Patent ID: 7459941

Claim:
A device for detecting an interface voltage, comprising: a first control circuit receiving the interface voltage to generate a first control signal and drive a first voltage level indicator if the interface voltage level is less than a first voltage level; and a second control circuit receiving the interface voltage to generate a second control signal and drive a second voltage level indicator if the interface voltage level exceeds a second voltage level; wherein the first control circuit comprises a first detecting circuit and a first driving circuit, wherein the first detecting circuit detects the interface voltage to generate a first detect signal, allowing the first driving circuit to turn on the first voltage level indicator if the interface voltage level is less than the first voltage level; wherein the first detecting circuit comprises: a first resistor receiving the interface voltage; a second resistor coupled between the first resistor and ground; and a first detecting element coupled to a junction of the first and second resistors, generating the first detect signal in response to a voltage at the junction of the first and second resistors; wherein resistances of the first and second resistors are determined according to the interface voltage and a reference voltage of the first detect element; and wherein the first detecting element comprises a first Zener shunt regulator having a reference terminal coupled to the junction of the first and second resistors, an anode coupled to ground, and a cathode generating the first detect signal transmitted to the first driving circuit.