Low-loss magnetic powder core, and switching power supply, active filter, filter, and amplifying device using the same

A method for making a magnetic powder core comprising:

• a powder preparation step of preparing a powder of a glassy alloy comprising Fe and at least one element selected from Al, P, C, Si, and B, having a texture primarily composed of an amorphous phase, and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature;
• a molding step of mixing the glassy alloy powder with an insulating material and compacting the mixture to form a magnetic core precursor;
• and
• an annealing step of annealing the magnetic core precursor at a temperature in the range between (Tg−170) K and Tg K to relieve the internal stress of the magnetic core precursor.

A switching power supply comprising:

• a switching element for converting a DC voltage into a rectangular waveform voltage;
• a transformer for transforming the rectangular waveform voltage;
• and
• a rectification circuit and a smoothing circuit for converting the transformed rectangular waveform voltage into a DC voltage;
• wherein the transformer comprises a magnetic core comprising a molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy powder having a texture primarily composed of an amorphous phase and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature.

A switching power supply comprising:

• a switching element for converting a DC voltage into a rectangular waveform voltage;
• a transformer for transforming the rectangular waveform voltage;
• and
• a rectification circuit and a smoothing circuit for converting the transformed rectangular waveform voltage into a DC voltage;
• wherein the smoothing circuit comprises a capacitor and a coil provided with a magnetic core, the magnetic core comprising a molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy powder comprising Fe and at least one element selected from Al, P, C, Si, and B, having a texture primarily composed of an amorphous phase, and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature.

A step-down converter circuit comprising:

• a switching element;
• a coil provided with a magnetic core generating a back electromotive force when the switching element breaks a DC current;
• a capacitor for smoothing a current generated by the back electromotive force;
• and
• a rectifying element connected to the coil provided with the magnetic core in an antiparallel state, the rectifying element, the coil provided with the magnetic core, and the capacitor constituting a circulating current path;
• wherein the magnetic core comprises a molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy having a texture primarily composed of an amorphous phase and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature.

A boosting converter circuit comprising:

• a switching element;
• a coil provided with a magnetic core generating a back electromotive force when the switching element breaks a DC current;
• a rectifying element connected in series in the forward direction to the coil provided with the magnetic core for rectifying a current generated by the back electromotive force;
• and
• a capacitor for smoothing the rectified current;
• wherein the magnetic core comprises a molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy having a texture primarily composed of an amorphous phase and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature.

A polarity-reversing converter circuit comprising:

• a switching element;
• a coil provided with a magnetic core generating a back electromotive force when the switching element breaks a DC current;
• a capacitor for smoothing a current generated by the back electromotive force;
• and
• a rectifying element connected in series in the backward direction to the coil provided with the magnetic core for blocking the DC current;
• wherein the magnetic core comprises a molded article of a mixture of a glassy alloy powder and an insulating material, the glassy alloy having a texture primarily composed of an amorphous phase and exhibiting a temperature difference ΔTx, which is represented by the equation ΔTx=Tx−Tg, of at least 20 K in a supercooled liquid, wherein Tx indicates the crystallization temperature and Tg indicates the glass transition temperature.