What I'm doing:
I am designing a DCDC converter to generate ±24v from an incoming supply of 18v - 36v. For this I am using the TI TPS54160, and following the document Create a Split Rail Power Supply with a Wide Input Voltage.
To save space, I designed a planar transformer, using a split transformer core. I put 12 turns on each side of the transformer, which according to the datasheet of the core should give 244uH (12x12x1700nH).
I have been using an Excel based calculator provided by TI to calculate the correct component values. The calculator is specifically for designing this circuit topology with this IC.
The problem is that at 500kHz switching frequency, the transformer is getting very hot. If I reduce the switching frequency, I can get it a little cooler, but if I reduce too far, the circuit no longer has enough drive current.
What should I try in version 2? Would a physically larger transformer core help? Should I try reducing the number of turns on the transformer? At 500kHz, I calculate that I only need 65uH, so I could certainly go down to 8 turns.