Overvoltage detection circuit

The schematic diagram of the overvoltage detection circuit is shown in the figure. When an overvoltage signal is generated, the varistor is broken down and presents a low resistance value or even close to a short-circuit state. This generates a large current on the primary side of the current transformer, and a small current
is generated on the secondary side through coil mutual inductance.
, and then convert the current signal into a voltage signal through a precision resistor; after this signal is input to the voltage comparator LM393 ,
the voltage comparator LM393 outputs a high level, and the control pulse 1 output by the NOT gate A controls the power loop and disconnects the switching power supply circuit. ,
start the backup power supply. Control pulse 2 is sent to the interrupt of the microcontroller, and the microcontroller control loop starts the A/D conversion and samples the instantaneous value of the overvoltage
.