| 摘要 |
<p>PURPOSE:To prevent a temperature increase of a head, by a method wherein a thermal resistance changing element is provided on a substrate member of the thermal head and a feedback stabilizing circuit is provided in a line which is to be a supply power source for driving a heating element in the thermal head. CONSTITUTION:An output voltage V0 from a power source circuit portion 1 is divided at resistances R3, R4 and a variable resistance VR1. At this time, with the divided voltage higher than Vref, a transistor Tr3 is turned ON and the base voltage of a transistor Tr2 lowers, which decreases the output voltage V0. On the other hand, the connection of a thermal resistance changing element (a thermistor TH) disposed on a thermal head 10 in place of the resistance R3, if the heat due to printing increases a temperature of a substrate of the thermal head, lowers the resistance of the thermistor TH and turns the transistor Tr3 On and lowers the base voltage of the transistor Tr2, which decreases the output voltage V0. In this manner, an applied voltage to the thermal head is lowered, thus a smaller quantity of current is passed through a heating element working as a fixed resistance, which results in reduction in a heating energy and prevention of a temperature increase of the head.</p> |
