WO2023279639A1

WO2023279639A1 - Coil, wireless charging transmitting device, wireless charging receiving device, and mobile terminal

Info

Publication number: WO2023279639A1
Application number: PCT/CN2021/134910
Authority: WO
Inventors: 程世友; 戴飞; 陈莉娟; 范俊杰
Original assignee: 浙江晶日科技股份有限公司
Priority date: 2021-07-05
Filing date: 2021-12-02
Publication date: 2023-01-12
Also published as: CN113364144A

Abstract

The present invention relates to the technical field of electric power. Disclosed are a coil, a wireless charging transmitting device, a wireless charging receiving device, and a mobile terminal. Aiming at the prior art problem of a low coil quality factor due to a limited space and area, the present invention provides a coil, a wireless charging transmitting device, a wireless charging receiving device, and a mobile terminal. In the present solution, in view of the situation that the quality factor of the coil is low due to the limited space and area, the coil structure design is optimized on the basis of the original process. The provision of filling threads at intervals between wires effectively minimizes AC loss of the entire coil, reduces the proximity effect and skin effect, and ensures the quality factor of the coil, thereby achieving a higher quality factor with a certain area and volume, and achieving higher charging efficiency.

Description

Coil, wireless charging transmitter, receiver and mobile terminal

technical field

The present invention relates to the field of electric power technology, and more specifically, relates to a coil, a wireless charging transmitting and receiving device and a mobile terminal.

Background technique

With the development of technology, the existing technology of wireless charging of electronic equipment is to realize the wireless transmission of electric energy through electromagnetic induction. For wireless charging based on electromagnetic induction, the quality factor (Q factor) of the wireless charging coil is the key factor affecting the charging efficiency. . The higher the figure of merit, the lower the proportion of power loss, that is, the higher the charging efficiency. The quality factor of the wireless charging coil is related to the impedance and inductance of the wireless charging coil.

technical problem

However, in order to reduce the resistance of the wireless charging coil and increase the inductance of the wireless charging coil, it may be necessary to use larger and thicker wires, resulting in an increase in the area required for the wireless charging coil. However, during the use of wireless charging, it is often used The environment is different, the thickness and use space are limited, and larger and thicker wires cannot be used. The corresponding space and structure limit the development of coil efficiency.

technical solution

Aiming at the problem of low quality factor of the coil in the limited space and area in the prior art, the present invention provides a coil, a wireless charging transmitting and receiving device and a mobile terminal, which can realize a coil with constant space and size. situation, improve the quality factor, and obtain better electricity efficiency.

The purpose of the present invention is achieved through the following technical solutions.

A coil device, including a wire group formed by several wires and a filler wire group formed by a number of filler wires, the wire group and the filler wire group are arranged side by side, and are wound on the winding surface to form a coil structure, and the filler wire is insulated. Conductive material.

Furthermore, the wire group is provided with an incoming wire end and an outgoing wire end, and the incoming wire end and the outgoing wire end are electrically connected to external components.

Furthermore, the filling thread is a single-strand integral thread or a multi-strand braided thread.

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

Furthermore, the ratio of the diameter of the filling wire group to the diameter of the wire group is (1-1.5):1.

Furthermore, magnetic cores are provided on one or both sides of the filler wire group.

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

The input end of the inverter circuit is connected to a DC power supply;

The output end of the inverter circuit is connected to the coil device;

Under the control of the control unit, the inverter circuit inverts the DC power output by the DC power supply into AC power and outputs it to the coil device;

The coil module is used to emit the alternating current in the form of an alternating magnetic field.

A wireless charging receiving device, comprising: a rectifying circuit, a control unit, a load, and the coil device described in any one of the above;

The coil device is used to receive alternating current in an alternating magnetic field;

The input end of the rectification circuit is connected to the coil device;

The rectification circuit is used to rectify the alternating current into direct current and output it to the load under the control of the control unit, so as to provide electric energy for the load.

A wireless charging system, comprising the wireless charging transmitting device described above and the wireless charging receiving device described in claim 7;

The wireless charging transmitting device is used for performing wireless charging for the wireless charging receiving device.

A mobile terminal, comprising a working load circuit, a rectifier circuit, a charging control unit, and the above-mentioned coil device;

The input end of the rectification circuit is connected to the coil device;

The rectification circuit is used to rectify the alternating current into direct current under the control of the charging control unit and output it to the working load circuit.

