TWI642254B - Mobile device - Google Patents

Abstract

A mobile device comprising: a housing including a conductive area; and a wireless power receiver, the wireless power receiver including a receiving coil for receiving a wireless power source through the conductive region; wherein the conductive The thickness of the region is less than δ /10, where δ is the skin depth of the conductive region at the dominant frequency of the electromagnetic signal providing the wireless power source.

Description

Mobile devices

The present invention relates to the field of wireless power transmission technology, and more particularly to mobile devices.

Wireless Power Transfer Systems (WPTS) has become increasingly popular due to the power transfer in a simple manner without the use of cables or connectors. The WPTS currently used in the industry can be divided into two main types: Magnetic Induction (MI) systems and Magnetic Resonance (MR) systems. Both types of systems include a wireless power transmitter and a wireless power receiver. These two types of systems can be used to power or charge mobile devices (eg, smart phones, tablets) in other applications.

Inductive WPTS systems typically operate at a specified frequency range of a few hundred hertz, which uses frequency variations as a power flow control mechanism. Magnetic resonant WPTS systems typically operate at a single resonant frequency, which uses input voltage regulation to regulate the output power. In a typical application, the magnetic resonance WPTS system operates at a frequency of 6.78 MHz.

Many industry committees have been working to advance international standards for consumer products based on wireless power transmission.

The present invention discloses a mobile device that allows an electric/magnetic field generated by a wireless power transmitter to reach a receiving coil of a wireless power receiver within the mobile device.

A mobile device provided by the present invention may include: a housing including a conductive area; and a wireless power receiver, the wireless power receiver including a receiving coil for receiving a wireless power source through the conductive region; Wherein the thickness of the conductive region is less than δ /10, wherein δ is a skin depth of the conductive region at a main frequency of providing an electromagnetic signal of the wireless power source.

It can be seen from the above that the mobile device provided by the present invention includes a conductive area on the outer casing, and the receiving coil of the wireless power receiver can receive the wireless power through the conductive area. Based on this, embodiments of the present invention may allow an electric/magnetic field generated by a wireless power transmitter to reach a receiving coil of a wireless power receiver within the mobile device.

1a, 1b, 1c‧‧‧ mobile devices

10‧‧‧ Shell

2‧‧‧ Conductive layer

9‧‧‧User interface

3‧‧‧Wireless power receiver

4, 14‧‧‧ receiving coil

5‧‧‧Electrical area

6‧‧‧ Non-conductive support

15, 16‧‧ ‧ isolated area

11‧‧‧ Ribs

21‧‧‧Wireless Power Transmitter

22‧‧‧Stable voltage source

27‧‧‧Drive circuit

23‧‧‧Inverter

26, 33‧‧‧ Matching network

30‧‧‧Drive transmitting coil

29‧‧‧Signal Generator

25‧‧‧ Controller

34‧‧‧Rectifier

35‧‧‧DC/DC Converter

Vout‧‧‧ output voltage

Figure 1A shows the B-field transparency of the aluminum and stainless steel layers of different thicknesses at a wireless power transmission frequency of 175 kHz.

Figure 1B shows the B-field transparency of the aluminum and stainless steel layers of different thicknesses at a wireless power transmission frequency of 6.78 MHz.

2A and 2B show a side view and a rear view, respectively, of the mobile device 1a.

3A and 3B show side and rear views, respectively, of the mobile device 1b, in accordance with some embodiments of the present invention.

4A and 4B show side and rear views, respectively, of the mobile device 1c, in accordance with some embodiments of the present invention.

Figure 5 shows a plurality of ribs for mechanically supporting a thinner conductive layer.

FIG. 6 shows a wireless power transmission system including a wireless power transmitter 21 and a wireless power receiver 3.

