| 摘要 |
<p>PURPOSE:To provide a circuit for protecting an apparatus from temperature rise due to stoppage of operation of a cooling fan. CONSTITUTION:When revolution of a fan 1 stops, ripple element of a current flowing into the terminal A disappears and an output of a comparator IC 17 always becomes 'H' level. Therefore, a capacitor 15 continuously rises the input voltage to the terminal E of a comparator IC 18. Therefore, after a constant time period from stoppage of the fan 1, an output of the comparator IC 18 becomes 'H'. Upon reception of an output from the comparator 18, a CPU 22 starts a timer 23 and controls a CRT display 25 to display a warning sentence by instructing a display circuit 24. Thereafter, when the timer 23 continues the counting operation for a predetermined time period, CPU 22 sets an input to the photothyristor couplter 19 to the 'H' level to stop the supply of power source to the apparatus with an inverter circuit 21.</p> |
