| 摘要 |
<p>PURPOSE:To ensure that energization of heat generating elements occurs substantially only in printing and contrive satisfactory protection, by providing a circuit for operating a switching element and a discharging circuit when none of a condition that a CPU is in a state of printing, a condition that a thermal head is pressed against a platen and a condition that a power source voltage for control is maintained at a predetermined voltage are satisfied. CONSTITUTION:A NAND circuit 9 is supplied with the following three signals: a detection signal indicative of whether a power source voltage Vcc for a controlling circuit is lowered, a signal indicative of whether a thermal head is separated from a platen or pressed against the platen, and a signal indicative of that a CPU 5 is in a state of printing. When one of the three signals is at a low level, a switching element 6 and a discharging circuit 8 are operated through the NAND circuit 9, thereby immediately lowering the voltage level on the side of a common electrode for a group of heat generating elements 3.... Accordingly, none of the heat generating elements 3... are supplied with an electric current for a long period of time, even when the outputting condition of a head driver 4 becomes unstable.</p> |
