CN107306054B

CN107306054B - Wireless power transmission device and structure of metal foreign body detection coil thereof

Info

Publication number: CN107306054B
Application number: CN201610260838.3A
Authority: CN
Inventors: 黄子浩; 卢建智
Original assignee: Automotive Research and Testing Center
Current assignee: Automotive Research and Testing Center
Priority date: 2016-04-25
Filing date: 2016-04-25
Publication date: 2020-11-10
Anticipated expiration: 2036-04-25
Also published as: CN107306054A

Abstract

A wireless power transmission device and structure of its metal foreign body detection coil, the wireless power transmission device radiates an electromagnetic wave by a sending antenna, and induce the electromagnetic wave and produce a plurality of signals to be measured correspondingly by a plurality of metal foreign body detection coils, every metal foreign body detection coil is made up of three coil units connected in series, and the three coil units are arranged at intervals, wherein the distribution area of the sending antenna covers the plurality of metal foreign body detection coils; the controller judges whether metal foreign bodies enter the electromagnetic wave range of the transmitting antenna according to a reference voltage signal and the signals to be detected corresponding to the metal foreign body detecting coils, so that the generation of the electromagnetic wave is stopped when the metal foreign bodies are detected, and the metal foreign bodies are prevented from being heated by the electromagnetic wave.

Description

Wireless power transmission device and structure of metal foreign body detection coil thereof

Technical Field

The present invention relates to a wireless power transmission device and a coil structure thereof, and more particularly, to a wireless power transmission device with a metal foreign object detection function and a structure of a metal foreign object detection coil.

Background

The conventional wireless power transmission device mainly includes an AC/DC converter, a DC/AC converter and a transmitting antenna connected in sequence. The input end of the AC/DC converter can be used for receiving an alternating current power supply provided by commercial power, the AC/DC converter converts the alternating current power supply into a direct current power supply, the DC/AC converter is used for receiving the direct current power supply and converting the direct current power supply into an alternating current output power supply, and the DC/AC converter radiates electromagnetic waves outwards from the alternating current output power supply through the transmitting antenna. Therefore, a receiving device with a wireless charging function senses the electromagnetic wave of the transmitting antenna, and the receiving device can convert the electromagnetic wave into a charging power supply for charging, so that the non-wiring wireless charging action is achieved.

When a metal foreign object enters the range of the electromagnetic wave generated by the wireless power transmission device, the metal foreign object generates a high temperature under the action of the electromagnetic field, which may cause danger. Therefore, the conventional wireless power transmission device may have a function of detecting metallic foreign objects, in which the metallic foreign object detection technique directly measures parameters of the electromagnetic waves generated by the transmitting antenna, such as power, efficiency, S-parameters, quality factors, and the like, and determines whether any metallic foreign object enters the range of the electromagnetic waves generated by the wireless power transmission device according to the variation of the parameters.

However, the measurement results of the parameters are affected by the transmission distance of the electromagnetic wave, and particularly, when the size of the metal foreign object is smaller than the size of the transmitting antenna, it is difficult to accurately determine that the metal foreign object enters the range of the electromagnetic wave generated by the wireless power transmission device.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a wireless power transmission device and a structure of a metal foreign body detection coil thereof, so as to effectively detect metal foreign bodies.

In order to achieve the above object, the present invention provides a wireless power transmission device, comprising:

an AC/DC converter, one input end of which receives an AC power supply and converts the AC power supply into a DC power supply;

one input end of the DC/AC converter is electrically connected with one output end of the AC/DC converter, and the DC power supply is converted into an AC output power supply; the DC/AC converter comprises a compensation capacitor which is electrically connected with a transmitting antenna and radiates an electromagnetic wave to the outside by the AC output power supply through the transmitting antenna;

the detection coil is distributed on an insulating substrate to induce the electromagnetic wave and correspondingly generate a plurality of signals to be detected, each detection coil is formed by connecting three coil units in series, the three coil units are arranged at intervals, and the distribution area of the transmitting antenna covers the detection coils;

