Patent ID: 7821414
Filing Date: 2010-10-26
Classification: G01R

Abstract:
1. A polyphase source detecting circuit configured to detecting a polyphase source having three phase sources, comprising: three sampling circuits each having a control switch, a control terminal of the control switch of each of the three sampling circuits connected to one of the three phase sources of the polyphase source respectively; and an alarm circuit having a first transistor, a buzzer, a first light-emitting diode (LED), a first diode, and a second diode, the anode of the first LED connected to a power supply, the cathode of the first LED connected to the cathode of the first diode, the anode of the first diode connected to the anode of the second diode and the power supply via a first resistor, the cathode of the second diode connected to the base of the first transistor, the collector of the first transistor connected to the power supply via the buzzer, the emitter of the first transistor connected to ground, the cathode of the first LED connected to ground via the control switches of the three sampling circuits in turn, if one of the three phase sources ceases working, the corresponding control switch is turned off, thereby the first LED is turned off and the buzzer is turned on.