| 摘要 |
PURPOSE:To prevent memory data from being erased and destroyed owing to a drop in source voltage by interposing a diode between an external power supply terminal and a main power circuit and directly monitoring a main source voltage. CONSTITUTION:The diode D3 is connected between the main power source E and external power supply terminal C and the anode-side voltage of this diode D3, i.e., the voltage of the main power source E is monitored directly by a voltage monitoring circuit 3. Therefore, even when an external power source is connected, a voltage monitoring means 3 detects the no-voltage state of the main power source E in the absence of the voltage, so the system does not operate unless the main source voltage is sufficient. Namely, a memory 2 is closed when the voltage of the main power source E drops without reference to whether or not the electric power of the external power source is supplied. Consequently, even if a connector for external power supply is disconnected accidentally, the data in the memory 2 are neither erased nor destroyed and the reliability of the electronic equipment is improved. |
