Patent ID: 8624440

Claim:
A power management circuit coupled between a power supply and a load, the power management circuit comprising: a sampling unit for sampling an input voltage from the power supply to generate a sampling voltage; a reference voltage unit for receiving the input voltage and generating a reference voltage when the input voltage is larger than a predetermined value; a comparator for comparing the sampling voltage with the reference voltage, generating a first signal when the sampling voltage is larger than the reference voltage, and generating a second signal when the sampling voltage is smaller than the reference voltage; and a power managing unit for establishing an electrical connection between the power supply and the load according to the first signal, and cutting off the electrical connection between the power supply and the load according to the second signal; wherein the comparator comprising an operational amplifier, a fourth resistor and a fifth resistor, the operational amplifier comprising an inverting input terminal coupled to the reference voltage unit, a non-inverting input terminal coupled to the sampling unit, an output terminal coupled to the power managing unit, the fourth resistor is coupled between the non-inverting input terminal and the output terminal, the fifth resistor is coupled between the output terminal and the power supply.