PURPOSE: To completely prevent overheat, burnout of a driver, etc., by counting the length of a time when a driving time signal is output, outputting a protection signal if the counted value becomes the length of a set time or longer to forcibly cut OFF a drive signal.

CONSTITUTION: If a set time to a latch circuit 22 is erroneous due to runaway, etc., of a CPU 11, a driving time signal TS is continuously output. Then, when a counter 41 counts set number of pulse signals CLK, it outputs a carry up signal CU, and hence a protection signal G is output from the terminal Q of a flip-flop 42. Thus, gates 51 of signal cut-off means 50 are turned OFF to forcibly cut OFF a drive signal DRV, and a drive signal DRVa is not substantially input to a driver 30. Accordingly, even if the signal TS is continuously output, a driving current I can be cut OFF, and hence overheat, burnout of the driver 30, a printing head 1 can be prevented.