WO2020104134A1 - Antenna assembly and wireless charging device comprising such an antenna assembly - Google Patents

Antenna assembly and wireless charging device comprising such an antenna assembly

Info

Publication number
WO2020104134A1
WO2020104134A1 PCT/EP2019/078846 EP2019078846W WO2020104134A1 WO 2020104134 A1 WO2020104134 A1 WO 2020104134A1 EP 2019078846 W EP2019078846 W EP 2019078846W WO 2020104134 A1 WO2020104134 A1 WO 2020104134A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna
coil antenna
coil
terminals
pair
Prior art date
Application number
PCT/EP2019/078846
Other languages
French (fr)
Inventor
Stéphane SCHULER
Original Assignee
Valeo Comfort And Driving Assistance
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Valeo Comfort And Driving Assistance filed Critical Valeo Comfort And Driving Assistance
Publication of WO2020104134A1 publication Critical patent/WO2020104134A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2804—Printed windings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2866—Combination of wires and sheets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2871—Pancake coils
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/29—Terminals; Tapping arrangements for signal inductances
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/14—Inductive couplings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/06—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with core of ferromagnetic material
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/005—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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/20—Circuit arrangements or systems for wireless supply or distribution of electric power using microwaves or radio frequency waves
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/40—Circuit arrangements or systems for wireless supply or distribution of electric power using two or more transmitting or receiving devices
    • H02J50/402—Circuit arrangements or systems for wireless supply or distribution of electric power using two or more transmitting or receiving devices the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/255—Magnetic cores made from particles

