DC-DC

[onis_uk]

If I were to power an amplifier with a laptop smps brick is there a nice way to step down the voltage from  19v dc to 12v dc?

There are plenty of crusty ebay buck converters out there but i need about 50W capacity.

[Ian.M]

No,  50W out is 4.17A which would be really pushing it for an EBAY buck converter made of pure 'Chinesium' + there is a high probability that at light loads either it or the laptop PSU will go into discontinuous mode and produce a lot of AF ripple, and at higher outputs, the PSU and the buck converter may 'beat' with a difference frequency in the AF range.

If you need 12V at over a fraction of an Amp, for audio of any better quality than a 'Tannoy' style PA system, don't start from a laptop power brick!

[sleemanj]

Ones like this cc buck are commonly sold as 150w at usual places, of course thatis fantasy at least without fan, but I have pulled 40w out at 10v from 48w@32v input, my notes say continuous but I don't recall how long that was for exactly, but temperature rise was 32'c

I did not look at ripple

[ElectronicCat]

Does it need to be powered by a laptop charger? You'd probably be better off just buying a 12v 50W power supply or re-purposing a desktop power supply. If you do need it to be powered by the laptop charger, you might be able to get away with a beefy linear regulator which would be the simplest solution, but that's assuming the laptop supply can deliver ~80W and you'd also need a heatsink capable of dissipating ~30W. Not ideal and not very efficient either. I wouldn't trust any eBay-grade buck/boost converters but you could either look into designing one yourself or buy a module from a reputable distributor.

[dimkasta]

Be sure to check any inrush currents on those things.
A big inrush could trigger the charger's overcurrent protection.