Monday, Jun 29, 2015 at 08:19
Actually, most laptop switch mode supplies are less fussy about Modified sine wave than most people think.
The first thing their circuitry does in feed the AC through a
bridge rectifier & feed it into large filter caps to provide around 340 volts DC for the rest of the circuitry.
The diodes in bridges aren't at all phased by the modified sine, or almost square wave AC input.
What is more sensitive though, is wire wound transformers.
Because they rely on rise & fall of magnetic flux, they are very critical of input wave forms.
Earlier UPS units & the more basic models on the market are nowhere near sine wave & happily run computers & monitors with their switch mode supplies with no issues.
What I have learnt over 25 years in IT, is to be very wary of plugging transformer based power packs on the likes modems & smaller network switches into UPS outputs.
Have had many service call after power outages where the story is that the UPS kept things up running, but these other devices have now failed & invariably, their power packs now have open circuit primaries.
All that said, I've recently bought a pure sine wave unit, but still have 150 & 300 watt MSW
inverters, that I've still used right up to now.
They don't need totally ruling out of the equation. They have their price & uses in the right situations.
Cheers.
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