Definitions

  • the invention relates to wireless charging.
  • the invention relates to an antenna assembly and to a wireless charging device comprising such an antenna assembly.
  • Wireless charging devices are provided with an antenna assembly for generating an alternating magnetic field.
  • such an antenna assembly comprises at least a first pair of terminals, a second pair of terminals, a first coil antenna connected to the first pair of terminals and a second coil antenna connected to the second pair of terminals.
  • the first coil antenna and the second coil antenna may be arranged respectively in a first antenna layer (including at least said first coil antenna) and in a second antenna layer (including at least said second coil antenna).
  • the first coil antenna and the second coil antenna are stamped coil antennas; the quality factor of stamped coil antennas is low compared to other technologies such as those using Litz wires, negatively impacting the efficiency of the system.
  • an antenna assembly comprising:
  • first coil antenna and said second coil antenna are respectively arranged in a first antenna layer comprising at least said first coil antenna, and in a second antenna layer comprising at least said second coil antenna and distinct from the first antenna layer, wherein said first coil antenna and said second coil antenna at least partially overlap and wherein said second coil antenna has an unloaded in-air quality factor greater than the first coil antenna.
  • first (stamped-type) coil antenna was expectedly of little interest compared to the second coil antenna exhibiting a greater quality factor; the first (stamped-type) coil antenna was seen as problematic as detrimental to the quality factor of the second coil antenna.
  • the first antenna layer includes at least a third coil antenna (and possibly additional coil antennas) adjoining the first coil antenna in said first antenna layer;
  • the third coil antenna (and possibly each additional coil antenna) is of stamped-type;
  • the second coil antenna has an unloaded in-air quality factor above 60 (possibly above 100, for instance in the case of a Litz wire coil antenna mentioned below);
  • the second coil antenna comprises at least one wound insulated wire
  • the second coil antenna is a Litz wire coil antenna
  • the second coil antenna is formed by conductive tracks of a flexible printed circuit
  • the second antenna layer includes additional coil antennas adjoining the first coil antenna in said second antenna layer;
  • the first coil antenna lies on a first face on a printed circuit board
  • the second coil antenna is deposited at least in part overlapping the first coil antenna
  • the coil antenna layers lie on a first face of a printed circuit board in no prescribed order
  • a second face of the printed circuit board opposite the first face, carries a re-radiation antenna.
  • the invention also provides antenna assembly comprising:
  • said stamped coil antenna and said Litz wire coil antenna are respectively arranged in a first antenna layer comprising at least said stamped coil antenna, and in a second antenna layer comprising at least said Litz wire coil antenna and distinct from the first antenna layer, wherein said stamped coil antenna and said Litz wire coil antenna are at least partially overlapping.
  • the first antenna layer may include a further stamped coil antenna (connected to a third pair of terminals of the antenna assembly). This further stamped coil antenna and the Litz wire coil antenna may also partially overlap.
  • the invention also provides a wireless charging device comprising an antenna assembly as presented above.
  • Such a wireless charging device may also comprise a driver circuit for delivering an alternating current and/or a selection circuit for selecting at least a pair of terminals amongst at least the first pair of terminals and the second pair of terminals and/or a switching circuit for applying said alternating current across the selected pair of terminals.
  • Figure 1 shows a first embodiment of an antenna assembly according to the invention
  • Figure 2 shows a second embodiment of an antenna assembly according to the invention
  • Figure 3 shows elements of a possible electronic circuit for a wireless charging device according to the invention.
  • Figures 1 and 2 shows two possible embodiments of an antenna assembly 2 ; 102 according to the invention, respectively.
  • the antenna assembly 2; 102 includes a printed circuit board 4; 104 and a plurality of coil antennas 6, 8, 10; 106, 108, 1 10.
  • the coil antennas 6, 8, 10; 106, 108, 1 10 are here located on a first side of the printed circuit board 4.
  • the second side of the printed circuit board 4 may carry other electric and/or electronic circuits, such as a re-radiation antenna (not shown) in the first embodiment shown in Figure 1 , or such as a connector 124 in the second embodiment shown in Figure 2.
  • the coil antennas 6, 8, 10; 106, 108, 1 10 are arranged in a plurality of layers, here in a first layer of coil antennas 6, 1 0; 106, 1 10 lying on the first side of the printed circuit board 4; 104 and a second layer of coil antennas (including here a single coil antenna 8; 108) located on the first layer of coil antennas 6, 10; 106, 1 10 (such that the first layer is here interposed between the second layer and the printed circuit board 4; 104, although the invention is not limited to this construction, as indicated below).
  • coil antennas 6, 10 of the first layer are lying in contact with the printed circuit board 4.
  • a ferrite plate 105 is interposed between coil antennas 106, 1 10 of the first layer and the printed circuit board 104.
  • the antenna assembly could include at least a further antenna layer comprising one or several coil antenna(s), deposited on the second layer of coil antennas (the second layer then including a plurality of coil antennas).
  • At least one coil antenna of the first layer of coil antennas 6, 10; 106, 1 10 is a stamped-type coil antenna.
