| 摘要 |
PURPOSE:To obtain an optimum color density automatically and enable to mount and replace a head without requiring any adjustment, by a method wherein current passing times proportional to the resistance values of heating resistors in a head of a printer or the like are provided by using dummy heating resistors. CONSTITUTION:The thermal head 1 is provided with 8 blocks of resistor groups having N neating resistors 4 per block, and L dummy heating resistors 5 having the same scattering of resistance value as that in the resistors 4. The head 1 is connected to a selection-side driver 2, a picture signal side driver 3 and a pulse width control circuit 10 restricting the time of passing a current to the resistors 4. An electric current from a power source V flows through each of the resistors 5 connected in series and a driver 11 for discharging. When the resistor 4 is selected by selection signals SL1-SL8 and picture signals DV1-DV32 and a printing command signal Pr is supplied, the driver 11 is turned OFF, an output from a comparator 16 is changed according to the change in the terminal voltage of a capacitor 12, and a relevant gate 8 in the driver 2 is turned OFF to stop the supply of current to the resistor 4. |
