CN113346635A - Coil, wireless charging transmitting and receiving device and mobile terminal - Google Patents

Abstract

The invention discloses a coil, a wireless charging transmitting and receiving device and a mobile terminal, and belongs to the technical field of electric power. Aiming at the problem that coil quality factors are low in limited space and area in the prior art, the invention provides a coil, a wireless charging transmitting and receiving device and a mobile terminal, and the scheme aims at the problem that the coil quality factors are in limited space area and the coil structure is optimally designed in the original process; the structure of the single-layer coil is correspondingly improved, and the wires arranged in parallel can be selected to cross and pass through, so that the alternating current loss of the whole coil can be effectively reduced to the maximum extent. The proximity effect and the skin effect are reduced, the quality factor of the coil is ensured, better quality factor can be obtained under a certain area and volume under the condition of a single-layer structure, and better charging efficiency is obtained.

Description

Coil, wireless charging transmitting and receiving device and mobile terminal

Technical Field

The invention relates to the technical field of electric power, in particular to a coil, a wireless charging transmitting and receiving device and a mobile terminal.

Background

With the development of the technology, the wireless transmission of electric energy is realized through electromagnetic induction in the prior art of wireless charging of electronic equipment, and quality factor (Q factor) of a wireless charging coil is a key factor influencing charging efficiency based on the wireless charging of electromagnetic induction. A higher quality factor indicates a lower rate of power loss, i.e., a higher charging efficiency. The quality factor of the wireless charging coil is related to the impedance and inductance of the wireless charging coil. However, in order to reduce the resistance of the wireless charging coil and improve the inductance of the wireless charging coil, a larger and thicker wire may need to be used, so that the area required by the wireless charging coil is increased, but in the wireless charging use process, the application environments are different, the thickness and the use space are limited, the larger and thicker wire cannot be used, and the development of the coil efficiency is limited by the corresponding space and the structure.

Disclosure of Invention

1. Technical problem to be solved

Aiming at the problem of low coil quality factor in limited space and area in the prior art, the invention provides a coil, a wireless charging transmitting and receiving device and a mobile terminal, which can realize the condition of ensuring unchanged space and size, improve the quality factor and obtain better power utilization efficiency.

2. Technical scheme

The purpose of the invention is realized by the following technical scheme.

A coil device comprises at least two groups of leads which are arranged in parallel and wound on a winding surface to form a coil structure.

Furthermore, the lead group is provided with a wire inlet end and a wire outlet end, and the wire inlet end and the wire outlet end are electrically connected with an external component.

Furthermore, the lead is a self-adhesive wire, a Litz wire or a hollow lead.

Further, at least one group of the wires arranged in parallel is arranged to cross each other at a position of the coil.

Furthermore, one side or two sides of the filling wire group are provided with magnetic cores.

A wireless charging transmitting device, comprising: an inverter circuit, a control unit and any one of the coil devices described above;

the input end of the inverter circuit is connected with a direct-current power supply;

the output end of the inverter circuit is connected with the coil device;

the inverter circuit inverts the direct current output by the direct current power supply into alternating current under the control of the control unit and outputs the alternating current to the coil device;

the coil module is used for transmitting the alternating current in an alternating magnetic field mode.

A wireless charge receiving arrangement, comprising: a rectifier circuit, a control unit, a load, and the coil device of any one of the above;

the coil device is used for receiving alternating current in an alternating magnetic field mode;

the input end of the rectifying circuit is connected with the coil device;

the rectifying circuit is used for rectifying the alternating current into direct current under the control of the control unit and outputting the direct current to the load so as to provide electric energy for the load.

A wireless charging system, comprising the wireless charging transmitting device and the wireless charging receiving device of claim 7;

the wireless charging transmitting device is used for wirelessly charging the wireless charging receiving device.

A mobile terminal comprises a work load circuit, a rectifying circuit, a charging control unit and the coil device;

the coil device is used for receiving alternating current in an alternating magnetic field mode;

the input end of the rectifying circuit is connected with the coil device;

the rectifying circuit is used for rectifying the alternating current into direct current under the control of the charging control unit and outputting the direct current to the working load circuit.

