Simplistic MosFET HV Shunt Regs

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I would like to ask about some high wattage resistor types , which should be used in the HV shunt.( in 300 V , out 250V )d

I know there was sugestion to use carbon resistors for R2 ; R6; R9 as gate / base stopers - if I understand correctly it should be carbon composition because of the low inductance ( what about the noise ?)

But what about R3 ; R4 ; R5 ? Normaly I would use low noise , non inductive wire wound but here comes the voltage limitation.
Other solution would be film type non indutcive ( MP930 Caddock )
- but they cost a lot of $$$ and hard to find in all needed values

There is no serious thing with noise on gate stoppers, almost no current passes, but the loop phase margin is so big that if you don't have, use metal film.

Only R4 is the voltage reference and some normal 2W metal will do. Low ppm special is surely better. If you can afford only R4 will be OK.
 
I would mirror it for you guys but I have no symmetric HV gear to test it. Sorry.

Being me a proud owner of a OTL headphone amp (The Tube CAD Journal, Electrostatic Headphones), I'd like to try...
Currently, I'm feeding it with two (basic) positive regulators, one atop another, being the (minus) of the upper tied to the (plus) of the lower, and both to the ground. Is this a correct practice? Is it also applicable to shunt regs?

Thanks
 
I read all the thread. (That was long)

Why the idea of using the DN2450 or the IXYS as a ccs was abandoned ?

Salas and other expert, I posted in the GB thread a draft of step by step instruction on how to setup the regulator. Could you kindly have a look at them ?

Thanks,

Davide

I think the DN2450 and IXYS crap out at around 60mA's, so unless you paralell several they are too weak for a lot of applications.
 
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90% of pages in such threads are chronography.:) I hope you had a good picture of what people can do right wrong or how they feel about the application, ideas, examples, pride, frustration, learning curve etc. Let us know your experience too.

Regards
 
Lost in Translation

Salas,

Here are three Japanese candidate for a 400 V 100mA shunt. What do you think ?

It's funny how Japanese can be patriotic, they have all their components series. If you ask for a vulgar BC transistor they look at you like you are a loser :).

Thanks,

D.
 

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diyAudio Chief Moderator
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The pnp looks nice for a 400V device. Has nice hfe curve that holds for little current and good dissipation. Should work. The Mosfets look much slower, especially the PMOS VS IRF9610. But the NMOS is double the IRF840 Ciss also. Will change the loop gain shape and BW. There is a big stability margin built in the design, they may still work, but its a big risk to make off hand predictions. Will be inferior to the original most likely.

P.S. IRF9620 is good enough if you can't get IRF9610.

P.S.II Their low Rbb BJTs from ROHM, Hitachi, Sanyo, Toshiba, the Jfets, their Sankens, their laterar Mosfets etc. are works of art.
 
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Do they carry the IRF VMOSFET series in stores there easy to get?
 

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My build of Simplistic Mosfet HV Shunt Regs

Hello Salas,

I have completed and tested the build of Simplistic Mosfet HV Shunt Regs using Quanghao's PCB. It looks nice. :)

The voltage of my build after CRC filtration is about 308 volts. The CCS resistance is 33R and I use IRF610 as the CCS PMOS. I use 135K as the voltage reference after 2SK170 and 60K as the current limiter for the LEDs. Other components are exactly the same as your model build. My desired voltage is about 270 volts for the DAC-end tube stage that consumes about 30mA.

After the regulator is turned on and adjusting the VR, I got about 252 volts that slowly creeps to about 269 volts in an hour's time and settles down within +-0.5 volt. The voltage across the 33R is 1.803 and I assume that it's working perfectly. Am I right?

I also roughly measure the AC output ripple that's less than 0.5 mV using Fluke 189 but it's fluctating very rapidly (I know this is crude). Is the circuit oscillating? Should I use back IRFP9240 as the PMOS? :confused:

Thanks in advance for any response.

All the best,
housing
 
Hello Salas,


I also roughly measure the AC output ripple that's less than 0.5 mV using Fluke 189 but it's fluctating very rapidly (I know this is crude). Is the circuit oscillating? Should I use back IRFP9240 as the PMOS? :confused:

Thanks in advance for any response.

All the best,
housing

A shunt regulator won't hold a constant voltage (it will drift with the mains.)

Two things you can do without a scope.

1. See if you have this sort of oscillation on your mains.
2. Hold an am radio up to the regulator board and see if you here interferance, if you do there is an oscillation problem.