Re: Laptops being "dual-voltage"?

It's true that a cheap TRANSFORMER power supply designed for 60Hz may well overheat on 50Hz. However, all laptop power supplies are "switching" power supplies, which are incredibly indifferent to the AC line frequency, since the very first thing that they do is full-wave rectify it and minimally filter it to DC, without a transformer or any frequency-sensitive components.


John Doue wrote:

Were you asking a question when you wrote "Why does the different frequency cause the power supply to overheat?" And what do you mean by switchmode?

A cheap powersupply designed for 60Hz will more than likely overheat and fail on 50Hz (if you don't believe me, buy a cheap one from R'shack and try, or just buy an electric toothbrush not specified for 60Hz and try it in Europe. It will not work more than a few minutes) simply because the lower frequency allowes more juice to flow through the transformer which acts more as a resistor than intended. Plugging it on DC will shorten its life to milliseconds. What happens on 400Hz is the opposite, but I have no experience of the consequences. Just would not try on my own equipment.

Of course, more expensive bricks may have been designed to work for a wider range of frequencies and voltage. But as a rule, stick to what is indicated on the label unless you can accept the possibility it will fail, and may be damage the equipment downstream.

Sorry I cannot put my explanations in my electricity vocabulary is shot, my electricity years being too far behind, but the reasoning still stands!

.

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