The simplistic Salas low voltage shunt regulator

[iko]

I would like to share a bit of good news. Just finished a high voltage version of v1.5, however, using n-channel mosfets. Although this thread is about low voltage, I think it is relevant in that this topology is the same as the one I recommended earlier to Tham. So that should give him some hope that it's not just simulated vapor ware. I used two trimmers, not set to the exact value shown as resistors in the figure (R1 and R10).

As I said, this circuit is currently running in reality, and it is stable. My intention is to use this (or some variation) for the dht headphone amp I'm developing in another thread.

[av-trouvaille]

Hello Ikoflexer,

Great job. Without wanting to divert this thread too much (your email button is off), could you please indicate up to what voltage this version would be capable? I would be interested in a voltage range of 200 – 300V.

Arjen.

[AndrewT]

Hi Iko,
can you investigate what happens across J3 at start up on higher voltage supply?
I think J3 needs a high voltage cascode to protect it from full supply voltage at start up.

Am I allowed to quibble on the almost perfect schematic?

[stormsonic]

Iko, lets go back one step. Can you simulate this circuit if you replace Q3 (BC550C) with Darlington?
Darlington should be made from 2 x BC550C?

[AndrewT]

I think the tr2 needs a resistor from b to e.
This allows a near constant current to flow through tr1 and performance should be more predictable.

Can Iko refer us to the post where you rejected this Darlington idea to increase the voltage across the Q6 ccs.

[iko]

Thank you guys!

My email button is off? I'll look into that. Well, you can usually find me as ikoflexer AT gmail.com ... who would've thunk?

Arjen, the topology should work with higher voltages but some parts will need to be changed. I'll direct you to another thread where salas already developed a HV regulator as well.

Simplistic Mosfet HV Shunt Regs

Arjen, if you're interested in such a regulator, have a look first at the salas version; I'm not sure if I should open a whole new thread for the HV I'm working on... ?

Andrew, have a look at this:

http://www.diyaudio.com/forums/showt...22#post1886122

That was the "Christmas tree" circuit, with what I thought would be protection for turn-on voltages for the jfet and for the ccs mosfet. I stripped that in the process when I tried it for real (with and without). Also, your points are not quibble for me, I always appreciate the time you take so do your "quibbling" as much as you want.

Stormsonic, I will show you a little later what happens with darlington in that position (a bit short on time right now). But you should know that in v1 I've been using the mpsa18 in that position I have tried a darlington there too, long time ago. I like the mpsa18; if you're not familiar with it, look it up. It's a nice part.

Andrew:

Can Iko refer us to the post where you rejected this Darlington idea to increase the voltage across the Q6 ccs.

I have no idea what you're talking about, sorry. Who rejected the Darlington idea?

[stormsonic]

Iko, MPSA is 100 Mhz bandwith, gain 500 to 1500.

BC550C is 300 Mhz bandwith with gain 420 to 800. Darlington connection to increase gain.

[AndrewT]

20k R9 and D6 charge up the 470uF C6.
that turns on the pass FET.
Then we have to wait until the FET charges up C5.

What power will be dissipated in the 20k with 160 to 180V across it?

Without the 20k and Zener the Jfet will explode.

Once the caps are charged, what current will pass the 20k?
Will that be enough to keep the jFET turned on?

That Darlington proposal was raised months ago.
I thought you or someone else gave an explanation of why it was not possible.

[col_s]

Originally posted by Salas
Yes they are usable. Try them.

How did you like the subjective performance with those you built? For what circuits, and what you had there before? Thanks.

Thanks, i'll give them a try. I used them for the analog supply for a multi-channel volume control using multiple pga2320's and opamps. It replaced some teddyregs that were not working very well in this circuit. I think due to their high output impedance they are better suited to supplying less components and low currents. It now sounds much cleaner. There is more and better bass, and some nasty sibilance went away.

[iko]

Originally posted by stormsonic
Iko, MPSA is 100 Mhz bandwith, gain 500 to 1500.

BC550C is 300 Mhz bandwith with gain 420 to 800. Darlington connection to increase gain.

It's easy enough to try it out, I encourage you to do it. Try both, see which one you like.

I've extensively explored ideas like this, and arrived at v2 and then v1.5 after many, many things tried. But since you're curious, here's the darlington vs mpsa18.