a reference voltage generating circuit, one input end of which is electrically connected with the compensating capacitor of the DC/AC converter to receive the terminal voltage thereof, and generates a reference voltage signal according to the terminal voltage of the compensating capacitor;

the feedback detection circuits are respectively and electrically connected with the metal foreign body detection coils, and each feedback detection circuit receives a signal to be detected generated by the corresponding metal foreign body detection coil; and

and the controller is electrically connected with the reference voltage generating circuit and the feedback detection circuits to receive the reference voltage signal and the signals to be detected corresponding to the metal foreign object detection coils, and judges whether metal foreign objects enter an electromagnetic wave range radiated by the sending antenna according to the reference voltage signal and the signals to be detected.

In order to better achieve the above object, the present invention further provides a structure of a metal foreign object detection coil, wherein the metal foreign object detection coil is formed by connecting three coil units formed on an insulating substrate in series, and the three coil units are arranged at intervals.

The invention has the technical effects that:

the structure of the metal foreign body detection coil is formed by connecting three coil units in series, and the three coil units are arranged at intervals. In addition, compared with the prior art for measuring the parameters of the transmitting antenna of the wireless power transmission device, the invention has the advantages that the distribution area of the transmitting antenna covers the plurality of metal foreign body detection coils, namely, the size of each metal foreign body detection coil is smaller than that of the transmitting antenna, and each metal foreign body detection coil has the detection area, so that the metal foreign bodies smaller than the size of the transmitting antenna can be effectively detected, when the metal foreign bodies are detected, the controller immediately stops the transmitting antenna from generating electromagnetic waves, and the metal foreign bodies are prevented from being heated.

The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.

Drawings

Fig. 1 is a circuit block diagram of a wireless power transmission apparatus according to the present invention;

fig. 2 is a schematic perspective exploded view of the housing, the transmitting antenna disposed on the first insulating substrate, and the metal foreign object detection coil disposed on the second insulating substrate according to the present invention;

fig. 3 is a partial circuit block diagram of a wireless power transmission apparatus according to the present invention;

FIG. 4 is a block diagram of a reference voltage generating circuit, a controller and a feedback detecting circuit according to the present invention;

fig. 5 is a schematic plan view of an embodiment of a foreign object detection coil structure of the present invention;

FIG. 6 is a schematic cross-sectional view A-A of FIG. 5;

fig. 7 is a partial plan view schematically illustrating another embodiment of the foreign object detection coil structure of the present invention;

FIG. 8 is a schematic cross-sectional view B-B of FIG. 7;

fig. 9 is a schematic plan view of a further embodiment of a foreign object detection coil structure of the present invention;

fig. 10 is a schematic plan view of a further embodiment of a foreign object detection coil structure of the present invention;

fig. 11 is a schematic plan view of the foreign object detection coil shown in fig. 10 arranged in a polygonal structure;

fig. 12 is a flowchart illustrating a metallic foreign object determination process of the controller according to the present invention.

Detailed Description

The invention will be described in detail with reference to the following drawings, which are provided for illustration purposes and the like:

referring to fig. 1 to 3, the wireless power transmission device 10 of the present invention includes an AC/DC converter 11, a DC/AC converter 12, a transmitting antenna 13, a plurality of metal foreign object detection coils 14, a reference voltage generating circuit 15, a plurality of feedback detection circuits 16, and a controller 17.

Referring to fig. 1 and 3, an input end of the AC/DC converter 11 is used for receiving an AC power, for example, the AC power may be an AC power provided by a commercial power, and the AC/DC converter 11 converts the AC power into a DC power. The input end of the DC/AC converter 12 is electrically connected to the output end of the AC/DC converter 11 to receive the DC power and convert the DC power into an AC output power. The output end of the DC/AC converter 12 is electrically connected to the transmitting antenna 13, so that the AC output power is radiated to the outside by the transmitting antenna 13.

