Patent ID: 7528734

Claim:
A system adapted for automatically detecting power supply voltage, the system comprising: a voltage divider connected to a power supply source; an A/D converter connected to the voltage divider; a detection module connected to the A/D converter for comparing a digital signal converted by the A/D converter with a reference signal stored in the detection module; a relay driving circuit connected to the detection module; at least one relay connected to the relay driving module and the power supply respectively, said relay controlled by the relay driving module; at least one outlet coupled to said corresponding relay for outputting voltage; an alarm device; an alarm circuit connected to the detection module and the relay driving circuit, the alarm circuit adapted for driving the alarm device; and a button connected between the alarm device and the alarm circuit; wherein if the digital signal is the same with the reference signal, the detection module controls the relay driving module to turn on said relay to output voltage from a corresponding outlet, if the digital signal is different from the reference signal, the detection module controls the alarm circuit to drive the alarm device to give an alarm until the button is pushed, and after the button is pushed, the alarm circuit controls the detection circuit to drive said relay driving circuit to turn on said relay to output voltage from corresponding outlet, meanwhile the digital signal is stored in the detection module as the reference signal.