Hi,
Thanks for explaining how your circuit operates, appreciated. I've only had a relay chatter when input voltage was not quite high enough to turn coil fully on (at first I thought relays were that noisy until it finally clicked on properly....) I'm not using a relay, just BJTs, a couple of MOSFETS and a few Op Amps, only been thinking it through for three days, so there are mistakes aplenty to iron out yet! I'm a bit lost as to how to design in over-voltage shutdown for input supply over-voltage, so it's back to copious reading tomorrow...
Stupid suggestion: would putting the relay under the transistors (image 1) make any difference, as in then no V+ to the relay except through NPN emitters, or gating relay through PNPs and using NPN as PNP drivers?