Switching controller with outputting-power limitation and low-voltage protection

The present invention provides a low voltage output power limit protection switching control device for use in a power supply, comprising: a hysteresis comparator circuit, a clamping voltage generating unit, a power limit comparator, a drive signal generating unit, extraction unit and clamp the input supply voltage variation by a clamping voltage generator to output a maximum power limit voltage dynamic power limit as a critical reference. Furthermore, the power supply voltage and the input voltage range of critical value hysteresis carried out at low voltage comparison operation, the control unit stops the drive signal generating a drive signal output as a low input supply voltage protection.