I have an existing AC/DC flyback design with 5V/3A output. The design gets too hot and I’m looking for ways to reduce heat by improving efficiency. I’m considering replacing the secondary side output diodes with synchronous rectification (SR). I want a single part vs. IC controller + FET, if possible. Do you have any single chip solutions that will work for this?
MP9989 is a great fit for this application. Datasheet shows waveforms for 4A continuous operation in a 48W flyback design. Electrically, it is very simple with minimal external components because it generates its own supply voltage. For best thermal performance, use the QFN package. More/thicker PCB copper around the VD and VS connections will also help thermals and be sure to use lots of vias.
Also during the PCB layout, the connections between the secondary winding, MP9989and the Output cap should be as short as possible and the area enclosed by this loop should be kept to the minimum. Also the trace from the transformer to the Vs pin and from the Vd pin to the output cap should be placed directly above the ground copper fill on adjacent layers. This will minimize the area enclosed by the loop and the parasitic layout inductance.