Reducing voltage of a laptop charger

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Reducing voltage of a laptop charger

Post by tuberadiogeek on Thu Mar 16, 2017 6:25 pm

I recently tried to revive an old Sony laptop that was going to be scrapped, but it turned out to be junk. I ended up buying a new generic charger for it which is 19.5 volts at 4.5 amps and I just have no use for something with that much voltage. Is there a way I could reduce the voltage down to around 13.5 or so? That way I have another decent 12 volt power supply. I'm up for some slight modifications. Thanks.
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Re: Reducing voltage of a laptop charger

Post by willy3486 on Fri Mar 17, 2017 8:47 pm

Have you tried a 12 volt Zener diode? A circuit similar to this but with a 12 volt diode.
http://www.circuitsgallery.com/wp-content/uploads/2012/12/Zener-Diode-voltage-regulator-circuit.png

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Re: Reducing voltage of a laptop charger

Post by tuberadiogeek on Fri Mar 17, 2017 8:54 pm

I haven't messed with it, but that's a nice simple circuit. If I put a 12 volt zener diode in there, what would that bring my final voltage down to? As I'd like to have around 13 volts to compensate for some voltage drop, especially if I put it on an amp.
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Re: Reducing voltage of a laptop charger

Post by willy3486 on Mon Mar 20, 2017 4:03 pm

If you take the voltage at the point located it should be the Zenier diode voltage unless it pulls too much. If it is for a car amp or you want a really nice power supply find one from radio shack or make one like it from scratch. Radio shack made a 12 volt supply for years that was a great little supply. You can see a diagram at the link below. You can make one from junk parts, you probably have most or all the parts in a junk box if you save parts.
https://www.elektrotanya.com/radio_shack_micronta_22-120_12_volt_2.5a_power_supply_sch.pdf/download.html


You can also make one from scratch using a lm317. You could probably add a lm317 circuit to your supply. Do a search for a lm317 circuit as they are easy to find. I have made a lot of lm317 circuits.

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