Maximum current with the 555 nixie supply?

[kupfer_m]

Hi,

I've build the 555-based nixie supply that can be used with tube projects.
Searched the forum but did not find an actual maximum current that this switcher can supply.
Did someone used at say 150V/50mA?
(Drawing by 'Frequencycentral') - link to actual pdf : http://www.ledsales.com.au/kits/nixie_supply.pdf



Thanks,
Jim

[Earthscum]

if someone answers, got another question: would a IRF730 work in this?

[valdiorn]

I first saw that circuit after I had spent two days designing the extact same circuit  
It was nice to see that at least my design wasn't totally bonkers, but I did a lot of research during the design time and I was aiming for something that could power 3 tubes (6 stages, maybe 20mA at worst) but at a supply of 350 volts.

One thing you need to think carefully about is the frequency of the timer compared to your inductor size (smaller inductor = better to use higher frequency). tune it to fit and your max voltage and efficiency will increase dramatically. If you tune it to low with the pulsewidth too high you'll saturate the inductor and the current drawn goes up, up, up and efficiency goes down, down down!

I also incororated a pwm circuit to tune the voltage better. Spice simulations showed it provided better control over the output voltage than the feedback, so in the end I dropped the feedback part in exchange for PWM (feedback isn't really needed for a pre-amp type circuit where current drain is pretty stable. with a 2k res and 47u cap low pass filter on the output rail it was the best regulated power supply I'd ever designed )

Use an 1n4007 diode, I also added a protection diode in series with the IRF740, the voltage goes batsh*t crazy once you shut off the current maybe it could protect the mosfet a little bit in case something goes wrong.

PS: I haven't built my design yet, but I've simulated the f*ck out of it and have alot of faith in it. I'm going to try to build it sometime next month. should not take long since it's so simple, just need to order some 740's

PS2: simulating switch mode supplies is a PAIN! it takes so long, and is so bad, infact, that I started to look seriously into running Spice simulations on my cluster

[kupfer_m]

No one tested it ?

[Pigyboy]

Check out Rick's thread. I think the 1771 is a better way than the 555.
http://www.diystompboxes.com/smfforum/index.php?topic=79736.0