Micro SSTC - problems
Dr. H., Sun Sept 16 2007, 06:34PMHi to all. I am new to this site so don't be tu harsh on me
. I have built a VTTC a while ago and i decidet it was time to go to something little . So few days ago i decided to build a sstc based on Steve Ward's Mirkro SSTC (everyone has to start from somewhere 
)So i built the circuit and it looks like this
I've tried it a few times and for about 10min without any problems so i decidet to box it
But now when i turn it on it doesn't wont to start oscilate every time. Because my gate drive chip is inverting (icl7667) when it doesn't oscilate it shorts out my power suply. What might be the cause of these problem? Short antena ?!?!
Hire are some pic while it is running, it;s casing and what's inside the box . And one wast question - how do you insert picture like a link ???
Any help will be useful
Excuse my english i am from bulgaria
Re: Micro SSTC - problems
Marko, Sun Sept 16 2007, 08:01PM
Hi Huben, and welcome
Oscillation start and massive turn-off losses are among standard problems with that kind of circuit.. Can be changed to class E, but I don't think it's worth for you.
What do the other IC's in your circuit do? Are you using start-up oscillator?
You actually put too much effort into that coil and board. I think it would be great to transform it into a small H-bridge coil.
Marko, Sun Sept 16 2007, 08:01PM
Hi Huben, and welcome
Oscillation start and massive turn-off losses are among standard problems with that kind of circuit.. Can be changed to class E, but I don't think it's worth for you.
What do the other IC's in your circuit do? Are you using start-up oscillator?
You actually put too much effort into that coil and board. I think it would be great to transform it into a small H-bridge coil.
Re: Micro SSTC - problems
Sulaiman, Sun Sept 16 2007, 09:09PM
Temporarily for testing try moving the coil and primary away from the box
the metal box may be causing problems ?
Sulaiman, Sun Sept 16 2007, 09:09PM
Temporarily for testing try moving the coil and primary away from the box
the metal box may be causing problems ?
Re: Micro SSTC - problems
Dr. H., Mon Sept 17 2007, 11:49AM
Hi to all. The other ic is a cd4000. I use the inverter for the signal from the interuptor (wich i now remove bacause there is no need for it in this smal coil). The two other IC's are the gate drive chip on the right and the 555 for the start-up oscilator.
Alsou i've tried the cass E operation, but wit the same input voltage i get smaller streamers. The only benefit is that the mosfet isn't warming at all.
Hi Sulaiman. When it was out from the box it was running OK. But when i put it into the box i took the antena out of the box (it can be seen on the pics - a orange wire). The antena is going out from the box from very smal hole and the box is groundet (the socndary base is attached to the box also so they are groundet at one point, i don'd know if this is a problem, you will answer this ). I was thinkin is there any possibility that the capacitance where the antena is going through the matel casing to be causing problems ?
And one more question - how do you determine the coupling ?
Dr. H., Mon Sept 17 2007, 11:49AM
Hi to all. The other ic is a cd4000. I use the inverter for the signal from the interuptor (wich i now remove bacause there is no need for it in this smal coil). The two other IC's are the gate drive chip on the right and the 555 for the start-up oscilator.
Alsou i've tried the cass E operation, but wit the same input voltage i get smaller streamers. The only benefit is that the mosfet isn't warming at all.
Hi Sulaiman. When it was out from the box it was running OK. But when i put it into the box i took the antena out of the box (it can be seen on the pics - a orange wire). The antena is going out from the box from very smal hole and the box is groundet (the socndary base is attached to the box also so they are groundet at one point, i don'd know if this is a problem, you will answer this
). I was thinkin is there any possibility that the capacitance where the antena is going through the matel casing to be causing problems ?And one more question - how do you determine the coupling ?
Re: Micro SSTC - problems
Dr. H., Thu Sept 20 2007, 11:25AM
Is there any suggestions guys
Dr. H., Thu Sept 20 2007, 11:25AM
Is there any suggestions guys
Re: Micro SSTC - problems
Marko, Thu Sept 20 2007, 12:24PM
I would definitely go for a small half or full bridge. Designs like this are favourite and work great:
The coil looks big enough, what's it's resoant frequency?
Marko, Thu Sept 20 2007, 12:24PM
I would definitely go for a small half or full bridge. Designs like this are favourite and work great:
The coil looks big enough, what's it's resoant frequency?
Re: Micro SSTC - problems
Dr. H., Thu Sept 20 2007, 04:32PM
I was also thinking the same Marko. I was looking around and i found the ctc-labs circuit http://www.ctc-labs.de/html/micro_sstc_2.html
But i have some questions. In the description of the ciruit he says that he uses a irf740 but in the circuit is shown as irf640. I was thinking is it possible if i use a irf740 to power it directly from one way rectified mains (220v). The transistors are 400v (740s) so they must survive, but would i need to change the number of the turns of the primari? Also i will make a new secondary that will be with lower resonant frequency (about his size so i won't need changing values). Also i can't de drive chips he use. Is it possible to change them with ICL7667 (2x 1.5A in IC ) ?
