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+150V DC Vacuum Tube Regulated Power Supply?
+150V DC Vacuum Tube Regulated Power Supply?
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Old 11th June 2018, 10:49 PM   #71
Wavebourn is offline Wavebourn  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Here was my exercise with soft starting source of B+ and filament voltages from the single supply. It was an overkill, so I never used it any more.
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Old 12th June 2018, 02:48 AM   #72
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Wow, lots of great stuff to think about here! Thanks Elvee. Let me ask about one thing:

Quote:
Originally Posted by Elvee View Post
Why do the sim figures look so good for the IRF820-based follower? I suspect that their origin is to be found in the spice model, which does not include the lambda parameter, just a Rds value
You're right! Since these are just models, meant to get me in the ballpark, do you think it would be helpful to use a different MOSFET model in place of the IRF820? I have one for STMicro STP8NM60 (600V) which has Lambda=0.005 in its model.

Do you think it might be helpful to add Lambda=0.005 to the IRF820 model, to see what happens?

More later. I haven't had time to look at your suggestions today. Weird day today, lots of distractions.
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Old 12th June 2018, 04:30 AM   #73
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
I put the version of the series regulator with 150V voltage reference, DN2540 error amp and STP8NM60 series pass element into LTspice. It does squash ripple a lot better than the cap-multiplier/source follower with VR.

Adding "lambda=0.005" to the IRF820 model only resulted in an error and failure to find DC operating conditions. That's a fail.

Differences in simulation between IRF820 and STP8NM60 are minimal.

If I did the vacuum tube version I'd have to make a single psu for both channels, so 115mA total load. I have three octal sockets in the chassis that could be used for power supply devices. I could see using a triode-wired 6AC7 and a paralleled-up 6AS7G along with the 0D3.

The solid state version would be easier to wire up.
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Old 12th June 2018, 06:23 AM   #74
Wavebourn is offline Wavebourn  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Wavebourn View Post
Here was my exercise with soft starting source of B+ and filament voltages from the single supply. It was an overkill, so I never used it any more.
Oops... sorry, I meant bias, not filament. Bias is shunt regulated, and acts as a reference voltage source for B+ regulator. They are connected in series. It starts slowly, while tubes do not draw current, and as soon as they start drawing current, voltages go up then get stabilized.
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Old 12th June 2018, 02:41 PM   #75
Elvee is offline Elvee  Belgium
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If the polarity of the ground is indifferent, it is possible to rationalize the circuit, and make it LDO, which can be useful in some situations.

A small complication is necessary to handle the startup, but it could be used to advantage to implement a standby switch with two (or maybe one) pushbuttons.

Otherwise, many options are workable, for example a RC circuit or a diode like here.
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Old 12th June 2018, 05:46 PM   #76
Wavebourn is offline Wavebourn  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Elvee View Post
If the polarity of the ground is indifferent, it is possible to rationalize the circuit, and make it LDO, which can be useful in some situations.

A small complication is necessary to handle the startup, but it could be used to advantage to implement a standby switch with two (or maybe one) pushbuttons.

Otherwise, many options are workable, for example a RC circuit or a diode like here.
You can add a current sensing resistor in source with Zener to gate, to limit current. Also, a cap in series with resistor R6 and a button across it, for latching when output is shorted, and starting back manually.
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Old 13th June 2018, 02:41 PM   #77
Elvee is offline Elvee  Belgium
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Something like that:

+150V DC Vacuum Tube Regulated Power Supply?-simplehv7wb-png

Here is the one-button toggle. C3 cannot be too large, otherwise the supply restarts by itself when switched off (C1 could be increased, if necessary)

+150V DC Vacuum Tube Regulated Power Supply?-simplehv7sw-png
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File Type: png SimpleHV7sw.png (32.7 KB, 115 views)
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Old 13th June 2018, 07:21 PM   #78
Wavebourn is offline Wavebourn  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Yep. Bench power supply.
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Old 14th June 2018, 04:46 PM   #79
rongon is offline rongon  United States
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+150V DC Vacuum Tube Regulated Power Supply?
Quote:
Originally Posted by Elvee
most of the efforts involved in this circuit are in fact wasted

Click the image to open in full size.

The reason is that a simple, no-feedback source follower or capacitance multiplier has a finite ripple rejection, no matter how clean is the reference: the fault is on the lambda parameter, which has an equivalent in tubes (particularly triodes) or bjt's.

This means that M4, the regulator tube and C9 are mutually redundant.
OK, I think that means the DN2540 CCS does not improve performance over a simple resistor to set current draw for the zener+0D3. If so, point taken.

Let's say I decide that the simpler form of this circuit has acceptable ripple suppression and output impedance for my needs. I would then use a 3.3k 2W resistor in place of M4 and R17, R18.

That would leave me with the IRF820 source follower (M3) with the 0D3 and 15V zener diode in series as a 165V reference, with the bypass caps for the zener and 0D3, and R16 (220k 2W, the bleeder resistor).

The 0D3 is just for looks. I have a few and I want to use them.

R15 (47k) and C9 (33uF) are meant to provide a slow ramp-up of voltage from the 0D3+zener. That sounds like it should be useful, it's very easy to implement, and I have those parts handy.

(See second attached schematic)

I can mount the zener diode, 220k and 3.3k resistors, and bypass caps for the zener and 0D3 right on the 0D3 octal socket. That leaves only the IRF820 and a handful of small resistors on the perfboard (which is now stuffed), with plenty of room for R15 and C9 (the slow-start RC network for the IRF820+zener+0D3).
--

I'm curious whether this simple source follower will do the job. If not, I can convert to the circuit you recommended earlier (see first attached schematic).
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File Type: png 160V_series-reg_psu.png (10.5 KB, 21 views)
File Type: png 160V_source-follower+Vreference.png (7.3 KB, 22 views)
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Old 14th June 2018, 06:49 PM   #80
Sodacose is offline Sodacose  United States
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I've used the simple no-feedback source follower to set B+ in circuits in the past, but it is preceded or followed by additional filtering. I haven't tried feeding the VR with a CCS personally and just suggested that on a hunch, thinking it may reduce ripple picked up at the gate of the pass MOSFET by increasing the impedance of the upper part of the reference divider.

What Elvee is saying makes sense to me though and I'm happy to learn something in this case. Saves parts cost/complication at any rate. I do like the simple all SS closed loop regulator Elvee posted, too. Like rongon, I like to add some visual interest to a PSU occasionally, hence the original FET+VR circuit.
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