The micro has three main outputs - a PWM signal for the lower side of the bridge and a 'selector' to select which pair of IGBTs are in operation. The selector output goes through a series of NAND gates which passes the PWM signal to the correct lower IGBT while turning on the correct upper IGBT. The third output is a PWM signal to the boost stage. There's a hardware shutdown for overvoltage that will stop the boost PWM signal if it goes really high (400V or so).
The overall PCB layout is pretty poor and I would completely redo it if I have another opportunity. First, I forgot to put pull down resistors on the micro's PWM outputs. Unfortunately, it took me a pair of blown IGBT modules to figure that out. There's a couple other minor things like an LED status indicator would be nice and adding the pads for the 2nd current sensor.
The big issues involve separating the analog and digital circuits. Unfortunately, the voltage sensor output trace runs directly over the boost opto-LED PWM drive traces which results in little spikes every time the LED turns on or off. This isn't a big deal as far as voltage regulation goes, but the little spikes cause the hardware protection to trip at a lower output voltage. This is compounded by the fact that the desired output voltage produces a sensor output that is near the 5V rail so the reference voltage couldn't be adjusted high enough to avoid false trips. Adding RC filters helped reduce the spikes and hacking the reference voltage pot to use the 12V supply instead of the 5V supply solved this.
Here's a screenshot of the PCB. The top part is one of the power boards and the lower part is the control board.
