Overvoltage detection circuit schematic, overvoltage detection circuit analysis

Overvoltage detection circuit schematic

    The schematic diagram of the overvoltage detection circuit is shown in the figure. When an overvoltage signal is generated, the varistor is broken down, presenting a low resistance value or even close to a short-circuit state, so that a large current is generated on the primary side of the current transformer, and a small current is generated on the secondary side through the mutual inductance of the coil, and then the current signal is converted 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 supply circuit, disconnects the switch power supply circuit, and starts the backup power supply. Control pulse 2 is sent to the interrupt of the microcontroller, and the microcontroller control circuit starts the A/D conversion and samples the instantaneous value of the overvoltage.

Overvoltage detection circuit (I)

    D19 is a voltage-stabilizing diode. When the input voltage VIN is greater than (Vz+0.7)V, IO_IN changes from a high level to a low level, which can be easily detected using the GPIO interrupt of the MCU.

Overvoltage detection circuit (II)

    Optocoupler is used for isolation detection. D1 is a voltage-stabilizing diode. When the input voltage VIN is greater than (VZ+VF), the optocoupler is turned on. VF is the turn-on voltage drop of the primary-side light-emitting diode of the optocoupler. IO_IN changes from a high level to a low level. The isolation detection can be easily realized by using the GPIO interrupt of the MCU.

Overvoltage detection circuit (III)

    D2 is a voltage-stabilizing diode. When the input voltage VIN is greater than (Vz+0.7)V, IO_VIN changes from high level to low level, which can be easily detected by the GPIO interrupt pin of the MCU.

Overvoltage detection circuit (IV)

    Using a comparator, the overvoltage detection point can be set by R5 and R7; the input voltage VIN is divided by resistors R11 and R12 before comparison. When IO_IN changes from a low level to a high level, the detection can be easily achieved using the GPIO interrupt of the MCU.