  • both coil antennas 6, 10; 106, 1 10 of the first layer are stamped-type coil antennas.
  • a stamped-type coil antenna is a coil antenna stamped to the shape of a coil from a metal plate and therefore consisting of plain metal.
  • Such stamped-type coil antennas for use in wireless charging devices have an unloaded in-air quality factor generally below 60.
  • the coil antenna 8; 108 of the second layer is a Litz wire coil antenna.
  • a Litz wire coil antenna is a coil antenna formed from a wounded Litz wire, i.e. an insulated wire comprising a plurality of strands insulated from one another.
  • Litz wire coil antennas for use in wireless charging devices generally have an unloaded in-air quality factor above 100 (thus higher than the unloaded in air quality factor of a stamped-type coil antenna).
  • the coil antenna 8 could be formed by conductive tracks of a flexible printed circuit.
  • Such an antenna generally has a unloaded in-air quality factor around 70 (thus higher than the unloaded in-air quality factor of a stamped-type coil antenna).
  • the coil antenna 8; 108 is here placed on the coil antennas 6, 10; 106, 1 10 of the first layer, i.e. on coil antennas 6, 10; 106, 1 10 of the stamped-type.
  • coil antennas 6, 10; 106, 1 10 are arranged adjoining each other in the first layer and coil antenna 8; 108 is placed on the coil antennas 6, 10; 106, 1 10 in such a way it partially overlaps each of the coil antenna 6, 10; 106, 110.
  • the antenna assembly 2; 102 includes a plurality of pairs of terminals 12, 14; 16, 18; 20, 22; 1 12, 1 14; 116, 1 18; 120, 122 respectively associated with the plurality of coil antennas 6, 8, 10; 106, 108, 1 10.
  • terminals 12, 14, 16, 18, 20, 22 are conductive pads of the printed circuit board 4 to which an end part of the related coil antenna 6, 8, 10 is soldered.
  • coil antenna 6 is connected to a first pair of terminals 12, 14, coil antenna 8 is connected to a second pair of terminals 16, 18 and coil antenna 10 is connected to a third pair of terminals 20, 22.
  • the antenna assembly 2 also includes a connector 24 making it possible to connect the various pairs of terminals 12, 14; 16, 18; 20, 22 to other electric components of the wireless charging device equipped with the antenna assembly 2, as further explained below.
  • the antenna assembly 2 is for instance assembled to a distinct (main) printed circuit board (not shown) such that coil antenna 8 faces a ferrite plate possibly carried by this main printed circuit board and that connector 24 connects the antenna assembly 2 to electronic circuits of the main printed circuit board.
  • coil antenna 106 is connected to a first pair of terminals 1 12, 1 14, coil antenna 108 is connected to a second pair of terminals 1 16, 1 18 and coil antenna 110 is connected to a third pair of terminals 120, 122.
  • coil antennas 106, 108, 1 10 may in this case be connected, via apertures in the ferrite plate 105, to electronic circuits of the second side of the printed circuit board 104.
  • Figure 3 shows elements of a possible electronic circuit for use in a wireless charging device 30 according to the invention.
  • This electronic circuit aims at controlling the injection of current in coil antennas of the antenna assembly.
  • Several methods are known in the art to perform this control of the current injected in the coil antennas and the electronic circuit now described should therefore be understood as an exemplary and non limiting solution to perform this control.
  • the wireless charging device 30 includes the antenna assembly 2 as described above (or, as a possible variation, the antenna assembly 102 described above), a processor 32, a driver circuit 34 and a switching circuit 36.
  • the driver circuit 34 includes two terminals P, N aimed at delivering an alternating current, the delivered alternating current energizing one of the coil antennas 6, 8, 10 (via the switching circuit 36) as explained below.
  • the switching circuit 36 includes a first controllable switch 38 and a second controllable switch 40 that are simultaneously controlled by a command signal C generated by the processor 32.
  • the first controllable switch 38 connects a first terminal P (among the two terminals P, N of the driver circuit 34) to either one of first terminals 12, 16, 20 of the pairs of terminals of the antenna assembly 2, depending on the command signal C received from the processor 32.
  • the second controllable switch 40 connects a second terminal N (among the two terminals P, N of the driver circuit 34) to either one of second terminals 14, 18, 22 of the pairs of terminals of the antenna assembly 2, depending on the command signal C received from the processor 32
  • this arrangement makes possible the connection of one of the coil antennas 6, 8, 10 and the driver circuit 34 so that the driver circuit 34 energizes the coil antenna with an alternating current (the connected coil antenna being determined based on the command signal C received from the processor 32).
  • the energizing alternating current injected in the connected coil antenna produces an alternating magnetic field meant to wirelessly charge an electronic device placed on the wireless charging device 30.
  • the processor 32 is programmed to select one of the coil antennas 6, 8, 10 and to generate the command signal C suited to control the switching circuit 36 in such a way it connects the driver circuit 34 (precisely its terminals P, N) to the selected coil antenna (precisely the respective pair of terminals associated to the selected coil antenna).
  • the processor 32 is for instance programmed to select the coil antenna providing the best coupling for charging an electronic device placed on the wireless charging device 30.
  • the coil antenna providing the best coupling is for instance determined (by the processor 32) based on measurements made in the driver circuit 34 and transmitted to the processor 32.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

