[TCML] SMPS as voltage source for a tesla coil

[Bert Hickman]

Hi Thomas,

The quick answer is yes, but the design can be a bit tricky. There are 
many ways, but all methods rely on being able to prevent the main spark 
gap from directly shorting out the HVDC supply.

A fairly elegant method uses a relatively large DC storage cap, an 
inductor and a high voltage blocking ("de-Q'ing") diode in a technique 
called DC resonant charging. This approach has the advantage of almost 
doubling the eventual voltage developed across the tank cap. This is the 
method Greg Leyh used on his large Electrum coil, and similar approaches 
are used extensively in many pulsed power applications. These systems 
are very efficient but may require a bit of balancing between inductor 
and tank cap sizes, gap dwell time, and gap break rate.

Another method simply charges the tank cap through a power resistor from 
the HVDC source. Although considerably less efficient than DC resonant 
charging, it will work and has the advantage of being simple. This 
approach burns up about 50% of the total input power in the series 
resistor.

Another method uses a clever arrangement of switching (via a properly 
configured rotary spark gap) to disruptively charge the tank cap from a 
"stiff" DC source (a larger HVDC storage cap). Similar to an H bridge, 
the spark gap reverses the charging polarity to the tank cap on 
alternate gap electrode presentations. Each "bang" does two things 
simultaneously:

1. disruptively charges the tank cap to the opposite polarity (from the 
previous bang) through the primary winding

2. The high current tank capacitor charging transients power the TC 
primary with a oscillatory waveform

Steve Young has used this approach with great success. As with resonant 
charging, this method effectively doubles the HVDC supply voltage seen 
by the tank cap, but it does not require a large inductor and de-Q'ing 
diode. This can be advantageous, since doubling the tank cap voltage 
quadruples the bang size for a given tank cap. Check Richie Burnett's 
site for details and equations on resistive and resonant charging:

http://www.richieburnett.co.uk/dcresist.html

Search the Pupman archives for the terms such as "DC Coil","H bridge 
RSG", "DC Resonant charging", and "DC H-Bridge" for additional information.

Good luck,

Bert

Ryckmans, Thomas wrote:
> Mmh I did read the Wikipedia entry beforehand, but I am still
> wondering... I have a few solid-state NSTs, 15kV, that I used to power a
> Jacob's ladder.
> 
> My question is, basically, "can one power a TC with a high voltage DC
> source"?
> 
> Many thanks
> 
> Thomas
> 
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of Mddeming at aol.com
> Sent: 16 April 2008 16:59
> To: tesla at pupman.com
> Subject: Re: [TCML] SMPS as voltage source for a tesla coil
> 
> 
>  
> In a message dated 4/16/08 11:27:32 A.M. Eastern Daylight Time,  
> Thomas.Ryckmans at pfizer.com writes:
> 
> Hello,
> 
> I am sure this has been debated to death... but I can't  find it. Can
> one
> use a SMPS to drive a Tesla coil? I understand that SMPS  are high
> frequency (>20 kHz) but what about rectifying this input? The  tank cap
> would get charged to breakpoint, the spark gap will fire...etc. I  think
> Greg is using this with a MOT setup (this give a 60 Hz pulse,  while
> rectifying a SMPS would give a 20 kHz pulse).
> 
> I am asking this  because I find it difficult to source cheap NST in UK,
> while SMPS are  easier to find
> 
> Cheers
> 
> Thomas
> 
> 
> Hi Thomas,
>  
> This may offer some useful background 
> 
> 
> 
> 
> 
> _http://en.wikipedia.org/wiki/Switched-mode_power_supply_ 
> (http://en.wikipedia.org/wiki/Switched-mode_power_supply) 
>  
> Matt D
> 
> 
> 
> **************It's Tax Time! Get tips, forms and advice on AOL Money & 
> Finance.      (http://money.aol.com/tax?NCID=aolcmp00300000002850)
> _______________________________________________
> Tesla mailing list
> Tesla at www.pupman.com
> http://www.pupman.com/mailman/listinfo/tesla
> _______________________________________________
> Tesla mailing list
> Tesla at www.pupman.com
> http://www.pupman.com/mailman/listinfo/tesla
>