromagnetic environment becomes more complex. Electromagnetic pollution gets more concern continually as water and air pollution. How to restrain electromagnetic interference, use frequency spectrum resources reasonably, cleanse the electromagnetic environment are pre-requisite measures that mankind be survival in continuing development way in the future must be taken.The subject is imbursed by Natural Science Foundation Committee (NSFC), and the paper mainly studies around switching power supply, and focuses on principle of electromagnetic interference of switching power supply and effective disincentive. The main contents are the following:1. The paper firstly introduced the concept of EMC, the researched content of EMC and the current research in domestic and foreign, and made depth comprehension to EMC. It studies electromagnetic interference mechanism deeply. From EMI three elements, it discusses and analyses the characteristic of disturbance sources and coupling path, and mainly illustrates the characteristic of conductivity coupling, shared impedance coupling, induction coupling and radiation coupling, the conductivity coupling is solved by shielding and filter, and the paper adopts grounding method to solve shared impedance coupling, and coupling is solved by shielding, changing the line direction and grounding method, and the radiation coupling is solve by grounding method usually. It provides theory and analysis method to solve the practical problems of products.2. Theoretically it given harmonic balance finite element method to analyze electromagnetic compatibility of high-frequency switching power supply. Harmonic balance finite element method is different from the traditional time-domain finite element method and transient analysis method. Harmonic balance finite element method uses linearity synthesis of sine function to generate the solution. And it uses coefficient of sine function to express waveform. It combines the finite element method to get steady-state response of electromagnetic field directly in the frequency domain. Experiments prove that harmonic balance finite element method is usually more effective than the traditional time domain method.3. It analyses PCB layout of switching power supply. Compute the distributing capacitance bulk of PCB in real time by 'coupling coefficient' concept which had already been put forward. Designer can amend PCB timely and reduce the conductive disturbance of PCB effectively. The circuit principle of passive EMI filter and several topology circuit of active EMI filter were introduced. Active EMI filter with feedforward, active EMI filter without current detection sensors installed and active EMI filter for three-phase inverter motor were researched. The problem that following the frequency rising of switching power supply, the EMI noise pollution was becoming more and more serious than before was solved. It analyses the principle of electromagnetic shielding and some ways of grounding: single-point grounding, Multi-point grounding, mixed grounding and suspension grounding.