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Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
I asked Sulaiman, he said Z1 is to stop bad primary voltage spikes, Z1 is 440v, Q1 is 2SK2698.
He used a 440v TVS as the FET is rated at 500v I think. It's was used with a 12Vdc 1A supply, I'm trying to push 60w through it, and even higher when I understand. I have read through notes of this circuit, and if more power is required a external voltage clamp (TVS) is needed. D1 is UF1007, My diode tester shows D1 and TVS/Z1 working? For some reason my diode test shows Ohms, and it's 470~Ohms.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
try puting some capacitance in parallel with the primary say .5uf poly cap if your transformer is a flyback. the object would be to create a resonance in the primary that equals the secondary fo. in this way there will be a circulating current and your fet wont have to work so hard and you wont get the reversal from primary that is killing your TVS. another option is to put a 1kv 3A diode in series with your drain to block the reversal voltages.
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
It's working now, and I will put a few 22nf MKP caps in parallel, Only diodes I have are about 200v 1A fast RU47Z/A, Will I be able to put 45vdc in this driver? my 19vdc supply short circuits, because it is only mean't for charging laptops..
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
I've never had much luck with 555 circuits either. I believe R4 is going to limit your power through the primary unless it's a really low value. how about using an RCD snubber across the output? I think that should address the voltage spike problem and then you could take out the tvs.
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
I have taken out the TVS, and I'm using a few MKP cap in parallel, the MOSFET isn't heating at all, I'm using 20turns, so my PSU won't shut off, How do I make the snubber?
R4 is 0.1Ohm for 'scoping. A snubber is only a resistor and capacitor???
On extended run the MOSFET does get hot, and I've tuned the Toff and Ton pots for maximum voltage, it sprays like a tesla coil, I can tune it better but my PSU turns off, It can spark 65mm's and spray over 80mm, I added a ru47 to check if it helps, and it cools the mosfet, and because I added more caps, I need to retune it, How can I stop the MOSFET from getting hot, a I want to run this circuit on 45vdc.
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 525
Sorry for the double post but I'm having trouble hooking audio to my 555, I have 5 wires in one headphones, the tip is + one channel? and the small length is - second channel, and the long sleeve/bit is GND? Still won;t work :(
I want to play Iron man, and Fortunate son :(
The phones I have now have a gold cable which I assume is GND, a red and green I think this is for the left ear and right ear, the arc produces no sound, it only picks up bad voltage? from my hands and makes a screech. Because when I hold the earphone on the 555's GND I will only make a sound if you hold it on with your hand.
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555 driver very hot
