Voltage Multipliers (for our tube projects...)

frequencycentral · October 30, 2009, 01:13:07 PM

A verified layout for the Nixie SMPS, I just built and tested it today. It's putting out 313 volts without a load. I haven't added the snubber yet, I want to experiment with that part. The snubber is made up of the 2.2K resistor and the 100pF cap in the Nixie schematic. I've an idea that changing the snubber values slightly will keep the B+ higher, so I thought I'd build the main part and hook it up to my breadboard to test different filterings. I used two 100uF caps instead of the 330uF, mainly to save on space.

Here's the link to the original file again: http://www.ledsales.com.au/kits/nixie_supply.pdf

tranceracer · October 30, 2009, 02:56:44 PM

Very nice!

Ice-9 · October 30, 2009, 05:05:15 PM

Thats looking really good Rick, and 313v as well. Were did you get that inductor i think i will build this SMPS to try with one of my 12ax7 designs.

frequencycentral · October 30, 2009, 05:15:48 PM

Quote from: Ice-9 on October 30, 2009, 05:05:15 PM
Thats looking really good Rick, and 313v as well. Were did you get that inductor i think i will build this SMPS to try with one of my 12ax7 designs.

Thanks guys. The inductor is this one: http://www.rapidonline.com/Electronic-Components/Inductors-And-Chokes/Leaded-Inductors/High-current-leaded-suppression-chokes/79278/kw/

The SMPS is for my next amp. I've got some 12AX7 and 12AU7 left over from my Valvecaster builds last year, and I bought a bulk lot of Fender Reverb Transformers (for my Murder Ones), so I thought I'd try a SE amp with 'proper big tubes' and a SMPS.

Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off! Completely useless to consider a 9 volt battery powered tube amp though.

tranceracer · October 30, 2009, 11:46:42 PM

Quote from: frequencycentral on October 30, 2009, 05:15:48 PM
Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off!

LOL!

Ice-9 · October 31, 2009, 02:24:51 PM

Quote from: frequencycentral on October 30, 2009, 05:15:48 PM

Just for fun, I connected the SMPS to a 9 volt battery today - and got 254 volts! I titter'd me t!ts off! Completely useless to consider a 9 volt battery powered tube amp though.

Yeah ! but to get 254v from a 9v battery is just something you have to try just to see it for real. Lol

frequencycentral · November 01, 2009, 01:04:09 PM

Here's a variation on the 555 SMPS with the addition of a negative charge pump section. Probably of interest to only one person on the planet (me), but developed so I can play with negative grid biasing my 5902 beam pentodes. Verified today on the breadboard. The red stars indicate where it is possible to tap off -11.5 volts and -22 volts, possibly useful for negative grid biasing other tube types.

earthtonesaudio · November 02, 2009, 07:34:22 AM

Does this require a heatsink for the FET?

frequencycentral · November 02, 2009, 01:22:55 PM

Quote from: earthtonesaudio on November 02, 2009, 07:34:22 AM
Does this require a heatsink for the FET?

Yeah, the IRF740 gets pretty hot. Without thermal dissipation it would eventually burn out I believe. I used the simplified version (ie without the negative charge pump) in my Superfly, there are pics of the heatsink I used in that thread: http://www.diystompboxes.com/smfforum/index.php?topic=78302.0

maarten · November 04, 2009, 11:00:58 AM

Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten

frequencycentral · November 04, 2009, 12:52:13 PM

Quote from: maarten on November 04, 2009, 11:00:58 AM

Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten

Bummer! My mistake, I'll correct the layout and schematic......

Cliff Schecht · November 04, 2009, 12:53:44 PM

It looks like a snubber circuit to me which goes in parallel with the FET's drain and source terminals. Or in this case, because you've got voltage-mode control, it goes from the drain to ground. These can increase efficiency in the FET by 20-30%, sometimes more with excessively ringing circuits!

frequencycentral · November 04, 2009, 01:06:06 PM

Quote from: frequencycentral on November 04, 2009, 12:52:13 PM
Quote from: maarten on November 04, 2009, 11:00:58 AM

Hello Rick,
why did you move the 2K2/100p to the other side of the 1N4004?
Maarten

Bummer! My mistake, I'll correct the layout and schematic......

Ok, both the layout and schematic (above) are now corrected. You may need to refresh your browser to see them. Oops.

g. · November 05, 2009, 05:24:24 AM

thanks for sharing !
i'm curious,
how many mA this supply can output ?

frequencycentral · November 07, 2009, 04:52:33 AM

^
^
Not sure how to measure for how many ma it puts out.

I was thinking that it should be possible to double the ma output by dupilcating the IRF740, snubber, inductor, diode and reservoir cap. ie two parallel SMPS running from the same 555. Obviously the current draw would be significantly higher, but using each of the parallel outputs to drive one dual triode (in a two dual triode design) should give significantly higher voltages and increased performance before saturation of the inductors occurs.

crystal · November 10, 2009, 03:17:14 AM

Neat design, but I do wonder why you've connected the negative grid biasing circuit to the gate of the mosfet. As long as there is virtually no load on the negative rail you will be fine else it will reduce the efficiency of the mosfet because the gate isn't driven hard enough. Wouldn't it be better to connect the negative charge pump to the drain of the mosfet?

Cliff Schecht · November 10, 2009, 03:45:05 AM

Quote from: frequencycentral on November 07, 2009, 04:52:33 AM
^
^
Not sure how to measure for how many ma it puts out.

I was thinking that it should be possible to double the ma output by dupilcating the IRF740, snubber, inductor, diode and reservoir cap. ie two parallel SMPS running from the same 555. Obviously the current draw would be significantly higher, but using each of the parallel outputs to drive one dual triode (in a two dual triode design) should give significantly higher voltages and increased performance before saturation of the inductors occurs.

You would have to sync the two oscillators to prevent beat frequencies from occurring. Just being 30 Hz off is enough to give you audible noise..

Also, I'm not sure how well a direct duty cycle supply will handle being paralleled. Current mode supplies are good at this because both can sense when the load has changed and will adjust accordingly. Direct duty cycle control OTOH just knows that more current = more duty cycle. One of the supplies may be able to try to pull too much current and fail. It may not be a problem with what you're trying to do but it's something to be aware of with simple switchers like these.

niopren · November 10, 2009, 11:32:05 AM

Quote from: g. on November 05, 2009, 05:24:24 AM
thanks for sharing !
i'm curious,
how many mA this supply can output ?

Nixie PS max. 10ma
just for one or two 12a*7

g. · November 11, 2009, 05:30:21 PM

i found this one : here http://www.unitechelectronics.com/NE-555.htm

QuoteA simple circuit to power a NEON lamp. Primarily used to test neons where safety is a requirement.
The R1 - R2 - C1 circuit determines the NE-555 to oscillate producing a voltage at Pin 3 driving
the small 8 ohm transformer's primary windings, the secondary windings are 1K ohms. It works.
This results in a ratio of 125 times gain, however we all know that's not going to fly. Losses ??
The theoretical voltage of 500 Volts AC passing through R3 10K dropping to around 180V AC
thus striking the gas within the neon and lighting it. This circuit was designed for pocket use.

manis404 · November 12, 2009, 12:42:47 PM

Is it possible to obtain like 400-422v with this system? I would use it to build a tube dual rectifier preamp - 4 12AX7s.

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Voltage Multipliers (for our tube projects...)