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Registered Member #4230
Joined: Sat Nov 26 2011, 05:50AM
Location: Socketville
Posts: 53
Here are the trace shots as well as a picture of the board before I soldered everything in just to make sure I'm doing everything right. The first one is with the ferrite and the second is without. Sorry I forgot to take a streamer pic. It's not all that impressive anyway.
Strangely enough, it won't produce a streamer without the ferrite. The streamer won't start by itself either. I have to get it going with a screwdriver. I'm actually surprised there is one at all considering how far above the resonance frequency it's running. Also the ferrite is getting pretty warm. I probably should find one made from a better material.
Registered Member #4230
Joined: Sat Nov 26 2011, 05:50AM
Location: Socketville
Posts: 53
I have an update and question on this project, which I am calling the leaning coil of Tesla. ^_-
All I can get is a small streamer. As I turn up the voltage on the variac, the streamer grows as expected, and the fluorescent tube next to it gets brighter. Then as I keep turning up the voltage past a certain point it starts to decrease until around 50V it goes out. Does anyone have an idea of what could be causing this?
Thank you.
Edit: I should also say that the scope shows no change in the gate/drain waveforms aside from the increasing voltage, Just no output from the secondary.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Well, as I said it's a fiddly circuit and you may need to re-adjust the feedback coil coupling and the bias voltage as supply voltage is increased. While doing so, blowing mosfets is highly probable...
It would probably be helpful to have some way of measuring tab temperature, or just watching the voltage and current waveforms closely ona fast oscilloscope.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
Just wondering, shouldn't the load be connected across the switching device (in this case, a MOSFET)? The class E amplifiers I've seen all do this since they need a constant current supply across the switching device and shunt capacitance. Having the load connected in series means that you have less control of the voltage across the MOSFET. Normally, it should follow the integral of the current through the shunt capacitance.
You should also be careful of self resonant topologies because if you lose gate drive and the MOSFET gets stuck on, it'll probably die.
Registered Member #4230
Joined: Sat Nov 26 2011, 05:50AM
Location: Socketville
Posts: 53
It is switching just fine at higher voltages, just no secondary output. I'm starting to think maybe I should just abandon this secondary and wind a new one.
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Class E Coil Woes
