Simplistic MosFET HV Shunt Regs

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
The input CCS is critical for compactness primarily. In the GB PCB it works with 100 Ohm gate resistors which is generally not that common, people use >=1K to damp the depletion semis, alas if you need to, it cuts PSRR dB max spec in the highs.
 
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AndrewT

R.I.P.
Joined 2004
crazyfrog said:
Those Sense and Force connections are needed to get the regulator performing well.
Click to expand...
No. they are used to minimise the effect of long resistive/reactive connections between the sensing circuit and the load. If the load is located at the Shunt mosFET and the sense traces were tapped into the same points then separate S & F would not be required. But, we can't build a practical load circuit where the load is at the FET leadouts.
Similarly if the load is directly connected across the reg output terminals, then the S would be connected to the F at the output terminals, as I suggested above for "easy" implementation.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
crazyfrog said:
Forgive my lack of knowledge but that four wires out looks complicated to me. Usually I just have to deal with "in, out and adjust"...

I want to use the SSHV2 with my 12B4 preamp (Salas version).

A bit more information would be welcome.

Thanks.
Click to expand...

The subjective upgrade will not reach 100% potential if you will skip the 4 wire connection. The longer the cables the more the benefit to have by changing your now traditional power feed double wire run in an already made build. It will work in the classical way if the force and sense are closed right at the reg's output connections if rewiring is a hassle no problem, but do try to upgrade later. Recommended for SSHV2.

Caution: Don't operate the reg without sense and force closing circuit either remotely or locally. It may bring damage to the reg.
 
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crazyfrog

Member
Joined 2009
AndrewT said:
No. they are used to minimise the effect of long resistive/reactive connections between the sensing circuit and the load. If the load is located at the Shunt mosFET and the sense traces were tapped into the same points then separate S & F would not be required. But, we can't build a practical load circuit where the load is at the FET leadouts.
Similarly if the load is directly connected across the reg output terminals, then the S would be connected to the F at the output terminals, as I suggested above for "easy" implementation.
Click to expand...

Got the picture in the meantime. It looks like a commercial power supply I saw with some kind of "probe system" inside. It was connected to a pair of twisted cables. But the current was much higher and the voltage much lower. The situation is different here. High voltage with low current seems less critical.
 
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gianmaria

Member
Joined 2004
SSHV1 for 60 Volts / 50mA output

Dear Salas, All,
I built SSHV1 for 300v, I would kindly like to know if the same circuit may be adapted for 55-60 vout and 80-90vin with 50-60mA load and which value I may use.

I searched the threads (not all) :( but I didn't find it.
I found one in the SSLV1.1 but I would like to implement it with the SSHV1 circuit.

Which value should I modify on the SSHV1 official schematic that can be find here:

http://www.diyaudio.com/forums/powe...stic-mosfet-hv-shunt-regs-97.html#post2084348



Thanks a lot in advance for your help!

Gianmaria
 
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AndrewT

R.I.P.
Joined 2004
@ 60mA & 35Vdrop, the CCS FET will need to dissipate 2W. It needs a sink.

If the output is shorted, the dissipation jumps to 5.4W. Will the FET survive a shorted output? and return to normal working when the accidental short is removed?

One of the really nice features of a CCS Shunt regulator is that it can be bomb proof. But high input voltage makes this more difficult to design for, not impossible.
 
Brouilly

Brouilly

Member
Joined 2009
Salas said:
Stixx is correct.

Also if there isn't any special Wattage need for R6, you can use 1/4W. C3 is a dead end for DC, so virtually no energy consumption on R6.
Together they form a Zobel terminal block that helps transient overshoot performance. See how it overshoots at IRF840's gate for current without the Zobel.
Click to expand...

OK, so that is the reason for it. How about value? The smallest I have is 1R or 2R.

Thanks
 
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