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Make a desktop psu from an old laptop? Answered

Hi, I was recently looking into making a desktop power supply because I have needed one for some time, and I enjoy making my own tools whenever possible. But I had just dismantled my last power supply a week or so ago for parts, but I have like 4 or 5 old laptops sitting in my closet. I was wondering if I could possibly make a power supply form a laptop. Is this possible? And if so, how would I do it?

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verence
verence

5 years ago

Not from the laptop, but you can use the power supply of the laptop. Although they have normally only one output voltage (19V is quite common).

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LoneWolf0
LoneWolf0

Answer 5 years ago

Sorry, could have been more clear on that. I meant i wanted to make something like this.

https://www.instructables.com/id/atx-bench-power-supply-diy/

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verence
verence

Answer 5 years ago

Desktops have kind of universal power supplies that have to have voltages for whatever card / drive / other extra you build into the computer. So desktops have big beefy PSUs with -12V / 5V / 12V etc...

Laptops by contrast don't have many options for extras. So the get a simple power supply with one voltage and any other needed voltage is produced internally at the point of use. You may probe around and find some 5V / 3.3V rails inside, but you will most probably have to leave the whole laptop together.

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LoneWolf0
LoneWolf0

Answer 5 years ago

ok, thanks. ill do that and hopefully get something going tonight

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-max-
-max-

5 years ago

It would not be a good idea. Even if your desktop draws less power than the laptop charger unit, you would need to take the output and use additional regulating circuitry to get all the necessary power rails for inside the desktop. Desktops are usually not built with power usage as a high priority. CPUs for them can take 100W or more just by it self, not even including the motherboard or any video cards. Laptops and ultrabooks on the other hand are built with the mobile version of the desktop parts which are often better optimized for low heat output and low power consumtion vs raw performance.

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LoneWolf0
LoneWolf0

Answer 5 years ago

https://www.instructables.com/id/atx-bench-power-supply-diy/

oops sorry, I could have made that clearer. I meant something more like this, except from a laprop psu

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-max-
-max-

Answer 5 years ago

Well, sure! You don't really need to do much modifying. You get 19 or 20 volts on the output. If you pull too much current the power supply will shut down. I have a Xbox power supply that has 12V 12A and 5V 1A outputs. However it is really easy to cause the power supply to shut down. Simply connecting it to some bulk filter capacitors causes enough of a current transient to make it shut down. I hacked the power supply by installing a mod wire between a optocoupler and the safety chip that was responsible for overcurrent protection. Even though I've had it for over a year, I don't trust that PSU enough to leave it plugged in all the time. I have no clue what it might do if it shorts out for more than a few seconds.

ATX PSUs make lousy power supplies and are not replacements for a decent fully adjustable voltage/current power supply. The ability to set a custom voltage and current limit and having dual rail output is really nice. With a real lab power supply, when you "overload" it, it goes into current limiting mode, and starts regulating the current instead of the voltage. That is more desirable for prototyping in many cases. However, ATX supplies (as far as I know) just basically shut down until the overload condition goes away. That is easier and cheaper for PSU manufacturers to incorporate. No need to spend more money to make the power supply limit current accurately because that should never need to happen in the final product.