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a different breed of tesla coil

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teravolt

Thu Mar 30 2006, 06:03AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

In my last thread I am asking about the series capasitance for a reson witch may have applications about the circuit I am working on and I am interested in what the forum thinks. My current circuit that I built is a little different in its construction and the same in principal. The controle part of it has a master oscillator, an interuptor, and a bridge ON time width adjustment. To create my bridge controle signal the master 555 generator is chopped with the intineruptor (555) that has a width adjusment (74HC4538) of its own. They syncronised together with a D-type flip-flop (74HC74) and a AND (74HC08) gate curtisy of Steve ward's circuit with the 74109 I believe. This then goes into a divide by 2 (74HC74) to create my A and B signal. A & B are then put into a one-shot (74hc4538) to controle the width of A & B. To this point all our SSTC are the same. I Am shure that the next part of my circuit has been thought of and that is this. Each quarter of the H-bridge is isolated eleticaly buy using optoisolators and 4 indipendant power supplies insted of transformers and transformer driver circuits. A and B TTL go into mic4427 drivers to drive the LED portion of the opto. The output of the opto (HCPL2630) is inverted and level shifted (MIC4426) from 5 to 15v. Each drive circuit has its own set of power supplies 5v, 15v, 20v and one 5v for the TTL. After A, B is shifted to 5v to 15v this drives a 14A (IXDD414CI) mosfet driver. I had the best results when I used 12 of the 8 pin dip version when I was using 12 igbt H-bridge and creating 6A's and 6B's. So now I am using 4 IXDD414CI to drive 4 40N60's for my bridge. Each has its own transorb and blocking diode rurg80100 hyper fred. The output of my H-bridge goes to a series RESONANT primary tank of 7-5 turns that exsites a 14" secondary of around 250KHz.

I apoligise for the oral description and no shematic. I am working to lern psice to generate schematics and pictures. Any how the point of this exersise for me is to eliminate the cupling transformers and its associated parts. I intend to try Cprim. as a cupling and resonant. As a test bead want to see how efficiant I can get it and see if frequency and modulation controles spark length and shape. I also plan at some point to recofigure it as a DRSSTC. Right now I am blowing fets with the new configuration and I need to scope out the new setup and sweep it. stay tuned. N.B.

Steve Conner

Thu Mar 30 2006, 10:06AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I prefer gate drive transformers to optoisolators. They're simpler, cheaper, and have built-in protection against arm shoot-through. I also found it pretty hard to understand what your post was trying to say

Dr. Shark

Fri Mar 31 2006, 10:30AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I apologize for my previous post (now deleted). I know a lot of smart people with dyslexia, so until I know better I will assume you are.

I can see some advantages not using transformer coupling, e.g. you can have a negative bias on the IGBTs during the interruptors off period. But unless you are very good with electronics (your generous use of level shifters and flip-flops actually suggests you are...), I think the added trouble of building the additional circuitry would not be worth it.

Dr. Drone

Fri Mar 31 2006, 06:14PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

GimpyJoe

Fri Mar 31 2006, 07:23PM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

wow! Did the brick actually blow apart or are those just big cracks? I bet that was interesting.

Dr. Drone

Fri Mar 31 2006, 07:28PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

williamn

Fri Mar 31 2006, 08:07PM

Registered Member #55 Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149

On drive transformers vs opt isolators, only issue I had on my drive transformers was I had a flash over on my 10kva DRSSTC and the inductive kick on the transformers took out everything behind them. The kickback was so bad it blew my TVSâ€™s and Zeners right out of the board, ugggggg. Even the OCD feedback CT blew the bridge behind it.

I had the exact same thing happen, I even lost all of my 5V logic ICs.

teravolt

Fri Mar 31 2006, 09:01PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Sorry about the wordy description and I am rushing to make a scematic. I know it looks like I went over the deep end but I wanted to try something different. There is nothing wrong with transformers and even Glassmen power supply's H-bridges are diven with transformers. With mosfet drivers that are opticaly isolated I can drive the H-bridge mosfets much harder and directly and faster to turn them on inside 100ns. this has the advantage of higher frequencys. maby the elusive 10Mhz coil. Ask questions. thanks N.B.

teravolt

Tue Apr 04 2006, 04:46AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hear are a cupple of picturs

Dr. Shark

Tue Apr 04 2006, 09:36AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Very nice! Would you care to provide a closeup of the driver electronics?

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