24vIN to 12V (3A) voltage regulator, without coil? (LM2576 must use a coil?)
fcassia
fine but in this schematic there´s a "L1" inductor coil.
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 scattered throughout the
house when moving my work from one room to another while carrying
around my netbook) to feed this system. In other words the goal is
not having to carry around the original power supply.
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://ho.io/kess
Thoughts? comments? expletives? ;-)
Thanks in advance...
F
Cydrome Leader
> 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://ho.io/kesp
>
> I wonder what is its function, and if the circuit would work anyway
> without it?. I hate coils and making them is a PITA...
the inductor stores energy and is necessary in a switching power supply.
It will not work without it.
Pimpom
The LM2576 needs a coil, period. It's a switching type of
regulator and the coil is essential. The MC78T12AC is/was a
linear (non-switching) regulator and does not need a coil.
Switching types are more efficient in that less power is lost in
the regulator circuit. This means less heat to dispose of. A
linear regulator like the MC78T12AC has to continuously absorb
the difference between the input and output voltages - 12V in
this case. Multiply that voltage with the current and you get the
amount of power that's converted into heat. At 3A, that's 36W.
This requires a massive heatsink, otherwise, the regulator will
overheat and burn up in no time.
There are other linear regulators that can do the same job, but
the heating issue is always there.
fcassia
> The LM2576 needs a coil, period. It's a switching type of
> regulator and the coil is essential. The MC78T12AC is/was a
> linear (non-switching) regulator and does not need a coil.
> Switching types are more efficient in that less power is lost in
> the regulator circuit. This means less heat to dispose of.
Thanks Pimpom... I didn´t know about the difference between the LM2576
and the MC78T12 ...
A big heatsink is no problem for me... in fact, I prefer that to the
hassle of having to make or obtain a coil...
So what linear regulator with the same specs as the MC78T12 is there,
that is currently being produced?.
FC
Pimpom
There are many models from various manufacturers. Here are three
examples, all from National Semiconductor:
LM350 - 3A, adjustable voltage (you set the desired output
voltage with 2 resistors)
LM338 - 5A, same as above
LM1084 - 5A, comes in both adjustable and fixed voltage versions.
I checked at Digikey and they're all available. Look up the
datasheets on Nat Semi's site or from
http://www.datasheetarchive.com
dohi
> 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://ho.io/kesp
>
> I wonder what is its function, and if the circuit would work anyway
> without it?. I hate coils and making them is a PITA...
If your purpose is getting a low cost P/S for your new notebook,
I recommend to you buy a cheap switching P/S from radio shack.
I believe that's most cost efficient and comfortable.
If it's re-using old P/S, to keep it for next chance for 24V device.
If it's re-using old P/S for your new notebook, I want to say that
inductors are good reliable industrial products much than you think.
Bad efficiency is big disadvantage of using LDO as like 78T12,
versus using step down switch as like LM2576.
Especially it's wasteful to use a power supply inefficient
though PC of low power consumption is used with great pains.
Good Luck, F
dohi
mike
> 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://ho.io/kesp
>
> 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 scattered throughout the
> house when moving my work from one room to another while carrying
> around my netbook) to feed this system. In other words the goal is
> not having to carry around the original power supply.
So, you're unwilling to carry around a 5 ounce power supply that was
designed to operate the netbook, but you ARE willing to carry around
a 5 pound heat sink with a linear regulator that still needs to be plugged
into something, the 24V supplies scattered around the house?????
Your question suggests that you don't have a clue.
Power supply designers who don't have a clue have a tendency to make
a fireball of their $250 netbook. A power supply schematic is trivial...
assuming you don't leave out components critical to its operation.
The devil is in the details you learn the first few times you build
one that blows up and takes out whatever it's powering.
Get yourself some AC power cords and let the end dangle next to your
24V cords. Carry the proper supply with the netbook.
who where
wrote:
>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://ho.io/kesp
>
>I wonder what is its function, and if the circuit would work anyway
>without it?. I hate coils and making them is a PITA...
Hey, I'm not sure any here actually LIKE winding coils, especially
toroids - that's probably why they are a cheap-as off-the-shelf
commodity for the sort of load you require.
A linear stepdown is going to dissipate bulk power, as others have
pointed out. More cost, more weight, the *only* benefit is a slightly
lower component count.
