| 摘要 |
PURPOSE:To obtain the optimum pulse width in output power, by providing a means for controlling a switching (SW) element according to the current supply control pulse width determined on the basis of the ON-time of the SW element. CONSTITUTION:The title apparatus is adapted to the printing head driving part of a wire dot printer and printing head driving coils H1-9 are driven by a pulse like current made intermittent by transistors Q1-9. When either one of the coils H1-9 is in an ON-state, an input port P1 becomes low and, on the side of an MPU, it is detected that the transistors are in an ON-state. The MPU makes output ports P1-9 high (low) to make it possible to turn the transistors Q1-9 ON(OFF). Therefore, by measuring the time before the input port P1 becomes low after the output ports P1-9 are made low, an accumulation time tst is cleared. When a current is actually supplied to the heads H1-, the width of the high level outputted to the output ports P1-9 is adjusted with due regard to said accumulation time. |
