| 摘要 |
PURPOSE:To enable a thermal head to be securely protected from being burned due to an overcurrent, by a method wherein it is detected whether or not printing data are present in a normal period of time, it is detected whether or not a thermal head is located at a normal printing position making contact with a platen, and supply of a driving power source is controlled by the logical sum of the detection outputs. CONSTITUTION:The first position sensor part 10 detects whether or not the thermal head 5 is located at the printing position, and outputs a detection signal to a signal input terminal 30A of a thermal head protective circuit 30. The printing data are supplied to a printing data input terminal of a thermal head driving part 25 through a signal input terminal 20, and are supplied to a signal input terminal 30B of the protective circuit 30. The protective circuit 30 detects whether the printing data to be supplied to the driving part 25 are present in a normal period of time, detects whether or not the head 5 is located at the normal printing position making contact with the platen 1, and a relay coil switch 40B is opened and closed by the logical sum of the detection outputs, thereby controlling the supply of the driving power source to the driving part 25. |
