| 摘要 |
PURPOSE:To prevent the burnout accident of a thermal head, by mounting a circuit detecting the pulse width of the current flowing to a heat generating element or a drive voltage value on the same substrate as the thermal head. CONSTITUTION:A pulse width setting circuit 10 is provided on a thermal head substrate 5 as hardware and the max. pulse width value optimizing the operation of each part inclusive of a heat generating element group is preset prior to printing. When printing operation is started, the pulse width setting circuit 10 continuously monitors the drive time of a thermal head. When the thermal head is continuously driven for a time exceeding the aforementioned max pulse width value, the enable signal to a drive circuit 2 is changed to a drive stop side. This means is provided in order to block the drive current to the heat generating element but a drive voltage detection circuit is preliminarily provided with respect to drive voltage (h) to perform the monitoring of voltage according to circumstances. By this constitution, the heat generation of the thermal head is blocked when drive voltage becomes abnormal and an abnormal state causing the burnout of the heat generating element can be avoided. |
