| Electronics > Beginners |
| PSU supporting both 120v and 240v. |
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| dmills:
The actual trick with modern PC power supplies (at least good ones) is that the first stage of a decent supply in the reasonably high power class is generally a BOOST converter that takes the input up to somewhere around 390V or so..... This is independent of the input voltage and is done by some cleverness with a dual loop controller that makes the input current track the voltage waveform so that the load appears resistive. It is a requirement in larger supplies to control the power factor and harmonic distortion. If you have to have such a stage to meet regulations it is cheap to accommodate a wide input range, hence the common 85-265V range seen on equipment. Once you have your (more or less fixed) DC bus at 390V or thereabout you then do the main switching converter that produces the outputs and also provides the isolation. The half wave voltage multiplier (with the slide switch) trick was common before PFC became a requirement. Regards, Dan. |
| soldar:
Active PFC is expensive to implement and not really required on PC PSUs which can achieve harmonic reduction with passive low pass filters which are simpler and cheaper. I do not think active PFC is common in computer PSUs. Yes, I know they exist, just like 500 euro bank notes, I have heard of a guy who once talked to someone who said he had seen one. :) |
| CJay:
--- Quote from: soldar on June 11, 2019, 11:34:34 am --- You made me look. I have three desktops right here and I was sure I was going to find a switch that switches to voltage doubler configuration. You know what I found instead? Stickers that say "230 volts only". On all three. I remember the 110/220 sliding switches on the older PSUs but I guess they got cheap and removed them. I went to pccomponentes.com, an online PC components vendor, and most of the PSUs are 230 volt only. Only one says "full range". --- End quote --- A bit of a mystery then as only one out of the first ten PSUs I looked at on a local supplier site was 230V only (it was one of the cheap ones, I might order one to satisfy my curiosity), I can't remember ever seeing a 230V only PSU in the past ten years in any PC, all the machines I have here (site with 800 users) and at home (with the possible exception of a HP Vectra 486) are wide input range. I had thought it might be because your supplier offers high power gaming PSUs as some server PSUs derate output if operated on 110V (some HP supplies are derated to 960W from 1200W) but even that doesn't seem to be a reason for limiting to 230V as Scan offer similar and higher rating PSUs which are 100-230V input so I'm mystified as to why it would still be a thing when it's so simple to implement. (BTW, the first two PSUs your supplier offers are wide input ones) |
| soldar:
Maybe in the UK they have different requirements. |
| senso:
Dont look to the crap from Nox.. Look at decent PSU's, like Seasonic, and they all state this: AC Input Voltage: 100 V - 240 V And, they have active PFC, who knew.. https://www.pccomponentes.com/seasonic-s12ii-520w-80-plus-bronze |
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