PURPOSE: To prevent the electrode from being broken by a method wherein at least one of the levels of the output voltage and the output current of the charging electrode is detected to effect the stopping or the like of a charging signal.
CONSTITUTION: A detecting circuit, for example, is obtained by adding a circuit AD same as a driving driver A for the charging electrode A1. When the charging electrode A1 connected to the driver is operating normally, the output 5 of a comparator 4 is at L level. On the other hand, when the charging electrode A1 is short-circuited to a neighboring electrode with ink and the voltage of the charging electrode A1 is at H level while the same of the neighboring electrode side is at L level, the output of the driver A is lowered than H level during the normal operation thereof. If the output of the driver A is lower than a reference level, the comparator 4 is operated to output a pulse. This pulse is inputted into the control circuit and the breakage of the electrode may be prevented by controlling the charging output in the control circuit.
KIKUCHI MASAJI
UEDA MICHIO