Beneficial effect

Compared with the prior art, the present invention has the advantages of:

This solution makes a corresponding improvement on the structure of the single-layer coil, and effectively reduces the AC loss of the entire coil by spacing the filling lines between the wires. By reducing the proximity effect and skin effect and ensuring the quality factor of the coil, a better quality factor can be obtained under a certain area and volume, and better charging efficiency can be obtained.

Description of drawings

Fig. 1 is a schematic diagram of the structure of adjacent wires according to an embodiment of the present invention;

Fig. 2 is a diagram of the internal current density of the section under different wire spacings according to an embodiment of the present invention;

Fig. 3 is a structural diagram of a coil for wireless charging according to an embodiment of the present invention;

Fig. 4 is a structural diagram of a coil for wireless charging according to another embodiment of the present invention;

Fig. 5 is a structural diagram of a coil for wireless charging according to another embodiment of the present invention;

6 is a structural diagram of a coil for wireless charging according to another embodiment of the present invention;

Fig. 7 is a schematic diagram of various shapes and structures of the coil winding of the present invention.

Embodiments of the present invention

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

This scheme is aimed at the quality factor of the coil in the case of limited space area, and optimizes the design of the coil structure on the original process;

For a fixed operating frequency, the quality factor Q mainly depends on the geometric shape of the coil, the size and number of turns of the coil, the material used and the internal wiring structure of the coil.

The internal resistance Rs of the coil mainly includes DC resistance and AC resistance. In a low-frequency environment, the current density in the conductor is relatively evenly distributed, and Rs is mainly determined by the DC resistance, namely:

In the formula, represents the resistivity of the coil-wound conductor material, represents the total length of the coil-wound conductor material, and A represents the sum of the cross-sectional area of each coil of conductor. It can be seen from the formula that under the premise of using conductors of the same material and conductors of the same length to wind the coil, the coil loss resistance is inversely proportional to the total area of each conductor, so thicker wires are generally selected in the coil design process Winding the coil can effectively improve the transmission efficiency of the coil. However, as the resonance frequency increases, the AC resistance of the conductor increases due to the skin effect, proximity effect and eddy current effect. When the conductors close to each other are connected with alternating current, each conductor is not only in the electromagnetic field generated by its own current, but also in the electromagnetic field generated by the current in other conductors, so the current density distribution in each conductor will change, which This phenomenon is called the proximity effect. The proximity effect will aggravate the inhomogeneity of the current density distribution in the conductor cross section, increase the equivalent resistance of the conductor, and thus increase the AC loss. Therefore, choosing an appropriate distance between wires, that is, the turn spacing, can effectively reduce the AC resistance, thereby improving the coil quality factor. The adjacent wire structure is shown in Figure 1, and the AC resistance caused by the proximity effect is expressed as follows:

In the formula, is the operating frequency, is the wire length, is the magnetic permeability, and is the resistivity.

The AC resistance caused by the proximity effect is most affected by the turn spacing. It can be seen from the formula that, under the premise that other conditions remain unchanged, the turn spacing D is inversely proportional to the coil loss. In particular, when the turn spacing is 2 to 2.5 times the wire diameter, the coil loss can be kept basically constant. Therefore, when winding the coil, the adjacent turn spacing S (= D-2r) between each turn can be wound with a wire that is 1 to 1.5 times the wire diameter, which can minimize the AC loss of the entire coil.

Figure 2 shows the cross-section of two circular copper wires with a diameter of 1mm. A current of 1A in the same direction is passed through the wires, and the current frequency is 100kHz. The distribution of the internal current density of the cross-section under different wire spacings. It can be seen from the figure that due to the loss of symmetry of the current density distribution in the proximity effect section, the current density on one side of the two sections is significantly lower than that on the other side, and the closer the distance between the two wires, the lower the current density on the adjacent part of the section. The proximity effect is more pronounced. Therefore, in order to reduce the proximity effect, the wire spacing should be increased as much as possible.