Referring to fig. 2, the transmitting antenna 13 may be disposed on a surface of a first insulating substrate 30, the plurality of metal foreign object detection coils 14 are arranged in an array and distributed on a surface of a second insulating substrate 31, wherein the second insulating substrate 31 is disposed on the transmitting antenna 13, so that the plurality of metal foreign object detection coils 14 are located above the transmitting antenna 13, a distribution area of the transmitting antenna 13 covers the plurality of metal foreign object detection coils 14, the plurality of metal foreign object detection coils 14 and the transmitting antenna 13 are isolated by the second insulating substrate 31, a shell 32 is disposed on the second insulating substrate 31, and the shell 32 covers the plurality of metal foreign object detection coils 14 to avoid exposure. The electromagnetic wave emitted from the transmitting antenna 13 can penetrate through the second insulating substrate 31 and the housing 32.

As shown in fig. 1, the receiving device 20 includes a receiving antenna 21, a rectifier 22, a communication module 23 and a controller 24, when the receiving antenna 21 senses the electromagnetic wave emitted by the transmitting antenna 13, an inductive power is generated correspondingly, and the rectifier 22 converts the inductive power into a dc charging power. Correspondingly, when the transmitting antenna 13 radiates electromagnetic waves, since each metal foreign object detecting coil 14 is also located in the radiation range of the electromagnetic waves, each metal foreign object detecting coil 14 can also sense the electromagnetic waves to correspondingly generate a signal to be measured Vsensor.

The structure of the metal foreign body detection coil 14 is formed by connecting three coil units in series, and the three coil units are arranged at intervals, so that the structure of the metal foreign body detection coil 14 can have uniform magnetic field induction capability in a space to be detected, and the space to be detected is a magnetic field induction area of the three coil units.

Referring to fig. 5, in the first embodiment of the metal foreign object detection coil 14, the three coil units are a first coil unit 141, a second coil unit 142 and a third coil unit 143, respectively, and the first coil unit 141 includes a central line segment 400, a 1 st line segment 401, a 2 nd line segment 402, a 3 rd line segment 403, a 4 th line segment 411, a 5 th line segment 412, a 6 th line segment 413, a plurality of connection lines 42 and a plurality of bridge lines 43.

The center line segment 400 is formed on a surface of the second insulating substrate 31 and has a U-shaped structure and two ends, the 1 st to 3 rd line segments 401 to 403 are formed on the surface of the second insulating substrate 31 and are sequentially distributed on one side of the center line segment 400 from inside to outside, that is, the 1 st line segment 401 is closest to the center line segment 400, and the 4 th to 6 th line segments 411 to 413 are formed on the surface of the second insulating substrate 31 and are sequentially distributed on the other side of the center line segment 400, which is opposite to the 1 st to 3 rd line segments 401 to 403 from inside to outside, that is, the 4 th line segment 411 is closest to the center line segment 400. One end of the 3 rd segment 403 is a current output (or input) end, and the other end thereof is electrically connected to one end of the 5 th segment 412 through a bridge 43, the other end of the 5 th segment 412 is electrically connected to one end of the 1 st segment 401 through a connection line 42, and the other end of the 1 st segment 401 is electrically connected to one end of the central segment 400 through a bridge 43; the other end of the central segment 400 is electrically connected to one end of the 4 th segment 411 through a connection line 42, the other end of the 4 th segment 411 is electrically connected to one end of the 2 nd segment 402 through a bridge line 43, the other end of the 2 nd segment 402 is electrically connected to one end of the 6 th segment 413 through a connection line 42, the other end of the 6 th segment 413 is electrically connected to the second coil unit 142 through a bridge line 43, and the structures of the second coil unit 142 and the third coil unit 143 can be similar; referring to fig. 6, the connecting lines 42 are formed on the surface of the second insulating substrate 31, an insulating layer 44 is disposed on the surface of the connecting lines 42, and the bridge lines 43 are formed on the insulating layer 44, so that the bridge lines 43 and the connecting lines 42 are separated by the insulating layer 44, and the short circuit caused by direct contact between the connecting lines 42 and the bridge lines 43 is avoided. Therefore, the central line segment 400, the 1 st to 3 rd line segments 401 to 403 and the 4 th to 6 th line segments 411 to 413 are connected in series through the plurality of connecting wires 42 and the bridging wires 43 to form a winding coil structure.

