Patent ID: 7317604
Filing Date: 2008-01-08
Classification: G01R,H02H

Abstract:
1. An over-current protection device for shutting off power to a load when an overloaded current flows, comprising: a switching element for switching a current from a power-supply source to the load, a current detector for detecting a current supplied from the power-supply source to the load, and a controlling power-supply source for supplying power to each of the switching element and current detector, wherein said current detector includes magnetism detection elements having a magnetic impedance effect and corresponding to phases of the power-supply source; AC-current supply means for applying an AC current to each magnetism detection element through one oscillating means and a first switch corresponding to each magnetism detection element; bias-current supply means formed of bias coils wound on the respective magnetism detection elements and a third switch for supplying a current to the bias coils via the third switch; wave detection means corresponding to the magnetism detection elements for converting an impedance variation into a voltage and for passing a peak of the voltage; second switches corresponding to the wave detection means for selecting an output of the wave detection means; holding means for holding the selected voltage of the wave detection means; and amplifying means for amplifying the voltage held by the holding means, and the current for each phase is detected based on selective operations of the first, second, and third switches.