| 摘要 |
PURPOSE:To make it possible to automatically supplied printing voltage optimum to set printing density to a heat generating resistor, by controlling voltage applied to the heat generating resistor by measuring the resistance value of the heat generating resistor of a thermal head. CONSTITUTION:The output terminal of a voltage generation circuit 26 is connected to the common electrode of heat generating resistors 181 through a connector 29 and a detection resistor 30 by attaching a thermal head 18 to a thermal printer, and a resistance measuring circuit 25 and a voltage control circuit 27 are connected to said common electrode while a drive circuit is connected to the individual electrode of the heat generating resistors 181 through the connector 29. When a power source is closed, a drive pulse for simultaneously driving all of the heat generating resistors 181 is sent out from a drive pulse generation circuit 28 and both terminal voltages of the resistor 30 are measured by the measuring circuit 25 to calculate the resistance value of the group of the heat generating resistors 181 and, on the basis of said resistance value, the voltage control circuit 27 sets the output voltage of the voltage generation circuit 26 so as to bring the same to a preset optimum value corresponding to printing density.
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