FOREIGN OBJECT DETECTION DEVICE, FOREIGN OBJECT DETECTION METHOD, AND NON-CONTACT CHARGING SYSTEM

• US 20150355360A1
• Filed: 08/19/2015
• Published: 12/10/2015
• Est. Priority Date: 02/19/2013
• Status: Active Grant

• Current Assignee: PANASONIC AUTOMOTIVE SYSTEMS CO., LTD. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Inventors: MIYASHITA, Norihiro
• Granted Patent: US 9,933,539 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 detection circuit comprising:

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

a 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.

2. The foreign object detector of claim 1, wherein

the detection circuit detects the foreign object based on an amount of change in matching frequency of the reflected power.

3. The foreign object detector of claim 1, wherein

the detection circuit recognizes the foreign object as metal if a matching frequency of the reflected power is higher than a reference matching frequency, and

recognizes the foreign object as water if the matching frequency of the reflected power is lower than the reference matching frequency.

4. The foreign object detector of claim 1, 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.

5. 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.

6. 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.

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

transforming an unbalanced signal to a balanced signal, 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.