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Introducing the PowerReg

neiljadman said:
Ismail - Perhaps I shouldn't have to avoid any confusion, but I changed the resistor numbering on the PowerReg boards omitting the original R4 in order to keep the numbering consecutive. So my R4 is Teddy's R5 and my R5 is Teddy's R6. I then simply continued the counting for the negative side of the board.

As for values - I believe it's whatever you have - though I'm sure Teddy will be along soon to confirm.

Hope this helps. Neil

PS - The Chinese boards may be working now!
Click to expand...
Thanks for taking the time to reply Neil!

P.S.
Wanted to ask you first but did not wish to disturb you while you sort out the clone problem.
Encouraging to know it'll be sorted soon.
 
Hi,

Two important updates regarding the PowerReg:

1. Actually the original R4 *is* required. Well, not required but better to have it. I found that without it the fet is not biased correctly and adding it improves performance. Value should be such that there is a dropout of at least 2V on R3.

2. A 12K resistor between the base and the emitter of T3 further improves performance, making the regulator faster.

These two modifications can be implemented by adding the resistors at the back side of the PCB.

Cheers, Teddy

P.S. The accelerated TeddyReg mode is applicable to the PowerReg too.
 
Thanks Teddy.

"1.... Value should be such that there is a dropout of at least 2V on R3."

Can you please elaborate?

If I feed 39v into the PowerReg, would 35v be too high to expect?
What is the minimum total drop out?

The accelerated mod on the Powerreg will take away the slow start feature which would be welcomed in a power amp.
 
If you feed 39V on no-load, it will probably drop to 36V on load due to the transformer internal impedance. I'd suggest therefor a total no-load dropout of around 7V.

3V the transformer
2V the 317/337
2V the Gyrator
 
teddy_pardo said:
Hi,

Two important updates regarding the PowerReg:

1. Actually the original R4 *is* required. Well, not required but better to have it. I found that without it the fet is not biased correctly and adding it improves performance. Value should be such that there is a dropout of at least 2V on R3.

2. A 12K resistor between the base and the emitter of T3 further improves performance, making the regulator faster.

These two modifications can be implemented by adding the resistors at the back side of the PCB.

Cheers, Teddy

P.S. The accelerated TeddyReg mode is applicable to the PowerReg too.
Click to expand...

Teddy,

1. can you please suggest some default value(s) for R4?

2. is 12K resistor value specifically determined for BC550/560 and D44/45 or it can be used elsewhere (bipolar TeddyReg, Sziklai or the other way etc.)?

Thanks, Baki
 
Hi Teddy,
Thanks for sharing your knowledge. With regards to power reg.
Can we scale it up for higher current by replacing the 317 with
say an LM 138 ? Also what caps value do you recommend prior to the power reg ? Thinking of using this in my Moskido build.

Thanks in advance
 
The PowerReg is already scaled up... The 317 is only used to create a reference for the power transistor, and passes only few milliamperes. With the D44H11 you can use it for up to 10A. If you need more you can use other transistors, or use several transistors in parallel.

You don't need too large capacitors before the PowerReg 5000uF will do, and you can use simple capacitors, no need to look for low ESR etc.

Teddy
 
Hi Teddy,
Got a question. In your component list T3 is listed as
D45H11. Is this the correct item or is it a typo error ?

Thanks
 
jc951t said:
Hi Teddy,
Got a question. In your component list T3 is listed as
D45H11. Is this the correct item or is it a typo error ?

Thanks
Click to expand...

Look at the first page schematics and you will see that T3 is a PNP for the (+) reg (and NPN on the (-) one). ;)

Good luck,
M
 
Hi Teddy,

I am used to make a TeddyReg with different orientation of LM3x7 reg in relation to D4xH transistor. A layout is a bit easier to make that way.

I want now to make a PowerReg with same approach.

Question is: does LM3x7 needs substantial cooling as D4xH does or it can be left as is?

Thanks, Baki
 
Hi Teddy.

Considering Powerreging the LM3886 in my CA amp. You did this earlier right? Can you give your opinion of the sound quality before and after?
 
teddy_pardo said:
2. A 12K resistor between the base and the emitter of T3 further improves performance, making the regulator faster.
Click to expand...

This resistor may well make the transistor T3 faster, but wouldn't it also let through the very noise that the gyrator has taken all this trouble to get rid of?

Thanks, Andy
 
No, I don't think it adds noise. The output follows the base of T2 not the base of T3. The base of T3 is noisy by definition as it follows the emitter of T3 (like a diode).

This resistor is important as it provides biasing for T2, which otherwise gets only the total current divided by T1 hfe.

BTW, further improvement can be achieved by connecting a resistor between the source of T1 and the ground. The value of this resistor depends on the Idss of the jfet used and the output voltage. The purpose of this resitor is to bias the jfet to its linear area of operation. For most jfets it's about 1-2 mA, so for 24V use a 12K resistor.

Teddy
 
teddy_pardo said:
No, I don't think it adds noise.
Click to expand...

OK thanks Teddy. Silly me!

Out of interest, roughly what is the output impedance of the PowerReg at say 1A and does this depend on the voltage drop across T3? In other words, is it better to minimise T3's voltage drop to 2V (as you suggest)?

Andy

Edit: OK I'm getting mixed up. I meant the voltage drop across R3, not T3. I guess this doesn't matter. Please ignore me.
 
teddy_pardo said:
Only tried it with LM3875, and it turned it to one of the best amps I've ever heard.
Click to expand...

Cool.:) What kind of PSU would you advise with the powerreg? I guessing ca.300VA trafo and at least 10'000uF per rail? Any snubbers or bypass caps required?

Assuming the powereg is used close to the LM chip, what kind of local decoupling is reccomended or is it not necessary?

Thanks,
Mike.
 
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