| 摘要 |
<p>PURPOSE:To prevent erroneous printing and the damage of a heating element from occurring by providing two enable signal input terminals corresponding to the positive and negative logics of printing enable signals in a printing current drive circuit, which drives the heating element, and attaching an open detection circuit to the respective enable signal input terminals. CONSTITUTION:In terminal open detection circuits, an input terminal 19 for a printing enable signal ENABLEX having a negative logic is connected to a resistor 1 for a positive power source VDD and to a resistor 2 for a negative power source VSS and further connected to the minus input terminal of a comparator circuit 3 and to the plus input terminal of a comparator circuit 4. An input terminal 20 for a signal ENABLE is connected to a resistor 5 for a positive power source VDD and to a resistor 6 for a negative power source VSS and further connected to the minus input terminal of a comparator circuit 7 and to the plus input terminal of a comparator circuit 8. In the case where both of the two enable input terminals of a thermal head are not open, the open detection circuits are operated to forcibly interrupt signals to a printing current drive direction, and erroneous printing and the damage of a heating element are prevented.</p> |
