 IGBT oscillators
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thrival
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Thu Nov 29 2007, 06:31PM
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Registered Member #1019
Joined: Sat Sept 22 2007, 02:39AM
Location:
Posts: 29
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A few years ago I built a relaxation oscillator using an IGBT (figure A); the damn thing
actually worked although I'm not sure how or why, given that IGBT's are voltage-controlled devices with a capacitive gate, I think the external capacitor could have stayed charged.
I do recall thinking the diode would give the cap a discharge path in parallel with the source, once the gate opened. The waveform was pretty ragged.
Anyway now I'm playing with the idea of a saturable core oscillator using an IGBT and
resistors. I figured that the IGBT's gate should open almost instantly as set by the R
voltage divider, which should then drop out once the coil saturates, and repeat, etc.
Problem I'm running into is I get no action at all. I tried a 2.5" dia toroid with 8 turns of
18 AWG transformer wire as the primary. Thinking maybe I wasn't getting enough XL I tried
a MOT primary, still nothing. The IGBT seems to be good, can't see what I'm doing wrong.
Open to advice anyone might have to offer.
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