Kevin McMurtrie
<bba6f30d-f380-45b5...@f18g2000yqd.googlegroups.com>,
fcassia <fca...@gmail.com> wrote:
> 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://ho.io/kesp
>
> 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 scattered throughout the
> house when moving my work from one room to another while carrying
> around my netbook) to feed this system. In other words the goal is
> not having to carry around the original power supply.
> So questions:
>
> 1) Would the LM2576 do without the induction coil?
It will explode. It needs the inductor for regulation and overload
protection.
The "Simple Switcher" series isn't exactly rocket science. Input
capacitor, output diode, output coil, output capacitor, and feedback
divider. Put the parts on a flatbed scanner, scan, place into photo
editor, draw traces connecting the pictures, print traces on blue peel
with a laser printer, iron onto a board, peel, etch, add solder paste,
drop the parts on it, heat, and you're done. It's all Digikey parts and
you don't even need custom software.
I have one inside the handle of a 0-50W LED flashlight with plenty of
room to spare:
http://www.pixelmemory.us/Photos/Nerd/Alien%20Bike%20Light%205.0/regulato
r.jpg
> 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://ho.io/kess
>
> Thoughts? comments? expletives? ;-)
>
> Thanks in advance...
> F
Try the "Simple Switcher Power Module" line if you don't need much
current. LMZ14203H has a built-in coil.
--
I will not see posts or email from Google because I must filter them as spam
Jasen Betts
> 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://ho.io/kesp
>
> I wonder what is its function, and if the circuit would work anyway
> without it?. I hate coils and making them is a PITA...
> 1) Would the LM2576 do without the induction coil?
no. it doesn't need a very big inductor.
> 2) Anything better than then LM2576 for 24v to 12V (3A)?.
dunno.
> 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://ho.io/kess
That part can do 3A or 24V input not both at the same time.
the max dissibation is 25W (and that's when attached to an "epic"
heatsink) which for a drop of 12V in gets you a little over 2A
> Thoughts? comments? expletives? ;-)
If you don't want to build a voltage converter buy one.
--
⚂⚃ 100% natural
hamilton
fcassia,
Have you looked at the data sheet for the LM2576 ??
http://www.national.com/mpf/LM/LM2576.html#Overview
Its called a "simpler switcher" for a reason.
If you do not know what a "switching regulator" is. please goolge.
http://www.google.com/search?q=switching+regulator+basics
Your requirement of 24v - 12V@3A = 36Watts is a lot of power to burn up
as heat is a series regulator.
http://www.google.com/search?q=series+regulator+basics
This will require a large heat sink and maybe a fan.
In todays internet age, you could have had an answer and solution within
10 minutes of your first question.
hamilton
Don Klipstein
fcassia wrote:
>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://ho.io/kesp
>
>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 scattered throughout the
>house when moving my work from one room to another while carrying
>around my netbook) to feed this system. In other words the goal is
>not having to carry around the original power supply.
>So questions:
>
>1) Would the LM2576 do without the induction coil?
Absolutely not - the LM2576 is a switching / "switchmode" type, which
requires an inductor. (Unless abused so badly that it can be improved
upon by use of a "linear" [non-switching] regulator.)
>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://ho.io/kess
>
>Thoughts? comments? expletives? ;-)
MC7812AC is a "linear" voltage regulator. Difference between input
voltage and output voltage, multiplied by output current, becomes heat.
Furthermore, 12V voltage difference times 3 amps is 36 watts, more than
the 25 watts max power dissipation of MCT78xx.
For that matter, 25 watts heat dissipation is the rated max, also max
at merely upper 30's degrees C ambient temperature when the combined
thermal resistance of heatsink, any heatsink insulator, and preferable-
over-lack-thereof "heatsink compound"/"heatsink grease" all add up to a
mere 2.4 degrees C per watt.
This gets me in a bad mood to go inductor-less...
LM2576-12 at input voltage up to 27.5-28 voltage, with 3 amp load
current (max that LM2576 is up to doing), requires 150 microhenries.
Its datasheet (http://www.national.com/ds/LM/LM2576.pdf) names 3 mfrs
and part numbers, including DigiKey-available PE-53115, or maybe-use the
-116 version (fair chance more reliably achieving at least 150
microhenries).
--
- Don Klipstein (d...@misty.com)
Don Klipstein
<SNIP from here>
The feedback divider is not even necessary for the 4 fixed-voltage
options of LM2576, one of which is 12V.