A hysteretic comparator and voltage monitoring circuit in a POE power system

Abstract

This utility model relates to the field of voltage detection technology in PoE power supply, and discloses a hysteresis comparator and a voltage monitoring circuit in a PoE power supply system. The hysteresis comparator includes a startup unit, a bias unit, and a dual-input comparison unit. The startup unit includes a startup resistor R1, a MOSFET M18, and a MOSFET M19. In actual use, the startup unit of this utility model provides startup current to the bias unit through the MOSFET M18. After the reference voltage output by the bias unit reaches the bias point, the MOSFET M18 is turned off. In this way, after the circuit enters the working state, the current in the branch where the startup resistor R1 is located goes to ground through the MOSFET M19. By dynamically switching the current path of the startup unit, the MOSFET M18 is not working, which reduces power consumption on the one hand, and avoids power consumption interference of the startup unit to the bias unit and the comparison unit on the other hand.

Images