Dr. H., Thu Sept 20 2007, 04:32PM
I was also thinking the same Marko. I was looking around and i found the ctc-labs circuit http://www.ctc-labs.de/html/micro_sstc_2.html
But i have some questions. In the description of the ciruit he says that he uses a irf740 but in the circuit is shown as irf640. I was thinking is it possible if i use a irf740 to power it directly from one way rectified mains (220v). The transistors are 400v (740s) so they must survive, but would i need to change the number of the turns of the primari? Also i will make a new secondary that will be with lower resonant frequency (about his size so i won't need changing values). Also i can't de drive chips he use. Is it possible to change them with ICL7667 (2x 1.5A in IC ) ?
Re: Micro SSTC - problems
Sync, Fri Sept 21 2007, 05:09AM
You can use the ICL7667, they're fine... But take care of the different pinout. (Mmm. It actually could be the same o.0)
IRF740s and IRF640s are the same but the breakdown voltage.
I don't think that you have to change the primary... Just try it and tell us how it works (;
Sync, Fri Sept 21 2007, 05:09AM
You can use the ICL7667, they're fine... But take care of the different pinout. (Mmm. It actually could be the same o.0)
IRF740s and IRF640s are the same but the breakdown voltage.
I don't think that you have to change the primary... Just try it and tell us how it works (;
Re: Micro SSTC - problems
Sulaiman, Fri Sept 21 2007, 06:20AM
Irrespective of the type of SSTC that you choose
I still think that putting a steel box directly beneath the TC is a bad idea
the steel will kill the performance.
I wouldn't have steel within a couple of coil diameters proximity
e.g. 6" primary requires 12" clearance.
The distance is debatable - but the principle isn't.
Sulaiman, Fri Sept 21 2007, 06:20AM
Irrespective of the type of SSTC that you choose
I still think that putting a steel box directly beneath the TC is a bad idea
the steel will kill the performance.
I wouldn't have steel within a couple of coil diameters proximity
e.g. 6" primary requires 12" clearance.
The distance is debatable - but the principle isn't.
Re: Micro SSTC - problems
Dr. Drone, Fri Sept 21 2007, 07:10AM
Dr. Drone, Fri Sept 21 2007, 07:10AM
Re: Micro SSTC - problems
Dr. H., Fri Sept 21 2007, 11:38AM
thenks for the replys guys :)
I was asking for the MOSFETs because i want to drive it directli from the mains (not throug a stepdown transformer like he shows in his circuit).
For the new coil (ctc-circuit) i will definetely not use steel box but with the micro sstc i didn't see any difference in performance with or without the box.
I will start a new threath for the new coil and i will put my results there. The only question is will the mosfets survive at 300v half wave rectified (irf740 are 400v 10A )
Dr. H., Fri Sept 21 2007, 11:38AM
thenks for the replys guys :)
I was asking for the MOSFETs because i want to drive it directli from the mains (not throug a stepdown transformer like he shows in his circuit).
For the new coil (ctc-circuit) i will definetely not use steel box but with the micro sstc i didn't see any difference in performance with or without the box.
I will start a new threath for the new coil and i will put my results there. The only question is will the mosfets survive at 300v half wave rectified (irf740 are 400v 10A )
Re: Micro SSTC - problems
Tom540, Fri Sept 21 2007, 05:52PM
They should survive as long as you don't run it in DRSSTC mode. I had a coil that ran at 1MHz CW using those FETS and was powered by two dual power supplies running in series @120VDC. Current limiting with a cap on the line voltage might not be a bad idea.
Tom540, Fri Sept 21 2007, 05:52PM
They should survive as long as you don't run it in DRSSTC mode. I had a coil that ran at 1MHz CW using those FETS and was powered by two dual power supplies running in series @120VDC. Current limiting with a cap on the line voltage might not be a bad idea.
Re: Micro SSTC - problems
Dr. H., Fri Sept 21 2007, 07:14PM
In the original sheme they use a step down transformer one way rectified with irf640. It is written that the maximum voltage is 200V. Because i want it driven directly from the mains one way rectified i will change the mosfets with some that can survive 300v
Dr. H., Fri Sept 21 2007, 07:14PM
In the original sheme they use a step down transformer one way rectified with irf640. It is written that the maximum voltage is 200V. Because i want it driven directly from the mains one way rectified i will change the mosfets with some that can survive 300v
Print this page