LM338 regulated snubberized PSU for audio amplifiers

[Upupa Epops]

Why don't make some discrete one or regulator + power transistor ? You can make it for both polarity and these circuits are quite primitive, so it can make everyone and there are practicaly any current limits like with integrated ones.

 

[peranders]

Why don't make a high current super regulator? A fast regulator seems to be appropiate for a LM3875/3886.

I see no (theorectical) trouble to magnify the original concept.

 

[Nuuk]

If we are going to talk about discrete regulators, perhaps it should be in a separate thread!

 

[peranders]

Maybe it's a good idea if this thread was about the LM338 in particular.

 

[thomasfw]

Why don't make a high current super regulator? A fast regulator seems to be appropiate for a LM3875/3886.

I am looking for a simple and good HIGH Current for the BPA200
project !

Anyone can help !


Thomas

 

[Bricolo]

why not a LM431 reference with a high power pass transistor?

it can be used either open loop (reference on the base) or with feedback (reference on the emitter)

and it certainly can be snubberized

 

[jackinnj]

why not a LM431 reference with a high power pass transistor?

it can be used either open loop (reference on the base) or with feedback (reference on the emitter)

and it certainly can be snubberized

Don't forget that the LM431 LT431 like to be "compensated" -- this is a complete "reference + error amp" which cause some nasties --

 

[Bricolo]

can you developp?

 

[Nuuk]

This is moving away from the thread and I see that PerAnders has opened a regulator thread here !

 

[jackinnj]

here's a snapshot from Dr. Riddley's discussion in Switching Power Magazine:

An externally hosted image should be here but it was not working when we last tested it.

unfortunately, the article isn't on the switching power magazine website (you just have to register, btw, it's a very good resource).

there's a schematic for the TL431 on Texas Instruments website which will help to understand the device.

there's a SPICE model for the TL431 on the LTSPICE Yahoo Group

 

[Nuuk]

Carlos - did you get my email?

 

[carlosfm]

Carlos - did you get my email?

I'm reading now.
Tell ya later.

Btw I don't know why are there some questions about the LM1085.
The LT1083 is much more appropriate for those who want to try a different reg.
It would need snubberizing too, and probably with different values (it's a question of checking the impedance graphs).

But it's quite expensive...

 

[Nuuk]

In order to try and avoid confusion, and save Carlos some grief, I have added a snubberized page to the Gainclone pages on Decibel Dungeon.

Please note that DD is only updated on the Tiscali server now so please adjust your Bookmarks/Favorites.

 

[slackman]

Hi all,
did anyone calculated the resistors for voltage regulation (R3...R6) on the chip?
In my calculations, they only have to be 1/4W , max. 1/2 W. So why are these so great ones? For R3, R4 i come up to 0,01W, so 1/4 W would be large enough. R5 and R6 need 0,27W so here 1/2 W would be fine...

I ask this because in smaller dimensions it's easier to get the fitting Resistors.

And: why don't using higher values, in the datasheet 120R - 240R for R3(R4) is used usually. If using 150R for R3 and 3.6k for R5 you have values which are be easyer buy... And if you can't get R5 in one value and have to split you can also use 1/4 W resistors for R5(R6) (for ex. 2 x 1.8k).

I ask this because i don't like those big components... if needed, ok. But if not small is beautiful...

Ah, NUUK: you forgot to label the protecting diodes at the regulator (2 x 1N4002)...

Michael

 

[Upupa Epops]

Use typ 0204, Michael . They are pretty nice and have dissipation 0.4 W.

 

[Nuuk]

Ah, NUUK: you forgot to label the protecting diodes at the regulator (2 x 1N4002)...

So did Carlos - why pick on me?

Yes, you are right Michael. I think that I used IN4002's there, I'll update the site when I have time.

 

[peranders]

Notice that those diodes are completely unnecessary in this application.

Those are for protection when the unregulated side has less smoothing than the regulated, which hardly will happen here.

If the regulator shall feed unkown loads it's wise to have those diodes diodes.

 

[slackman]

So did Carlos - why pick on me?

You mean Mr. Snubber-Man?

You've put it on your (btw: great) site without re-reading...

Notice that those diodes are completely unnecessary in this application.

I'm not sure because the Amp-module (in my case LM4780) hast some caps (1500 uF) in the powerlines and the recharge current may flow into the regs.
On Amp-fault there may be a short circuit and then the regulator may be also damaged...
... the only cost some cent...

Use typ 0204, Michael . They are pretty nice and have dissipation 0.4 W.

Yes, maybe, but my dealer doesn't have so many types (Reichelt). I don't want to buy at so many shops...

btw: for the LM4780-boards, should i take 220 VA toroids or 330VA?
I want to take two toroids, one for each board.

Michael

 

[Upupa Epops]

With 200 VA toroid and +/- 35 V DC you get without problems 2*60 W/4 or 2*45 W/8 with this chip. Bigger toroid is unneccessary, it is only " trafomania " .

 

[jackinnj]

With 200 VA toroid and +/- 35 V DC you get without problems 2*60 W/4 or 2*45 W/8 with this chip. Bigger toroid is unneccessary, it is only " trafomania " .

To the power (or VA) delivered to the speakers you must add the power that the chip dissipates through the heat sink.

FWIW -- when I run the Bridgeclone @120 watts the supply draws 2.5 amps from the 120V mains. If our interest is using the amplifier for some industrial purpose then the 200 VA transformer will be inadequate. For music, otoh, the continuous power demand is a fraction of the full rated power.