Purpose of SCRs in Power Factor Circuit

Posted on Feb 7, 2014

I have a Power Factor Correction board that was taken from an old Sun Microsystem Spark450 power supply p/n 300-1359-xx. It has everything I need for a 650 watt inverter. The entire PFC circuit is not detailed in this image. The only part of the circuit I don`t understand is the purpose of the SCRs. I searched unsuccessfully for a circuit where th

Purpose of SCRs in Power Factor Circuit
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e cathodes of SCRs are tied together. I did find some very usesful SCR information from ON Semiconductor but nothing that matched. I have seen many PFC and Boost circuits, but none with SCR`s. My guess is that the SCRs inject a part of the half wave AC current into the inductor when the voltage level is sense by Q3/Q5 is low. Your help on this would be greatly appriciated.

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