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Re: Parallel resonant DRSSTC

Original poster: Sue Gaeta <sgsparky@xxxxxxxxxxx>

Thanks to all who replied. Most seem to agree on the impedance matching being a very big issue. I didn't think of that, and it makes sense since the solid state circuitry utilises much higher currents.

>Original poster: "Steve Conner" <<http://us.f814.mail.yahoo.com/ym/Compose?To=steve.conner@xxxxxxxxxxx&YY=84617&order=down&sort=date&pos=0&view=a&head=b>steve.conner@xxxxxxxxxxx>
>"Just my $.20 worth on this-

>1) Parallel resonant DRSSTCs do exist. I have seen two made by Vladimiro
>Mazzilli and Liviu Vasiliu. The secret is to make the inverter current-fed rather than voltage >fed.They used the so-called "Royer oscillator"push-pull circuit with two IGBTs. IMO this >SSTC design is very simple and elegant and deserves more attention than it gets. But it's not >so easy to use in pulsed operation because of the choke in the DC link."
There are quite a few of you guys on 4HV using this circuit to power flyback transformers, and getting really phenominal flaming discharges. Very impressive. Burt Hickman also mentioned this circuit to me quite a while ago, and said that it is a very good circuit. I want to persue this as a SSTC project for the future. As of this morning, I am finished playing with the P460s and I am going to start working on my DRSSTC using the 45 amp IGBTs. After I am done with that I want to play with a Royer circuit. As you said it looks like it needs more attention.

>"This is true. But remember that in the DRSSTC we need a very fast and violent delivery of >power to a resonator with a Q of about 10."

I like the way you worded that. "Violent delivery" :-)

>Original poster: "Black Moon" <<http://us.f814.mail.yahoo.com/ym/Compose?To=black_moons@xxxxxxxxxxx&YY=61015&order=down&sort=date&pos=0&view=a&head=b>black_moons@xxxxxxxxxxx>
>Just a random note, but maybe look at class C or class E rf amps? they effectively use solid >state parallel resonant circuits with low conduction time (or a ring circuit to provide low turnon >voltage/current in class E and hence very low turnon loss and extream efficancy 90%+)
I remember that I posted a link on here a while ago, where the guy went into a lot of detail about how to design class E transmitters. <http://www.classeradio.org/>http://www.classeradio.org/ I have to admit that I only read a little bit of it. I think I need to go back and study it more thoroughly now. Alot of it doesn't pertain to what we are doing but I think a lot of good info can be gleaned from that. Somewhere he mentions something about tuning out the output capacitance of a MOSFET so that it can be used at higher frequencies. I thought that it would be interesting to choose devices with an output capacitance that would be easily resonated with a primary, and a secondary would have to be designed for that frequency. I don't know how practical this would be since I have not really studied it in depth yet. The people who simulate circuits could probably figure out how rediculous this idea is relatively quickly :-)

>Original poster: "Bob (R.A.) Jones"
>An other way of looking at it is to note that a parallel L C is low impedance at all frequencies >other than resonance. So if you apply a square wave from a low impedance to it the harmonic >currents are huge because it effectively a sort circuit.

This square waves with all the it's harmonics is something I didn't even think about. That is a very good point!

>To address your particular question about almost no current thru the switched. That's not >true. The current thru the switches is determined by the power you decide to pump in to the >system by selecting the primary turns, operating frequency and mode etc.

I was actually thinking of the massive ringing current that would flow between the primary and resonating capacitor if the parallel resonant circuit was used instead of series. When the switch closes current would flow through it to charge up the capacitor. I see your point, it would look like a short in the very beginning of the pulse.