PROBLEM TO BE SOLVED: To maintain high resolution of a signal waveform while reducing the number of signal lines when generating a waveform of a driving signal for driving a driving element.SOLUTION: Data of a prescribed bit number are sequentially switched at prescribed timing corresponding to a change point of a waveform of a driving signal, and the data of the prescribed bit number thus switched are held until timing corresponding to a next change point. The held data are added to previous output data for each prescribed addition period to be new output data and are converted to the driving signal to be output. Thus, though the number of signal lines is small, the waveform of the driving signal can be generated with high resolution.
