| 摘要 |
PURPOSE:To obtain a constant printing density all the time even when thermal heads are exchanged by a method in which the same resistor elements as heating elements are provided to the thermal head having plural resistor heating elements, and on the basis of the resistance values of the elements, applied voltage is controlled. CONSTITUTION:A resistor element 5 made of the same material as that of a heating resistor element 2 is provided to part of a thermal head in which heating resistor elements 2-1-2-7 are provided on a ceramic base plate 1, and also the resistor element 5 is connected to the terminals Ra and Rb of a constant- voltage regulation circuit through a lead pattern. When connecting a thermal head in which the resistance value of the heating element 2 is lower than that of standard heating element, the base voltage of a transistor Tr2 rises because the resistance value of the resistor element 5 is also lower than standard, and therefore, collector cuttent is increased and the voltage drop of the resistor R1 is increased. By this, the impedance between the collector bases of the transistor Tr1 is increased and output voltage Vout becomes lower than standard. When the resistance value of the heating element 2 is high, the output voltage also becomes higher. |
