power suply for laptop

[kk11]

Hi To All,
Is it possible to design a power suply for laptop without using transformer.
the input is 100-260v and output is 19.5v 6ma.
please can some one help me with a schematic.
thanks.

 

[eem2am]

it is , you could use linear regulator but the heatsink would be enormous..........

...i presume you mean 6A not 6mA?

....You could use a buck converter, but the duty cycle would be very low, unless you used a tapped buck.

In fact, with a buck you would end up with huge pulses being drawn from the input cap, and high rms cap ripple current..

so a transformer solution would be best......and power factor corrected too at your power levels...........

so what about a pfc followed by a two switch forward for you ?

you can get pfc chips that do both operations...eg LT1509 ........etc

 

[FvM]

It's not feasible because of the missing isolation.

 

[Sadegh.j]

Of course, they using a technique with switches, and then averaging the output. We were doing this is my previous company for the AC-DC converter, which would convert 220v to 5v. Cannot exactly remember what the name was, but google it.