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Old 26th July 2013, 02:07 AM   #1
qwe123 is offline qwe123  United States
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Default Inductor Fed VR Tube

Would it be beneficial to feed a voltage regulator tube with an inductor (as in the following pic)?


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I'm thinking that a 50vdc air-gaped reed relay coil would do the trick. They measure about 1.9k each (@ 2mH), so they should be able to handle around 25mA.


Perhaps this would filter some of the power line RF which the tube is unable to regulate.


Would there be any potential issues?


Would a flyback diode be in order? So as to prevent subtle sagging in the regulation if switches happen to open/close the load.


Would this actually be useful at all, or just a fancy resistor substitute?
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Old 26th July 2013, 02:16 AM   #2
AJT is offline AJT  Philippines
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for me yes, the inductor present more impedance to ripple frequency
than a resistor alone....
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Old 26th July 2013, 03:23 AM   #3
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The voltages you have posted are in line with a CCS application using a DN2540 or the IXYS equivalent. Will work better than the inductor and cheaper too. Only possible catch would be meeting the needed striking voltage, which is greater than the operating voltage.
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Old 26th July 2013, 03:32 AM   #4
qwe123 is offline qwe123  United States
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Quote:
Originally Posted by zigzagflux View Post
The voltages you have posted are in line with a CCS application using a DN2540 or the IXYS equivalent. Will work better than the inductor and cheaper too. Only possible catch would be meeting the needed striking voltage, which is greater than the operating voltage.
Good point, but I want to avoid solid-state components in the signal path; I probably should have stated such.
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Old 26th July 2013, 12:58 PM   #5
DF96 is offline DF96  England
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Won't affect ripple at all. 2mH is far too small for that.

It may reduce RF, provided that the coil is wound in a way that it has a fairly high self-resonance frequency. This is unlikely for a relay coil. You will get some reduction of ultrasonic noise, but that is about all.
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Old 26th July 2013, 04:02 PM   #6
Magz is offline Magz  United States
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Quote:
Originally Posted by zigzagflux View Post
Only possible catch would be meeting the needed striking voltage, which is greater than the operating voltage.
I've found a neat way to do that is to use a choke input supply, set up so that the current needed for critical choke function can only be drawn if the VR tube is conducting. So, at initial turn on, the system acts more like a cap input and the voltage rises until the VR tube strikes, then it all settles down nicely into critical choke input.

The only caution I'd have is to be sure your compnents can handle the full cap input supply voltage, just in case of VR tube failure.
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Old 26th July 2013, 04:17 PM   #7
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VR tubes generally don't exhibit catastrophic failure.

you could add A zener diode specified at 10-20 volts above the neon striking voltage as a safety precaution.

V4lve.
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Old 28th July 2013, 03:33 AM   #8
qwe123 is offline qwe123  United States
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What about the flyback diode: useless?
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Old 28th July 2013, 03:07 PM   #9
DF96 is offline DF96  England
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What is the flyback diode for? Are you planning to frequently change the current draw and, if so, so what? What problem do you think you are guarding against?
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Old 28th July 2013, 03:51 PM   #10
qwe123 is offline qwe123  United States
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Snap action switches will be used to vary the load current from 0 - 7mA. Since diodes are so inexpensive, I always use flyback diodes on inductors if I can manage to convince myself that there may be a potential benefit.


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What is the flyback diode for? Are you planning to frequently change the current draw and, if so, so what? What problem do you think you are guarding against?
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