Thermal printer that effectively controls heat buildup

摘要

A thermal head has heating elements and is movable relative to a printing medium. A pulse application portion applies a drive voltage pulse selectively to the heating elements. A voltage measurement portion measures a head voltage applied to the thermal head. A total-dot counting portion adds a number of dots which are printed from a reference time point, thereby obtaining a total dot count. An adjustment portion adjusts the total dot count based on a predetermined adjustment dot count corresponding to an ambient temperature. A heat-buildup-coefficient storing portion stores a heat buildup coefficient corresponding both to the ambient temperature and to an excess dot count. A pulse-width setting portion sets the width of the drive voltage pulse based on the head voltage and the heat buildup coefficient. A pulse-width correction portion corrects the width of the drive voltage pulse based on the head voltage measured by the voltage measurement portion.