So the half-bridge blew up again. This time it was bad, since it was my final design (printed on proper PCB). It is also the design I thought I had prototyped enough that I was confident that it would work. It blew up while stopping the motor suddenly from about 1/4 speed (with no load).
Considering this was the fifth complete redesign of the half-bridge, with countless smaller changes, I had chewed through $100′s of dollars of MOSFET’s, many hours of debugging time, “cloudsourced” (using Facebook) h-bridge help, and still could not design one that would not blow up, I thought it was high time to cheat and buy one off-the-shelf.
I found and purchased this one of AliExpress for just over $US50 (including shipping). It is rated for 60V and 30A (over-current protection trips at 35A). This should be perfect for my design (48V nominal, up to 58V), with a maximum current of about 30A also. The controller comes with three terminals for a POT to adjust the speed, so I will have to connect this directly up to a PSoC DAC (if the voltages allow, but I doubt it), or more likely a PWM-based DAC (with a RC low-pass filter) so that I can match the voltage the controller requires.