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THE AM BULLETIN BOARD => Technical Forum => Topic started by: KK4YY on May 02, 2019, 08:00:33 PM



Title: A Dual Regulated HV DC Power Supply
Post by: KK4YY on May 02, 2019, 08:00:33 PM

Needing a dual rail HV regulated power supply, and not wanting to buy p-channel mosfets, I put this together and it worked. As can be seen, there are two identical voltage doublers/filters/regulators connected in series and tapped at their junction for the common leg.

A dual secondary transformer is required and I had a Triad N-68X isolation transformer on hand. Wiring it "backwards" did the trick.

I was worried that the negative rail might oscillate, but it didn't. Maybe I'm just lucky.

Most of the components used were items I had in the junk box so the values shown are not specific to the design. The drawing is "as built".

I haven't seen this implementation used anywhere else, so I'm posting it here.


Don


Title: Re: A Dual Regulated HV DC Power Supply
Post by: Opcom on May 02, 2019, 10:43:37 PM
Very nice! I'm glad to see worked-out linear type MOSFET regulators of one polarity for these voltages. Some things like this were done with tubes back in the old CRT scope days. I appreciate this for tube op-amps.  :)


Title: Re: A Dual Regulated HV DC Power Supply
Post by: MikeKE0ZUinkcmo on May 03, 2019, 07:09:36 AM
FETS make these types of projects SO easy.   

I made a few HV and bias, adjustable, regulated supplies (https://mikeharrison.smugmug.com/PROJECTS/Power-Supply-Project/i-gLS93gs/A) so I could run most any tube rig.


Title: Re: A Dual Regulated HV DC Power Supply
Post by: KK4YY on May 03, 2019, 08:51:49 AM
I built this to power a mosfet audio driver that I've been planning for my DX-100.

I could have taken excising power from the transmitter by bridging the LV power supply, but then I would need a p-channel fet to regulate it because there's no way to work this out with a center-tapped transformer. So, I ventured into the unknown (at least to me) and went with this circuit.

My thought was to let this supply run constantly and bias the audio driver fets to cut-off during stand-by. This would remove the load from the supply and prevent audio drive to the tube grids during receive. I haven't yet worked-out the details of how I'm going to do that, but it will be part of the T/R switching one way or the other.


Don


Title: Re: A Dual Regulated HV DC Power Supply
Post by: WBear2GCR on May 03, 2019, 09:25:21 AM
Hey Don!!

Maybe you could share the supplier of those "0 ufd/400v caps??   :o 8) ;D




Title: Re: A Dual Regulated HV DC Power Supply
Post by: WBear2GCR on May 03, 2019, 09:34:37 AM
FETS make these types of projects SO easy.   

I made a few HV and bias, adjustable, regulated supplies (https://mikeharrison.smugmug.com/PROJECTS/Power-Supply-Project/i-gLS93gs/A) so I could run most any tube rig.

Mike, very nice job!
I got worn out just looking at the work that went into it! :D
Had to sit down, rest.

Did you use a decal for the meter face, or was the paint to keep from the old meter face
from bleeding through?

No need to sand it off, just flip it over??

                           _-_-

I had no idea that Daystrom was ever in Newark NJ!!


Title: Re: A Dual Regulated HV DC Power Supply
Post by: KK4YY on May 03, 2019, 05:41:27 PM
Bear,

Thanks for noticing the zero cap — I can see that you're paying attention. It's on the drawing because I intend to use a cap there but, being true to "as built", I zeroed it out for this posting. I can tell that I won't be able to get much past your keen eye. ;)


Don


Title: Re: A Dual Regulated HV DC Power Supply
Post by: KK4YY on May 03, 2019, 06:00:02 PM
Admittedly, this design is a work-around for not using a p-channel fet. I wondered if I could find a way of doing it. It looked good on paper, so...

About the only time this circuit may be necessary would be where the desired voltage is high enough that p-channel fets aren't available, perhaps above 600V.


Don


Title: Re: A Dual Regulated HV DC Power Supply
Post by: Opcom on May 03, 2019, 08:47:21 PM
The regulation quality and simplicity combination is exceeding good compared to similar-function bipolar or vacuum tube circuits. I tried LTspice on it, very nice performance.

Modulator!! Hmm.. a conventional MOSFET audio amp running on a nice regulated +/- 250V supply could destroy many speakers! haha >3KW into 8 Ohms.


Title: Re: A Dual Regulated HV DC Power Supply
Post by: MikeKE0ZUinkcmo on May 03, 2019, 11:06:03 PM
Quote
...No need to sand it off, just flip it over!!...
Randy, I'm not that smart, I had to do it the hard way!! ;)

Actually just printed it on regular paper with the Lazer, using TONNE (http://www.tonnesoftware.com/) software.


Title: Re: A Dual Regulated HV DC Power Supply
Post by: KK4YY on May 04, 2019, 08:10:42 AM
Patrick,

My measurements show...

At turn-on the voltage quickly reaches about 98% of the stable voltage. The last 2% takes a few minutes before settling down (the rails track each other well though). This would cause a very small, proportional change of the modulator grid bias of perhaps 0.2%. I could live with that. Better still, letting the supply run constantly eliminates that warm-up characteristic.

When I apply a 10k load (24mA) I get an initial 1% voltage drop that slowly settles to about 2%.

Considering that there's no thermal compensation or feedback circuitry, I'm well pleased with the result. It should be more than adequate for my application.

Thanks for running the sim.


Don
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands