Zener diode and transistor

[Akshatha Venkatesh]

This is an over voltage protection circuit , the resistor R706 is connected to the input of a high side driver , 10F and 11H are the signals from and to the microcontroller, UVP is the point where over voltage occurs , can anyone explain the operation of the circuit?

 

[RLP123123]

Showing a little more of the circuit would have been helpful. I would venture a guess that a voltage of greater than 18.1 to 18.7 volts would be required and the condition should last for perhaps 40uS or more to trigger the BC846. Not knowing more about the load the BC846 is pulling down, what is shown in the schematic is a very light load requiring perhaps 10 to 20uA base drive into the BC846 to pull the signal line low to the ucontroller. No circuit showing what you are calling a high side driver is shown, but if it was a mosfet switch, the BC846 pulling low would turn off the high side switch. As I said, a guess without more info.