Referring to fig. 7 and 8, in another embodiment, the second insulating substrate 31 may be a double-sided printed circuit board and includes a top surface and a bottom surface, the central line segment 400, the 1 st to 3 rd line segments 401 to 403, the 4 th to 6 th line segments 411 to 413, and the plurality of connection lines 42 are formed on the top surface of the second insulating substrate 31, each of the bridge lines 45 is formed on the bottom surface of the second insulating substrate 31, and the plurality of bridge lines 45 are connected between the two corresponding line segments through the vias 46 penetrating through the second insulating substrate 31.

Referring to fig. 9, in the second embodiment of the metal foreign object detection coil 14 ', the three coil units are a first coil unit 141', a second coil unit 142 'and a third coil unit 143', respectively. The second coil unit 142 'is wound into an isosceles triangle coil structure by a single line 472 and has a first oblique edge portion and a second oblique edge portion opposite to each other, and two opposite ends of the second coil unit 142' respectively form an inner connection end and an outer connection end; the first coil unit 141 ' is wound from a single line 471 into a right triangle coil structure and includes a bevel portion, the bevel portion is located outside the first bevel portion of the second coil unit 142 ' and parallel to the first bevel portion, and two opposite ends of the first coil unit 141 ' respectively form an inner connection end and an outer connection end. The third coil unit 143 ' is a right-angled triangle coil structure formed by winding a single line 473, and includes a beveled portion, the beveled portion is located outside the second beveled portion of the second coil unit 142 ' and is parallel to the second beveled portion, and two opposite ends of the third coil unit 143 ' respectively form an inner connection end and an outer connection end; as shown in fig. 9, the plurality of coil units 141 ', 142 ', and 143 ' are arranged at intervals to have a rectangular structure as a whole. The inner terminal of the first coil unit 141 'is connected to the outer terminal of the second coil unit 142' via a first connection line 474, the inner terminal of the second coil unit 142 'is connected to the inner terminal of the third coil unit 143' via a second connection line 475, the outer terminal of the first coil unit 141 'is a current input (or output) terminal, and the outer terminal of the third coil unit 143' is a current output (or input) terminal. As described in the first embodiment, the connecting

lines

474, 475 may be formed over the

single line segments

471, 472, 473, and an insulating layer (not shown) is disposed between the connecting

lines

474, 475 and the

single line segments

471, 472, 473; alternatively, the

single line segments

471, 472, 473 can be formed on the top surface of a double-sided printed circuit board, the connecting

lines

474, 475 can be formed on the bottom surface of the double-sided printed circuit board, and the

single line segments

471, 472, 473 and the connecting

lines

474, 475 can be connected in series via vias extending through the double-sided printed circuit board.

