Power supply circuit with symmetrically tapped auto-transformer

• US 4,906,859 A
• Filed: 11/28/1988
• Issued: 03/06/1990
• Est. Priority Date: 11/30/1987
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kobayashi, Kenji, Mochizuki, Tetsuya
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): Sterrett, Jeffrey
• Application Number:
  US07/276,621
• Time in Patent Office: 463 Days
• Field of Search: 323/255, 323/259, 323/262, 323/305, 323/340, 323/344, 323/359, 336/148, 336/180, 307/17
• US Class Current: 307/17
• CPC Class Codes: H01F 29/02 with tappings on coil or winding; with provision for rearrangement or interconnection of windings
• CPC Class Codes: H01F 30/02 Auto-transformers

Abstract

An auto-transformer has first and second input terminals and first, second and third output terminals, the second output terminal being connected to a center tap of a coil and the first and third output terminals being connected to such points of the coil which are symmetrical with respect to the center tap. The first and second input terminals are connected to such points of the coil which are symmetrical with respect to the center tap. A first group of loads is coupled across the first and second output terminals and a second group of loads is coupled across the second and third output terminals. By equalizing the load currents to the first and second groups, the total current of the auto-transformer can be made significantly small.

Claims

1. A power supply circuit comprising:

a coiled structure having first, second, third and fourth taps, and a center tap, said first and second taps being substantially symmetrically located with respect to said center tap and inwardly along said coiled structure from said third and fourth taps, and said third and fourth taps being substantially symmetrically located with respect to said center tap and located at opposite ends of said coiled structure;

first and second input terminals connected to said first and second taps for supplying an input current through a portion of said coiled structure which is between said first and second taps;

a first output terminal connected to said center tap, and second and third output terminals connected respectively to said third and fourth taps;

a first load circuit connected between said first and second output terminals so that a first load current flows through a portion of said coiled structure between said center tap and said third tap in a direction opposite to the direction of said input current; and

a second load circuit connected between said first and third output terminals, said second load circuit having substantially the same impedance as said first load circuit to cause a second load current of substantially the same magnitude as said first load current to flow through a portion of said coiled structure between said fourth tap and said center tap in a direction opposite to the direction of said input current.

2. A power supply circuit comprising:

a coil having first, second, third and fourth coil sections, said first and fourth coil sections having substantially an equal numbers of turns, and said second and third coil sections having substantially an equal numbers of turns;

a first input terminal connected to a junction between said first and second coil sections, and a second input terminal connected to a junction between said third and fourth coil sections for supplying an input current through said second and third coil sections;

a first output terminal connected to a junction between said second and third coil sections, a second output terminal connected to a first end of said coil, and a third output terminal connected to a second end of said coil which is opposite to said first end;

a first load circuit connected between said first and second output terminals so that a first load current flows through said first and second coil sections in a direction which is opposite to the direction of said input current; and

a second load circuit connected between said first and third output terminals, said second load circuit having substantially the same impedance as said first load circuit to cause a second load current of substantially the same magnitude as said first load current to flow through said third and fourth coil sections in a direction opposite to the direction of said input current.

3. A power supply circuit comprising:

a series of first, second, third and fourth coils, beginning and ending points of each of said first, second, third and fourth coils, being interconnected so that an equally oriented magnetic flux is generated in each of said coils, said first and fourth coils having substantially an equal numbers of turns, and said second and third coils having substantially an equal numbers of turns;

a first input terminal connected to a tap between said first and second coils, a second input terminal connected to a tap between said third and fourth coils for supplying an input current through said second and third coils;

a first output terminal connected to a tap between said second and third coils, a second output terminal connected to a first end of said series of coils, and a third output terminal connected to a second end of said series of coils which is opposite to said first end;

a first load circuit connected between said first and second output terminals so that a first load current flows through said first and second coils in a direction which is opposite to the direction of said input current; and

a second load circuit connected between said first and third output terminals, said second load circuit having substantially the same impedance as said first load circuit to cause a second load current of substantially the same magnitude as said first load current to flow through said third and fourth coils in a direction which is opposite to the direction of said input current.