An over-current protection device is constituted of a current detection unit for detecting a current from a power-supply source to a load having a magnetism detection element with a magnetic impedance (MI) effect, an AC-current supply device for supplying an AC current to the detection element, a bi
An over-current protection device is constituted of a current detection unit for detecting a current from a power-supply source to a load having a magnetism detection element with a magnetic impedance (MI) effect, an AC-current supply device for supplying an AC current to the detection element, a bias-current supply device for supplying a bias current to a bias coil, a peak detection device for detecting a peak of impedance of the magnetism detection element as a variation of voltage, and a switch corresponding to a phase for selecting an output of the peak detection device. In the current detection unit, a holding device for holding a switch output and an amplifier are disposed in common for detecting the current in each phase, thereby expanding a current detectable range and reducing power consumption and cost.
대표청구항▼
What is claimed is: 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 sourc
What is claimed is: 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. 2. An over-current protection device according to claim 1, wherein when said first and second switches corresponding to one of the magnetism detection elements disposed in the power-supply phase are selected, said third switch is selected. 3. An over-current protection device according to claim 1, wherein said oscillating means is operated synchronously with the third switch. 4. An over-current protection device according to claim 1, wherein said controlling power-supply source comprises at least two power-supply transformers having primary and secondary coils and connected to a current-supply line linked between the power-supply line and the load, a capacitor for storing a current at a secondary side, and a voltage adjuster. 5. An over-current protection device according to claim 1, wherein said controlling power-supply source comprises a power-supply transformer having at least two primary coils and one secondary coil and connected to a current-supply line between the power-supply line and the load, a capacitor for storing a current at a secondary side, and a voltage adjuster. 6. An over-current protection device according to claim 5, wherein said at least two primary coils and one secondary coil are wound on a single iron core, and said primary coils have different winding turns for each phase. 7. An over-current protection device according to claim 6, wherein said two primary coils of the power-supply transformers have a winding ratio of 1:2. 8. An over-current protection device according to claim 1, wherein said magnetism detection element, a terminal for applying an AC current to the magnetism detection element, the bias coil, and a terminal for supplying a bias current to the bias coil are integrated with a resin molding process. 9. An over-current protection device according to claim 1, wherein said magnetism detection element, a terminal for supplying an AC current to the magnetism detection element, the bias coil, a terminal for supplying a bias current to the bias coil, and a circuit for outputting a signal proportional to an output of the magnetism detection element are integrated with a resin molding process. 10. An over-current protection device according to claim 1, wherein said magnetism detection element is formed of a thin-film.
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