An antenna assembly (2) comprises: - at least a first pair of terminals (12, 14) and a second pair of terminals (16, 18); - a first coil antenna (6) connected to the first pair of terminals (12, 14); - a second coil antenna (8) connected to the second pair of terminals (16, 18). The first coil antenna (6) is of stamped-type. The first coil antenna (6) and the second coil antenna (8) are respectively arranged in a first antenna layer comprising at least the first coil antenna (6), and in a second antenna layer comprising at least the second coil antenna (8) and distinct from the first antenna layer. The first coil antenna (6) and the second coil antenna (8) at least partially overlap. The second coil antenna (8) has an unloaded in-air quality factor greater than the first coil antenna (6). A wireless charging device comprising such an antenna assembly is also described.

Description

Antenna assembly and wireless charging device
comprising such an antenna assembly
T ECHNICAL FIELD OF THE INVENTION
The invention relates to wireless charging.
More precisely the invention relates to an antenna assembly and to a wireless charging device comprising such an antenna assembly.
BACKGROUND INFORMATION AND PRIOR ART
Wireless charging devices are provided with an antenna assembly for generating an alternating magnetic field.
In some embodiments, such an antenna assembly comprises at least a first pair of terminals, a second pair of terminals, a first coil antenna connected to the first pair of terminals and a second coil antenna connected to the second pair of terminals.
In such an antenna assembly, the first coil antenna and the second coil antenna may be arranged respectively in a first antenna layer (including at least said first coil antenna) and in a second antenna layer (including at least said second coil antenna).
When it is sought to reduce costs, the first coil antenna and the second coil antenna are stamped coil antennas; the quality factor of stamped coil antennas is low compared to other technologies such as those using Litz wires, negatively impacting the efficiency of the system.
SUMMARY OF THE INVENTION
In this context, the invention provides an antenna assembly comprising:
- at least a first pair of terminals and a second pair of terminals;
- a first coil antenna connected to the first pair of terminals, said first coil antenna being of stamped-type;
- a second coil antenna connected to the second pair of terminals, wherein said first coil antenna and said second coil antenna are respectively arranged in a first antenna layer comprising at least said first coil antenna, and in a second antenna layer comprising at least said second coil antenna and distinct from the first antenna layer, wherein said first coil antenna and said second coil antenna at least partially overlap and wherein said second coil antenna has an unloaded in-air quality factor greater than the first coil antenna.
The usage of distinct types of coil antennas respectively for the first and second antennas was predictably ineffective. For instance, the first (stamped-type) coil antenna was expectedly of little interest compared to the second coil antenna exhibiting a greater quality factor; the first (stamped-type) coil antenna was seen as problematic as detrimental to the quality factor of the second coil antenna.
It appears to the opposite that the construction proposed above is relatively balanced when considering the Quality Factor (QF) of both coil antennas and achieves satisfactorily good results at a reduced cost.
According to possible optional features:
- the first antenna layer includes at least a third coil antenna (and possibly additional coil antennas) adjoining the first coil antenna in said first antenna layer;
- the third coil antenna (and possibly each additional coil antenna) is of stamped-type;
- the second coil antenna has an unloaded in-air quality factor above 60 (possibly above 100, for instance in the case of a Litz wire coil antenna mentioned below);
- the second coil antenna comprises at least one wound insulated wire;
- the second coil antenna is a Litz wire coil antenna;
- the second coil antenna is formed by conductive tracks of a flexible printed circuit;
- the second antenna layer includes additional coil antennas adjoining the first coil antenna in said second antenna layer;
- the first coil antenna lies on a first face on a printed circuit board;
- the second coil antenna is deposited at least in part overlapping the first coil antenna;
- generally speaking, the coil antenna layers lie on a first face of a printed circuit board in no prescribed order;
- a second face of the printed circuit board, opposite the first face, carries a re-radiation antenna.
The invention also provides antenna assembly comprising:
- at least a first pair of terminals and a second pair of terminals;
- a stamped coil antenna connected to the first pair of terminals; - a Litz wire coil antenna connected to the second pair of terminals;
wherein said stamped coil antenna and said Litz wire coil antenna are respectively arranged in a first antenna layer comprising at least said stamped coil antenna, and in a second antenna layer comprising at least said Litz wire coil antenna and distinct from the first antenna layer, wherein said stamped coil antenna and said Litz wire coil antenna are at least partially overlapping.
As explained above, the first antenna layer may include a further stamped coil antenna (connected to a third pair of terminals of the antenna assembly). This further stamped coil antenna and the Litz wire coil antenna may also partially overlap.
The invention also provides a wireless charging device comprising an antenna assembly as presented above.
Such a wireless charging device may also comprise a driver circuit for delivering an alternating current and/or a selection circuit for selecting at least a pair of terminals amongst at least the first pair of terminals and the second pair of terminals and/or a switching circuit for applying said alternating current across the selected pair of terminals.
Other features and advantages of the embodiments of the present invention will be better understood upon reading of preferred embodiments thereof with reference to the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a first embodiment of an antenna assembly according to the invention;
Figure 2 shows a second embodiment of an antenna assembly according to the invention;
Figure 3 shows elements of a possible electronic circuit for a wireless charging device according to the invention.
DETAILED DESCRIPTION OF EXAMPLE(S)
Figures 1 and 2 shows two possible embodiments of an antenna assembly 2 ; 102 according to the invention, respectively.
The antenna assembly 2; 102 includes a printed circuit board 4; 104 and a plurality of coil antennas 6, 8, 10; 106, 108, 1 10.
The coil antennas 6, 8, 10; 106, 108, 1 10 are here located on a first side of the printed circuit board 4. The second side of the printed circuit board 4 (situated opposite the first side) may carry other electric and/or electronic circuits, such as a re-radiation antenna (not shown) in the first embodiment shown in Figure 1 , or such as a connector 124 in the second embodiment shown in Figure 2.
