Photoelectric conversion device and method of driving photoelectric conversion device

A method of driving a photoelectric conversion device including a pixel including a photoelectric conversion unit, and an AD conversion unit configured to perform an AD conversion on an analog signal generated in the pixel by comparing a level of the analog signal with a level of a reference signal whose level changes with time, the method comprising:

• performing a plurality of times of the AD conversion with different lengths of AD conversion periods on the same analog signal generated in the pixel to acquire a plurality of digital signals corresponding to the plurality of times of the AD conversion;
• and
• generating an image signal by compositing the plurality of digital signals,
• wherein a length of a first AD conversion period of the plurality of times of the AD conversion is shorter than a length of a second AD conversion period of the plurality of times of the AD conversion, a rate of change with respect to time of the reference signal used in the second AD conversion period is smaller than a rate of change with respect to time of the reference signal used in the first AD conversion period, a potential of the reference signal changes to a first level in the second AD conversion period, and a potential of the reference signal changes to the first level in the first AD conversion period.