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+150V DC Vacuum Tube Regulated Power Supply?
+150V DC Vacuum Tube Regulated Power Supply?
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Old 25th May 2018, 08:41 PM   #21
GoatGuy is offline GoatGuy  United States
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Quote:
Originally Posted by Lingwendil View Post
Also, GoatGuy, check your PM inbox lol
LOL - OK, I will.

But in the meantime … shouldn't the cathode-ring of D3 and D2 be reversed? I would think you're trying for a full-wave bridge. (Actually, without their legend reversal, this is a "do nothing" circuit.) … just saying.

Also, it looks like you've shown both sides in the upper drawing (blue & red), but only one side (red) in the lower graphic. No worries… we "get it", I'd guess.

PRETTY SWEET layout. Might I suggest … "since its free", that the yellow colored legend layer also have "VAC-IN" on the left connector and V+ on U₃, and V- on U₂. Its free.

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Old 25th May 2018, 08:58 PM   #22
Lingwendil is offline Lingwendil  United States
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+150V DC Vacuum Tube Regulated Power Supply?
I'll add those, and I know there are some obvious (diode) errors, I'm ironing it out slowly but surely

I'm going through it in more detail in my flea amplifier thread too, so feel free to lurk over there too.
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Old 25th May 2018, 09:58 PM   #23
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Sodacose View Post
Right, I was referring to replacing R2 but maintaining the MOSFET pass device.
I tried that too. In simulation it made zero difference.

Quote:
Originally Posted by Sodacose View Post
Lingwendil's board looks good too. I recently made some boards that use an LR8 in place of the zener string (yet to stuff and test though). Only problem is these don't glow
Yeah, and I'd have to buy stuff, too. This is a definite junkbox project.

That National Bureau of Standards Preferred Circuits book that Merlin suggested has a nice circuit, the NBS Preferred Circuit No. 1. I altered it a little to use 6AC7 and 0D3, by changing the -150V negative supply to -225V. I also had to futz with some resistor values, but I think I got it.

With a 100mA load and the 100k adjustment pot set to 50%, the output voltage is +168V. That's fine. Adjustment range is from 152V to 182V. Ripple attenuation is about -70dB. It looks pretty OK.

I need to check out GoatGuy's refinements to that MOSFET-0D3 circuit you suggested. That's a lot simpler.
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File Type: jpg NBS Preferred Circuit No1 - 150V voltage regulator.jpg (164.9 KB, 211 views)
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Old 25th May 2018, 10:48 PM   #24
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by GoatGuy View Post
Here's circuit I'd use, incorporating the advice, and showing markedly improved ripple rejection.
Thanks. That really does look like a winner. Kinda nice that it's a collaborative effort.

I changed a couple things.

- Changing R1 to 47k makes a 3W part necessary. If I have one, I'll do it. But I know I have some 100k 2W. Changing the values around doesn't seem to change things very much. Why did you want to see more current going through R1?

- If R2 is changed to 10k, the output voltage goes down to 142V, because the 0D3's voltage dips with less current through it. The sim says an R2 of 4.7k gets the 0D3 to draw about 12.5mA, and output voltage rises to 145V. I guess that 3V won't matter. This will need to be sorted out if/when built.

- I added a gate protection zener (12V).

- For R0, a 1k resistor with 110mA through it would dissipate 12W, which is way more heat than I want to deal with. Instead, I substituted a 10H choke with 141 ohm DCR I have on hand. If C1 is 100uF, LTspice says there will be a low-Q +5dB resonance centered around 5Hz. I have some 800uF 330V caps, so I put that in for C1. The resonance was completely smoothed out, and ripple is reduced a lot. What I don't know is what that high a capacitance will do at turn on. It'll make for quite a surge, I'm sure. If I blow rectifier diodes, then I'll swap in a smaller value.

- With all that filtering before the stabilizer, it doesn't make much difference what value is chosen for C3. Since I have some 20uF 400V metalized polypropylene caps, I figure this would be a good place to use one. The ESR of the film cap will be very low.

With all that in place, LTspice says ripple rejection will be on the order of -95dB. That's crazy good. Schematic attached.
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File Type: jpg 150VDC_VoltageStabilizer_IRF820-0D3_00.png.jpg (59.1 KB, 204 views)
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Old 25th May 2018, 11:35 PM   #25
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
oops. Mistake in that last schematic. The zener diode D2 destroys it. Take that out.
With D2 from gate-source of the MOSFET, the output voltage drops to 86V.
I don't know why it does that. I don't understand...
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Old 26th May 2018, 05:25 AM   #26
PRR is offline PRR  United States
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Quote:
Originally Posted by rongon View Post
... Hey Merlin! That's very helpful indeed. Preferred Circuit No. 1 fills the bill. The only problem is the need for that negative supply...
The negative supply is not essential. If you are an experienced circuit-bender you can re-rig without it.
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Old 26th May 2018, 10:18 AM   #27
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by rongon View Post
oops. Mistake in that last schematic. The zener diode D2 destroys it. Take that out.
With D2 from gate-source of the MOSFET, the output voltage drops to 86V.
I don't know why it does that. I don't understand...
Did you put the diode the wrong way ? Or has it to much leaking current ?
Originally Posted by rongon Click the image to open in full size.
... Hey Merlin! That's very helpful indeed. Preferred Circuit No. 1 fills the bill. The only problem is the need for that negative supply...

Perhaps try it this way

Mona
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File Type: jpg 150Vregulator.jpg (42.2 KB, 176 views)
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Old 26th May 2018, 03:28 PM   #28
euro21 is offline euro21  Hungary
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by rongon View Post
oops.
It's working.
But... output impedance below 5kHz is over 1 Ohm!
10kHz 0.7 Ohm
100kHz 0.08 Ohm
Attached Images
File Type: jpg simple 150V PSU.jpg (64.8 KB, 160 views)
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File Type: asc 150V PSU.asc (2.3 KB, 8 views)
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Old 27th May 2018, 01:25 AM   #29
PRR is offline PRR  United States
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Quote:
Originally Posted by euro21 View Post
It's working. ... But... output impedance below 5kHz is over 1 Ohm! ....
Of course. It is a cathode- (source-) follower with no error amplifier. The true Z out will be the cathode (source) impedance. Which *varies* with device current. And at 50mA, probably several Ohms.

Here this device impedance is swamped by 20uFd, which is why you have Zout as low as you do.

Note that (without a cap) the Zout is true only for the device passing current, pull-up. If the load "kicks back", device current goes to zero and device Zout goes to infinity.
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Old 27th May 2018, 01:33 PM   #30
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Thanks for your input everyone. Okay, about that simple source follower...

If the usage is in a stereo headphone amplifier, with a pair of triodes run as common cathode amplifiers loaded by output transformers, the load on this simple source follower/voltage stabilizer would be pretty much constant... Correct?

If the load (current draw) is constant, then under what circumstance would the load "kick back"?
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