An embodiment of the present invention provides a wireless charging coil structure to reduce the AC resistance of the wireless charging coil and improve the quality factor Q of the coil, thereby improving the efficiency of wireless charging. When the coil is wound into a single-layer coil, the filler wire is used between the wire groups to separate the adjacent turn spacing between each turn, which can reduce the AC impedance caused by the proximity effect loss of the wireless charging coil and significantly improve the quality of the wireless charging coil factor.

For the design of high-frequency systems, the influence of the system skin effect must be considered. Generally speaking, due to the skin effect, the electrons are concentrated on the surface of the conductor near the outer skin, thus increasing the AC loss of the wire. In engineering, the phenomenon of reducing the effective current flow area is generally replaced by an equivalent resistance, and the main parameter of the resistance is the skin depth. The AC resistance caused by the skin effect is expressed as follows:

w represents the width of the part covered with the coil, represents the total length of the coil winding, represents the resistivity of the coil winding wire, represents the skin depth, and its expression is:

For example: the magnetic permeability of copper wire, copper = 1.2567x10-6 H/m; the resistivity of copper wire = 1/conductivity of copper wire, the conductivity of copper wire σ copper = 59.6 x10-6 S/m, different Under the frequency, the size of the skin depth is as follows:

As shown in FIG. 3 , a schematic diagram of the coil for wireless charging in this embodiment. The wireless charging coil includes a plurality of wire groups and a plurality of filler wire groups, and the plurality of wire groups and the plurality of filler wire groups are at least one wire and a filler wire, which are arranged side by side on the same winding surface. Winding; the filling wire does not need to be electrically connected to the outside, but is arranged at intervals between adjacent turns of the wire, and the wire is provided with an incoming wire end and an outgoing wire end, and the incoming wire end and the outgoing wire end are electrically connected to other external components;

Since multiple wires are electrically connected to each other and connected in parallel, the wound coil can increase the cross-sectional area of each coil to reduce the DC impedance of the wireless charging coil without increasing the thickness of the wireless charging coil, enabling wireless charging The coil also has good elasticity when installed. Multiple insulated wires are used instead of single-strand wires with the same total cross-section to reduce the negative impact caused by the skin effect. The distance between the adjacent turns of the wireless charging coil is widened, which can reduce the AC impedance caused by the proximity effect loss of the wireless charging coil, and significantly improve the quality factor of the wireless charging coil.

The diameter of the filler wire is about 1 to 1.5 times the diameter of the conductor wire. It can be a single-strand overall wire or a multi-strand braided wire. There is no restriction on the type and specific shape of the wire. The time and the conductor wire can be well glued and fixed, so that the coil has a stable structure when it is working.

As shown in the above table, the conductor wire and the filler wire are not limited to a single wire. When multiple wires are wound side by side, the number of strands of the filler wire in the middle can be increased or decreased according to the actual use conditions. It can be the conductor wire and the filler wire 1: 1 for mutual filling intervals, or other ratios for mutual filling intervals.

Preferably, in order to reduce the skin effect, the wires in the scheme can use multi-strand side-by-side self-adhesive wires, Litz wires, hollow wires, etc. instead of single-strand wires with the same total cross-section, which can effectively improve the skin effect. Litz wires can be used as required You can choose enameled wire twisted Litz wire or acetone litz wire, etc.

Therefore, when implementing this patent, it is necessary to select and design the wire material according to the actual application scenario to reduce the skin effect and ensure the improvement of the quality factor of the coil. The self-adhesive wire is composed of an insulated wire and a self-adhesive layer, and the self-adhesive layer covers the surface of the insulated wire, so as to ensure that the filler wire can be connected to each other, and better ensure smooth installation and winding.

The specific winding conditions are shown in the table below

Usually the working frequency of wireless charging is 100 KHz, and the optional frequency is 100 KHz -205KHz. At 100 KHz, the skin depth of the copper wire is 0.21mm, so the first step in designing the coil is to select the wire. , The maximum diameter of the wire that can be selected under this working frequency is 0.42mm, so the coil within 0.42mm uses self-adhesive wire, and the coil larger than 0.42mm uses litz wire or hollow wire. Of course, if the frequency is adjusted, the corresponding selection also needs to be adjusted.

