I am trying to build induction heater with the help of the following schematics(taken from this page):
So I am using 220:10Vrms(15Vpeak) transformer with fullbridge rectifier and a capacitor to get 15V DC. If I disconnect everything from this simple "PSU", I do get 15V DC.
But, when I actually connect the circuit and measure my voltage rails I get this strange behavior on my oscilloscope, as you can see it shows 5V with some ripples.
The circuit draws 0.27 Amps on the primary and 1.84 on secondary of a transformer, which I measure with the voltage clamp.
My coil is 1.2 uH (measured with LCR meter). I use 0.47 uF 250V Polypropylene capacitor. This should result in approximately 220 kHz resonant frequency.
I also use the choke of 2.2 mH on center tap.
My MOSFETS are IRFP460A.
So, questions:
1) The circuit doesn't work for me, i.e. if I probe the coil there is nothing on it, zero. If I put metal object inside(screwdriver) nothing changes. Also the overall current consumption is not affected(looking at clamp meter) if metal part is introduced.
I already tried to:
Re-wire everything from scratch, making sure everything is connected properly.
I checked the mosfets with simple testing circuit - they both work fine.
I tried to measure MOSFET output on the Drains without coil or cap in the circuit - it also shows zero on both mosfets.
2) Why if I measure voltage on my 15V rail it shows 5V with ripples? It shows perfect 15V DC if nothing is connected to it. Is this some kind of feedback? I have a choke to eliminate high frequency feedback, but overall it doesn't make sense, since the circuit does nothing to cause feedback as I think. The capacitor after full-bridge rectifier is 1000uF, seems enough too.
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