| 摘要 |
<p>PURPOSE:To prevent a heat-generating element from being damaged, in case if the heat-generating element was impressed with a signal for operating longer than a prescribed period of time, by disconnecting the power supply after a fixed period of time by a time constant circuit. CONSTITUTION:When a heat-generating element 26 started driving, a transistor 33 becomes OFF and a capacitor 35 starts being charged. As a capacitor 35's terminal voltage is lower than a comparator 36's basic voltage, a transistor 38 is kept in OFF position until a set time T elapses, and a signal wire 30 is kept on a high level. During this time, the heat-generating body is electrified and generating heat. If a driving signal is continued longer than the prescribed time and becomes more than the time T, the capacitor 35's terminal voltage becomes higher than the basic voltage, and an high output is issued from the comparator 36 to turn the transistor ON. And therefore, the signal wire 30 becomes down to a low level and the power supply to the heat-generating element 26 is stopped.</p> |
