12v 3a regulator without coil ?

[aissacf]

I´m building a 24v to 12v converter using a LM2576 regulator. All is fine but in this schematic there´s a "L1" inductor coil.

http://schematicwiring.com/wp-content/uploads/2009/11/regulator-lm2576.jpg

I wonder what is its function, and if the circuit would work anyway
without it?. I hate coils and making them is a PITA...

Unlike in the above diagram, I won´t plug it into AC but begin with the output form an old notebook switching power supply which outputs 24v at 3.6 amps. So the output will be very "clean" to begin with. I just need to reduce the 24v to 12v.

My idea is to feed an Atom powered Netbook with this voltage regulator (so I can re-use my old 24v power supplies scatterd throughout the house) to feed this netbook, without having to carry around the original power supply. No, please do not suggest buying new 12v netbook chargers. I don´t want that, I want to give some use to the three (3) 24v power supplies that I already have. And no, bigger batteries for the netbook won´t do the trick, I want to use the system while plugged in from an external source, for maximum performance.

So questions:

1) Would the LM2576 do without the induction coil?

2) Anything better than then LM2576 for 24v to 12V (3A)?. I found
about OnSemi´s MC78T12AC which was sadly discontinued and allowed
12v3A output from a 24v input with just a couple of caps as external components. See
http://www.digchip.com/datasheets/parts/datasheet/343/MC78T12AC.php

Thoughts? comments? expletives? ;-)

Thanks in advance...
F

 

[(*steve*)]

1) Sure, the circuit will work without the inductor. However, you will have to redefine "work" to mean "not work at all".

The inductor is probably the single most important part of the circuit.

Wouldn't you simply buy the correct inductor?

2) the 7812 solution is totally different with approximately the same power dissipated in heat as passed through to the PC,

Read up on the differences between linear (7812) and switch mode (2576) style regulators.

Other thoughts: For a 12V 3A load, and being powered from 24V, the switch mode solution will draw a little more than 1.5A (possibly as much as 2A) where the linear solution will draw a little more than 3A.

 

[Resqueline]

1) No, it's a switchmode regulator.. You usually buy the coil, it's not that expensive. It won't need a heatsink.

2) I'm sure there are linear 3A regulators available, but you'll waste 36W as heat with that approach, thus needing an expensive heatsink.