Thermal head driving device

Details

Inventors: Noda, Atsushi; Hanagata, Takayoshi;
Assignee: Canon Kabushiki Kaisha (Tokyo, JP)
Primary Examiner: Rubinson; G. Z.
Assistant Examiner: Brady; W. J.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto

A thermal head driving device is provided with a safety circuit for preventing the heating resistors of a thermal head from being burnt or reduced in life by an abnormal printing pulse signal being applied to the heating resistors. The device is also provided with a temperature correcting circuit for controlling the heating temperature of the heating resistors to prevent the printing density of the thermal head from being varied under the influence of the ambient temperature. The device is further provided with a compensation circuit for varying the printing conditions graded for each range of resistance values of the heating resistors in a plurality of thermal heads to prevent a difference in printing density from being caused by the difference between said resistance values. At least two of the safety circuit, the temperature correcting circuit and the compensation circuit are combined.

DETAILED DESCRIPTION It is a first object of the present invention to prevent burning or reduced life of the heating resistors in a thermal head.
It is a second object of the present invention to prevent the printing density of the thermal head from being varied under the influence of the ambient temperature.
It is a third object of the present invention to provide printing conditions suited for each grade of the heating resistors graded for each range of resistance value.
It is a fourth object of the present invention to combine the above-described first to third objects to thereby improve the printing quality and reliability.
The invention will become fully apparent from the following detailed description thereof taken in conjunction with the accompanying drawings.

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