Open-loop regulators, series or shunt, is here accepted name for no-feedback regulators. Mr. Perez regulators, showed here, are open-loop types. They consist of zener voltage source and shunt transistor, without any error amplifier. Constant current source or resistor are used with both feedback and no feedback shunt regulators. No feedback regulators have very high output impendance . Jung super regulators current/sense connecting method was developed to eliminate mutial influence between stages you have mentioned. Blowtorch preamp uses LM317/337 series IC regulators and then feedback-free shunts to improve HF regulation, and even cap. multiplier near the audio circuits.janneman said:
But Jung/Didden regulators are much better, especially in current/sense connecting mode.
Bear,
Those (the bjt's) are self-biased constant current sources biased by other self-biased current sources (the FET's) so to speak, and therefore you need a bit of voltage drop (a few Volts or so) on the pass bjts to get the FET ccs's to operate properly, additional to the needed drop along the emitter-R's + Vce's abve saturation.
- Klaus
Those (the bjt's) are self-biased constant current sources biased by other self-biased current sources (the FET's) so to speak, and therefore you need a bit of voltage drop (a few Volts or so) on the pass bjts to get the FET ccs's to operate properly, additional to the needed drop along the emitter-R's + Vce's abve saturation.
- Klaus
Jan said: "The ground current with a shunt back to the supply cap is constant (DC) because the sum of load current and shunt current is constant (= the CCS current). So mutual influence between stages is much less. But it anyway depends a lot on the implementation, you really have to know what you are doing of course."
Bear wonders out loud: "well sure, on paper... but what if the tracking between the two is less than ideal in the real world? ...what would the 'difference' waveform look like, would it be nasty higher order stuff? And, of what magnitude? If the series regulator has more sinusoidal ground currents, might that end up sounding better? So, in practice how good is the tracking of the shunt requlator, and what sort of HF response and bandwidth does it need to have?..."
_-_-bear
PS. Jan I think your diagrams alone are not accurate, they really need to reflect the constant DC claim for the shunt going to the main return, and the AC varying current with the series regulator??
Bear wonders out loud: "well sure, on paper... but what if the tracking between the two is less than ideal in the real world? ...what would the 'difference' waveform look like, would it be nasty higher order stuff? And, of what magnitude? If the series regulator has more sinusoidal ground currents, might that end up sounding better? So, in practice how good is the tracking of the shunt requlator, and what sort of HF response and bandwidth does it need to have?..."
_-_-bear
PS. Jan I think your diagrams alone are not accurate, they really need to reflect the constant DC claim for the shunt going to the main return, and the AC varying current with the series regulator??
bear said:
That would be a very simple current source. The JFET is injecting Idss in the diodes. One Vbe drop divided by the emitter resistor defines the current throungh the series bipolar transistor.
A relatively poor configuration, due to the dependency on temperature, pretty low output impedance and mediocre frequency response. Replacing one diode with a 1.2V bandgap reference will do some good.
kamis said:
You might be dissapointed, but all those regulators have negative feedback. They are not open loop, although the loop gain is not very large. The parallel regulator (MOSFET) has a significan current gain and acts both as error amplifier and regulator.
EDIT: the small signal output impedance at low frequencies is 1/Gm where Gm is the MOSFET transconductance. That's a hell of a poor regulation, at least for the current levels involved in a preamp (and the required MOSFET ratings thereof).
Well, I seem to think I disagree! Once you know in advance what Jan is aiming at, the diagram makes sense, but there is current flowing on the shunt regulator diagram back to the main PS, none shown by arrows, yes?? The issue is nominal DC (constant) vs AC (varying), yes?
Without the text, it is unclear, was to me. Maybe I am unfamilliar enough with common engineering style diagrams to miss the idea with just the diagram...?
_-_-bear
Without the text, it is unclear, was to me. Maybe I am unfamilliar enough with common engineering style diagrams to miss the idea with just the diagram...?
_-_-bear
The shunt regs provide the low Z and the stable output voltage, the ccs in front of them try to isolate AC components to the amount they act as ccs (vs. freq), and the series regs bootstrap the ccs to help them isolate even more.bear said:
Basically a shunt reg also works with a simple series resistor, fed from noise supply... but not that good.
BTW I don't quite get is why people don't use like circuits instead of complementary ones, when using two-pole designs.
And as for the Perez schemo, don't chop the mains xformer capacitance with individual bridges, even with common-mode chokes. Workaround: 4 secondaries or capacitive bypasses at the right place.
- Klaus (off to lunch now)
KSTR said:
Mmmm... of course in modern solid state consumer work, small size is of paramount importance, but for those in high-end not.
So I am thinking why not a choke or a pi filter in the same spot?
Why not a second high performance series reg in the same spot?
Inquiring minds want to know!!
_-_-bear
bear said:
Yes you're right. But I would think that it would be a really badly botched job if that shunt wouldn't be orders of magnitude better than the series reg in avoiding ground ripple currents. But yes, not zero.
bear said:
This is to illustrate the principle. It mainly shows the AC component differences between series and shunt. I have no intention to present a cookbook-ready design for anuone to copy
Jan Didden
KSTR said:
OK, are we talking about this post (and following):
http://www.diyaudio.com/forums/attachment.php?s=&postid=1870159&stamp=1246503992 ?
I see a constant current source as the last element. A fet with a constant Vgs drawing a constant current?
Jan Didden
First schematics, those posted by flg where only intended for learning, trying and illustration purposes…
Last ones in post 93 are fully functional Zout is about 0.5R from 0 to a few tenth of Mhz(I cant measure beyond) noise is -150 db from 100hz to 100 kHz (can't measure beyond neither ) and decreasing to -130 db at 10Hz of course there is no feedback "loop", for me the shunt bjt is 100% “feedback”.
New PSU
Last ones in post 93 are fully functional Zout is about 0.5R from 0 to a few tenth of Mhz(I cant measure beyond) noise is -150 db from 100hz to 100 kHz (can't measure beyond neither ) and decreasing to -130 db at 10Hz of course there is no feedback "loop", for me the shunt bjt is 100% “feedback”.
New PSU
Yes, that would work also, the choke being a non-perfect constant current source for AF only (not at DC and not at HF), and you'd need one with a high-ish DCR, otherwise the series reg would only fight the shunt reg (the shunt would win probably, forcing the series reg into current limit).bear said:
- Klaus
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