| Based on a 30V/40A low output ripple precise DC power supply with voltage and current mode used for instrument, this dissertation researches on ripple reduction, rectifier reverse-recovery problem and parallel technique.This dissertation analyzes the causation of output ripple. Novel schemes of three stages in series and double-stage linkage are proposed to reduce output ripple. Three stages of the power supply are respectively the circuits of PFC, full-bridge circuit and buck inverter. The first stage, PFC, can increase the power factor of front end and simultaneously reduce the harmonic pollution brought by the power supply. Moreover, the steady DC voltage is obtained in this very stage. The second stage, isolated DC/DC, separates the DC input from the DC output. As the last stage, buck gives the desired output. The scheme of the stages in series can effectively alleviate low frequency ripple, and the system with double-stage linkage has lower ripple when lower voltage output is needed.The rectifier reverse-recovery problem is introduced in this dissertation. Some methods are compared and Using amorphous beads as saturable inductor is suggested to solve it.Parallel connection of two power blocks with interleaved control method is introduced and some methods are proposed to solve EMI problem.Finally, the analysis and schemes are verified by circuit experiment. |
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