Referring to fig. 10, in the third embodiment of the metal foreign object detection coil 14 ", the three coil units are a first coil unit 141", a second coil unit 142 "and a third coil unit 143", respectively. The second coil unit 142 ″ is wound into an isosceles triangle coil structure by a single line segment 482 and has a first oblique edge portion and a second oblique edge portion opposite to each other, and two opposite ends of the second coil unit 142 ″ respectively form an inner connection end and an outer connection end; the first coil unit 141 ″ is wound from the single line 481 into a right triangle coil structure and includes a bevel portion, the bevel portion is located outside the first bevel portion of the second coil unit 142 ″ and parallel to the first bevel portion, and two opposite ends of the first coil unit 141 ″ respectively form an inner connection end and an outer connection end. The third coil unit 143 ″ is a coil structure wound into a right triangle by a single line segment 483, and includes a beveled portion, the beveled portion is located outside the second beveled portion of the second coil unit 142 ″ and parallel to the second beveled portion, and opposite ends of the third coil unit 143 ″ respectively form an inner connection end and an outer connection end; as shown in fig. 10, the plurality of coil units 141 ", 142", 143 "are arranged at intervals to form a fan-shaped structure as a whole. The inner connection end of the first coil unit 141 "is connected to the inner connection end of the third coil unit 143" via a first connection wire 484, the outer connection end of the first coil unit 141 "is connected to the inner connection end of the second coil unit 142" via a second connection wire 485, the outer connection end of the second coil unit 142 "is a current input (or output) end, and the outer connection end of the third coil unit 143" is a current output (or input) end. As described in the first embodiment, the plurality of connecting

lines

484, 485 may be formed above the plurality of

single line segments

481, 482, 483, and an insulating layer (not shown) is disposed between the plurality of connecting

lines

484, 485 and the plurality of

single line segments

481, 482, 483; alternatively, the plurality of

single line segments

481, 482, 483 can be formed on the top surface of a double-sided printed circuit board, the plurality of connecting

lines

484, 485 can be formed on the bottom surface of the double-sided printed circuit board, and the plurality of

single line segments

481, 482, 483 and the plurality of connecting

lines

484, 485 can be connected in series via vias extending through the double-sided printed circuit board.

Referring to fig. 11, four metal foreign object detection coils 14 ″ shown in fig. 9 may be disposed on the second insulating substrate, such that the four metal foreign object detection coils 14 ″ have an octagonal structure as a whole.

Based on the metal foreign object detection coils 14, when the transmitting antenna 13 radiates electromagnetic waves, each metal foreign object detection coil 14 is also located in the electromagnetic wave range, so that each metal foreign object detection coil 14 can sense the electromagnetic waves and correspondingly generate a signal to be measured Vsensor.

Referring to fig. 1 and 3, the DC/AC converter 12 includes a plurality of compensation capacitors Cp connected in series, the compensation capacitors Cp are electrically connected to the transmitting antenna 13, an input terminal of the reference voltage generating circuit 15 is electrically connected to two terminals of any compensation capacitor Cp of the DC/AC converter 12 for receiving a terminal voltage thereof, referring to fig. 4, the reference voltage generating circuit 15 includes a differential amplifier 151, a full-wave rectifier 152 and a DC filter 153 connected in series in sequence, an input terminal of the differential amplifier 151 is an input terminal of the reference voltage generating circuit 15, and an output terminal of the DC filter 153 is an output terminal of the reference voltage generating circuit 15. Therefore, the reference voltage generating circuit 15 performs differential amplification, full-wave rectification and dc filtering on the terminal voltage of the compensation capacitor Cp to generate a reference voltage signal Vref.

The input terminals of the feedback detection circuits 16 are electrically connected to the metal foreign object detection coils 14 respectively to form a one-to-one connection structure, and fig. 1 and 3 only disclose a feedback detection circuit 16 and a metal foreign object detection coil 14 as an example. Referring to fig. 4, each feedback detection circuit 16 includes a low pass filter 161, a differential amplifier 162, a rectifier 163 and a dc filter 164 connected in series in sequence, an input end of the low pass filter 161 is an input end of the feedback detection circuit 16, an output end of the dc filter 164 is an output end of the feedback detection circuit 16, and each feedback detection circuit 16 performs low pass filtering, differential amplification, rectification and dc filtering on a signal to be detected Vsensor generated by the corresponding metal foreign object detection coil 14.

The controller 17 has a plurality of signal input terminals, and the signal input terminals are respectively electrically connected to the output terminal of the reference voltage generating circuit 15 and the output terminals of the feedback detecting circuits 16 to receive the reference voltage signal Vref and the signals to be detected vseener corresponding to the metal foreign object detecting coils.

