The Research And Design Of Switching Power Supply In High Frequency Electro-surgical Equipment

With the development of power electronics, high frequency switching powersupply has been widely used in the areas of communication, computer, aviation andindustry process. It can turn coarse and strong electricity into exquisite and preciseelectricity, which can be used by many kinds of instruments and electrical equipment,and it’s the―heart blood supply system―of modern electrical equipment. This thesis,using the work pattern of PWM, aims at designing a medical high frequencyswitching power supply. This circuit can output steady electric current and voltagewhich can satisfy the need of high frequency electrotome. Meanwhile, theminiaturization of devices was realiced by replacing traditional linear power.This thesis analyzes the development and present situation of high frequencyswitching power supply overseas and domestically, studies the system power supplyin high frequency electrotome system, analyzes the common DC-DC converter’selement’s characteristics and topologist’s structures, points out each converter’sdisadvantages and advantages, and the principles of selecting the suitable topology forthe different switching power supply, studies the main part of the switching powersupply and the design method, selects a reasonable design and sets design on thisbasis. The design process includes the following sections: the control circuit and maincircuit design, analysis and design of the various parts of the circuit diagram, the pulsewidth modulation COMS circuit SG3525’s driving circuits, structure, workingprinciples, high frequency transformer’s design and calculated the parameters in thecircuit, which focuses on the various calculated parameters of high frequencytransformer, selects the appropriate device on this basis.Due to designed switching power supply using in strong electromagneticinterfere environment, vulnerable to outside interference, in order to reduce theelectromagnetic interference (EMI) and enhance the dependability, protection circuitwith complete performance must be used and we must have the ways and meanswhich can reduce EMI, this thesis concludes with the measures to solve EMI.This thesis has designed the circuit system of high frequency switching powersupply, including PCB and schematic.The experimental results show that the circuitperformance has met the requirements and security has reached design targets for highfrequency electrotome.