WFC VIC

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Kali,
In Stans circuit,there is a 5 amp 1000 volt diode between the TIP120 and the primary coil.The way you keep explaining your ideas,sounds like your putting the TIP120 after the primary coil.That diode protects the TIP120 from high voltage back emf as I see it.
 
Stan also put a diode across the inputs to the primary.From ground to positive.
 
As for testing my coils,if you don't find resonance,the voltages are all over the place at any gien frequency,and the scope traces look like junk.
 
Yes 57 khz is the primary resonance frequency with my coil.It is very easy to find,I'll take a picture and post here.
Don
 
Update: Pics added
 
1st Picture primary resonance @54khz
2nd picture out of resonance @ 2.4khz

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In Stans circuit,there is a 5 amp 1000 volt diode between the TIP120 and the primary coil.The way you keep explaining your ideas,sounds like your putting the TIP120 after the primary coil.That diode protects the TIP120 from high voltage back emf as I see it.

I actually always thought, there must be a series diode, but I rather talked about the freewheeling diode. This diode in series, IMHO doesn't (just) protect the TIP, but rather protects the resonant circuit from the primary, so that the primary doesn't take a lot of power out of the resonant circuit. The internal reverse diode of the TIP would otherwise clamp the reverse primary voltage to 12volts. If anything is resonating above that, it would take energy out of the oscillator.

If the TIP wouldn't have a reverse diode, or if the reverse diode amperage is too high, or if the diode is too slow, the TIP would need protection by the diode. Unfortunately in the datasheet I have about it, these values are not indicated.


But why did he use there a 1000volts diode, but just a 600v diode in the VIC-circuit??? Seems quite strange to me...
One guess could be, that he needed a diode for higher currents in the VIC. For when the surge would come, for a short moment quite a current would probably flow for a short time. This would again match Stans notes on Graneaux' experiments (high current density for a short time is needed, followed by a reverse voltage).

Stan also put a diode across the inputs to the primary.From ground to positive.

I'm not quite sure what you mean here. By across the primary, and from ground to positive (as one side of the primary isn't connected to ground). Do you mean a freewheeling diode? But then the resistors would make absolutely no sense...

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Now i understand across thanks don.
I already used this in the past, cause i wanted to assure that the pulse didn't come back in the mosfet.... Kali this resistors automatically cancel the chance of it being driven in the kick back or flyback mode, one of the reasons is that it would consume the discharge pulse... Other reason is that the core must be free to oscillate.

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I already used this in the past, cause i wanted to assure that the pulse didn't come back in the mosfet.... Kali this resistors automatically cancel the chance of it being driven in the kick back or flyback mode, one of the reasons is that it would consume the discharge pulse... Other reason is that the core must be free to oscillate.

The problem is it would only "consume" an amount of the discharge pulse at a time. Let's say, e.g. the primary had 1 Amp flowing when it is switched off. The one Amp "wants" to continue to flow. Therefore the voltage immediately rises until one amp can flow through the resistors. This would mean, that the reverse voltage would then rise to 80 volts (1A*(70+10)Ohm). And these 80 volts are then again stepped up, by the usual Step-up ratio. This is, how a flyback works. Usually you don't take just a resistor for this, but rather a resistor and a capacitance (to get a nice smooth waveform). But principally it remains the same.
And as strange as it may seem. As you also indicated: With these resistors you take out much much more energy out of the core as if you would by taking a freewheeling diode. For with the diode, you would always only have the diode voltage drop (e.g. 1.2V). So if 1Amp wants to flow, it would just dissipate (1.2V*1A+10Ohm*1A^2=11.2Watts) instead of the resistors ((70+10)Ohm*1A^2=80Watts)...
But by introducing the resistors you would exactly get, what a flyback is for, you would get a short high reverse voltage spike. The only limiting question would be  how much current flowed in the primary, when it becomes turned off. If this current is so low, that the return voltage spike is neglectable, then you are right, then it would just dissipate the remaining energy. But unfortunately it would also take energy out of the resonance circuit. But if the current is really low, it would even take less energy out of the oscillator than with the diode.
The calculation is quite easy. For 70 Ohms, it would start to act like a flyback when the current in the primary gets higher than 150mA (12V/(70+10)Ohm).

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I see i understood. Like having also a diode in series with the capacitor and the resistor in parallel, for protection... Snubber...


 But this voltage will be lost voltage only in the primary i'm right? how about the time constant? Would be not very slow. Maybe if we knew the primary inductance we could try to shoot some calculations..


I think it could also be a choice for the filtering of a frequency...

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These are the diodes I'm talking about. Q9 is the TIP120
Kali can you see my pics I post?
Don

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Yes, the newer ones I can see. This is the patent circuit.
So you are saying, that the original 5-VIC-coil, you looked at, had actually really 3 220Ohm resistors in parallel with the diode and additionally a freewheeling diode (an additional 1N4005 diode in parallel to the primary)? Am I correct?


The funny thing is, that a 1N4005 is actually extremely slow (it's made for use in mains frequency designs). So it would start to really switch long after any flyback pulse would have been made...

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Yes how many times do I need to repeat myself.Everything I tell people here is just how it was.Not every coil pack had three 220 ohm resisters on them,I don't know why,but most just had one 5 watt 220 ohm.The one I took the picture of had three.
 
I don't know why he had them different,I can just tell you how they were.Some of his things just don't add up at times.
 
Those two diodes were on the VIC circuit card and not in with the coil pack.
 
I only use the diode in between my mosfet and primary coil.If I add the diode across my primary,it makes the current jump by about 10 times.From 30 milliamps to 300 milliamps,so I don't use it.
 
Don