Hi
I'm looking at the MAX845 IC:
It is a push-pull forward driver for a center-tapped transformer (see page 5)
It has a flip/flop to get 50% duty cycle, but how do they prevent flux- walking? Is that only done by the on-resistance of the MOSFETs? (higher current leads to more voltage drop - regulating the flux)
Regards
Klaus
I took a quick look, and as far as I can tell it's that and the resistance of the transformer winding -- which can problem be relatively significant given the low powers involved.
Pretty much. A way to really combat staircase saturation would be current mode control like on this one:
But usually it's not a huge problem. If EMI is an issue this converter might need a small inductor after the output rectifier. Also, the transformer should be able to handle a small DC load caused by stuff like not quite equal diodes etc. Sometimes people use airgapped cores but I never had to on forward converters.
-- Regards, Joerg http://www.analogconsultants.com
The break-before-make action guarantees about 200nS of dead-time per cycle. That's 10% at the 450KHz minimum operating frequency, which I'd think is enough time for a nearly-balanced core to reset, right?
Cheers, James Arthur
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.