All P-channel Regulator For TSSA Split Supply?

Jay

Banned
2003-02-11 9:02 am
Jakarta
What is the problem of using the same transistor regulator for both positive and negative supplies?

Mosfet complementary pairs rarely have good complementary characteristics, but such regulator as attached is rarely used. Why?
 

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Jay

Banned
2003-02-11 9:02 am
Jakarta
Hi Jay,

personally I will only regulate the front end and driver stage of the amp, it makes for a far less problematic design and the end results remains excellent. Besides you do not create another heat source.

I have used this regulator for single ended circuits with very good result (may be because it doesn't really regulate well). And I haven't seen circuits not improved with this. Yes, many top/successful class-A amps use it.

Actually, instinctively I prefer to regulate the front end only, especially if the bias is not so high (here it is 2A). The problem is then the front end will have lower voltage (unless 2 secondaries used), which is not suitable here (I mean no success try in my case).

And I have prepared to use high bias with TSSA. It has a very good chance to be the best amp. It outperforms F5 in almost all area. Where this excels is in power (that's why I prepared for high bias). F5 cannot go high power without excessively increasing distortion (read: F5 Turbo), but TSSA can.
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
The 2 N-channel MOSFETs would required to be closely matched, to prevent current-hogging.

Yes, thanks. I think you're right.

IRFP460 is a 20A 250W device. No problem with using only one device for any class-A amplifier. By paralleling I'm looking for better trans-conductance, not power handling.

Correct me if I'm wrong, I'm not worry with destruction due to thermal runaway, because one device is capable of handling all the heat.

What I'm worry about is the unbalance transconductance between positive and negative rail. I simulated 1 mosfet on the positive rail and 2 mosfets on the negative rail, and the result is much much worse than just using one mosfet for both rails. So I guess I will stick with using only one mosfet per rail.
 

31697B

Disabled Account
2012-05-19 12:53 am
Power Amp regulator with all passive part

[/QUOTE] Actually, instinctively I prefer to regulate the front end only, especially if the bias is not so high (here it is 2A). The problem is then the front end will have lower voltage (unless 2 secondaries used), which is not suitable here (I mean no success try in my case).

And I have prepared to use high bias with TSSA. It has a very good chance to be the best amp. It outperforms F5 in almost all area. Where this excels is in power (that's why I prepared for high bias). F5 cannot go high power without excessively increasing distortion (read: F5 Turbo), but TSSA can.[/QUOTE]

The most important thing about regulation is to keep both rails at the same voltage. It does not matter very much if the absolute value changes... as long as both supply voltages change by the same amount. This can be assured by placing a very large value capacitor Between the + and - supply rails. Differential changes will be cancelled. This is especially useful in power amplifier output stages. I have been doing this for almost 20 years.

-RNM
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
The most important thing about regulation is to keep both rails at the same voltage. It does not matter very much if the absolute value changes... as long as both supply voltages change by the same amount.

If what you meant by "both rails" are positive and negative rails, I think it depends on the amp design. Doesn't matter for me if one rail is lower than the other if the amp doesn't care about it (like in many cases).

This can be assured by placing a very large value capacitor Between the + and - supply rails. Differential changes will be cancelled. This is especially useful in power amplifier output stages. I have been doing this for almost 20 years.

I have done this also, simply based on listening test.

NP, if I'm not mistaken, mentioned the effect of this capacitor (from -V to +V) is increasing the effective capacitance (thus better filtering)?

What I have seen is that the effect of this capacitor can be positive but can be also negative. But...

I just simulated this and indeed it has good effect, thanks.
 
Let’s say for an example that you have an amplifier with output rails of +-45 V and you want to regulate a +-15V supply from these rails. On the positive side you would have +45, +15 and ground, On the negative side you would have -15, ground, and +30V only letting you use -15V for the output rail.

It’s not a problem if you are using a single negative supply and you do not want to use the unregulated supply. But with center tapped transformers and dual unregulated supplies the unregulated +- voltages are referenced to ground so you cannot float the unregulated negative ground.
 

