Patent ID: 7796048

Claim:
A polyphase source detecting circuit configured to detecting a polyphase source having at least two phase sources, comprising: at least two sampling circuits each having a control switch, a control terminal of the control switch of each of the at least two sampling circuits connected to one of the at least two phase sources of the polyphase source; and an alarm circuit having a first transistor, a first light-emitting diode (LED), and a second LED, the anodes of the first and second LEDs connected to a power supply, the cathode of the first LED connected to the gate of the first transistor and connected to ground via the control switches of the at least two sampling circuits in turn, the cathode of the second LED connected to the drain of the first transistor, the source of the first transistor grounded, if one of the at least two phase sources is abnormally, the corresponding control switch is turned off, thereby the first LED is turned off and the first transistor is turned on, and then the second LED is turned on.