Tool/software:
I am returning four years later for final product release of a prototype I discussed on this forum. After cleaning up the PCB design to try to get rid of a troubling spike in the current sense signal, I find no improvement. On the prototype, I managed to get adequate operation by filtering the current sense signal, and also removing it from the delay-adjustment control pins and substituting VREF. But I've now come to believe that this spike is not due to poor PCB layout, but rather due to inappropriate power transformer selection. I used an off-the-shelf transformer, which was a planar design. It was the only COTS product I could find that looked like it would suffice at the time, and now four years later it still appears to be. Planar transformers excel at minimizing leakage inductance, but this is no advantage for this full-bridge-phase-shift design which depends on rather high leakage for zero-voltage switching. And they are also infamous for very high winding capacitance. I think this is the source of my outsized primary current spikes.
I'd like to include the efficiency advantages of current-sense feedback into the delay-control pins, but don't believe I can achieve a stable design if I do so with the power transformer I have.
Having come to this realization, I contacted Vitec to see if I could get a suitable custom transformer for this design, along the lines of the transformer TI used in the Eval board but for different voltage and frequency requirements. It turns out I called just as Vitec was GOING OUT OF BUSINESS! Can TI recommend a new source of suitable power transformers for this circuit? I'm operating at 234kHz (468kHz sync), and need 250W out from 250-450VDC input.
If you're not able to recommend a transformer vendor, can you supply recommended design parameters for this transformer, including effective end-to-end primary winding capacitance?
