| 摘要 |
PURPOSE:To provide a device having high safety by controlling heater disconnection under the AND conditions of a detection signal for discontinuity of a heater and the on signal from a heater control part and integrating control circuits for detection in a printed board. CONSTITUTION:When a heater 4 is disconnected, a transistor Q4 is disabled irrespective of the on and off of a heater control part 2, and the potential at the point A goes to an H level, then a comparator IC1 emits an output. When the part 2 is off, the potential at the point C is an H level, and the potential at the point D is grounded through a transistor Q3 and goes to an L level, thus prohibiting the operation of transistors Q2 and Q3. When the part 2 is on, the potential at the point C is an L level, the TRQ3 does not operate. Therefore, the TRQ2 is turned on by the H level potential at the point D and the TRQ1 is changed to off. Thus, power relays RA1-1, RA1-2 are turned off, and the conduction of electricity to the heater and other primary circuit parts, for example, a main motor for driving, and power sources for electrostatic charging, transferring and exposing are interrupted. |
