CN103714953A - Wireless charging coil - Google Patents

Abstract

The invention discloses a wireless charging coil. The whole coil device has two outlet ends. The coil device is composed of N sets of coils in series, each set of coils is composed of n coils connected in parallel; the N sets of coils are concentrically distributed without overlapping each other, and the n coils in each set of coils are also concentrically distributed without overlapping each other. With the help of this kind of coil, the current in different areas in the coil can be controlled, and the magnetic field in the near-field area above the device can be evenly distributed. Using the coil provided by the invention, a large-area wireless charger can be designed to charge multiple devices at the same time. This kind of coil has a higher quality factor, which can significantly reduce loss and improve the efficiency of the wireless charging system.

Description

wireless charging coil

technical field

The invention belongs to the field of near-field wireless energy transmission. In particular, it relates to a coil device for wireless charging.

Background technique

In recent decades, with the advancement of large-scale integrated circuits and chip technology, electronic products have developed towards multi-function, miniaturization, portability, and wearability. The above-mentioned trends pose challenges to the supply and supplement of electrical energy for electronic devices.

When the electric energy stored inside the electronic device is insufficient, the user needs to use a charging device to supplement the electric energy. Traditional charging devices are all wire charging devices, which need to be connected to the grid with wires. This kind of linear equipment is not only inconvenient to use, but also causes huge waste due to repeated manufacturing caused by mutual incompatibility. In this context, wireless charging has been brought up again and has become a current research hotspot.

Wireless charging is an application branch of wireless energy transmission technology. Wireless energy transmission technology can realize wireless energy transmission between devices. The basic principle of the wireless charging system is: the AC adapter converts the 220V/50Hz mains power into a DC stabilized voltage, and the amplifier converts the DC power into the AC power in the transmitting coil, thereby generating an alternating magnetic field in the near field from the transmitting coil. The changing magnetic field generates an induced current on the receiving coil, and the rectifier circuit rectifies the induced AC current into a DC current. The whole system mainly includes a voltage stabilizing module, an amplifying circuit, a transmitting coil, a control circuit, a receiving coil, a rectifying circuit, a communication module, a control module, etc. With the upgrading of the manufacturing process and the progress of the control chip, safe near-field wireless charging is technically possible.

At present, a device capable of wirelessly charging portable electronic products has appeared on the market. This wireless charging device uses a planar helical coil as the transmitting coil and a helical coil with a smaller area as the receiving coil. Please refer to Figure 1. The large coil in the figure is the transmitting coil of the existing wireless charging system. The transmitter converts the direct current into the alternating current on the coil device through the amplifier, and the alternating magnetic field generated by the alternating current on the transmitting coil device induces on the receiving coil The current is converted from AC to DC by a rectifier circuit to realize wireless charging.

The coil used in the above-mentioned existing wireless charging system is a spiral structure, and its magnetic field is mainly distributed in the center, so this makes the coupling coefficient between the transmitting coil and the receiving coil maintain a large value only when the axes of the two are aligned. , to achieve greater charging efficiency. Once the axes of the receiving coil and the transmitting coil deviate, the coupling coefficient drops sharply, which will lead to a sharp drop in charging efficiency, affect the stability of the system, and reduce the availability of the system.

In addition, most of the above-mentioned wireless charging systems adopt a one-to-one energy coupling mode, and the areas of the transmitting coil and the receiving coil are not much different. Such a structure does not have the ability to charge multiple devices at the same time, and cannot meet the needs of users when there are multiple devices that need to be charged. Therefore, it is desirable to provide a transmitting coil device with a relatively large available charging area, so as to manufacture a wireless charger that can simultaneously charge multiple devices.

In order to keep the coupling coefficient between the receiving coil and the transmitting coil stable in the charging area, such a transmitting coil arrangement with a large charging area must provide a uniform magnetic field distribution. Another transmitting coil device has emerged in academia. Please refer to FIG. 2 , in which the structure of the coil device is wound by a helical structure that is dense on the outside and sparse on the inside. The transmitting coil arrangement shown in Fig. 2 can generate a uniform magnetic field distribution in the near-field region above the coil. However, the special structure of the coil, which is dense on the outside and sparse on the inside, leads to low area utilization and reduces the quality factor of the inductor.

