| 摘要 |
<p>PURPOSE:To enable energizing time for heating elements to be controlled through a simple circuitry, by setting a timer circuit such as a monostable multivibrator into an active state only when an energizing pulse signal with a fixed duration is supplied. CONSTITUTION:An arbitrary element in a heating element group 3 is selected by impressing inputs (c) to a NAND gate group 2, and an electric current is impressed for a fixed period of time by an input (f) of an energizing pulse signal, thereby generat ing heat. Since an input is also supplied to a reset terminal CLR of the monostable multivibrator 1, the multivibrator 1 is maintained in the active state for a period of time t3 for which the logic of input (f) is H. Further, the input (f) is differentiated on passing through an inverter 12, and the resultant trigger signal is inputted to a terminal A. A signal (h) is outputted at an output terminal Q for a fixed period of time t1 determined by a resistor 5 and a capacitor 6, and when t1 and t3 are so set that t1>t3, an electric current is impressed for the period of time t3. With such a simple circuitry, the energizing time for the heating elements can be controlled, and even when a trouble is generated in the energizing time control constituted of a micro computer or the like, the heating elements can be prevented from being breakdown.</p> |
