| 摘要 |
PURPOSE:To control generation of discharge at a minimum by a method wherein when contact resistance existing between each head electrode and a thermal transfer ink ribbon exceeds a preliminarily established value, the title head driving apparatus is so constructed that supply on a driving pulse is stopped. CONSTITUTION:A head electrode 1b is electrified following a driving pulse, and a printing current (i) is supplied to a thermal transferink ribbon 3. When output voltage of a transistor 11 [iX(Ra+Rb+Rc+Rd+Re)] exceeds reference voltage 14 by variation of contact resistance Ra existing between the head electrode 1b and the thermal transfer ink ribbon 3, output of a voltage comparator 13 becomes at a L level, and a flip-flop 15 is set. A transistor 16 turns on until the flip-flop 15 is reset, a transistor 9 turns off, and a driving pulse 8 is interrupted. Then, since the head electrode 1b is not electrified while the driving pulse 8 is interrupted, supply time of the printing current (i) to the terminal transfer ink ribbon 3 becomes short. Thereby, though the head electrode is separated from the thermal transfer ink ribbon, discharge is controlled at a minimum, and the head can be prevented from breaking. |
