| 摘要 |
PURPOSE:To compensate for the deterioration of picture quality by controlling effects of the variation in the voltage of power source and also in the temperature of a recording head with varying loads by a method in which a drive power source is supplied to heating resistors on the basis of pulse width from comparison of the output levels of an integrator and a temperature detector. CONSTITUTION:Terminal voltage Vt of a thermister 1 is applied to the plus (+) side input terminal of a comparator 3. An integrator 10 to integrate power source voltage E for driving the thermal head is made up of a resistor 4 and a condenser 5, and its integration output SI is applied to the minus (-) side input terminal of the comparator 3. A transistor 6 forms a discharge circuit to reset the integrator 10 and is driven by trigger pulse PT. The pulse width of drive pulse PD sent out from the comparator 3 is greater, the lower the power source voltage E becomes, but the pulse width is smaller, the higher the voltage E becomes. The pulse width tau is longer, the lower the voltage E becomes, and also the pulse width is shorter, the lower the output voltage Vt of the thermister 1 becomes with the rise of the temperature of the base plate. In the opposite case, opposite actions result. |
