ZVT soft-switching PFC switching regulated power supply circuit

Published:2011/11/14 2:42:00 Author:May | Keyword: ZVT soft-switching, PFC, switching regulated power supply | From:SeekIC

The diagram is power factor adjustment (PFC) switching regulated power supply circuit using zero-voltage converter (ZVT) soft-switch technique. Compared with hard switching active power factor adjustment (PFC) circuit, this circuit has one more out of auxiliary switch tube and resonant circuit. Main switching tube VTr and auxiliary switch VTr1 can becontrolled by a piece of IC chip-UC3855AN. In the diagram, auxiliary switch and resonance LC circuit can make main switch tube achieve ZVT soft switch working. UC3855AN outputs two ways pulse trains, and they separately control the turning on of main switch tube and auxiliary switching tube. The computation of its feedback sampling and duty factor is the similar to UC3854. The internal structure of UC3854 single chip integrated circuit is shown in the following diagram. It mainly consists of voltage amplifier, analog multiplier, current amplifier and the composition of fixed-frequency pulse width modulator. in addition, it contains gate driver which is compatible with power MOSFET, 7.5V voltage reference, load enabling comparators, voltage detection and over-current comparator. UC3854 can accurately keep the sine ratio of bus input current with no need to slop compensation to the current.



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