| 摘要 |
PURPOSE:To prevent preliminarily abnormality from being generated by detecting whether the abnormality of a thermal head is generated or not by providing a comparison means wherein a drop in voltage of a heating element to which electric power is supplied is compared with a threshold voltage and when both values being in a specific voltage relation is detected, an abnormality-generated signal is emitted. CONSTITUTION:When electric power is supplied, and if a heating element (r1) is damaged, in the case of a wire-broken state, a drop in voltage of the element (r1) is not generated. Then, a voltage VEC to a contact EC comes to be almost equal to that of a power source VDD. Further, since a comparator OP of an abnormality detection circuit compares the voltage VEC with a threshold voltage VTH, and emits an output at a high voltage level, a detection data DEC of a theoretical value H indicating occurrence of the abnormality is transferred to a central control circuit MPU. Besides, when the element (r1) is normal, a drop in voltage of the element (r1) is generated. Therefore, the voltage VEC at the contact EC comes to be lower than the threshold voltage VTH, an output of the comparator OP comes to be at a low voltage level, and the detection value DEC of a theoretical value L indicating the normal state is transferred to the central control circuit MPU. |
