A power supply over-voltage protection (OVP) system includes a transistor having a source terminal configured to connect to a power supply output terminal of a power supply. The transistor has a drain terminal configured to connect to a system load, and a body diode forward voltage drop. The power supply OVP system further includes a low voltage monitor circuit connected between the source terminal and a gate terminal of the transistor, and a high voltage monitor circuit connected to the source terminal and configured to be connected to a control circuit within the power supply. The low voltage monitor circuit is configured to monitor a source voltage at the source terminal and provide a gate control signal to the gate terminal. The high voltage monitor circuit is configured to monitor the source voltage at the source terminal and provide a power supply control signal to the power supply.

The embodiment the disclosure provides a monitoring circuit and a storage system. The monitoring circuit includes a voltage detection module and a logic circuit module. The voltage detection module is configured to output a first detection signal, a second detection signal and a third detection signal through a first node, a second node and a third node, respectively. The logic circuit module is configured to output a monitoring signal through a fourth node; determine whether the first detection signal has a first preset level, whether the second detection signal has a second preset level, and whether the third detection signal has a third preset level, respectively; determine the monitoring signal to be in a valid state in response to the first detection signal having the first preset level, the second detection signal having the second preset level and the third detection signal having the third preset level.