Patent ID: 7446574

Claim:
A voltage detecting circuit comprising: an output switching element; an input voltage comparing circuit arranged to control opening and closing of the output switching element in response to an output of a comparison of a first threshold value voltage or a second threshold value voltage lower than the first threshold value voltage with an input voltage, to select the second threshold value voltage when the input voltage changes from a low voltage to a high voltage and intersects the first threshold value voltage, and to select the first threshold value voltage when the input voltage changes from the high voltage to the low voltage and intersects the second threshold value voltage; and a threshold value voltage setting circuit arranged to compare a third threshold value voltage lower than the second threshold value voltage with the input voltage and, when the input voltage changes from a low voltage to a high voltage and intersects the third threshold value voltage, outputs a pulse for a predetermined period thereafter so that the second threshold value is selected in the input voltage comparing circuit; wherein the second threshold value voltage is compared with the input voltage in the input voltage comparing circuit when the input voltage increases.