by Tomi Engdahl on Mon Feb 15, 2010 9:11 am
Elektor Electronics magazine used to publish such circuit years ago.
The downsides of that circuit would be that it was pretty low powered (30W or so if I remember right) and could not be enough for many modern PCs (considerably lower power than the commercially available similar power supplies nowadays advertise). Most modern laptops can draw 30 to 40 watts just sitting there at a desktop! With a low battery that's being charged, while the laptop is on and running, they draw considerably more (could be 80-100W or so). For example the Dell laptop I use at works has power supply that gives out 20V 4.51A and the laptop says power rating 20V 4.5A. This means the laptop can use up to 90W power.
It might not be economically feasible to try to build such circuit, cheap commercial converters are so cheap nowadays that it pretty hard to even just to get the electronics components for such circuit with the same price, and to get working unit you would still need the circuit board, case and lots of building/testing...
Check for example this is pretty cheap (I have not tested but site gives mostly good comments):
Car Cigarette Lighter Universal Laptop Power Adapter: $12.76
http://www.dealextreme.com/details.dx/s ... r.85273703Elektor Electronics magazine used to publish such circuit years ago.
The downsides of that circuit would be that it was pretty low powered (30W or so if I remember right) and could not be enough for many modern PCs (considerably lower power than the commercially available similar power supplies nowadays advertise). Most modern laptops can draw 30 to 40 watts just sitting there at a desktop! With a low battery that's being charged, while the laptop is on and running, they draw considerably more (could be 80-100W or so). For example the Dell laptop I use at works has power supply that gives out 20V 4.51A and the laptop says power rating 20V 4.5A. This means the laptop can use up to 90W power.
It might not be economically feasible to try to build such circuit, cheap commercial converters are so cheap nowadays that it pretty hard to even just to get the electronics components for such circuit with the same price, and to get working unit you would still need the circuit board, case and lots of building/testing...
Check for example this is pretty cheap (I have not tested but site gives mostly good comments):
Car Cigarette Lighter Universal Laptop Power Adapter: $12.76
http://www.dealextreme.com/details.dx/sku.3438~r.85273703
