the two-switch flyback converter
Hi again,
It would seem to be the perfect time to bring up the good old equivalent circuit of the transformer.
**broken link removed**
Sorry for the crude drawing, Bill's good old Paint was what were available
I have put a rectifying circuit and a dummy load on the output and also put on the switches and clamping diodes.
If we can agree on that the two resistors and the two inductors can move freely from primary to secondary if we transform them correct, then picture this:
When both switches turn of, the magnetizing current will continue to flow. This means that the ideal transformer is not locked down at both ends:
At the secondary the voltage is clamped to the capacitor-voltage (it cannot change instantly).
The primary is not clamped to supply rail because there is an inductor in series with it, which provides the necessary voltage to make ends meat.
Or if you choose: the primary is locked to supply and the secondary has too little voltage --> which the freely flying magnetizing inductance corrects by jumping into series with the secondary winding and "boosting" the output voltage of the ideal transformer.
So I guess that it is perfectly alright to use a dual switch this way. I never really analyzed this particular scenario before now.
Cheers,
/Ghydda