The coil antennas 6, 8, 10; 106, 108, 1 10 are arranged in a plurality of layers, here in a first layer of coil antennas 6, 1 0; 106, 1 10 lying on the first side of the printed circuit board 4; 104 and a second layer of coil antennas (including here a single coil antenna 8; 108) located on the first layer of coil antennas 6, 10; 106, 1 10 (such that the first layer is here interposed between the second layer and the printed circuit board 4; 104, although the invention is not limited to this construction, as indicated below).
In the first embodiment (shown in Figure 1 ), coil antennas 6, 10 of the first layer are lying in contact with the printed circuit board 4.
In the second embodiment (shown in Figure 2), a ferrite plate 105 is interposed between coil antennas 106, 1 10 of the first layer and the printed circuit board 104.
According to a possible variation, the antenna assembly could include at least a further antenna layer comprising one or several coil antenna(s), deposited on the second layer of coil antennas (the second layer then including a plurality of coil antennas).
At least one coil antenna of the first layer of coil antennas 6, 10; 106, 1 10 is a stamped-type coil antenna. In the described embodiment, both coil antennas 6, 10; 106, 1 10 of the first layer are stamped-type coil antennas. A stamped-type coil antenna is a coil antenna stamped to the shape of a coil from a metal plate and therefore consisting of plain metal.
Such stamped-type coil antennas for use in wireless charging devices have an unloaded in-air quality factor generally below 60.
The coil antenna 8; 108 of the second layer is a Litz wire coil antenna. Such a Litz wire coil antenna is a coil antenna formed from a wounded Litz wire, i.e. an insulated wire comprising a plurality of strands insulated from one another.
Litz wire coil antennas for use in wireless charging devices generally have an unloaded in-air quality factor above 100 (thus higher than the unloaded in air quality factor of a stamped-type coil antenna).
According to a possible variation, the coil antenna 8 could be formed by conductive tracks of a flexible printed circuit. Such an antenna generally has a unloaded in-air quality factor around 70 (thus higher than the unloaded in-air quality factor of a stamped-type coil antenna).
As noted above, the coil antenna 8; 108 is here placed on the coil antennas 6, 10; 106, 1 10 of the first layer, i.e. on coil antennas 6, 10; 106, 1 10 of the stamped-type.
Precisely, coil antennas 6, 10; 106, 1 10 are arranged adjoining each other in the first layer and coil antenna 8; 108 is placed on the coil antennas 6, 10; 106, 1 10 in such a way it partially overlaps each of the coil antenna 6, 10; 106, 110.
According to possible variations, the order of the various layers (starting from the printed circuit board 4; 104) can be changed without departing from the present invention.
The antenna assembly 2; 102 includes a plurality of pairs of terminals 12, 14; 16, 18; 20, 22; 1 12, 1 14; 116, 1 18; 120, 122 respectively associated with the plurality of coil antennas 6, 8, 10; 106, 108, 1 10.
In the first embodiment shown in Figure 1 , terminals 12, 14, 16, 18, 20, 22 are conductive pads of the printed circuit board 4 to which an end part of the related coil antenna 6, 8, 10 is soldered.
Precisely, coil antenna 6 is connected to a first pair of terminals 12, 14, coil antenna 8 is connected to a second pair of terminals 16, 18 and coil antenna 10 is connected to a third pair of terminals 20, 22.
In the first embodiment shown in Figure 1 , the antenna assembly 2 also includes a connector 24 making it possible to connect the various pairs of terminals 12, 14; 16, 18; 20, 22 to other electric components of the wireless charging device equipped with the antenna assembly 2, as further explained below.
With such a construction, the antenna assembly 2 is for instance assembled to a distinct (main) printed circuit board (not shown) such that coil antenna 8 faces a ferrite plate possibly carried by this main printed circuit board and that connector 24 connects the antenna assembly 2 to electronic circuits of the main printed circuit board.
In the second embodiment shown in Figure 2, coil antenna 106 is connected to a first pair of terminals 1 12, 1 14, coil antenna 108 is connected to a second pair of terminals 1 16, 1 18 and coil antenna 110 is connected to a third pair of terminals 120, 122.
As shown in Figure 2, coil antennas 106, 108, 1 10 may in this case be connected, via apertures in the ferrite plate 105, to electronic circuits of the second side of the printed circuit board 104.
Figure 3 shows elements of a possible electronic circuit for use in a wireless charging device 30 according to the invention.
This electronic circuit is described in the context of the first embodiment shown in Figure 1 but also applies to the second embodiment shown in Figure 2.
This electronic circuit aims at controlling the injection of current in coil antennas of the antenna assembly. Several methods are known in the art to perform this control of the current injected in the coil antennas and the electronic circuit now described should therefore be understood as an exemplary and non limiting solution to perform this control.
In this example, the wireless charging device 30 includes the antenna assembly 2 as described above (or, as a possible variation, the antenna assembly 102 described above), a processor 32, a driver circuit 34 and a switching circuit 36.
The driver circuit 34 includes two terminals P, N aimed at delivering an alternating current, the delivered alternating current energizing one of the coil antennas 6, 8, 10 (via the switching circuit 36) as explained below.
The switching circuit 36 includes a first controllable switch 38 and a second controllable switch 40 that are simultaneously controlled by a command signal C generated by the processor 32.
The first controllable switch 38 connects a first terminal P (among the two terminals P, N of the driver circuit 34) to either one of first terminals 12, 16, 20 of the pairs of terminals of the antenna assembly 2, depending on the command signal C received from the processor 32.
Concurrently, the second controllable switch 40 connects a second terminal N (among the two terminals P, N of the driver circuit 34) to either one of second terminals 14, 18, 22 of the pairs of terminals of the antenna assembly 2, depending on the command signal C received from the processor 32
As shown in Figure 3, this arrangement makes possible the connection of one of the coil antennas 6, 8, 10 and the driver circuit 34 so that the driver circuit 34 energizes the coil antenna with an alternating current (the connected coil antenna being determined based on the command signal C received from the processor 32).
The energizing alternating current injected in the connected coil antenna produces an alternating magnetic field meant to wirelessly charge an electronic device placed on the wireless charging device 30.
The processor 32 is programmed to select one of the coil antennas 6, 8, 10 and to generate the command signal C suited to control the switching circuit 36 in such a way it connects the driver circuit 34 (precisely its terminals P, N) to the selected coil antenna (precisely the respective pair of terminals associated to the selected coil antenna).
In this connection, the processor 32 is for instance programmed to select the coil antenna providing the best coupling for charging an electronic device placed on the wireless charging device 30. The coil antenna providing the best coupling is for instance determined (by the processor 32) based on measurements made in the driver circuit 34 and transmitted to the processor 32.

