| 摘要 |
PURPOSE:To stably obtain voltage drop, by detecting voltage drop in the timing in the vicinity of the terminal of one gradation current supply period of each density data to form and output voltage drop data and reading correction data corresponding to the voltage drop data to control the current supply time of a heat generating resistor to be transferred. CONSTITUTION:The reference voltage VP obtained by holding the voltage source or that of the power source for a line thermal head 6 at the time of non-printing is supplied to an input terminal 31 while the head terminal voltage VT of the line thermal head 6 is supplied to an input terminal 32. A differential amplifier 33 amplifies the difference voltage of the reference voltage VP and the head terminal voltage VT to output the voltage drop VD corresponding to the voltage drop between the voltage of the power source and the line thermal head 6 to an A/D converter 42 in a wave form held as it is. The timing performing this data conversion is set in the vicinity of the terminal of a current supply period. Since the variation of the power source is stable in the vicinity of the terminal of the current supply period, when data is converted in this timing, voltage drop data can be obtained in a state sufficiently stable from a practical aspect. |