Referring to fig. 1 and 12, before use, a user may check whether a metal foreign object exists between the wireless power transmission device 10 and the receiving device 20, and if so, remove the metal foreign object. If there is no metal foreign object, the controller 17 of the wireless power transmission device 10 can execute a charging mode to control the transmitting antenna 13 to radiate electromagnetic waves, because each metal foreign object detecting coil 14 is also located in the range of the electromagnetic waves, each metal foreign object detecting coil 14 can sense the electromagnetic waves and generate a signal to be detected correspondingly. Therefore, the controller 17 receives the reference voltage signal Vref and the multiple signals to be detected vseneror in an initial state (i.e., a state without metal foreign objects), and calculates a Gain value Gain corresponding to each metal foreign object detection coil 14 according to the reference voltage signal Vref and the multiple signals to be detected vseneror, wherein the Gain value Gain is a ratio of the reference voltage signal Vref to the signals to be detected vseneror (i.e., Gain is Vref/vseneror), and then establishes a Gain table according to the Gain values Gain of the multiple metal foreign object detection coils 14 (step S101), and the Gain table can be stored in the controller 17; in other words, each metal foreign object detection coil has a corresponding Gain value Gain.

After the gain table is established, while the wireless power transmission device 10 executes the charging mode, the controller 17 also continuously receives the detection signal Vsensor of the plurality of metal foreign object detection coils 14, multiplies the instantaneous detection signal Vsensor generated by each metal foreign object detection coil 14 by the corresponding gain value to obtain an instantaneous monitoring signal Vm (step S102), and determines whether the difference between the reference voltage signal Vref and the instantaneous monitoring signal Vm corresponding to any metal foreign object detection coil 14 (i.e., | Vref-Vm |) is greater than or equal to a threshold value Vth (step S103).

When a metal foreign object enters the region between the wireless power transmission device 10 and the receiving device 20, the metal foreign object will affect the electromagnetic field generated by the transmitting antenna 13, and also affect the real-time monitoring signal Vm corresponding to each metal foreign object detection coil 14. Therefore, when the difference between the instantaneous monitor signal Vm and the reference voltage signal Vref is greater than the threshold Vth, the controller 17 determines that a metal foreign object enters the region between the wireless power transmission device 10 and the receiving device 20, and further shuts down to stop the charging mode, thereby effectively preventing the electromagnetic field from acting on the metal foreign object to generate high temperature. Referring to fig. 1, the controller 17 may be electrically connected to a communication module 18 to establish a connection with the communication module 23 of the receiving apparatus 20, and when the controller 17 of the wireless power transmission apparatus 10 determines that there is a metal foreign object, the controller may send a control instruction for stopping charging to the communication module 23 of the receiving apparatus 20, and the controller 24 of the receiving apparatus 20 may stop charging according to the control instruction.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A wireless power transmission apparatus, comprising:

2. The wireless power transmission device according to claim 1, wherein the plurality of metal foreign object detection coils are arranged in an array on the insulating substrate, and each of the coil units of each of the metal foreign object detection coils includes a central line segment, a first line segment, a second line segment, a third line segment, a fourth line segment, a fifth line segment, and a sixth line segment formed on a surface of the insulating substrate;

the central line segment is of a U-shaped structure and comprises two tail ends, the first line segment, the second line segment and the third line segment are sequentially distributed on one side of the central line segment from inside to outside, and the fourth line segment, the fifth line segment and the sixth line segment are sequentially distributed on the other side of the central line segment from the first line segment to the third line segment from inside to outside;

the third line segment is electrically connected with one end of the fifth line segment through a bridging line, the other end of the fifth line segment is electrically connected with one end of the first line segment through a connecting line, the other end of the first line segment is electrically connected with one end of the central line segment through a bridging line, the other end of the central line segment is electrically connected with one end of the fourth line segment through a connecting line, the other end of the fourth line segment is electrically connected with one end of the second line segment through a bridging line, and the other end of the second line segment is electrically connected with one end of the sixth line segment through a connecting line;

the central line segment and the first to sixth line segments form a winding coil structure.