3. Advantageous effects

Compared with the prior art, the invention has the advantages that:

the scheme is correspondingly improved aiming at the structure of the single-layer coil, and the wires arranged in parallel can be selected to be crossed and wired, so that the alternating current loss of the whole coil can be effectively reduced to the maximum extent. The proximity effect and the skin effect are reduced, the quality factor of the coil is ensured, better quality factor can be obtained under a certain area and volume under the condition of a single-layer structure, and better charging efficiency is obtained.

Drawings

FIG. 1 is a schematic diagram of a coil configuration according to one embodiment of the present invention;

FIG. 2 is a cross-sectional internal current density plot of a wire in proximity according to one embodiment of the present invention;

FIG. 3 is a cross-sectional view of a silk covered wire of the present invention;

FIG. 4 is a cross-sectional view of a twisted wire of the enamel wire according to the present invention;

FIG. 5 is a cross-sectional view of a self-adhesive enameled wire according to the present invention;

FIG. 6 is a graph of the current density inside the coil cross trace of the present invention;

FIG. 7 is a diagram of a coil cross-trace configuration according to one embodiment;

fig. 8 is a diagram showing a structure of a wireless charging coil according to another embodiment of the present invention;

fig. 9 is a diagram showing a structure of a wireless charging coil according to another embodiment of the present invention;

FIG. 10 is a schematic diagram of a three-wire routing structure according to the present invention;

FIG. 11 is a schematic diagram of a four-wire routing structure according to the present invention;

fig. 12 is a schematic diagram of various shapes of the coil winding of the present invention.

Detailed Description

The invention is described in detail below with reference to the drawings and specific examples.

Example 1

The scheme aims at the situation that the quality factor of the coil is limited in space area, and the coil structure is optimally designed on the basis of the original process;

for a fixed operating frequency, the quality factor Q depends mainly on the geometry of the coil, the size and number of turns of the coil, the material used and the internal routing structure of the coil.

The internal resistance Rs of the coil mainly comprises direct current resistance and alternating current resistance, the current density in the conductor is relatively uniformly distributed in a low-frequency environment, and the Rs is mainly determined by the direct current resistance, namely:

in the formula, rho represents the resistivity of the conductor material wound by the coil, l represents the total length of the conductor material wound by the coil, and A represents the sum of the cross-sectional areas of the conductors of each turn. According to the formula, on the premise that the coil is wound by adopting the conductors made of the same material and the conductors with the same length, the loss resistance of the coil is in inverse proportion to the total area of each circle of conductor, so that a thicker wire is generally selected for winding the coil in the design process of the coil, and the transmission efficiency of the coil can be effectively improved. However, as the resonant frequency increases, the ac resistance of the conductor increases due to the skin effect, proximity effect, and eddy current effect. When alternating current is applied to the conductors which are close to each other, each conductor is positioned in the electromagnetic field generated by the current in other conductors besides the electromagnetic field generated by the current of the conductor, so that the current density distribution in each conductor is changed, and the phenomenon is called a proximity effect. The proximity effect can aggravate the nonuniformity of current density distribution in the cross section of the conductor, increase the equivalent resistance of the conductor and further increase the alternating current loss.

The embodiment of the invention provides a wireless charging coil structure, which is used for reducing the alternating current resistance of a wireless charging coil and improving the quality factor Q of the coil, so that the wireless charging efficiency is improved.

The effect of the skin effect of the system must be considered for the design of the system. Generally, the ac loss of the wire is increased because electrons flow concentrated on the near-outer surface of the conductor due to the skin effect. In engineering, this phenomenon of reduced effective current flow area is generally replaced by an equivalent resistor whose main parameter is skin depth. The ac resistance due to the skin effect is expressed as follows:

w represents the width of the coil-covered portion, l represents the total length of the coil winding, ρ represents the resistivity of the wire wound with the coil, δ represents the skin depth, and is expressed as:

for example: the magnetic permeability of the copper wire is 1.2567x 10-6H/m; the resistivity of the copper wire is 1/the conductivity of the copper wire, the conductivity of the copper wire sigma copper is 59.6x 10-6S/m, and the skin depth under different frequencies is as follows:

