外文翻譯---單級(jí)單刀功率因數(shù)校正器acdc變換器-其他專業(yè)-展示頁(yè)
2025-01-31 09:23本頁(yè)面
【正文】 dback. The additional discharge path in the PFC inductorand DCbus voltage feedback effectively suppresses the DCbus voltage and increases the overallefficiency. Experimental results for a 60W converter at a constant switching frequency of 70 kHzare obtained to show the performance of the proposed converter. It is shown that the voltageacross the DCbus capacitor can be held below 405V even though the converter operates in a widerange of input voltages (90V265VAC) and the measured input current harmonics satisfy the IEC。 V2 is determined by Vd+(n1na)Vo where n1=N1/Ns and na=Na/ vi is higher than V2 the converter operation enters region C. In this region T1 works like a flyback transformer and T2 works like a boost inductor. Since the voltage vi is Vm sin ot in the first quarter of line period, the boundary times tx and ty for three modes are given by Fig. 1 Equivalent circuit Region A operation In region A the input voltage vi is lower than the DCbus voltage feedback value Vl =(N2/Np)Vd. Only the DC/DC part operates. It delivers power from the DCbus capacitor Cd to the load RL through T1. At to the switch S is turned on. Since the DCbus voltage Vd is applied across the magising inductance Lm1, the magising current iLm1 increases linearly from its lowpeak value ImA,L as follows: At t1 the switch S is turned off and the output diode D1 is on. Since npVo is applied across the magisinginductance Lm1, the current decreases linearly from its highpeak value ImA,H as follows: The diode current iD1 is given by From (3) and (4) the voltage gain is determined as follows: Since the DC/DC part operates in CCM, the duty cycle D does not change with the load variation. From (6) the turn ration np can be determined by The duty cycle D can be obtained as 咸寧學(xué)院本科畢業(yè)論文：外文翻譯 3 The duty cycle D is also effective in regions B and C. The power P1 delivered by the transformer T1 is determined as Since the power P1 delivered by the transformer T1 should be equal to the output power Po (=Vo2 /RL), the following relation is obtained: Consequently the DCbus capacitor provides the whole power to the load. From (3), (6) and (10), the high and low peak values of iLm1 are determined by Region B operation When the voltage vi is higher than V1 and lower than V2, the converter operates in region B. PFC cell operates as DCM flyback converter. At t0 the switch S is turned on. Since the DCbus voltage Vd is applied across the magising inductance Lm1, the magising current iLm1 increases linearly from its low peak value ImB,Las follows: The magising current iLm2 increases linearly from zero as follows: Since the DCbus capacitor current iCd, the current i2, and the switch current is are given by From (15) it can be seen that the magising current iLm1 is supplied by the magising current iLm2 and the discharging current iCd of the DCbus capacitor Cd. From (17) the switch current is is also posed of the two ponents. The condution loss can be reduced by selecting smaller np1. At t1 the
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