[ltp] car and airplance adapter

[James Knott]

Peter Stuge wrote:
> On Sun, Nov 07, 2004 at 12:48:11AM -0500, Eben King wrote:

>>(Check your AC adapter.)  BTW, anybody know how they raise the
>>voltage for DC?
> 
> 
> Probably using a charge pump.
> http://www.eecg.toronto.edu/~kphang/ece1371/chargepumps.pdf

Probably not.  Charge pumps put out approximate mulitples of the input 
voltage, not a minor increase as needed in notebook computers.  They 
also have poor voltage regulation.  Most power supplies convert DC to 
high frequency AC, which can then be stepped up (or down) with a 
transformer and then rectified.  The switching used to create the AC, 
can be modulated, for voltage regulation.  Also the higher frequencies 
used, mean that the transformer can be a small ferrite toroid, which 
allows for a small, efficient package.