| 摘要 |
PURPOSE:To executed printing at a specific density without heating a heating element beyond a necessary extent even though an ambient temperature changes, by sending a current setting signal to a drive control means on the basis of the detection signal for the temperature of a thermal head. CONSTITUTION:When, for instance, an ambient temperature is high, the resistance value of the thermistor 2 of a thermal head 1 decreases and its terminal voltage becomes, for instance, 3V or under. Since a voltage of 3V or over is inputted from an electric power source side for the non-inverting input of an operational amplifiers 10, 11, the output becomes H. Besides, a terminal voltage of 3V or under of the thermister 2 is inputted for the non-inverting input of an operational amplifier 12, and the output of the operational amplifier 12 becomes L. Therefore, L is outputted from an AND circuit 16 and a current setting signal Sg is changed to H, L to be supplied to a signal processing circuit 5. When this signal Sg is decoded by the circuit 5, a control signal Sc is sent to the input D1 of a latch circuit 4B, and the output Q1 of the circuit 4B is kept at H. The AND circuit 4a is worked and a frequency-divided signal T1 of a small pulse width is sent to a drive part 4A via an OR circuit 4D. |
