| 摘要 |
<p>PURPOSE:To obtain the title apparatus capable of protecting a heat generating resistor by a simple circuit provided with a protective circuit for controlling a current supply time so as to prevent the generation of quantity of heat higher than the heat generating quantity of the heat generating resistor. CONSTITUTION:A protective circuit 7 constituted of a monostable multivibrator 71 and an OR gate 72 is positioned at the input side from a control circuit 3 to control a current supply pulse. The current supply time of an input pulse is measured on the basis of a time when the quantity of heat generated at the supply time of a current to a heat generating resistor 1 becomes max. without damaging said heat generating resistor 1 and, when said current supply time is longer than the above mentioned time, the supply of a current is performed only for the above mentioned time to prevent the damage of the heat generating resistor 1.</p> |
