I have a 120VAC -> 24VDC power supply rated at 85% efficiency, and a 0.8W power dissipation with no load.
The device it is powering draws 110mA max = 2.64W.
I want to find a reasonable upper bound for the AC current draw and heat dissipation. Do the following calculations make sense:
2.64W DC load / 85% efficiency = 3.11W device AC load
3.11W device AC load + 0.8W power supply no load dissipation = 3.91W total AC load
3.91W total AC load / 120 VAC ≈ 33mA
So roughly 33mA load on the AC line max.
And also the power supply itself would dissipate 3.91W - 2.64W = 1.27W as heat max (assuming worst case that 0.8W no load dissipation is entirely heat).
Is that reasonable? If not, how can I estimate these values (and what other specs do I need on the power supply to do so)?
Thanks,
J