Contents of the invention

The purpose of the present invention is to provide a wireless energy transmission coil that can be used for near-field wireless charging. The coil can realize the uniform distribution of the magnetic field in the charging area, and can realize wireless charging for multiple devices at the same time, such as mobile phones, tablet computers, MP3, etc. At the same time, the uniform magnetic field distribution can improve the wireless charging efficiency and the stability of the wireless charging system.

The technical scheme provided by the invention is as follows:

A wireless charging coil, the entire coil device has two outlets, the coil device is composed of N groups of coils connected in series, each group of coils is composed of n coils connected in parallel, where N is a positive integer greater than 2, n≥1; The N groups of coils are concentrically distributed without overlapping each other, and the n coils in each group of coils are also concentrically distributed.

The above structure realizes that the current amplitude on the plane changes with the coil radius and position. By properly selecting the value of n in each group of coils, the current intensity in each area can be controlled, and finally a uniform magnetic field distribution above the plate can be realized.

In a preferred embodiment, the wireless energy transmission coil includes: three sets of coils connected in series, the three sets of coils are concentrically distributed in a square area, the outermost first set of coils is composed of a single helical coil, The second group of coils is composed of two parallel-wound helical coils, the third group of coils located in the center is composed of three parallel-wound helical coils, and the entire wireless energy transmission coil has two outlet terminals.

Compared with traditional wireless energy transmission coils, the wireless energy transmission coil provided by the present invention has beneficial effects in that: using the wireless energy transmission coil provided by the present invention can realize uniform magnetic field distribution, thereby enabling energy transmission to multiple devices at the same time. The wireless energy transmission coil provided by the present invention has the beneficial effect that the wireless energy transmission coil provided by the present invention has a higher quality factor than the wireless energy transmission coil that has appeared in academia and can realize uniform magnetic field distribution, thereby significantly reducing the Loss, improve the efficiency of the wireless charging system.

Description of drawings

FIG. 1 is a schematic diagram of a conventional wireless charging transmitting coil device and receiving coil system.

FIG. 2 is a schematic diagram of an existing large-area coil that can realize uniform distribution of a magnetic field.

Fig. 3 is a three-dimensional schematic diagram of a wireless charging coil provided by the present invention.

Fig. 4 is a plan view of a wireless charging coil provided by the present invention.

Fig. 5 is a simplified equivalent circuit diagram of a wireless charging coil provided by the present invention.

FIG. 6 is a preferred embodiment of a wireless charging coil provided by the present invention.

FIG. 7 shows the simulation and test results of a preferred embodiment of a wireless charging coil provided by the present invention and the comparison with existing wireless charging coils.

FIG. 8 is a comparison between simulation parameters of a preferred embodiment of a wireless charging coil provided by the present invention and existing wireless charging coils.

Wherein, the reference signs are explained as follows:

1,51 wireless charging receiving coil

2 An existing wireless charging coil

3Another existing wireless charging coil

4 A wireless charging coil provided by the present invention

5 wireless charging receiver

6 wireless charging transmitter

11,21,31,41,511,611 outlet

42 The first winding area

43 Second winding area

44 Third, fourth, ..., N-1 winding area

45 Nth winding area

52 wireless charging receiver control circuit PCB

61 wireless charging coil

62 wireless charging transmitter control circuit PCB

63 wireless charging transmitter power cord and plug

Detailed ways

The implementation example of a wireless charging coil provided by the present invention will be described in detail below in conjunction with the accompanying drawings:

A wireless charging coil designed by the present invention is shown in Figure 3 and Figure 4, including N groups of concentrically distributed coils connected in series, and each group of coils is composed of n _i (the subscript i represents the number of turns, i=1,2 , ..., N) concentrically distributed coils connected in parallel, the whole coil has two outlets 41, the first outlet is the input port of the first group of coils, the second outlet is the last group of coils located in the center output terminal. For the above N groups of coils, the number N of coil groups is a positive integer greater than 2, and the number of coils n _i contained in each group of coils satisfies the following conditions:

n ₁ >n ₂ >n ₃ >…>n _N

When the number of coil groups N=3, the equivalent circuit structure of the three coils is shown in Figure 5, in which the series resistance and capacitance are not shown.

