Voltage Converters and AC Adapters

Simple question, but one I can’t seem to find an answer to. If you are using 220V supply on a 110V device that uses an AC adapter, does the voltage need to be converted to 110 before it gets to the AC adapter?

Huh? When come back, bring coherent questions.

You are trying to plug a 110V device into a 220V outlet? Depending on the way the 220V is wired, you may get lucky and get 110V on the plug, but most likely you’ll get 220V and assert the SET_SMOKE bit.

With a different reading, your device has a multimode power supply, and can use 110 or 220V equally. In that case, choose the proper plug and use it. European house power is usually 220V 50 Hz, so some products, particularly laptop computers, have multimode options for travellers.

You can buy European to North American converters to handle case 1.

I have a number of devices (laptop, cell phone, etc) that use an AC adapter at 110V. Wall warts and the like, no multimode. Do I need to convert from 220 down to 110 before plugging in the 110 AC adapter?

Yes, and you can buy a converter to do that.

read the label carefully on the adapters you have. most if not all modern ones are universal-voltage, they’ll say something like “INPUT: 100-240 VAC, 50/60 Hz.” If it says that, you’ll just need something to let you plug it into the receptacle used.

If they don’t say that, then yes you’ll need a step-down transformer.

What jz78817 said; VunderBob’s advice is about 20 years out of date, at least when applied to electronic devices.


jz78817 just defined the spotting features of what I meant by saying multimode. That’s not 20 years out of date.

In the old days when men were men and mammoths roamed the earth many power supplies had switches that you set for 110 or 220. With new power supplies there is no mode. They can operate over a wide range of input voltages and frequency.

Just look at the AC adapter, it should have the input voltage range listed. If it says 110V, and your wall outlet supplies 220V, you need a transformer or converter. But most AC adapters these days handle 100-240V range; if that’s what you have, all you need is the appropriate adapter plug.

My apologies; I misunderstood your intent.

Bottom line: The device will say what range of voltages it accepts. The user must supply a voltage within that range. That may or may not require an external converter.

Easy, do not travel.