# Help understanding power requirements from computer datasheet

I wanted some advice on how to read power specs from a datasheet. There's a computer I'm trying to power. The datasheet simply says it needs 12-19V input voltage. However, it says the buyer is provided with a 19V, 90W power adapter.

Consider that all loads from the CPU are constant:

Suppose I have a 12V regulator that I want to use instead. Does this mean that my regulator has to supply the ratio in Amperage? Am I correct in assuming that at 12V input supply voltage, the required current draw would be =90/12 ~ 7.5A?

Would this also mean that the current draw at 19V input supply voltage would be =90/19 ~ 4.7A?

Understanding this will help me size my regulator.

Thanks.

• I'm inclined to say yes, in theory at least. In practice there are conversion losses that make things less linear, but the effect should be rather small, given modern converter efficiency. Can you tell us what computer it is? Commented Aug 18, 2022 at 22:59
• @Unimportant here is a link to one of the datasheets. These NUCs all have slightly different datasheets but this form factor tends to operate on the same equipment: intel.com/content/dam/support/us/en/documents/intel-nuc/… Commented Aug 18, 2022 at 23:14
• There's no mention of 12-19V supply in that document tough, only 19V. Commented Aug 18, 2022 at 23:38
• Yeah I noticed that but some of the NUC datasheets say 12-19V and the chassis of my product says 12-19V at the input. I think it's just a sloppy datasheet. Don't think Intel would make a mistake on their enclosure. Commented Aug 18, 2022 at 23:39

That is correct; match wattage between the two supplies.

The 90 watts will be a maximum rating. It may just be the rating of a supply that the supplier happened to have/was able to get, and not really related to the computer's actual power requirement.

The actual power requirement of the computer may be considerably less, but you can only determine that by measuring the power consumption when the computer is operating.

• So I should hook onto it with a multimeter or current clamp to check this? Commented Aug 18, 2022 at 23:15

Just choose the same or higher wattage power supply at 12V. Since the original supply is 90W, I'd suggest buying one of the very common 12V 100W or 125W models. Use a higher-rated supply if you intend to run it in hot environment, e.g. without air conditioning, right after taking it out of a hot car, exposed to sunlight, etc.