as shown in fig. 1, a schematic diagram of a coil for wireless charging is shown. When the coil is wound to form a single-layer coil, the wireless charging coil comprises a plurality of lead groups, and a plurality of leads are arranged in parallel and wound on the same winding surface; the coil for wireless charging of the embodiment is schematically illustrated. The wireless charging coil comprises a plurality of lead groups, and a plurality of leads are arranged in parallel and wound on the same winding surface; because many wires are each other's electric connection and parallelly connected, consequently the coil of coiling, can promote the sectional area of every round coil in order to reduce the direct current impedance of wireless charging coil, can not increase the thickness of wireless charging coil simultaneously, still have good elasticity when making the wireless charging coil installation, replace the single strand wires that have same total cross-section with many insulated wires, in order to reduce the negative effects that skin effect brought, adopt side by side line to form one or more interwoven structure in the coil, make the total current density of every turn coil reach evenly distributed as far as, near and can reduce the alternating current impedance that wireless charging coil proximity effect loss arouses, show the quality factor who promotes wireless charging coil. The lead is provided with a wire inlet end and a wire outlet end, and the wire inlet end and the wire outlet end are electrically connected with other external parts;

the plurality of wires are electrically connected and connected in parallel, and the wire inlet and outlet ends of the plurality of wires are provided with the tin and connected with the tin, so that the wound coils can improve the sectional area of each circle of coils to reduce the direct current impedance of the wireless charging coil, and meanwhile, the thickness of the wireless charging coil cannot be increased, so that the wireless charging coil has good elasticity during installation, and the negative effect caused by skin effect is reduced; because some applications need a winding mode which only can select a single-layer coil, the scheme ensures that the electric characteristics and the quality factor are strictly limited under the condition of using the single-layer coil. Since the single layer is crossed, this solution is also commonly used in the case of single-layer coil, because if the multi-layer coil is crossed many times, the skin effect will be offset to some extent, and negative effects may be generated.

The following were used: two coils are bifilar and wound, the inner diameter is 21 x 21mm, the number of turns is 12, and the wire is

Root of herbaceous plant

Internal routing cross	Ls：5.5	Rs：29	RDC：22	Q：127
					Internal wiring does not cross	Ls：5.45	Rs：48	RDC：22	Q：70

As shown in the above table, the cross ratio of the measured data under the same test conditions (100KHz,1V) for two coils with the same manufacturing process is significantly smaller than the non-cross RS (alternating current impedance), and the Q value is calculated as follows:

Q＝wL/R

wherein:

q is a quality factor

w is the angular frequency (2 pi f) at resonance of the circuit

L is an inductance

R is coil AC resistance

From this, we conclude that the main factor affecting the Q value of the coil is the ac impedance when the relevant factors such as the size and the like of the coil with the same specification are fixed.

As shown in the above table, the conductor wire is not limited to a single wire, and preferably, as shown in fig. 3, 4 and 5, in order to reduce the skin effect, the wire in the scheme can use a plurality of strands of self-adhesive wires, Litz wires, hollow wires and the like which are arranged side by side instead of single wires with the same total cross section, so that the skin effect can be effectively improved, and the Litz wires can be enameled wires stranded with Litz wires, acetone Litz wires and the like.

The working frequency selected for wireless charging is 100KHz, the selectable frequency is 100KHz-205KHz, and the skin depth of the copper wire under the frequency of 100KHz is 0.21mm, so the wire needs to be selected in the first step of coil design, the maximum diameter of the selectable wire under the working frequency working condition is 0.42mm, so the coil within 0.42mm selects a self-adhesive wire, and the litz wire or an air wire larger than 0.42mm is selected. Of course, the frequency is adjusted, and the corresponding type selection also needs to be adjusted.

Multi-strand flat coil (self-adhesive wire): diameter range of single wire: within 0.42mm, in the wireless use that charges, often the application environment is different, and thickness and usage space are limited, can adopt the flat coil scheme of stranded to the ultra-thin space of some thickness, arrange the insulated wire according to practical application interval in the middle of the wire of arranging side by side, pull open the interval of wire, the thickness of insulated wire can adjust the adaptation according to the wire rod diameter of coil body.

For some special application scenes, thicker wires are adopted when the coil is designed, but under the action of the skin effect, the current distribution in the middle of a copper wire with the diameter larger than 0.42mm tends to be zero under the action of the skin effect under the working frequency of 100KHz, and the loss of the overall coil is increased due to the alternating current resistance caused by the skin effect. And meanwhile, insulated wires are arranged among the wires arranged side by side at intervals according to practical application, so that the alternating current resistance in the application coil is further reduced.