Multi-strand flat coil (self-adhesive wire): single wire wire diameter range: within 0.42mm, in the use of wireless charging, the application environment is often different, the thickness and the use of space are limited, for some spaces with ultra-thin thickness can be used Multi-strand flat coil scheme, insulated wires are arranged in the middle of the wires arranged side by side according to the actual application, and the distance between the wires is opened. The thickness of the insulated wires can be adjusted and adapted according to the wire diameter of the coil body.

For some special application scenarios, thicker wires will be used when designing coils, but at a working frequency of 100 KHz, due to the skin effect, the current distribution in the middle of the copper wires with a diameter greater than 0.42mm tends to be zero. , the AC resistance caused by the skin effect increases the loss of the overall coil at this time. In this case, we can use hollow wires to wind the coil, which can effectively improve the skin effect. At the same time, insulated wires are arranged in the middle of the wires arranged side by side according to the actual application interval, so as to further reduce the AC resistance inside the application coil.

As shown in Figure 6, for some high-power wireless charging applications, when a large current and voltage are required inside the coil, it is necessary to choose thick wires, but ordinary solid wires work at a frequency of 100 KHz. Skin effect, the AC resistance caused by the skin effect increases the loss of the overall coil at this time. In this case, we can use Litz wire (enameled wire twisted Litz wire / acetone Litz wire) to wind the coil, which can Effectively improve skin effect. At the same time, insulated wires are arranged in the middle of the wires arranged side by side according to the actual application interval, so as to further reduce the AC resistance inside the application coil.

Preferably, as shown in Figures 4 and 5, this solution uses multiple wires to space the filling wires. Although the AC impedance in the coil can be reduced, the overall size of the coil will increase a lot, and the number of turns of the coil can be greatly reduced by using a magnetic core. Therefore, reducing the DC resistance of the wire is also beneficial to improving the Q value of the coil, which can reduce the overall volume without reducing the corresponding charging efficiency.

The magnetic core can be a magnetic isolation sheet, such as a ferrite magnetic isolation sheet, and the magnetic isolation sheet can be a sheet structure that matches the size of the coil. In the electromagnetic induction wireless charging system, soft ferrite is widely used , its material and shape play a decisive role in the conversion efficiency and electromagnetic compatibility of wireless charging. The magnetic isolation sheet made of soft ferrite material can increase the induced magnetic field and shield the magnetic field of the coil in the wireless charging system, and prevent the formation of eddy current loss and heat generation in the metal on the back of the coil. At present, the recommended materials for ferrite sheets mainly include Mn-Zn ferrite and Ni-Zn ferrite. Generally, Mn-Zn ferrite is suitable for medium and high frequency designs, and Ni-Zn ferrite is suitable for high frequency designs. . The basic requirements for ferrite performance include: (1) higher magnetic permeability and smaller coercive force, which is beneficial to enhance coupling; (2) smaller than loss factor, which is beneficial to reduce signal attenuation; (3) ) The resistivity is high to reduce the loss of energy efficiency when the sheet heats up; (4) It should have a certain thickness to prevent a large amount of leakage flux from entering the free area.

The following is the standard coil test data

The inductance value of the coil shown in the above table increases significantly after the magnetic isolation sheet is added. The coil size and the number of turns are a major factor affecting the coil inductance. The same inductance can be greatly reduced by adding a magnetic isolation sheet to the coil. The number of turns of the coil, thereby reducing the DC resistance of the wire, is beneficial to improving the Q value of the coil.

However, the present invention does not limit the wireless charging coil to be wound into a square or a circle. In other embodiments, the wire can also be wound into other polygons according to the requirements of the system. As shown in Figure 7, it can be arranged in various shapes and structures of polygons.

Preferably, to improve the quality factor Q of the coil, alloy conductors (such as: silver-containing wires, etc. to reduce resistivity), plated metals (silver-plated, magnetic-plated and other process materials) can be used to reduce high-frequency resistance; similarly, The transmission efficiency of the coil can be improved by improving the angle of the coil winding material. For example, by using high magnetic permeability wire (such as: iron, nickel, etc.) for coil winding, the current distribution in the coil is effectively improved, and the The effective flow area of each turn of the coil;

Based on the above-mentioned coil structure, the wireless charging transmitting device of this solution, the inverter circuit, the control unit and the above-mentioned coil device; the input end of the inverter circuit is connected to a DC power supply; the output end of the inverter circuit is connected to the coil device ; the inverter circuit inverts the direct current output by the direct current power supply under the control of the control unit into alternating current and outputs it to the coil device; the coil module is used to convert the alternating current in the form of an alternating magnetic field to launch.