Certain terminology is used throughout the description and the appended claims. Those skilled in the art will appreciate that a hardware manufacturer may refer to the same component by a different name. This document does not use the difference in name as the way to distinguish the components, but the difference in function of the components as the criterion for distinguishing. In the following description and claims, the terms "comprising" and "including" are used in an open term and should be interpreted as "including but not limited to". In addition, the term "coupled" is used herein to include both direct and indirect electrical connections. Therefore, if one device is coupled to another device, it can be directly electrically connected to the other device, or electrically connected to the other device indirectly through other devices or connection means.

Metal back covers are a common feature of mobile electronic devices such as smart phones and tablets. Unfortunately, the metal back cover also prevents the use of electromagnetic waves to transmit wireless power to the mobile device since the metal back cover is intended to circumvent electromagnetic fields within the mobile device.

The inventors of the present invention have recognized and appreciated that if the thickness of the metal back cover is substantially less than the skin depth at the frequency used for wireless power transmission, for the electromagnetic field generated by the wireless power transmitter, the metal The cover will be substantially transparent. The skin depth δ of a material can be given by the equation below, where f is the frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material.

A larger skin depth is required to enhance the transmission performance of the electromagnetic field transmitted through the metal back cover. To obtain the condition of δ >>T, that is, the skin depth δ is much larger than the thickness T of the metal back cover, the conductivity and/or thickness T of the metal back cover needs to be selected to be sufficiently small.

Table 1 below lists the electrical conductivity of a number of materials used to form the metal back cover and these The skin depth of the material at two frequencies commonly used for wireless power transmission, the two commonly used frequencies are 175 kHz and 6.78 MHz.

As indicated above, stainless steel will have a higher skin depth than aluminum or copper due to its lower electrical conductivity. Nickel is another suitable material in addition to stainless steel. However, if the metal back cover is made thin enough, aluminum or copper can also be used.

Multiple simulations were performed to evaluate the attenuation of the electromagnetic field as it passes through the metal layers of different materials and metal layers of different thicknesses. Figure 1A shows the B-field transparency of the aluminum and stainless steel layers of different thicknesses at a wireless power transmission frequency of 175 kHz. The term "transparency" refers to the ratio of the B-field to any one of the layers of metallic material. As shown in Figure 1A, due to the greater skin depth of stainless steel, the transparency of stainless steel is superior to the transparency of aluminum at the same thickness. The skin depth of aluminum and stainless steel is also shown in Figure 1A. When the thickness of the metal layer is less than δ / 40, most of the B-field can pass through the metal layer. A low degree of transparency is obtained at δ /20 and δ /10, which can be used in some applications. At 175 kHz, when an aluminum material is used, 50% of the B-field is passed through the metal layer, and the thickness of the metal layer needs to be less than or equal to 10 micrometers (μm). When a stainless steel material is used, 50% of the B-field is passed through the metal layer. The thickness of the metal layer needs to be less than or equal to 100 micrometers (μm). Figure 1B shows the B-field transparency of the aluminum and stainless steel layers of different thicknesses at a wireless power transmission frequency of 6.78 MHz. Figure 1B can obtain qualitatively similar results to Figure 1A. Again, when the thickness of the metal layer is less than δ / 40, most of the B-field can pass through the metal layer. In Figure 1B, due to the higher frequency, a thinner metal layer thickness is required to achieve the same transparency that can be seen at 175 kHz. At 6.78MHz, when using aluminum material, to make 50% of the B-field through the metal layer, the thickness of the metal layer needs to be less than or equal to 1-2 micrometers (μm). When using stainless steel material, make 50% of the B-field. The thickness of the metal layer needs to be less than or equal to 10-20 micrometers (μm) through the metal layer. In some embodiments, the thickness of the metal layer will be chosen to be below δ /10, for example, δ /20 or lower, δ /40 or lower. In some embodiments, the thickness of the metal layer can be greater than 0.01 microns, for example, greater than 0.1 microns or greater than 1 micron.

