by mike » Sat, 03 Feb 2007 07:00:41
>>>> I've read a few posts on using 115 VAC 400Hz power (commonly found on
>>>> aircraft) with a standard laptop power brick. Everything I've seen
>>>> basically amounts to "try at your own risk" or "didn't hurt my
>>>> laptop". Does anyone have switching power supply design experience
>>>> that may be able to shed a little light on why this would or would
>>>> not be a good idea for a modern laptop power brick. My extremely
>>>> limited testing with a multimeter/oem power brick/400Hz input shows
>>>> that the the power brick outputs the correct DC voltage. I would
>>>> feel a little better plugging it into the $6000 laptop we bought if
>>>> I could check for ripple output voltages at 400Hz compared to 60Hz
>>>> with a scope. If that turns out to be a non-issue then then the
>>>> next worry would be early failure of the power brick (minor concern)
>>>> and safety issues such as the brick catching on fire (slightly less
>>>> minor concern). Any info or reading suggestions much appreciated.
>>> Laptop switch mode power supplies (or indeed any switch mode supply)
>>> will work quite happily off a 400 Hz supply. We do it all the time. The
>>> ripple will be more or less the same as the power supply part is
>>> separated from the mains input by a DC bridge. The rating plate says
>>> 50-60Hz simply because that is what will be encountered by the vast
>>> majority of users. As it happens, they also work perfectly from DC
>>> (but do require a higher voltage ~150 volts for US supplies and ~300
>>> volts for Europe - though most supplies are universal).
>> OUCH! Your ignorance is showing; that is NOT why the 50/60Hz spec exists!
>> Doing so completely disregards heat dissipation and output current
>> limitations in most switching supplies.
Yes, it does, 'cause they're irrelevant!!!
You might wanna check the mirror for signs of ignorance...
You need to quit spewing garbage
>> and learn a little about these things. Also, because ONE worked, does not
>> mean the next one will.
>> If you bother to look, you'll also find that some are capable of 400Hz by
>> spec, and some are not. Most are capable of operating with no load on them
>> too, but not all.
>>> Power supplies containing a mains transformer won't work at all from
>>> 400Hz (but otherwise sustain no damage). These power supplies must
>>> not be run from DC.
>> Actually, this isn't true, either as there are a myriad of things that can
>> or maybe won't go wrong at 400Hz. It depends on the xfmr construction,
>> something you're apparently quite ignorant of. There will be an output from
>> the xfmr. Even audio xfmrs can be operated as a main xfmr under the right
>> circumstances, and they're rated to 20kHz and beyond.
You talk like this is a grand revelation. Audio transformers are
designed to run at 400 Hz...and 60 Hz...cause they're in the audio range.