移动通信开关电源的新技术及其应用电气工程及其自动化毕业论文中英文翻译

移动通信开关电源的新技术及其应用电气工程及其自动化毕业论文中英文翻译内容摘要：

witching power supply inputs to have some distortions. Below thepower factor young fellow produces to the electrical power systemaffects: (1) causes the electrical work input alternating current toincrease. With I expression input current, i expression wattfulcurrent, obtains through the putation: When Pf=,I=。 Pf=,I=。 Pf=, I=. Therefore in the load same situation, a power factor smaller electrical work input salternating current bigger, simultaneously the ring circuit loses increases, the electrical work power supply efficiency reduces (2)to cause the electrical work neutral electric current to increase,the line harmonic interference is serious. Take the star connection as the example, L expresses the neutral electric current,when Pf=, Ia, Ib, the Ic current waveform is a sine wave, also phase difference 120176。 , after profile superimposition, And is causing the profile is the sine wave as far as possible,reduces the wave distortion, thus causes the exchange input the powergroup number to be approximate is 1. The power factor pensation electric circuit may divide into the active pensating circuit andthe passive pensating circuit two kinds, at present various factories widely use are the active power factor pensation electric circuit, this electric circuit core part is American Unitrode Corporation39。 s UC3854, through pensates may enhance the power factorto above, the input alternating current is the sine profile,enable the switching power supply module work to approach the pureresistance condition, meanwhile has the pre constant voltage function. Uses the pulse width modulation (PWM) the soft switchtechnology zero potential transformation (ZVS) the electriccircuit At present the high frequency switching power supply power transformation unit selects the pulse width modulation method, alsosome factories select the frequency modulation method. The arteriesdecide the modulation the basic principle are the adjustment squarewave occupy through the adjustment pulse squarewave widthempty pared to, after causes the pulse squarewave rectificationfilter the direct ponent to change, achieves the output constantvoltage the goal, but the pulse squarewave frequency maintenance isinvariable. After the supposition switching power supply rectificationfilter voltage is U, L is the transformer primary coil, K1, K2, K3, K4 equivalent are four powers switching valves. When usesthe usual pulseduration modulation technology, when K1, K2 leadpasses, when K3, K4 have cut off, the L beginnings and ends voltage isVL。 When K1,。