Patent ID: 7759984

Claim:
A comparing circuit, comprising: a charging and discharging circuit to charge a capacitor with charging current and discharge the capacitor with discharging current by switching alternately between a charging operation and a discharging operation in response to a switch in level of an input pulse signal between a High-level and a Low-level; a first comparator circuit to compare a capacitor-voltage of the capacitor with a predetermined threshold voltage; an output-signal generating circuit to generate and output an output pulse-signal based on a first pulse-signal supplied from the first comparator circuit; and current-value adjusting means for adjusting a value of the charging current and a value of the discharging current of the charging and discharging circuit by generating a signal that is based on the first pulse-signal and is to adjust the value of the charging current and the value of the discharging current, and supplying the charging and discharging circuit with the signal thus generated, the first comparator circuit comparing the capacitor-voltage with a first threshold voltage and the capacitor-voltage with a second threshold voltage, which is higher than the first threshold voltage, to generate the first pulse-signal responsive to one of (a) a case in which the capacitor-voltage is lower than the first threshold voltage, (b) a case in which the capacitor-voltage is between the first threshold voltage and the second threshold voltage, inclusive, and (c) a case in which the capacitor-voltage is higher than the second threshold voltage, the first comparator circuit supplying, when the capacitor-voltage becomes higher than the second threshold voltage in charging the capacitor, the output-signal generating circuit with the first pulse-signal to switch a level of the output pulse-signal between a High-level and a Low-level, and the first comparator circuit supplying, when the capacitor-voltage becomes lower than the first threshold voltage in discharging the capacitor, the output-signal generating circuit with the first pulse-signal to switch the level of the output pulse-signal between the High-level and the Low-level.