Patent ID: 9013447
Filing Date: 2015-04-21
Classification: G06F

Abstract:
1. A method of sensing a change in an electrostatic capacity in a capacitor to be measured, the method comprising: a step of charging a reference capacitor by applying a power supply to the reference capacitor, in a status when the discharging of the reference capacitor is blocked; a step of stopping charging of the reference capacitor when a voltage on the reference capacitor exceeds an upper limit voltage, which is lower than the power supply; a step of sharing a part of charges of the reference capacitor with the capacitor to be measured; a step of discharging at least a part of the charges shared with the capacitor to be measured; a step of repeating at least one of the step of sharing a part of charges of the reference capacitor with the capacitor to be measured and the step of discharging at least a part of the charges shared with the capacitor to be measured until the voltage on the reference capacitor becomes lower than a lower limit voltage; a step of stopping the sharing and the discharging when the voltage on the reference capacitor is lower than the lower limit voltage; and a step of sensing the change in the electrostatic capacity in the capacitor to be measured using at least one of the number of sharing times and the number of discharging times, wherein the step of charging the reference capacitor by applying a power supply to the reference capacitor includes: a step of comparing the voltage on the reference capacitor with the upper limit voltage and the lower limit voltage; a step of inverting a comparison result with the upper limit voltage; a step of logically operating the lower limit voltage and the inverted comparison result with the upper limit voltage; and a step of maintaining the charging of the reference capacitor and the blocking the reference capacitor from being discharged, when the voltage on the reference capacitor is between the upper limit voltage and the lower limit voltage, based on the logical operation result.