Hans,
Is it possible to set an interrupt routine based on time to sample the 5-volt input and shut down the output when it reaches a threshold value greater than 5 volts but less than the 5.6-volt zener voltage?? If the timing of the power loop is 1 ms, the fast interrupt loop would need to be on the order of 0.25 ms to be effective.? This would be a very short routine to sample and shut down only.? I have used this concept in industrial control systems to handle alarm conditions with insufficient processor capability to run the entire program within the required time.?
An alternative is to store the value of the input voltage and turn off the PWM signal until the voltage stabilizes for several slower control loop cycles.
There are many strategies possible with the fast timed interrupt loop.??The A-to-D conversion times do come into play.? For the control situation, a direct read capability bypassed normal I/O processing.
73
Evan
AC9TU