For some wireless charging applications with larger power, when the inside of the coil needs larger current and voltage, a thick line needs to be selected, but under the working frequency of 100KHz, under the action of the skin effect, the loss of the overall coil is increased due to the alternating current resistance caused by the skin effect, and under the condition, the Litz line (enameled wire stranded Litz line/acetone Litz line) can be adopted to wind the coil, so that the skin effect can be effectively improved. And meanwhile, insulated wires are arranged among the wires arranged side by side at intervals according to practical application, so that the alternating current resistance in the application coil is further reduced.

Therefore, when the method is implemented, the wire needs to be selectively designed according to the practical application scene, the skin effect is reduced, and the quality factor of the coil is ensured to be increased. Under certain skin effect, a proper wire is selected, the self-adhesive wire is composed of an insulated wire and a self-adhesive layer, and the self-adhesive layer is coated on the surface of the insulated wire, so that the self-adhesive wire can be connected with a filling wire, and the smoothness of installation and winding is better guaranteed.

The specific winding conditions are shown in the following table

The proximity effect is mainly based on the existing coil manufacturing process, the internal wiring arrangement mode of the planar coil is optimized, and the total current density in each coil is uniformly distributed as much as possible, so that the alternating current resistance in the coil is reduced, and the quality factor (Q value) of the coil is improved, and the invention is a specific invention realization mode as follows;

in some special application scenes, in order to pursue the thickness of a product, the coil needs to be controlled to be thin, thinner wires are adopted, and the heat productivity of a system is larger because the internal resistance of the wound coil is too high, the loading capacity of the coil is too poor (the voltage resistance and current resistance are not enough), and the quality factor is lower, so that the loading capacity of the coil can be improved by winding a plurality of wires in parallel, the internal resistance of the coil is reduced, and the quality factor of the coil is improved. The coil made by winding a plurality of parallel wires has uneven current density distribution among turns due to the influence of the proximity effect, so that the alternating current resistance is increased, the interweaving arrangement mode of the internal parallel wires is changed, as shown in fig. 6 and 7, the specific method is implemented by adopting a cross winding mode, the current is mainly distributed on two sides, the total current density of each turn of the coil is uniformly distributed as far as possible, the current resistance caused by the loss of the proximity effect is further reduced, and the quality factor of the coil module is improved. The crossing position can be selected according to the requirement, the crossing can be selected only in one turn of the innermost circle of the coil, the crossing can also be selected in other positions, and the number of the crossing can also be adjusted according to the requirement.

As shown in fig. 10 and 11, the specific crossing form can be selected according to the number of different parallel wires, as long as any two wires are crossed, the number of parallel wires is not limited, at least 2 wires are crossed, the crossing combination mode is not limited, and any crossing combination can be performed, so that the quality factor of the coil module can be improved, and the charging efficiency of the coil can be improved. The positions of the cross points on the plane are not limited to one or two, when a plurality of wires wind the coil side by side, the cross points in the middle of the coil can be increased or decreased according to the actual use condition, and are not necessarily distributed symmetrically left and right or up and down, and the cross points can be distributed asymmetrically according to the practical application coil example.

Preferably, as shown in fig. 8 and 9, a plurality of wires are wound in a parallel and crossed manner, although the thickness of the coil and the alternating current impedance in the coil can be reduced, the external dimension of the coil can be greatly increased, and the number of turns of the coil can be greatly reduced by adopting the magnetic core, so that the direct current resistance of the lead wire is reduced, and the Q value of the coil is also improved. The whole volume can be reduced, and the corresponding charging efficiency can not be reduced.

However, the invention is not limited to winding the wireless charging coil into a square or a circle, and in other embodiments, the wire may be wound into other polygons according to the requirements of the system, and as shown in fig. 12, the wire may be arranged into polygons with various shapes and structures.

Preferably, the quality factor Q of the coil is improved, and alloy conductors (such as silver-containing wires and the like for reducing resistivity) and plated metals (such as silver plating, magnetic plating and other process materials) can be adopted to reduce high-frequency resistance; similarly, the transmission efficiency of the portable high-coil can be improved by improving the angle of a coil winding material, for example, the coil winding is carried out by adopting a wire with high magnetic permeability (such as iron, nickel and the like), the current distribution in the coil is effectively improved, and the effective flow area of each turn of the coil is increased;

based on the coil structure, the wireless charging transmitting device comprises an inverter circuit, a control unit and the coil device; the input end of the inverter circuit is connected with a direct-current power supply; the output end of the inverter circuit is connected with the coil device; the inverter circuit inverts the direct current output by the direct current power supply into alternating current under the control of the control unit and outputs the alternating current to the coil device; the coil module is used for transmitting the alternating current in an alternating magnetic field mode.

