Detecting circuit and associated detecting method

A detecting circuit of an electronic device includes a resistance detecting circuit and a voltage supplying circuit, wherein the detecting circuit is coupled to an input circuit which is coupled to the electronic device and comprises a plurality of resistors, and each resistor is coupled to a switch, wherein the resistance detecting circuit is arranged to detect whether the input circuit has a resistance variation and generate a detecting signal indicative of the resistance variation; the voltage supplying circuit coupled to the resistance detecting circuit to supply a first voltage signal, wherein the voltage supplying circuit receives the detecting signal, and selectively switches the first voltage signal to a second voltage signal according to the detecting signal; wherein the resistance detecting circuit determines whether at least one of the plurality of switches is closed according to the second voltage signal.