Regs - Shunt vs Series

[richie00boy]

Why is shunt perceived to be a better topology in terms of noise and regulation performance? Surely hum at the input will be equally attenuated by a series regulator as it uses feedback to maintain the output voltage at a constant level?

I can't understand why a series regulator would have the output corrupted with a triangle wave caused by the feedback, yet this wouldn't happen with a shunt. Or is this corruption just when using ICs?

I am interested in simple discrete implementations mainly, but welcome comments on ICs, too.

[peranders]

Originally posted by richie00boy
Why is shunt perceived to be a better topology in terms of noise and regulation performance?

Who says so? Normally a series regulator has a "shunt regulator" to create a reference voltage. There are differences between those two types of regulators but there are pros and cons of these types and I think noone is the best.

Have you read the gigantic thread about Super Regulator which I believe is far better than any shunt regulator.
Super Regulator, collecting the facts

If you are looking for a discrete circuit you can check how a LM431 is done but I doubt that you can make it better than the 431.

[jcarr]

Richie:

>Why is shunt perceived to be a better topology in terms of noise and regulation performance?<

It isn't, at least if you are looking at the voltage component of the regulator output

>I can't understand why a series regulator would have the output corrupted with a triangle wave caused by the feedback, yet this wouldn't happen with a shunt.<

The use of global feedback is a separate issue from the choice between series and shunt regulation. Feedback can be used in the design of both series and shunt regulators.

>Or is this corruption just when using ICs?<

Certainly the oft-mentioned TL431 IC shunt regulator does not have very good performance for audio applications. An impedance curve that rises steadily above 50kHz until it hits about 13~14 ohms in the 1~5MHz region, noise to spare...

Incidentally, I do feel that shunt regulation has its advantages, but I believe that you may need to look in a somewhat different direction from the questions that you have been asking so far.

A thread with (IMO) more pertinent information can be found here:

http://www.diyaudio.com/forums/showt...006#post135006

hth, jonathan carr

[richie00boy]

Thanks guys, picked up a few things there. I think I will stick with my simple series regulator for now.

[tschrama]

Hi all,

I noticed that a series regulator can suffer from the capacitance over it's juctions.. this limmits the high frequency PSRR... still I would prefer series-rugulator with good HF decoupling

just my 2 cts,
Thijs