Foreign object detection device, foreign object detection method, and non-contact charging system

• US 9,933,539 B2
• Filed: 08/19/2015
• Issued: 04/03/2018
• Est. Priority Date: 02/19/2013
• Status: Active Grant

• Current Assignee: Panasonic Automotive Systems Company of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: Miyashita, Norihiro
• Primary Examiner(s): Berhanu, Samuel
• Application Number:
  US14/830,691
• Publication Number:
  US 20150355360A1
• Time in Patent Office: 958 Days
• Field of Search: 320108
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings

Abstract

A foreign object detector includes a detection coil; a transmitting circuit generating an unbalanced signal; a balanced-to-unbalanced transformer transforming the unbalanced signal supplied from the transmitting circuit to a balanced signal; and detection circuit detecting a foreign object by sensing a change in frequency characteristic of reflected power that is a power component reflected by the detection coil. The foreign object detector detects a foreign object while preventing a wire between the detection coil and the detection circuit from functioning as a linear antenna even if the wire is long.

Claims

1. A foreign object detector comprising:

a detection coil;

a transmitting circuit generating an unbalanced signal;

a coaxial cable transmitting the unbalanced signal generated by the transmitting circuit;

a balanced-to-unbalanced transformer transforming the unbalanced signal supplied from the coaxial cable to a balanced signal, and outputting the balanced signal to the detection coil; and

a detection circuit detecting a foreign object by sensing a change in a frequency characteristic of reflected power that is a power component reflected by the detection coil and transmitted through the balanced-to-unbalanced transformer and the coaxial cable, wherein

the detection coil includes a plurality of coils, and

the foreign object detector further comprises a short circuit in which both terminals of a non-selected one of the plurality of coils in the detection coil are short-circuited together.

2. The foreign object detector of claim 1, further comprising:

a transmitting coil case housing a transmitting coil, wherein

the detection coil is arranged above the transmitting coil, and housed in the transmitting coil case, and

the detection coil is arranged such that a distance between a surface of the transmitting coil case and the detection coil is shorter than a distance between the transmitting coil and the detection coil.

3. A non-contact charging system comprising:

the foreign object detector of claim 1;

a transmitting coil; and

an RF oscillation source supplying RF power of a predetermined frequency to the transmitting coil.

4. A method of detecting a foreign object, the method comprising:

transmitting an unbalanced signal using a coaxial cable;

transforming the unbalanced signal supplied from the coaxial cable to a balanced signal using a balanced-to-unbalanced transformer, and supplying power of the balanced signal to a detection coil; and

detecting the foreign object by sensing a change in frequency characteristic of reflected power that is a power component reflected by the detection coil and transmitted through the balanced-to-unbalanced transformer and the coaxial cable, wherein

the detection coil includes a plurality of coils, and

the method further comprises a step in which both terminals of a non-selected one of the plurality of coils in the detection coil are short-circuited together.