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It doesn't work anyhow, I went back to the drawing board and... this works perfectly!
I've spec'd it to work up to 100V and cut off is 30V (play with the 18.8k resistors). At 100V there's about 6mA pull at the LM393 which is the rated max. Finding an ideal P-FET is more troublesome but FDMC86139P looks good. I couldn't get it to sim with their spice model though.
If anyone can assist with the over-voltage, you can see that I've added protection for the FET's but I'd appreciate an extra eyes on. Sim says it's ok.
More of a worry, the transistor collector-base will see 100v which may overstress it despite the 22k resistor. I added D12 as a fail safe but doubt it does anything useful.
An alternative would be to control each FET separately using two comparators. A few less diodes but more complexity.
LM339 is open-collector so R7 is required (or at least, good practice in a real circuit). For the simulation it may be more important since it needs a number to work with and a floating copper wire can't be handled numerically.
You're missing the point. D12 has nothing to do with it. Tell me, what voltage do you think the simulator should assign to the output of LM339 is not outputting a LO (i.e. when the output goes high impedance).
Do you just expect things to simulate when there are indeterminate values in the system?