Thermal printer for a portable data terminal

Abstract

A thermal printer is provided which is coupled to include a source of printing signals, such as a portable hand held computer or data terminal, for printing an image on a sheet of printing material in accordance with the printing signals. The thermal printer includes a printer controller and a thermal printing head which includes a plurality of thermal heating elements aligned in a row across the sheet of printing material to generate heat to thereby print dots on the printing material. These heat generating elements are powered by a battery having limited size and power. The printer controller receives the printing signals and generates dot signals in response thereto for activating selected heat generating elements. The printer controller includes a counter which counts the number of dot signals. Depending on the number of dot signals for each line or row, the printer controller activates an optimum number of groups of heat generating elements to maximize printing speed for the amount of power available. In some instances, all the heat generating elements in a particular row may be activated and in other instances, different combinations of groups of heat generating elements will be activated depending on the number and position of the heat generating elements which must be activated to form one row or line of the desired image.