Powering mini PCs from your TV’s USB port

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A recent comment to a previous post has one respondent having trouble powering a quad-core mini PC from his TV’s USB port.

That raises a few questions – can you actually power a mini PC from a TV’s USB port? How much power do these USB ports provide? How much power to mini PCs need?

Most TVs now have USB ports designed to handle portable storage – at the very least, USB-powered flash drives but increasingly hard drives as well.

However, when it comes to powering mini PCs, things are nowhere near as clear-cut. Think about it for a minute – portable hard drive power consumption is getting lower on the back of more efficient designs. But as more and more CPU cores are added to mini PCs, their power consumption is on the rise. So much so that it’s increasingly unlikely that a TV can provide enough power to reliably run a mini PC, especially when all four cores are firing up and demanding power.

My rule-of-thumb is that you need an absolute minimum of 500mA of current for each core in your mini PC’s SoC CPU. So, a single-core model could just get away with a 500mA PSU; a dual-core might just keep going on one-amp if you’re lucky. But a quad-core mini PC – and really, that’s any quad-core mini PC – will need at least a 2A PSU to keep from rebooting.

From an electrical viewpoint, what’s happening is that the USB port can’t supply enough current, which drags down the 5V USB supply voltage to the mini PC. If it drops too low, the mini PC stops working. The electrical load all of a sudden disappears, the supply voltage springs back up and the mini PC restarts. And it will keep going around in this loop.

Since mini PCs are not a high-priority for TV makers, the chances of getting anything more than a single-core mini PC operating reliably from a TV USB port are slim.

So bank on needing a separate power supply for any dual-core or newer mini PC if you want to run it on your big-screen TV.

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