It is also possible to provide a wireless charging receiving device, including: a rectifier circuit, a control unit, a load, and any coil module described above; a coil module for receiving alternating current in an alternating magnetic field; the input end of the rectifier circuit is connected to The coil module; the rectification circuit, used to rectify the alternating current into direct current and output it to the load under the control of the control unit, so as to provide electric energy for the load.

Since the wireless charging receiving device includes the coil described above, the corresponding loss can be reduced and the power receiving efficiency can be improved.

A wireless charging system is also provided, including the above wireless charging transmitting device and the above wireless charging receiving device; the wireless charging transmitting device is used to perform wireless charging for the wireless charging receiving device.

Since the wireless charging system includes the receiving device and the transmitting device described above, it can reduce the corresponding loss, improve the quality factor, and improve the charging efficiency of the electric equipment.

It is also possible to provide a mobile terminal, the mobile terminal includes a working load circuit, a rectifier circuit, a charging control unit and any of the above coil devices; the coil device is used to receive alternating current in an alternating magnetic field; the input end of the rectifier circuit is connected to the coil A module; a rectification circuit, used to rectify the alternating current into direct current under the control of the charging control unit and output it to the working load circuit.

The above has schematically described the invention and its implementation. The description is not restrictive, and the invention can be realized in other specific forms without departing from the spirit or basic features of the invention. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto, and any reference signs in the claims shall not limit the related claims. Therefore, if a person of ordinary skill in the art is inspired by it, and without departing from the purpose of the invention, without creatively designing a structure and an embodiment similar to the technical solution, it shall fall within the scope of protection of this patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" preceding an element does not exclude the inclusion of "a plurality" of such elements. Multiple elements stated in a product claim may also be realized by one element through software or hardware. The words first, second, etc. are used to denote names without implying any particular order.

Claims

A coil device, characterized in that it includes a wire group formed by several wires and a filling wire group formed by several filling wires, the wire group and the filling wire group are arranged side by side, and are wound on the winding surface to form a coil structure. The wire is insulated and non-conductive material.
The coil device according to claim 1, wherein the wire group is provided with an incoming wire end and an outgoing wire end, and the incoming wire end and the outgoing wire end are electrically connected to external components.
The coil device according to claim 1, wherein the filling wire is a single integral wire or a multi-strand braided wire.
The coil device according to claim 1 or 3, characterized in that the wire is a self-adhesive wire, a Litz wire or a hollow wire.
The coil device according to claim 1, characterized in that the ratio of the diameter of the filling wire group to the diameter of the wire group is (1-1.5):1.
The coil device according to claim 1, wherein a magnetic core is provided on one side or both sides of the filling wire group.
A wireless charging transmitting device, characterized by comprising: an inverter circuit, a control unit, and the coil device according to any one of claims 1-6;

The input end of the inverter circuit is connected to a DC power supply;

The output end of the inverter circuit is connected to the coil device;

Under the control of the control unit, the inverter circuit inverts the DC power output by the DC power supply into AC power and outputs it to the coil device;

The coil module is used to emit the alternating current in the form of an alternating magnetic field.
A wireless charging receiving device, characterized by comprising: a rectifying circuit, a control unit, a load, and the coil device according to any one of claims 1-6;

The coil device is used to receive alternating current in an alternating magnetic field;

The input end of the rectification circuit is connected to the coil device;

The rectification circuit is used to rectify the alternating current into direct current and output it to the load under the control of the control unit, so as to provide electric energy for the load.
A wireless charging system, characterized in that it comprises the wireless charging transmitting device described in claim 7 and the wireless charging receiving device described in claim 8;

The wireless charging transmitting device is used for performing wireless charging for the wireless charging receiving device.
A mobile terminal, characterized in that the mobile terminal comprises a working load circuit, a rectifier circuit, a charging control unit, and the coil device according to any one of claims 1-6;

The coil device is used to receive alternating current in an alternating magnetic field;

The input end of the rectification circuit is connected to the coil device;

The rectification circuit is used to rectify the alternating current into direct current under the control of the charging control unit and output it to the working load circuit.