There may also be provided a wireless charge receiving apparatus, comprising: the coil module comprises a rectifying circuit, a control unit, a load and any one of the coil modules described above; the coil module is used for receiving alternating current in an alternating magnetic field mode; the input end of the rectification circuit is connected with the coil module; and the rectifying circuit is used for rectifying the alternating current into direct current under the control of the control unit and outputting the direct current to a load so as to provide electric energy for the load.

Because the wireless charging receiving device comprises the coil, the corresponding loss can be reduced, and the electric energy receiving efficiency can be improved.

The wireless charging system comprises the wireless charging transmitting device and the wireless charging receiving device; the wireless charging transmitting device is used for wirelessly charging the wireless charging receiving device.

Because the wireless charging system comprises the receiving device and the transmitting device, the corresponding loss can be reduced, the quality factor can be improved, and the charging efficiency of the power consumption equipment can be improved.

Also, a mobile terminal may be provided, the mobile terminal including a workload circuit, a rectifying circuit, a charge control unit, and any one of the above coil devices; a coil device for receiving an alternating current in the form of an alternating magnetic field; the input end of the rectification circuit is connected with the coil module; and the rectifying circuit is used for rectifying the alternating current into direct current under the control of the charging control unit and outputting the direct current to the working load circuit.

The invention and its embodiments have been described above schematically, without limitation, and the invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The representation in the drawings is only one of the embodiments of the invention, the actual construction is not limited thereto, and any reference signs in the claims shall not limit the claims concerned. Therefore, if a person skilled in the art receives the teachings of the present invention, without inventive design, a similar structure and an embodiment to the above technical solution should be covered by the protection scope of the present patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Several of the elements recited in the product claims may also be implemented by one element in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims (9)

1. A coil device is characterized by comprising at least two groups of leads formed by leads, wherein the leads are arranged in parallel and wound on a winding surface to form a coil structure.

2. The coil device according to claim 1, wherein the lead wire group is provided with a wire inlet end and a wire outlet end, the wire inlet end and the wire outlet end being electrically connected to an external member.

3. The coil device according to claim 1, wherein the wire is a self-adhesive wire, a Litz wire, or a hollow wire.

4. The coil assembly of claim 1, wherein at least one of the sets of wires disposed in parallel crosses over each other at a position of the coil.

5. The coil assembly of claim 1 wherein the filler wire set is provided with a magnetic core on one or both sides.

6. A wireless charging transmitting device, comprising: an inverter circuit, a control unit and the coil device of any one of claims 1 to 5;

the input end of the inverter circuit is connected with a direct-current power supply;

the output end of the inverter circuit is connected with the coil device;

the inverter circuit inverts the direct current output by the direct current power supply into alternating current under the control of the control unit and outputs the alternating current to the coil device;

the coil module is used for transmitting the alternating current in an alternating magnetic field mode.

7. A wireless charging receiving device, comprising: a rectifier circuit, a control unit, a load and the coil device of any one of claims 1-5;

the coil device is used for receiving alternating current in an alternating magnetic field mode;

the input end of the rectifying circuit is connected with the coil device;

the rectifying circuit is used for rectifying the alternating current into direct current under the control of the control unit and outputting the direct current to the load so as to provide electric energy for the load.

8. A wireless charging system, comprising the wireless charging transmitting device of claim 6 and the wireless charging receiving device of claim 7;

the wireless charging transmitting device is used for wirelessly charging the wireless charging receiving device.

9. A mobile terminal characterized in that it comprises a workload circuit, a rectifying circuit, a charge control unit and a coil device according to any one of claims 1 to 5;

the coil device is used for receiving alternating current in an alternating magnetic field mode;

the input end of the rectifying circuit is connected with the coil device;

the rectifying circuit is used for rectifying the alternating current into direct current under the control of the charging control unit and outputting the direct current to the working load circuit.

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