| 摘要 |
<p>PURPOSE:To prevent a microcomputer from generating runaway or the like when the instantaneous disconnection of a primary power supply or its abnormal low voltage is generated by adding an input voltage detecting circuit to the above circuit. CONSTITUTION:The input voltage detecting circuit 15 for detecting the input voltage of a DC power supply device 1, and at the time of detecting an abnormal input voltage, forcedly resetting the microcomputer 5 is added to the microcomputer power ON reset circuit. At the time of generating the instantaneous disconnection or an abnormal low voltage in the primary power supply 1, the detecting voltage of the circuit 15 is set up to a value close to the minimum input voltage allowing the device 1 to maintain the output voltage. The microcomputer 5 is forcedly reset by forcedly discharging the charge of a capacitor 7 by the secondary transistor (TR) of a photocoupler 14 before the output voltage is dropped lower than the operation guarantee minimum voltage of the microcomputer 5. Since the same state as normal power ON reset can be obtained after normally restoring the primary power supply 1 again, the microcomputer can be prevented from falling into an abnormal state such that the microcomputer is not restored while running away or stopping its operation.</p> |
