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Circuit inside PC power supply

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foxOnTheRun

New Member
Hi,

my pc power supply broke yesterday, so instead of trashing it, I opened it to salvage some components. I found this small board inside:

**broken link removed**
**broken link removed**

The psu has and input connection and an aux port to power up the monitor.

This small board was fitted so that it received mains power from the left (from the main cable), then the output (right side) was connected to the main psu circuit board by a couple of wires and soldered to the monitor socket.

**broken link removed**

This should be the circuit, the "out" label is going to the monitor and the psu board.
Value for the resistor and cap are correct, no clues for the inductors value, as far as I could observe, there were no values written.

So, what's its purpose? passive PFC? how could I see something interesting from LTspice simulation?

Tnx!
 

foxOnTheRun

New Member
Thanks. The obsession may be driven by "efficiency", "energy saving" and so since ecology and clean environment are resonating in day to day talk, tv show, news and so :)

Can you give 1-2 tips on how to see filtering effect via LTspice? or at least, the name of the filter configuration?

Thanks!

(also, this thing it isn't fitted in all psus I disassembled, or not?)
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
Thanks. The obsession may be driven by "efficiency", "energy saving" and so since ecology and clean environment are resonating in day to day talk, tv show, news and so :)

Can you give 1-2 tips on how to see filtering effect via LTspice? or at least, the name of the filter configuration?

Thanks!

(also, this thing it isn't fitted in all psus I disassembled, or not?)

It's a low-pass filter.

It's fitted in all decent switch-mode PSU's - it helps to keep interference out of the PSU, and reduces interference from the PSU travelling back down the mains.
 

alec_t

Well-Known Member
Most Helpful Member
Can you give 1-2 tips on how to see filtering effect via LTspice?
Here's the asc file to do that. Run the sim and plot the voltage between L and N.
 

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  • MainsFilter.asc
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