# US 11,309,743 B1 · Balanced-current circuit structure and parameter design method for bifilar winding coil of wireless power transfer

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- Number: US 11,309,743 B1
- Document ID: US11309743B1
- Status: Granted
- Kind: B1
- Application number: 17/195,863
- Filed: 2021-03-09
- Granted: 2022-04-19
- Earliest claimed: 2020-11-17
- Assignees: Harbin Institute of Technology
- Applicants: Harbin Institute of Technology
- Inventors: Kai Song; Zhi Bie; Chao Wang; Guang Yang; Chunbo Zhu; Rengui Lu
- Web page: https://patentgrep.com/patent/US11309743B1

## CPC

- H01F 38/14: Inductive couplings
- H02J 50/12: of the resonant type
- H01F 27/28: Coils; Windings; Conductive connections
- H01F 27/2823: {Wires (H01F27/2866 takes precedence)}
- H01F 27/42: Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils (circuits for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output H02P13/00; impedance networks H03H)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY

## Abstract

The disclosure provides a balanced-current circuit structure and a parameter design method for a bifilar winding coil of wireless power transfer. The disclosure relates to the technical field of magnetic coupling wireless power transfer. The circuit includes a bifilar winding coil, a compensation capacitor array and a controlled voltage source array. The bifilar winding coil includes a first coil and a second coil, the compensation capacitor array includes a first compensation capacitor and a second compensation capacitor, and the controlled voltage source array includes a first controlled voltage source and a second controlled voltage source. Compared with the existing centralized series compensation scheme, the scheme proposed by the disclosure can realize the currents in two windings of the bifilar winding coil being basically the same, so as to eliminate the current imbalance problem existing in the traditional compensation mode, thereby fully exerting the current-carrying capacity of the bifilar winding coil, and improving the practicability of the bifilar winding coil in practical applications.

## Claims

### Claim 1

A balanced-current circuit for a bifilar winding coil of wireless power transfer, comprising a bifilar winding coil, and a compensation capacitor array,
wherein the bifilar winding coil comprises a first coil and a second coil, and the compensation capacitor array comprises a first compensation capacitor and a second compensation capacitor;
one end of the first coil is connected with one end of the first compensation capacitor;
one end of the second coil is connected with one end of the second compensation capacitor;
the other end of the first coil is connected with the other end of the second coil; and
the other end of the first compensation capacitor is connected with the other end of the second compensation capacitor.

### Claim 2 (depends on 1)

The balanced-current circuit of claim 1, wherein the other ends of the first coil and the second coil are both connected with one end of a load resistor or a third voltage source, and the other ends of the first compensation capacitor and the second compensation capacitor are both connected with the other end of the load resistor or the third voltage source.

### Claim 3 (depends on 1)

A method of using the balanced-current circuit of claim 1, comprising the following steps:
step 1: measuring self-inductance of the first coil and the second coil respectively, wherein L1 and L2 represent the self-inductance of the first coil and the second coil, respectively;
step 2: measuring mutual inductance between the first coil and the second coil in the bifilar winding coil, wherein M12 represents the mutual inductance between the first coil and the second coil; and
step 3: configuring compensation capacitors in a compensation capacitor array to the two coils in the bifilar winding coil, respectively, and when a working frequency is co, determining capacitance of a first compensation capacitor and a second compensation capacitor by the following formulas, respectively:
C1=1/(ω{circumflex over ( )}2*(L1+M12)),
C2=1/(ω{circumflex over ( )}2*(L2+M12)),
wherein C1 and C2 represent the capacitance of the first compensation capacitor and the second compensation capacitor, respectively.