| 摘要 |
PURPOSE:To enable appropriate printing, by generating a fly-back turning-OFF command after a preset period of time, in response to a turning-ON command for a transistor for starting the charging of a CR charging circuit, for supplying a head current and for a fly-back current. CONSTITUTION:When input points A and B are set to 0V and 5V, respectively, by a timing circuit 20, a transistor Tr4 is turned ON to start the charging of the CR circuit, and an output from an inverter INV is raised to a high level to turn ON transistors Tr3, Tr1, Tr2, whereby a head current I is passed to a coil 13. Next, when the charging voltage V becomes higher than a preset voltage Vr of a comparator IC1 with a predetermined time constant, the output of the comparator IC1 is inverted to turn OFF the transistors Tr3, Tr1, thereby stopping the supply of the current. However, a fly-back current is passed to a coil 13 through a diode D2, so that the head current is gradually lowered, and after a preset period of time, the circuit 20 sets the point B to 0V, thereby turning OFF the transistor Tr2 to rapidly reduce the head current I to zero. Accordingly, the current-passing time can be controlled so as to obtain an appropriate head current, irrespectively of variations in current or voltage. |