3. The wireless power transmission device according to claim 1, wherein the plurality of metal foreign object detection coils are arrayed on the insulating substrate, and three coil units of each of the metal foreign object detection coils are a first coil unit, a second coil unit, and a third coil unit, respectively;

the second coil unit is wound into an isosceles triangle coil structure by a single line segment and is provided with a first oblique edge part and a second oblique edge part which are opposite, and two opposite ends of the second coil unit respectively form an inner connecting end and an outer connecting end;

the first coil unit is wound into a right-angled triangle coil structure by a single line segment and comprises an oblique edge part, the oblique edge part is positioned outside the first oblique edge part of the second coil unit and is parallel to the first oblique edge part, and the two opposite ends of the first coil unit respectively form an inner connecting end and an outer connecting end;

the third coil unit is wound into a right-angled triangle coil structure by a single line segment and comprises an oblique edge part, the oblique edge part is positioned outside the second oblique edge part of the second coil unit and is parallel to the second oblique edge part, and two opposite ends of the third coil unit respectively form an inner connecting end and an outer connecting end;

the inner connection end of the first coil unit is connected with the outer connection end of the second coil unit through a first connection wire, and the inner connection end of the second coil unit is connected with the inner connection end of the third coil unit through a second connection wire;

the first coil unit, the second coil unit and the third coil unit are arranged at intervals and are integrally rectangular.

4. The wireless power transmission device according to claim 1, wherein the three coil units of each of the metal foreign object detection coils are a first coil unit, a second coil unit, and a third coil unit, respectively;

the inner connection end of the first coil unit is connected with the inner connection end of the third coil unit through a first connecting wire, and the outer connection end of the first coil unit is connected with the inner connection end of the second coil unit through a second connecting wire;

the first coil unit, the second coil unit and the third coil unit are arranged at intervals and are integrally in a fan-shaped structure.

5. The wireless power transmission device according to claim 4, wherein the insulating substrate is provided with four of the metal foreign object detection coils so that the four metal foreign object detection coils are in an octagonal structure as a whole.

6. The wireless power transmission device according to any one of claims 1 to 5, wherein the controller receives the reference voltage signal and the signals under test in an initial state when determining whether there is a metal foreign object, and calculates a gain value corresponding to each of the metal foreign object detection coils according to the reference voltage signal and the signals under test, wherein the gain value is a ratio of the reference voltage signal to the signals under test, and establishes a gain table according to the gain values of the metal foreign object detection coils, the gain table being stored in the controller;

after the gain table is established, the controller continuously receives the detection signals of the plurality of metal foreign body detection coils, multiplies the instant detection signal generated by each metal foreign body detection coil by the corresponding gain value to obtain an instant monitoring signal, judges that metal foreign bodies exist when the difference between the reference voltage signal and the instant monitoring signal corresponding to any metal foreign body detection coil is larger than or equal to a threshold value, and further shuts down the machine.

7. The metal foreign body detecting coil structure is characterized in that the metal foreign body detecting coil is formed by connecting three coil units formed on an insulating substrate in series to induce electromagnetic waves and correspondingly generate a plurality of signals to be detected, and the three coil units are arranged at intervals.

8. The structure of a metal foreign object detection coil according to claim 7, wherein each of the coil units includes a center line segment, a first line segment, a second line segment, a third line segment, a fourth line segment, a fifth line segment, a sixth line segment formed on a surface of the insulating substrate;

9. The structure of the metal foreign object detection coil according to claim 7, wherein the three coil units are a first coil unit, a second coil unit, and a third coil unit, respectively;

10. The structure of the metal foreign object detection coil according to claim 7, wherein the three coil units are a first coil unit, a second coil unit, and a third coil unit, respectively;