Update: got it working... Fix: replace diodes for proper schottky. Result: got oscillation but no resonans. Fix: replace cap with 1 uF polystyrene. result: got resonans.
But now my problem is i cant get any power out of it! I know the freq is a bit high to properly heat steel, its around 330kHz. But it draws 3.5A running empty peaking at 50V, and only goes to 5A at 20V when i insert a workpiece.
How to upp the effect? or is this generally an ineffective design?
old question I´m getting a bit interested in resonans and found a circuit for a very simple self oscillating inductuiong heating circuit. im new to using powertransistors.
In addition i put a 12V zener diod and an a 10kR between node R1,T1,D1 and ground to protect my gates from overvoltage
My problem being the circuit wont oscillate. One MOSFET turns on, stays on. The circuit draws ca 3A at 12 V. And nothing much more happens.
I have a hard time understanding why..
Im was thinking that the mosfet needs a negative flank with respect to drain in order to turn of proper (enhancement mode?). But the page explaining uses STP30NF10 which are similar to mine. I am using IRF540 enhancement mode Mosfets 100v 28A.
Anyways... below is schematic of my current non-functional stup. .. please help as to what might be causing the problem.
actually, while doing the drawing s i noticed that my diodes d3,4 are not schottky diodes. but have a 0.6 Vdrop. would that do it? the circuit is theoretically supposed to osc @ 240kHz.