Stupid ZVS Flyback Problem

Discussion in 'The Projects Forum' started by oidium45, Apr 30, 2010.

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  1. oidium45

    Thread Starter Active Member

    Apr 24, 2010
    Hello everyone! I am new to the forum (and a circuit rookie) but am hoping that someone can lend me a hand here... Please hang in there here is some back info...

    I setup the standard zvs flyback driver with the IRFP250 mosfets and it worked great. I then setup a small tesla coil that I made and things were going pretty good as well. The only difference between the standard ZVS and mine was a rectifier diode on the HV out and a 500pf cap for the coil... For this setup I was varying between a 25.5v 2A transformer with a rectifier and several lantern batteries connected at 48v. I was trying to figure out how much this flyback could handle. And at the same time fine tune the coil. Unfortunately the circuit seemed to want more amperes out of the transformer and it was getting way too hot so I started using a re-wound MOT at 48v with a 400v 8A rectifier. The MOT produced vary good results for a few minutes and then one of the mosfets shorted and then the rectifier quickly followed. I replaced the mosfet and the rectifier and after a few minutes the mosfet shorted again. This happened three times!

    After re-checking the circuit for errors, I purchased the IRFP460 mosfets and a 50v 25A rectifier thinking that maybe i needed a more durable setup. After installing the new transistors the results were great! Much better then the IRFp250's. Unfortunately after a few minutes one of the new transistors shorted as well. It seems to be the same transistor in the circuit (the lower one in the schematic) that is shorting. Perhaps this one has more load?

    Does anyone have any suggestions? I would really like to get this circuit running. I can post a schematic and parts list if that helps. Any constructive feedback would be greatly appreciated!!!
  2. oidium45

    Thread Starter Active Member

    Apr 24, 2010
    Just to add a bit of extra info:
    Here is the zvs driver schematic that I was following.

    Here is the parts list from mouser that i purchased.
    1. Mosfet's------ IRFP250PBF-------------- 2
    2. Zener Diodes------ 1N5349BG--------------- 2
    3. FRED Diodes------ HFA15TB60PBF ---------- 2
    4. 470 Ohm 2W Resistors------ 282-470-RC----------- 2
    5. 10k 2W Resistors------ 282-10K-RC----------- 2
    6. 1uf 100v Bipolar Capacitor------ 140-NPAL100V1.0-RC------------ 1
    7. 47UH 10.7A Inductor------- 2309-V-RC----------- 1

    Here are the additional parts that I added after the HV out.
    Rectifier Diode
    30kv 500pf ceramic capacitor
    Tesla Coil (primary 20 turns center tapped every 2 turns 14awg wrapped around 2" pvc/secondary-approx 900-1000 turns 30awg wrapped around 1" pvc)
  3. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    That site does not allow external links, the actual schematic is the last one on this page:

    I'm not commenting on that operation of the circuit as I don't want to have your electrocution on my concience...
  4. bertus


    Apr 5, 2008

    We do not allow these circuits here.
    They are dangerous.
    People can get hurt or even killed (electrocution like rjenkins said).

    Last edited: Apr 30, 2010
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