Reply 40 of 42, by analog_programmer
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watson wrote on 2023-10-03, 10:46:The two caps are not in parallel, they are in series, and they are typically rated at 200V. This enables you to get a higher vol […]
The two caps are not in parallel, they are in series, and they are typically rated at 200V.
This enables you to get a higher voltage out of 120 V line voltage. You rectify the positive half-wave on one cap, and the negative half-wave on the other.
This mode of operation is adjusted by the "115/230" switch. The resulting DC voltage is then ideally 120*sqrt(2)*2.
When operating in 230V mode, the DC voltage is simply 230*sqrt(2) stored across an effective "400V" capacitor.Active PFC is basically a boost converter, meaning that it can theoretically boost any input voltage to (most often) slightly below 400V.
That's why you have a single 400V or 420V rated cap in PSUs with active PFC.
The only thing that I don't understand is why not all PSUs with active PFC have a full range input (110V-230V). Some are rated only for 230V. Maybe it is to save a few cents on some components?
I live in place where mains is ~230 V and I have not even one old or new PSU with voltage switch (110/230 V), so when i mean two caps in parallel I mean two caps in parallel in therms of higher capacitance, rated at 250+ V. And there is bridge rectifier before the caps, what they will "rectify" in this case?
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