Analog-to-digital converter

An analog-to-digital convertor of an integration type, comprising:

• a charging circuit having a capacitor configured to store electric charges based on an input current;
• a discharging circuit configured to discharge the electric charges stored in the capacitor;
• and
• a counting circuit configured to count a charge-discharge count of the capacitor in a first conversion period and in a second conversion period, in order to convert a current value of the input current into a digital value,
• wherein the first conversion period includes a first pre-charging period and a first counting period,
• the second conversion period includes a second pre-charging period and a second counting period,
• the discharging circuit has a switch provided for discharging the electric charges stored in the capacitor, and
• the analog-to-digital convertor further comprises a random-pulse-width modulation circuit provided for generating a random-pulse-width modulation signal for changing an open-close time period of the switch in the first pre-charging period and in the second pre-charging period.