| 摘要 |
<p>PURPOSE:To supply electric power to the heat-generating part of a resistor in a thermal head in the most appropriate manner by providing a limiting means which limits the maximum value of electric energy to less than a predetermined value. CONSTITUTION:The pulse width T2 of a pulse signal from a monostable multivibrator 70 changes in accordance with environmental temperature at the time of printing. Accordingly, a switching transistor 75 is turned on to energize a resistive heat-generating element 38 during a period of pulse width (T1+T2). When a timer circuit 47 reaches a predetermined time (1.8[msec]) during a period (T1+T3), the timer circuit 47 generates an interruption signal into CPU 41. The CPO 41, upon reception of this interruption signal, reduces the voltage of an authorization terminal from high level to low level. If any significant drop in environmental temperature or fault in a thermister 66 or time change occurs, the maximum value of the resistive heat generating element 38 is limited to less than a predetermined value (1.8[msec]). Therefore, an excessive electric energy will not be supplied to the resistive heatgenerating element, and extraordinary consumption of the resistive heat-generating element 38 is prevented.</p> |