2A and 2B show a side view and a rear view, respectively, of the mobile device 1a, which includes a conductive layer 2 on the back of the casing 10. Conductive layer 2 spans most of the area of the backside region of the mobile device. Conductive layer 2 can comprise a metal and be thick enough and have sufficient conductivity to prevent transmission of wireless power therethrough. As shown in FIGS. 2A and 2B, the mobile device may include a wireless power receiver 3 including a receiving coil 4. The wireless power receiver 3 is for receiving an AC signal from the receiving coil 4 and processing the AC signal to generate a DC voltage, which can be used to charge the battery of the mobile device 1a and/or for the mobile device 1a, by way of example Powered by itself. In order to enable electrical and/or magnetic field energy to be transmitted to the receiving coil 4, the back side of the mobile device 1a may include a conductive region 5 that adds transparency to the electrical and/or magnetic fields. The conductive area 5 can serve as a transparent "window" for the receiving coil 4 of the wireless power receiver 3 to pass through the back of the mobile device 1a, allowing the electrical and/or magnetic fields generated by the wireless power transmitter. As previously mentioned, the electrically conductive region 5 can be a metal. Metals suitable as conductive regions 5 may include stainless steel, nickel, aluminum, and copper. However, the mobile device according to the embodiment of the present invention is not limited to the use of the above material as the conductive region 5. In some embodiments, the thickness of the conductive region 5 (in the level direction of FIG. 2A) may be lower than δ /10, for example, δ /20 or lower, δ /40 or lower, wherein δ is the conductive region 5 Skin depth. In some embodiments, unlike the conductive layer 2, the conductive region 5 will cover at least 50% of the area of the receiving coil 4 (as viewed from the rear of the mobile device) to facilitate wireless power transfer to the receiving coil 4. In some embodiments, the electrically conductive region 5 can cover at least 75%, at least 90% of the receiving coil 4 (as viewed from the rear of the mobile device), to 100% of the area. The conductive region 5 can be aligned with the receiving coil to promote overlap of the conductive region 5 and the receiving coil 4 over the region. As shown in FIG. 2B, in some embodiments, the conductive region 5 can extend beyond the area of the receiving coil.

The mobile device described herein can be any suitable type of mobile device, such as a smart phone, tablet, or wearable device (eg, a smart watch) or the like. The front end of such a mobile device includes a user interface 9, such as a touch screen. The housing of the mobile device can be formed from any type of material and can provide structural integrity to the mobile device. Behind the mobile device, the surface of the outer casing can include a layer of metal that allows a user to perceive and see metal behind the mobile device. In some embodiments, in the described embodiments of the present invention, wireless power can be transmitted through the back of the mobile device while maintaining the feel and vision of the metal back cover.

3A and 3B show side and rear views, respectively, of the mobile device 1b, in accordance with some embodiments of the present invention. In the mobile device 1b, the conductive material forming the receiving coil 14 of the wireless power receiver 3 is the same as the conductive material of the conductive layer 2 (for example, at the same layer). An isolation region (insulation region) 15 on the rear surface of the mobile device separates the receiving coil 14 from the conductive layer 2. An isolation region 16 on the rear surface of the mobile device separates the receiving coil 14 from the conductive region 5. Similar to the mobile device 1a, the conductive area 5 can act as a transparent window that allows the electrical and/or magnetic fields generated by the wireless power transmitter to reach the receiving coil 14 through the back of the mobile device 1b.

4A and 4B show side and rear views, respectively, of the mobile device 1c, in accordance with some embodiments of the present invention. In the mobile device 1c, the area in which the conductive area 5 spans is larger than the area it spans in the mobile devices 1a and 1b. In the mobile device 1c, the conductive area 5 will span most of the area of the back side of the mobile device, and there is no conductive layer 2 on the rear surface of the mobile device 1c. Thus, the electrical and/or magnetic fields generated by the wireless power transmitter can pass through the conductive region 5 through the back of the mobile device 1c. In some embodiments, the thickness of the conductive region 5 may be lower than δ /10, for example, δ /20 or lower, δ /40 or lower, wherein δ is the skin depth of the conductive region 5.

