| 摘要 |
<p>PURPOSE:To judge a condition to be abnormal and stop the suply of printing pulses or a driving power to a thermal head when a converted voltage exceeds a reference voltage, by a method wherein the pulse width and the pulse separation of printing pulses supplied to a thermal head are converted into voltages, and the voltages are compared with reference voltages. CONSTITUTION:For example, where the printing pulses PP include pulses P1 having a width larger than a predetermined width, the charging voltage of an integrating circuit 52 is raised above the reference voltage VTH by the pulses P1, as shown at (b) in the figure. Therefore, an output signal from a comparator 54 is brought to a low level in the condition wherein the charging voltage of a capacitor 522 is higher than the reference voltage VTH, as shown at (c) in the figure. As a result, a resetting output terminal Q of a flip-flop circuit 56 supplied with this signal is brought to a low level as shown at (d) in the figure, whereby a gate of an AND circuit 51 supplied with a signal from the circuit 56 is closed, and outputting of the printing pulses PP to the thermal head 11 is stopped, as shown at (e) in the figure. Accordingly, the thermal head 11 is prevented from being overloaded.</p> |
