Electronics > Beginners

How to power laptop from Lab Power supply ?

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tonycstech:
Looking for a power supply that i can use to power modern laptops with.
My understanding is that they do not just take straight DC 19v but instead they communicate with the charger via data pins and charger responds back as requested.
Obviously average power supply cant do that so is there anything i can look at ?
Something that can limit the current also.

Thanks !

Berni:
For the classical 19V barrel jack there is no fancy communication or anything. Just give it power and it charges. The bigger laptops might be careful and ramp up the current until they see the voltage sag too much, but that's about it.

But there are laptops with weird proprietary plugs that might do more fancy stuff. The USB-C charging port laptops is where you definitely have communication going on before it will actually charge, but at least it is standardized to the USB PD spec.

Why do you need to power it from a lab PSU anyway?

Solder_Junkie:
It depends on the laptop brand. I have an Asus Vivobook and apart from the awkward sized connector, it powers and charges correctly from a 19V OEM car adapter.

On the other hand, my Dell Vostro uses what looks like a standard barrel connector... except the inside of the tubular barrel is a 3rd connection to the charger. Without the correct charger, the Dell laptop will not charge, however it can be powered without charging using a 19V supply.

There was some discussion elsewhere on this forum on the subject of "fooling" these laptops, but it's far from straightforward as the device in the charger of the Dell is some kind of 1 wire data comms IC that appears to exchange data with the laptop before it will commence charging. I have been unable to find much information as to how it communicates, nor have I been able to source a 12V to 19V car adapter... other than using the clumsy approach of a 12V to 230V inverter to power a standard mains Dell charger.

SJ

Jwillis:
The sense wire is for the computer to determine the power capability of the power supply so it doesn't exceed it or to just turn on the power supply only when a demand is required. In most cases is just a matter of jumping the sense pin with a resistor to either ground or positive or both as a voltage divider. Did it to a Lenovo with a resistor from positive to sense. But can't remember the value of the resistor. In that particular case, the power supply can't be tested without the resistor because it won't turn on.

tonycstech:
Great. So basically no such power supply exist and ill have to make something of my own.

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