Simplistic MosFET HV Shunt Regs

[merlin el mago]

To adjust Vout I'm using 1K trimmer

 

[nemo1968]

Minimal Vin

Hi
Which is the minimal allowed Vin for this shunt to work properly.I need the voltage from 100 - 150.I don't have higher voltage transformers but only 110 - 130V on secondary and want to try the shunt.I use lot of subminiature valves with limited max. voltage possibility and this way the tubes would be protected to not get 250V in case of shunt failure with 250v input voltage (if I understood well what happening with the regulator failure).

Is that possible with filtered 150 - 170V on the shunt input?

Thanks to Salas and everybody around the shunt.

 

[Salas]

There is no downwards limit.

 

[nemo1968]

Thanks Salas. I was afraid of oscillations and eventual failure in that case.

 

[Salas]

You can make R3 33K so to keep around 5mA through the Leds when under 200VDC input too.

 

[nemo1968]

Yes, I was just in doubt which value to put there because of over 300 and under 300V R3 mods.

Thank you, again Salas.

 

[merlin el mago]

CCS

How to test CCS because LEDs don't lit & I have checked IRF9610 with a DVM & it's not crossed, also I checked proper oritentation LEDs also lit with 9V battery

 

[Salas]

Just check connections against schematic, exchange Mosfet, the usual troubleshooting.

 

[merlin el mago]

Fixed, was IRF9610

 

[pedefede]

Bypass C2 with Teflon if you can. Then we roll big way.

Since C1 also is important:
- can you bypass it as well
- i suppose so - but should the bypass cap be over just C1, or over both C1 and the 47ohm resistor?
- should the bypass be closest to the LEDS, or the mosfet?

 

[Stixx]

I'd say that C3 is way more important being the last one before the load...

 

[Salas]

C1 don't bypass, has a function as it is exactly. C2 is the voltage reference filter and has subjective impact. C3 is part of the Zobel termination, judge its influence.

 

[merlin el mago]

C1 don't bypass, has a function as it is exactly. C2 is the voltage reference filter and has subjective impact. C3 is part of the Zobel termination, judge its influence.

Good to know thank you, I wil bypass C2 with 0,1uF Russian teflon FT-3

 

[pedefede]

C1 don't bypass, has a function as it is exactly.

- does the value have to be excact 100uF - or can you go above/below ()?
- any suggestions for type? or just use normal "good" electrolyt caps? (I have some 180uF OS-con)

 

[Salas]

100uF normal electrolytic tolerance is sufficient. You don't need any special ESR, since its highly loaded with external series resistance. The function is to fill out a phase bump in the loop gain at the lows. Just use a reliable make.

 

[merlin el mago]

Good to know thank you, I wil bypass C2 with 0,1uF Russian teflon FT-3

Wooooooooooow big, big upgrade, thanks Salas

 

[Salas]

What type is your C2 you bypassed?

 

[merlin el mago]

Auricap 1uF

 

[Salas]

Good combination.

 

[merlin el mago]

Yes sounds very very good.