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Last edited:
What is the problem of using the same transistor regulator for both positive and negative supplies?

Mosfet complementary pairs rarely have good complementary characteristics, but such regulator as attached is rarely used. Why?

Are you suggesting that in some way it would be good to have exact complementary devices in a + and - regulator??

Anyway, what you want would work with shunt regs. Shunt regs are two-terminal circuits so can be used in the + or - position without modifications.

Jan Didden
 
Are you suggesting that in some way it would be good to have exact complementary devices in a + and - regulator??

Anyway, what you want would work with shunt regs. Shunt regs are two-terminal circuits so can be used in the + or - position without modifications.

Jan Didden

Yes. An example you will find by the commercial phono RIAA head amp PP2 from NAD - go to the second attachement by post #5 about
http://www.diyaudio.com/forums/analogue-source/155449-head-pre-denon-dl-103-a.html
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Are you suggesting that in some way it would be good to have exact complementary devices in a + and - regulator??

Yes. Something I'm missing?

Anyway, what you want would work with shunt regs. Shunt regs are two-terminal circuits so can be used in the + or - position without modifications.

High current shunt regulator??? I haven't used or even seen one. Please give me a reference to a shunt regulator capable of around 2A. May be not an efficient solution but I'm after a good sound, so why not.

May be I need to regulate the front end only with a shunt regulator (with or without a capacitance multiplier), in line with Nico's suggestion (I forgot that in my circuit I lowered the front end voltage rail, which has good effect, with RC filter).

But I really like the above regulator in single ended circuits. If RJM1 or somebody else give a "no-go" with the same regulator for both + and - rails, I will use IRF640 and IRF9540 as used by Ayre V3 amplifier (I have plenty of IRFP460 but only a few IRF640/IRF9540 pairs so I tried to avoid using them in power supply. But I think I have no use for them in an output stage anyway).

EDIT: In the Ayre, the output is not regulated with the IRF640/9540, and I remembered Samuel Jayaraj comment about current hogging in paralleled mosfets, so... I wish the post#1 circuit has no issue...?
 
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Yes. Something I'm missing?

I don't know - I wasn't sure you were serious about your priority to have perfect complement fets in the + and - reg.
I guess you were...

High current shunt regulator??? I haven't used or even seen one. Please give me a reference to a shunt regulator capable of around 2A. May be not an efficient solution but I'm after a good sound, so why not?

There's lots if circuits around, if you don't want to design your own. Google is your friend.

jan
 
Yes. Something I'm missing?

High current shunt regulator??? I haven't used or even seen one. Please give me a reference to a shunt regulator capable of around 2A. May be not an efficient solution but I'm after a good sound, so why not.

As you can see in the NAD PP2 schematic, the shunt regulator consists of two parts:
1) the constant current source so as
2) the zener diode

If you want a 2A shunt regulator, you must design an appropriate current source for 4A (have a look to the CCS from the single ended amp "ZEN" from Mr. Nelson Pass) so as an appropriate power zener diode (normal zenerdiode include Sziklai-Darlington or MOSFET e. g.) also for 4A.
By normal operating you need 2 A for your amp and 2 A for the "Power Zener" itself.
Please note:
In case of failured amp, your power zener must be able to work with the full current of 4A.
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
There's lots if circuits around, if you don't want to design your own. Google is your friend.

I couldn't find it.

As you can see in the NAD PP2 schematic, the shunt regulator consists of two parts:
1) the constant current source so as
2) the zener diode.

Can you show me how to do it for split supply +/-45V capable of at least 2A? I have built many zens, and have googled as well, but have no idea but the current source in post#1 which seems to have "con" from RJM1 and Janneman.

Of course, I'm not a new EE graduate who likes to design sub-quality circuits when much better circuits are free from experts. Hence my preference will go to shunt regulators used in respected amplifiers (not my own design, even if I could). But I cannot find such regulator in my collection of amp circuits, so I guess it is not feasible?