Electronics > Power & Renewable Energy

Laptop brick running off DC 300V?

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elektrinis:
I want to ask if anyone has investigated this - can any laptop brick, and any modern PSU for that, run off DC 300V source instead of AC 230V? Since most of modern PSUs have an initial PFC stage, which is just a rectifier with boost converter, it kinda should? But is there any kind of protection, checking for AC? Anyone know of a "DC-ready" study, where they check how many modern devices will actually run off DC?

f4eru:
Most will, but there could be some road block :
- a rare X cap active discharge circuit could make problems
- PFCs could make problems.

Also, note that this is not a working mode for which it was safety tested, so, it's at your own risk.

NiHaoMike:
That has been looked at for data centers, it turns out most devices with switching power supplies just work.

station240:

--- Quote from: elektrinis on May 23, 2021, 02:04:20 pm ---I want to ask if anyone has investigated this - can any laptop brick, and any modern PSU for that, run off DC 300V source instead of AC 230V? Since most of modern PSUs have an initial PFC stage, which is just a rectifier with boost converter, it kinda should? But is there any kind of protection, checking for AC? Anyone know of a "DC-ready" study, where they check how many modern devices will actually run off DC?

--- End quote ---

I've done this experiment with a small 100W PC power supply that has PFC.
Only changes I made (mostly for efficiency) were:
1) Remove the bridge rectifier (-1.2V from 240VAC = 0.5% losses).
2) Remove the AC input common mode chokes (clearly designed for AC mains)
3) Remove the X2 filter capacitor and parallel discharge resistor (again designed for AC frequencies)
4) Add a fat 400V capacitor to the input. (for noise/peak current reasons)
Worked fine on as little as 60V DC.

Most PFC controller chips show internal block diagrams, it's just dumb logic gates and opamps.
To actually check for AC would require some form of memory, to calculate changes in input voltage over time.
Plus that would leave PSUs to shutdown in areas with poor/noisy mains, eg industrial, rural.

I've got a few spare laptop PSUs lying around, newest is probably 5 years old. Not sure if any are PFC without cracking them open.

David Hess:
The ones I have tested all just worked, but I have read that some active PFC input stages will not correctly operate with a DC input.

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