Given the large size of the printer (600mm), for the heat bed I decided to use two pad (from china), with dimensions each 300x300mm.
So instead of a *big* power supply of more than 600w, I decided to use 2*350w power supply at a reasonable cost (35€) each.
To control these power supply, instead of using SSD relay with doubts about the end of life, I use two electronic boards with mosfet.
That works perfectly already on my other printer 3D, and it decouple the electronic+heat head+motors+fans from the Bed power supply. More than 10A is used by bed, reste of electronic requires only 1A. A large current consomption from BED does not impact the rest of the printer.
The Bed regulator control board schematic comes from here:
and I adapted in on prototype PCB with strips.
*Be careful to NOT link both GND , or you may damage all*
Orange power supply is 12V, for electronic board, motors, heat head, fans.
Black power supply is 24V and for each PAD of the heat bed.