Claims

1. Antenna assembly comprising:
- at least a first pair of terminals (12, 14; 1 12 , 1 14) and a second pair of terminals (16, 18; 1 16, 1 18);
- a first coil antenna (6; 106) connected to the first pair of terminals, said first coil antenna being of stamped-type;
- a second coil antenna (8; 108) connected to the second pair of terminals,
wherein said first coil antenna and said second coil antenna are respectively arranged in a first antenna layer comprising at least said first coil antenna, and in a second antenna layer comprising at least said second coil antenna and distinct from the first antenna layer,
wherein said first coil antenna and said second coil antenna at least partially overlap and
wherein said second coil antenna has an unloaded in-air quality factor greater than the first coil antenna.
2. Antenna assembly according to claim 1 , wherein the first antenna layer includes at least a third coil antenna (10; 1 10) adjoining the first coil antenna in said first antenna layer.
3. Antenna assembly according to claim 2, wherein the third coil antenna is of stamped-type.
4. Antenna assembly according to any of claims 1 -3, wherein the second coil antenna comprises at least one wound insulated wire.
5. Antenna assembly according to any of claims 1 -4, wherein the second coil antenna is a Litz wire coil antenna.
6. Antenna assembly according to any of claims 1 -3, wherein the second coil antenna is formed by conductive tracks on a flexible printed circuit.
7. Antenna assembly according to any of claims 1 -6, wherein the second coil antenna is deposited at least in part overlapping the first coil antenna.
8. Wireless charging device comprising an antenna assembly according to any of claims 1 -7.
9. Wireless charging device according to claim 8, further comprising:
- a driver circuit for delivering an alternating current;
- a selection circuit for selecting at least a pair of terminals amongst at least the first pair of terminals and the second pair of terminals;
- a switching circuit for applying said alternating current across the selected pair of terminals.
PCT/EP2019/078846 2018-11-21 2019-10-23 Antenna assembly and wireless charging device comprising such an antenna assembly WO2020104134A1 (en)

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