Patent ID: 7271819

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