Half Bridge Magnetics Integration

[hofcake]

Hello,

I have been reading a paper to familiarize myself with the techniques people have used to integrate all the magnetic components in half bridge topologies. I have a design with a half bridge, current doubling topology with a coupled inductor for ripple cancelation and I would like to integrate this into a single core if possible.

I found a paper claiming to show an implementation of a current doubling circuit, however, to me, it just looks like an integrated center tap. Am I missing something here? I just see a transformer with a high reluctance leg added to a square core and a winding added to the center tap, imitating the discrete inductor of a center tapped rectifier.

[T3sl4co1l]

Turns around the legs are generally going to be counted as half-turns, so they would technically have current doubling in that case.  It is something of a "duh" case, as you've noticed.  Note also that, to ensure the half turns work correctly, a flux balancing winding is needed around both legs -- which will still give higher leakage than if both windings were around the center (where they can be on top of each other).  (They could've made the primary halves in parallel instead.)  (Or maybe the three-way choke topology cancels this out and it works fine anyway; I'd have to draw it out, I think.)

Tim

[mtwieg]

Could you explain what your objective is in integrating the transformer and choke together? And link to the paper you're referring to?

One thing to note about this diagram is that the output current (equal to I1+I2) will cause the core's flux density to be biased away from zero. That means there will be less available flux swing due to primary current before saturation sets in. I'm guessing the small air gap on the center pole doesn't prevent this, but at least encourages the flux from the output current to be distributed more evenly in each leg.