>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 26 September 2005 17:51
>To: Microcontroller discussion list - Public.
>Subject: RE: [OT] Laptop wall-warts
>
>
>
>
>> > discovered an unexpected dividend -- the wall-wart that comes with 
>> > it has an output of 12 volts at 2.5 amps.
>> 
>> Are you sure?  My stock of toshiba laptop supplies are all 15V...
>
>This is fairly common in newer designs. I use the same trick. 
>They don't want you to power it directly from the car, because 
>the LT does not have enough protection built in. So, they set 
>the required voltage higher than the car will get to, so it 
>won't charge/run with a direct cable.

Plus the new laptops use a higher voltage battery pack anyway, 4 lithium-ions in series is very common now giving ~16.5volts when charged.  It makes more sense to for the PSU to supply a voltage high enough for charging rather than having to use a step-up switcher on board the laptop.

Regards

Mike

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