This picture show my latest test upset. I am still only testing a single PWM channel on MC4X15A, but it has caused a few Challenges.
I finally got hold of 100W resistors that can sustain heavier load and using a 4 Ohm 100W I can continue my testing without being concerned about the load melting the solder tin as my previous one did. I expect the load to heat up as I am throwing out 40-100W on it. I did however not expect the MOSFET’s to heat up this fast.
I tested with 28V for a while getting a nice 1.2A out which is OK since I had low PWM duty. I connected a DC motor with the 2 Ohm load in series and it instantly span up in 80ich Watt and maxed out the PSU on 3A. I assume I broke the MOSFET at this point due to spikes as I was running without capacitance/protection on the PSU feed.
Gate drivers and MCU are ok, so I assume the supercap/diodes did it’s job and protected the MCU, but I fear I might have 8 x broken MOSFET’s – well, will find out tomorrow! My own fault for attaching a motor without adding the capacitor/diodes on the PSU.