Electronic – How to reduce MOSFET heating in Buck Converter

buckconverterdc/dc converterheatmosfet

I have designed this Buck Converter which convert 60VDC to 12VDC at 10A.
Switching Freq 100KHz.
Facing MOSFET too much heating issue.
MOSFET ON time and OFF time is decided by a UC3845B based circuit. MOSFET gate is biased with 2.2R resistor and pull down of 5.1K
is there any way to reduce MOSFET heating?
I've increased MOSFET rating to 110A 80V. Previously was 75V 75A but no succcess.

Edit 1: Updated Schematic for better understanding.

Edit 2: Previously tried this INFINEON MOSFET. Heating was less.

Then used this ST MOSFET.
Heating was more in ST MOSFET

enter image description here
enter image description here

Hello, here is an update, can I use below circuit as bootstrap?
here in place of 5V Input either I can use 60V directly or 12V from output.

enter image description here

Best Answer

If it is confirmed the MOSFET needs a better drive then the best is to advise a suitable circuit. A simple bootstrap circuit described by Monsieur Balogh in a TI application note can do the job nicely in a cost-sensitive application. As noted in some of the comments, the UC384x was not really meant for hi-side drive - unless you make it entirely float and tie its GND pin to the MOSFET source and supply the IC via the rectified buck output - but this little circuit does the job fine:

enter image description here

Below is the circuit I tested with component values:

enter image description here

This is excerpted from a seminar I taught in an APEC seminar in 2019.