electronaut
Well-known member
Hmmmmmm.......
I've been trying to work out a solution to this regulated B+ circuit and every direction I turn I seem to bump into a different wall.
Here's the goal:
Design a (reasonably simple) regulated high voltage (325V) power supply circuit capable of providing up to 40 mA, and as little as 12 mA, while being as clean and ripple-free as possible. Soft-start or timed delay required.
In order to keep with the "reasonably simple" requirement, I've decided against tube regulation, favoring a floating LM317 instead -- a modified and tweaked version of the circuits in Morgan Jones' book.
For the soft-start, I initially chose a 6X4 since those tubes are indirectly heated and have a natural delay, but I need about 50V drop-out across the regulator which means I need a minimum 375V at the second filter cap, and about 395 at the first filter cap. The regulator eats a few mA so round up to 50 mA, which at 395V is just outside the permissible range of the 6X4.
So I looked into the 6X5, but it is directly heated which means another transformer winding, plus I assume it will not have the same soft-start characteristics as an indirectly heated tube.
The EZ80 and EZ81 seem like possibilities, but from I can tell by looking at the datasheets, they would produce nearly 500 volts DC at input to filter when loaded lightly (12 mA), which means the regulator would have to drop out like 155 volts after the second filter which seems kind of insane.
So I could go with a solid-state rectifier and some kind of timed relay thing, but admittedly that kind of bugs me -- seems like just another gadget to break, plus I like the coincidental advantages of the indirectly heated tubes... but I am open to such a thing if there are no other practical options.
Lastly, I'm stumped by this whole idea that the resistance in series with the rectifier plates must be greater than Rs + N2 * Rp, where:
Rs = secondary resistance
N2 = square of the turns ratio
Rp = primary resistance
What the heck are they talking about? What resistance in series with the plates? I've tried to work this out but all my numbers seem very high, which I guess is a good thing but I may be doing it wrong.
Here's the current, not-quite happening plan:
Anyone have any suggestions?
Thanks, as always.
E.
I've been trying to work out a solution to this regulated B+ circuit and every direction I turn I seem to bump into a different wall.
Here's the goal:
Design a (reasonably simple) regulated high voltage (325V) power supply circuit capable of providing up to 40 mA, and as little as 12 mA, while being as clean and ripple-free as possible. Soft-start or timed delay required.
In order to keep with the "reasonably simple" requirement, I've decided against tube regulation, favoring a floating LM317 instead -- a modified and tweaked version of the circuits in Morgan Jones' book.
For the soft-start, I initially chose a 6X4 since those tubes are indirectly heated and have a natural delay, but I need about 50V drop-out across the regulator which means I need a minimum 375V at the second filter cap, and about 395 at the first filter cap. The regulator eats a few mA so round up to 50 mA, which at 395V is just outside the permissible range of the 6X4.
So I looked into the 6X5, but it is directly heated which means another transformer winding, plus I assume it will not have the same soft-start characteristics as an indirectly heated tube.
The EZ80 and EZ81 seem like possibilities, but from I can tell by looking at the datasheets, they would produce nearly 500 volts DC at input to filter when loaded lightly (12 mA), which means the regulator would have to drop out like 155 volts after the second filter which seems kind of insane.
So I could go with a solid-state rectifier and some kind of timed relay thing, but admittedly that kind of bugs me -- seems like just another gadget to break, plus I like the coincidental advantages of the indirectly heated tubes... but I am open to such a thing if there are no other practical options.
Lastly, I'm stumped by this whole idea that the resistance in series with the rectifier plates must be greater than Rs + N2 * Rp, where:
Rs = secondary resistance
N2 = square of the turns ratio
Rp = primary resistance
What the heck are they talking about? What resistance in series with the plates? I've tried to work this out but all my numbers seem very high, which I guess is a good thing but I may be doing it wrong.
Here's the current, not-quite happening plan:
Anyone have any suggestions?
Thanks, as always.
E.