In order to provide mechanical stability, the electrically conductive region 5 may alternatively be disposed on the non-conductive support 6. The support 6 can be formed from any suitable material, such as plastic. However, support 6 is optional and not required. In some embodiments, the electrically conductive region 5 can be set small enough so that it does not affect the mechanical robustness of the outer casing, but it is still large enough to facilitate the transmission of the wireless power source. For example, in some embodiments, the area of the conductive region 5 can be less than 150% or 120% of the area enclosed by the receiving coil 4. In some embodiments, zero, one or more conductive supports or ribs span the conductive region 5. The ribs 11 can be an elongated version of a conductive or non-conductive material. In some embodiments, the ribs 11 and the electrically conductive material 2 may be formed from the same material and have the same thickness, such as the ribs 11 covered on the electrically conductive regions 5 as seen from the rear view of the mobile device. If the ribs 11 are electrically conductive, they will avoid the formation of a pattern of closed loops in the window 5 to avoid eddy currents. By way of example, the rib 11 shown in Fig. 5 has a star shape that does not form a closed circuit in the window 5. However, in some embodiments, the ribs 11 may be formed from a non-conductive material, such as plastic. The ribs can be used in any of the embodiments described herein, such as the embodiment shown in Figures 2 and 3. Further, the ribs may be provided in any figure, not limited to a star shape.

FIG. 6 shows a wireless power transmission system including a wireless power transmitter 21 and a wireless power receiver 3. The wireless power transmitter 21 includes a drive circuit 27 that includes an inverter 23 that drives the transmit coil 30 through a matching network 26. The wireless power transmitter 21 can include a stable voltage source 22 (e.g., a voltage regulator) for providing a stable DC voltage to the inverter 23. The stabilized voltage source 22 produces a stable DC output voltage based on the control stimulus output by the controller 25. In some embodiments, the driver circuit 27 can be a Class D or Class E amplifier for converting the DC voltage at the input of the inverter 23 to an AC output voltage to drive the transmit coil 30. The generation of the AC output voltage allows the wireless power supply to be electromagnetically induced transmission. The controller 25 can control the signal generator 29 to drive the inverter 23 using the signal of the selected wireless power transmission frequency. By way of example, according to the Qi specification corresponding to the low Qi receiver, the inverter 23 switches at a frequency between 100-205 kHz to transmit power to the wireless power receiver desiring to receive the wireless power source, and, for the medium power source Qi The receiver, inverter 23, can switch at a frequency between 80-300 kHz to transmit power. Inverter 23 can switch at a higher frequency, such as a frequency greater than 1 MHz in the ISM band (eg, 6.765 MHz - 6.795 MHz) to transmit power to a receiver designed to receive wireless power using magnetic resonance techniques . However, the frequencies recited herein are merely examples, as the wireless power supply can be transmitted at a variety of suitable frequencies in accordance with any suitable specifications. Controller 25 can be an analog circuit or a digital circuit. The controller 25 can be programmable and can command the signal generator 29 to generate a signal at a desired transmission frequency based on the stored program instructions so that the inverter 23 can switch at the desired transmission frequency. Matching network 26 may facilitate the transmission of wireless power by exhibiting an appropriate impedance to inverter 23. The matching network may include one or more capacitive or inductive components or any suitable combination thereof. Since the transmit coil 30 can have an inductive impedance, in some embodiments, the matching network 26 can include one or more capacitive elements that, when combined with the inductive impedance of the transmit coil 30, are reversed The output of the phaser 23 exhibits an impedance suitable to drive the corresponding transmit coil. In some embodiments, the resonant frequency of the matching network 26 can be set equal to or approximately equal to the switching frequency of the inverter 23. The transmit coil 30 can be implemented by any suitable type of conductor. The conductor may be a wire, such as a single wire or strand and wire, or may be a patterned conductor, such as a printed circuit board or a patterned conductor of an integrated circuit.

