| 摘要 |
PURPOSE:To prevent the faulty turn-on of a heater due to CPU runaway by integrating the output of an output port which drives a heater and supplying this integrated value to an input of an A/D converter of a CPU. CONSTITUTION:A temperature detecting thermistor 1 set close to a fixing roll 6 of a copying machine is connected to a CPU2, and the input data is compared with the value corresponding to a prescribed roll temperature programmed previously. A heater 4 of the roll 6 is driven at an output port P1 of the CPU2. The signal sent from the port P1 is integrated (R2, C1) and then compared with the threshold values set by two comparators CMP1 and CMP2. An SSR3 is turned on within said threshold value to conduct a heater 4. Thus the port P1 is latched at H(L) in case the CPU2 has a fault such as a runaway, etc. owing to the external noises, etc. Therefore no output is delivered from both comparators and the SSR3 is turned off. |
