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Mobile communication switching power supply new technology and its
application ABSTRACT
This article introduce the new technology and its practical application which at present moves which in the communications network to use the switching power supply uses, understood and grasped these new technologies has theimportant practical significance to the maintenance of equipment andthe engineering construction.
Key word:switching power supply ;new technology; application.
Foreword
20 kHz switching power supply in overseas starts from the 70'sto appear, to present switching power supply already in do main wide spread application and so on computer, corre spondence, domestic electric appliances. Along with the integrated circuit, the powerswitch component development, the switching power supply experienced from the separative element to the integration, from has compared the low frequency to compare the high-frequency, since childhood the capacity to the large capacity process. The switching power supply technology also conforms to simplicity only develops complex and thetrend is mature. Because the power source is in the heart in the communications system the status, therefore communications system to high frequency switching power supply each target request all extremely strict, especially to the power factor, the constant voltage precision, the noise voltage and the efficiency request is very high.Therefore may say in the communications system uses the high frequency switching power supply has represented the switching power supply over all profession level, also has represented the switching power supply newest technology. At present the Jiangsu Province mobile communication equipment mainly uses American LORAIN, Hangzhou exhibitsone's power (center is permanent), the Beijing concerted effortlink, Wuhan 517 and so on the factory high frequency switching powersupply product, may divide into +27V and the -48V two kind of seriesaccording to the output voltage value.These factories
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products although in seemingly difference bigger, but all has used some same or the similar new technology, therefore the product quality and the performance index relative are better. Underunifies several kind of switching power supplies which the Jiangsu Province mobile communication equipment uses, summarizes introduced ,now in the high frequency switching power supply uses some new technologies as well as use these new technical the reason and its thepractical significance.
Uses the new power switch component
Starts from the 90's intermediate stages, the power switchcomponent development obtains the rapid development, the high voltage,the big electric current, leads passes the resistance small powerswitch component gradually to develop. Because is oxidizes the objectfield effect tube (MOSFET) to have the switching time to be short (<10ns). The grid-driving power small (voltage drive component), to the tempera ture insensitive, does not have two time penetrates, the switch loses the merit which low, the pulse trailing electric current issmall also easy parallel to use, has substituted for the tradition aldouble pole transistor in the switching power supply to become the newpower switch component. At present the MVOS power metal oxidizes the object field effect tube turn-on frequency to be possible to achieve 450 MHz, already widely to frequency higher switching power supply,but ordinary VMOS tube when high voltage big electric current work leads passes the resistance to be very big, the component gives off heat, the output efficiency drops. Recent years developed the IGBT insulation grid double pole transistornot only had the MOSryT voltage drive and so on all merits, meanwhile had the double-pole big power tube to saturated to lead passes the pressure drop low characteristic, mainly used in the hectowatt levelto the kilowatt level capacity frequency is about in the 2kkkHz switching power supply. According to the daily maintenance and the maintenance work statistics, in several kind of factories switching power supply modules which Jiangsu Province used uses the IGBT insulation grid double pole transistor to take the power switch component.
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Uses the power factor compensation electric circuit.
The power factor in the electrical power system is a count for muchtarget, the power group number (Pf) the definition changes suddenly the active power for the electrical network in and the load ratio of apparent power which or the pulsating current produces, in the ideal situation the power factor is 1. Creates the power factor small main reason is the alternating voltage and the electric current work(flows voltage and electric current in the different phase has phase-shift) or the alternating voltage and the electric current profile has the distortion. In the high frequency switching power supply mainly is because the power source input end rectification filter circuit is the accommodating load, causes the alternating voltage and the electric current has the phase deviation to cause thepower factor reduction. Moreover, because in electric circuit otherfactors influences, also can cause the alternating current which the switching power supply inputs to have some distortions. Below thepower factor young fellow produces to the electrical power systemaffects: (1) causes the electrical network input alternating current toincrease. With I expression input current, i expression wattfulcurrent, obtains through the computation: When Pf=1.00,I=1.00i;Pf=0.92,I=1.09i;Pf=0.75, I=1.45i. Therefore in the load same situation, a power factor smaller electrical network input salternating current bigger, simultaneously the ring circuit loses increases, the electrical network power supply efficiency reduces (2)to cause the electrical network 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=1.00, Ia, Ib, the Ic current waveform is a sine wave, also phase difference 120°, 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 compensation electric circuit may divide into the active compensating circuit andthe passive compensating circuit two kinds, at present various factories widely use are the active power factor compensation electric circuit, this electric circuit core part is American Unitrode Corporation's UC3854, through compensates may enhance
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