Driving method for thermal head in thermal printer

Abstract

Abstract PURPOSE:To enable an optimum printng quality to be secured over the range from a character pattern with a high black/white ratio to one dot line, by varying an impressed voltage in accordance with the quantity of impressed power. CONSTITUTION:When a printing power source 15 is connected to a terminal 4 of a common electrode, a voltage drop is generated between the terminals 4, 5 of the common electrode due to a resistance element 6 and an operating current, whereby a voltage proportional to the number of heating elements in a heating element group 2 which are simultaneously supplied with an electric current to generate heat. A controlling voltage amplified by a comparing operational amplifier 11 is received by a voltage-controlling part 14, the black/white ratio of the pattern being printed is discriminated, and the value of a voltage to be impressed is determined. This information is transmitted to the power source 15, which generates an optimum impressed voltage based on the information. Accordingly, since the impressed voltage is controlled in accordance with the black/ white ratio of the pattern to be printed, the optimum printing quality can be obtained over the range from a character pattern with a high black/white ratio to one dot line.

Inventors

• 👤 Takeshi Hirano
• 👤 毅 平野

Bibliographic Details