Variable step up dc-dc converter.

I used a simpler circuit to generate hv for a dekatron clock I built, I used a 555 and a voltage doubler nicked from another better supply using a motorola chip, heres a ref to the said supply let me know if its of interest(second and third schematic on the page):

https://threeneurons.wordpress.com/nixie-power-supply/

Its been used a lot in the neon clock world and seems efficient and reliable.

dr pepper said:

I used a simpler circuit to generate hv for a dekatron clock I built, I used a 555 and a voltage doubler nicked from another better supply using a motorola chip, heres a ref to the said supply let me know if its of interest(second and third schematic on the page):

https://threeneurons.wordpress.com/nixie-power-supply/

Its been used a lot in the neon clock world and seems efficient and reliable.

Click to expand...

I Don't find it Any Simpler if you want 300 Volts and I am Quite Sure that will Draw a LOT More than the 10mA of my circuit.

What I had in mind was fairly similar to the circuit you linked us to, I meant it was simpler than the circuit the o/p posted earlier, wasnt knocking your design.
It is possible to get 300v without the doubler no problem, I've needed multiple supplies so I've used a doubler in my circuits.
10ma is very efficient.
Didnt see on your page what the transformer was, is it part of the original counter or is it a fuji disposeable camera transformer, if the latter some of the guys on the nixie forum might be interested.
For some reason 555's are frowned on by some for making power supplies for clocks, I find it a perfectly acceptable circuit, the circuit I modded uses an npn transistor to regulate the o/p via pin 5 of the 555, the dekatron version regulates the 500v o/p.

The Transformer is from the Origional Circuit, but it is Available as a Seperate part from Goldmine Electronics
It is VERY TINY, only about a 3/8 * 3/8 * 3/8 inch Cube.
Their Part number is G13599.

I had a go at making something that size, and that voltage, didnt work that well, I dont know how they get the insulation good enough to make high voltage.
I spsoe it'll be wound on a machine.
It looks a bit like the disposeable camera ones, core material could be wildy different though.

chemelec said:

Here is the Origional Circuit.

I Assume that the Leakage through the Transformer In Both these circuits is Completing the path.

If I Connect the Common of the Transformer to the Battery Negative it Makes NO Difference in the Operation of Either of these.

YES the Transformer is ISOLATED between Primary and Secondary.

Click to expand...

Hi,


Oh ok, well i would go with the more definitive return path, but it's up to you.

I would check one more thing also, the reverse voltage of the base emitter of Q3 (this current drawing) to see if it ever goes exceptionally negative. I suppose a scope should do it. Waveforms on the + of the tube would be nice to see too

Interesting circuit there. I've never built one myself but a friend of mine and me were talking about the possibility because of the problem in Japan not too long ago. We dont know what we are getting from them now.

dr pepper said:

I had a go at making something that size, and that voltage, didnt work that well, I dont know how they get the insulation good enough to make high voltage.
I spsoe it'll be wound on a machine.
It looks a bit like the disposeable camera ones, core material could be wildy different though.

Click to expand...

A Close-up Picture of T1
Primary = 510uH
Secondary = 470Mh

I would have thought that, given the specs of the tube, it would be prudent to design your own from scratch. The hardest part would be the transformer, but as these often use audio transformers, given a bit of measurement and maths you could work out the best frequency to drive it with. Back in the day I used to copy/test circuits from the web, with some success, many failures. That is not because people post 'bad schems' but purely because available parts vary widely across the world, and often they are the critical parts to the function (in this case, the transformer etc..).

Disposable camera transformers are flybacks, not really designed for forward operation, basically coupled inductors rather than transformers. Also given the fact they tend to quite quite massive turns ratio's to reduce the stress on the switching transistor, along with the fact they run of 1.5-3V (stepping up to ~300V) the output voltage *could* be huge. But of course, no-one likes winding their own transformer. As we're talking <mA here, audio transformers should be fine, and with a voltage multiplier the secondary voltage of said transformer will be orders of magnitude lower than the voltage required by the tube, so insulation shouldn't be a worry.

Looks like the primary is on top there, I dont spose really close coupling would be critical though.

I dont think an audio transformer esp the likes of an op44 or lt77 would be a good idea, they are not meant for such voltages, I remember years back there was an article in ee that lit a neon with a op44 trans, a blobking oscilltor or as they now call it a 'joule thief'.

dr pepper said:

I remember years back there was an article in ee that lit a neon with a op44 trans, a blobking oscilltor or as they now call it a 'joule thief'.

Click to expand...

A neon bulb needs at least 70V to light.
But an LED needs only 1.8V for a red one or about 3.5V for a white or blue one.