Patent ID: 7397267

Claim:
A voltage detecting circuit, comprising: a comparative circuit for comparing a reference voltage with a voltage from a power supply; a voltage regulating circuit for providing the reference voltage to the comparative circuit; a display circuit for revealing a status of the voltage from the power supply; and a timer circuit electrically connected between the comparative circuit and the display circuit to cause the display circuit to maintain a status display when there has been an occurrence of abnormal voltage from the power supply, wherein the comparative circuit comprises a first operational amplifier and a second operational amplifier, both a negative input of the first operational amplifier and a positive input of the second operational amplifier receiving the reference voltage; a positive input of the first operational amplifier receiving the voltage from the power supply via a first resistor; a negative input of the second operational amplifier connected in series with a second resistor connected to the positive input of the first operational amplifier, and grounded via a third resistor.