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毕业设计(论文)外文翻译
（原文）
院（系）：桂林电子科技大学
专 业： 电子信息工程
学生姓名： xx 学 号： xxxxxxxxxxxxx 指导教师单位：桂林电子科技大学 姓 名： xxxx
职 称： xx
2014年x月xx日
桂林电子科技大学毕业设计（论文）报告用纸
Timing on and off power supply uses
The switching power supply products are widely used in industrial automation and control, military equipment,scientific
equipment,LED
lighting,industrial medical equipment,communications
equipment,electrical
equipment,instrumentation, equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD monitor, LED lighting, communications equipment, audio-visual products, security, computer chais, digital products and equipment and other fields.Introduction
With the rapid development of power electronics technology, power electronics equipment and people's work, the relationship of life become increasingly close, and electronic equipment without reliable power, into the 1980s, computer power and the full realization of the switching power supply, the first to complete the computer Power new generation to enter the switching power supply in the 1990s have entered into a variety of electronic, electrical devices, program-controlled switchboards, communications, electronic testing equipment power control equipment, power supply, etc.have been widely used in switching power supply, but also to promote the rapid development of the switching power supply technology.Switching power supply is the use of modern power electronics technology to control the ratio of the switching transistor to turn on and off to maintain a stable output voltage power supply, switching power supply is generally controlled by pulse width modulation(PWM)ICs and switching devices(MOSFET, BJT)composition.Switching power supply and linear power compared to both the cost and growth with the increase of output power, but the two different growth rates.A power point, linear power supply costs, but higher than the switching power supply.With the development of power electronics technology and innovation, making the switching power supply technology to continue to innovate, the turning points of this cost is increasingly move to the low output power side, the switching power supply provides a broad space for development.The direction of its development is the high-frequency switching power supply, high frequency switching power supply miniaturization, and switching power supply into a wider range of application areas, especially in high-tech fields, and promote the miniaturization of high-tech products, light of.In addition, the development and application of the switching power supply in terms of energy conservation, resource conservation and environmental protection are of great significance.桂林电子科技大学毕业设计（论文）报告用纸
claification
Modern switching power supply, there are two: one is the DC switching power supply;the other is the AC switching power supply.Introduces only DC switching power supply and its function is poor power quality of the original eco-power(coarse)closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magnetic buffer.However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching loes, but also to control the occurrence of surges.This switch is called the resonant switch.Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching loes reduced to zero, and the noise is expected to become one of the high-frequency switching power supply The main ways.At present, many countries in the world are committed to several trillion Hz converter utility.the principle of Introduction
The switching power supply of the proce is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor Vthe step-down chopper, the average output voltage U0 is le than the input voltage Ui, the same polarity.Boost Circuitbuck or boost chopper, the output average voltage U0 is greater than or le than the input voltage Ui, the opposite polarity, the inductance transmiion.Cuk circuit-a buck or boost chopper, the output average voltage U0 is greater than or le than the input voltage Ui, the opposite polarity, capacitance transmiion.The above-mentioned non-isolated circuit, the isolation circuit forward circuits, feedback circuit, the half-bridge circuit, the full bridge circuit, push-pull circuit.Today's soft-switching technology makes a qualitative leap in the DC / DC the U.S.VICOR company design and manufacture a variety of ECI soft-switching DC / DC converter, the maximum output power 300W, 600W, 800W, etc., the corresponding power density(6.2 , 10,17)W/cm3 efficiency(80-90)%.A the Japanese Nemic Lambda latest using soft-switching technology, high frequency switching power supply module RM Series, its switching frequency(200 to 300)kHz, power density has reached 27W/cm3 with synchronous rectifier(MOSFETs instead of Schottky diodes), so that the whole circuit efficiency by up to 90%.AC / DC conversion
AC / DC conversion will transform AC to DC, the power flow can be bi-directional power flow by the power flow to load known as the “rectification”, referred to as "active inverter power flow returned by the load power.AC / DC converter input 50/60Hz AC due must be rectified, filtered, so the volume is relatively large filter capacitor is eential, while experiencing safety standards(such as UL, CCEE, etc.)and EMC Directive restrictions(such as IEC, FCC, CSA)in the AC input side must be added to the EMC filter and use meets the safety standards of the components, thus limiting the miniaturization of the volume of AC / DC power, In addition, due to internal frequency, high voltage, current switching, making the problem difficult to solve EMC also high demands on the internal high-density mounting 桂林电子科技大学毕业设计（论文）报告用纸
circuit design, for the same reason, the high voltage, high current switch makes power supply lo increases, limiting the AC / DC converter modular proce, and therefore must be used to power system optimal design method to make it work efficiency to reach a certain level of satisfaction.AC / DC conversion circuit wiring can be divided into half-wave circuit, full-wave circuit.Pre the power phase can be divided into single-phase three-phase, multiphase.Can be divided into a quadrant, two quadrant, three quadrants, four-quadrant circuit work quadrant.he selection of the switching power supply
Switching power supply input on the anti-jamming performance, compared to its circuit structure characteristics(multi-level series), the input disturbances, such as surge voltage is difficult to pa on the stability of the output voltage of the technical indicators and linear power have greater advantages, the output voltage stability up to(0.5)%.Switching power supply module as an integrated power electronic devices should be selected