Please refer to FIG. 6 . FIG. 6 is a schematic structural diagram of a wireless charging coil provided by the present invention placed in a preferred embodiment. As shown in Figure 6, the wireless charging coil is placed in a transmitter, and the outlet terminal 611 is connected to the PCB-shaped transmitter control circuit PCB62. The power cord and plug 63 realize the connection between the wireless charger and the power grid. Voltage and amplification, the transmitting control PCB inputs the alternating current into the wireless charging coil provided by the present invention, the transmitting coil transmits the changing electromagnetic energy to the receiving coil 51 through near-field coupling, and the receiving coil 51 inputs the changing electrical signal To the receiver control circuit PCB52, a stable DC output is realized through rectification and voltage stabilization. In this embodiment, the transmitting coil is divided into three winding areas (N=3), the first winding area includes a helical coil inductor with 12 turns, and the second winding area includes two coils with 6, For the spiral coil inductors connected in parallel, the third winding area includes three spiral coil inductors with 4 turns connected in parallel, and the connection mode between the three inductor groups in the three areas is series connection. The size of the wireless energy transmission coil provided in this embodiment is 20cm×20cm.

Figure 7 and Figure 8 are the comparison between the simulation results of an embodiment of the wireless charging coil provided by the present invention and the existing wireless charging coil (the structure shown in Figure 1), a 5cm×5cm receiving coil is placed in The plane at a distance of 5mm above the transmitting coil is used to detect the uniformity of the magnetic field generated by the wireless energy transmission coil. Figure 7 shows the variation of the coupling coefficient between the receiving coil and the wireless charging coil with the offset center distance of the receiving coil. When the receiving coil is located at the center of the wireless charging coil, the offset is 0 mm. When the receiving coil is located at the edge of the transmitting coil, The offset is 7.5mm. It can be seen from Figure 7 that when the traditional wireless charging coil is used, the coupling coefficient is larger when the receiving coil is located in the center, but as the receiving coil deviates from the center position, the coupling coefficient decreases rapidly, and when the receiving coil approaches the edge, the coupling coefficient decreases 12.5% of the coupling factor to the central location. When using the wireless charging coil provided by the present invention, the coupling coefficient changes slowly as the receiving coil deviates from the center position. When the receiving coil is located at the edge position, the coupling coefficient only drops to 36.4% of the coupling coefficient at the center position, and the stability of the coupling coefficient Significantly better than traditional coils.

Fig. 8 is the accurate modeling and parameter extraction results of the above-mentioned embodiment using the three-dimensional electromagnetic simulation software Ansys Maxwell. It can be seen from FIG. 8 that although the Q value of the wireless charging coil provided by the present invention is smaller than that of the wireless charging coil shown in FIG. 1 , the present invention achieves uniformity of the magnetic field. Compared with the structure shown in Fig. 2 which can also achieve uniform magnetic field distribution, the Q value of the coil provided by the present invention is 32.6% higher than its Q value, and the wireless energy transmission coil provided by the present invention has a higher quality factor.

Claims (3)

1. The wireless charging coil is characterized in that the entire coil device has two outlet terminals, and the coil device is composed of N groups of coils connected in series, and each group of coils is composed of n coils connected in parallel, wherein N is a positive value greater than 2. Integer, n≥1; the N groups of coils are concentrically distributed without overlapping each other, and the n coils in each group of coils are also concentrically distributed. the 2. The wireless charging coil according to claim 1, wherein the coil device is composed of three sets of coils connected in series, the three sets of coils are concentrically distributed in a square area, and the outermost first set of coils is composed of a Composed of individual helical coils, the second set of coils consists of two parallel-wound helical coils, and the third set in the center consists of three parallel-wound helical coils. the 3. The wireless charging coil according to claim 2, wherein the number of turns of the helical coil contained in the outermost first set of coils is 12, and the turns of the two helical coils included in the second set of coils are both 6. The third group of coils in the center contains three helical coils with 4 turns. the

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