Patent ID: 6633471
Filing Date: 2003-10-14
Classification: H02H

Abstract:
An overcurrent protection circuit comprising:an AC relay; a silicon controlled rectifier which controls said AC relay; a trigger circuit which drive said silicon controlled rectifier; a micro current detection amplifier which serves as a triggering signal source for said trigger circuit; and an alarm device; wherein said AC relay has a common contact connected to a first power line, a normal close contact for electric current output of said first power line to which said common contact is connected, and a normal opening contact bridged to a second power line through said alarm device, characterized in that said micro current detection circuit comprising: a winding enclosing a power wire of an AC current; said winding being induced to generate a current due to a current flow in the power wire; a diode connected to said winding CT1; one input ends of said diode in forward biased direction being grounded a first capacitor and a plurality of serial connected first resistors; said first capacitor and said plurality of serial connected first resistors are connected in parallel as a RC pair, two end of the RC pair being connected to two end of the diode; a second, capacitor and a Zener diode which are connected in series as a first pair CZ pair, said CZ pair is coupled to one of said plurality of first resistors; and a second resistor which are connected in parallel to the CZ pair; one end of the CZ pair is grounded and another end of said CZ pair is as an output of said micro current detection circuit.