A DC voltage in input (~24V-18V) is decreased to 12V and 5V using modules (DC-DC step down regulators). And then these 5V and 12V voltages are distributed to different devices. One module DC=DC step down regulator is for the raspberry pi4B alone. In theory the pi4B needs 3A, and the module is supposed to deliver 2-3Amax. I will try to add a heatsink on the LM2596 chip.