| 摘要 |
PURPOSE:To evade a thermal breakdown due to abnormal feeding to a heating resistor by comparing a voltage applied to a control circuit with a specific voltage and controlling a voltage applied to the heating resistor. CONSTITUTION:The power circuit of a printer head is equipped with a switch circuit 8 which intermits the voltage applied to the heating resistor 2 and a comparing circuit 9 which judges whether a voltage VCC applied to the control circuit 1 is normal or not between the downstream side of the 1st rectifying circuit 4 and the circuit 8. The circuit 8 consists of a transistor (TR), a switching TR, and a resistance and the circuit 9 consists of a Zener diode and a resistance. Those circuits 8 and 9 form a protecting circuit 10. Then even if a false signal is inputted when the voltage is unusable during power-on or power-off operation, or when the voltage can not be applied to the control circuit 10, the voltage applied to the heating resistor 2 is cut by the circuit 1 to prevent the heating resistor 2 from being broken down thermally. |
