Abstract: A line thermal printer has a line thermal head comprised of a plurality of physical blocks arranged in a line. Each physical block has a plurality of heat generation elements to which power is selectively supplied for dot printing a line. A driving circuit has driving blocks corresponding to the physical blocks and selectively supplies power to the heat generation elements line-by-line in line sequence in accordance with the printing dot data. Printing dot data memory blocks are connected to corresponding ones of the driving blocks and supply the printing dot data to the driving circuit in synchronism in line sequence timing. A printing dot counter has counter blocks connected to corresponding ones of the printing dot data memory blocks and counts the printing dot number on the basis of the printing dot data held in the memory blocks for each line of print.

Abstract: This invention is directed to provide a line thermal printer which controls a power supply quantity to a thermal head by high speed control below a second unit and can insure always a predetermined printing density. The line thermal printer includes circuit elements for multiplying a heat accumulation counter for counting cumulatively the number of dot data for each line by a heat radiation constant in a predetermined cycle and for controlling a power supply pulse width on the basis of the count value of the heat accumulation counter.