The alternating current in the transmitting coil 30 generates an oscillating magnetic field in accordance with the amperage law. The oscillating magnetic field induces an alternating voltage to the receiving coils 4 and 14 of the wireless power receiver 3 according to Faraday's law. The alternating voltage induced by the receiving coils 4 and 14 is supplied to the rectifier 34 through the matching network 33 to produce an unregulated DC voltage. The rectifier 34 can be a synchronous rectifier or implemented by a diode. The unregulated DC voltage is regulated by a DC/DC converter 35, the output of which is filtered as an output voltage Vout is provided to the load. In some alternative embodiments, the DC/DC converter 35 can be replaced by a linear regulator or a battery charger or can be removed from the circuit.

In the present invention, the description "frequency of wireless power transmission" and the like describe the use of electromagnetic signals to transmit the primary frequency of the wireless power source. At the main frequency, the amount of power transmitted can be maximized. Those skilled in the art will recognize that when power is transmitted wirelessly at a particular frequency, one or more harmonics may occur at a lower power level. The harmonics may be located at a high frequency several times higher than the fundamental frequency. Since the skin depth depends on the frequency, the skin depth at the harmonics is different from the skin depth at the fundamental frequency. Since the fundamental frequency is the primary frequency at which the wireless power source is transmitted, the skin depth at the fundamental frequency is the most important criterion when selecting the thickness and/or type of material to allow wireless power transmission, compared to the skin depth at the harmonics. .

The use of ordinal numbers such as "first," "second," etc., used to modify elements in the scope of the claims is not intended to suggest any priority, prioritization, or It is only used as an identifier to distinguish different components with the same name (with different ordinal numbers).

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

Claims (20)

A mobile device comprising: a housing including a conductive area; and a wireless power receiver, the wireless power receiver including a receiving coil for receiving a wireless power source through the conductive region; wherein the conductive The thickness of the region is less than δ/10, wherein δ is the skin depth of the conductive region at a primary frequency of the electromagnetic signal providing the wireless power source; wherein the conductive region is on the outer casing of the mobile device a first conductive region, the housing further comprising: a second conductive region on the outer casing of the mobile device; wherein the second conductive region spans the first conductive region and the first conductive region a portion of the area outside the portion, and the first conductive region partially overlaps the receiving coil, the first conductive region forming a window in the second conductive region to allow wireless power transmission through the first conductive region To the receiving coil. The mobile device of claim 1, wherein the first conductive region has a thickness less than δ /20. The mobile device of claim 2, wherein the first conductive region has a thickness less than δ /40. The mobile device of claim 1, wherein the first conductive region is aligned with the receiving coil. The mobile device of claim 1, wherein the first conductive region comprises a metal. The mobile device of claim 5, wherein the metal comprises at least one of copper, aluminum, stainless steel, and nickel. The mobile device of claim 6, wherein when the metal is the stainless steel, the thickness is less than or equal to 100 micrometers. The mobile device of claim 1, wherein the outer casing is located at a rear of the mobile device. The mobile device of claim 8, wherein the outer casing is located on an outer surface of the mobile device. The mobile device of claim 1, wherein the receiving coil is located inside the mobile device. The mobile device of claim 1, wherein the receiving coil is located on a back side of the mobile device. The mobile device of claim 11, wherein the receiving coil and the second conductive region are made of the same metal. The mobile device of claim 12, further comprising: One or more insulating regions for isolating the receiving coil from the second conductive region. The mobile device of claim 1, wherein the second conductive area spans a majority of the area of the housing of the mobile device. The mobile device of claim 1, further comprising: a non-conductive support for supporting the first conductive region. The mobile device of claim 1, further comprising: a plurality of ribs spanning the first conductive region and for supporting the first conductive region. The mobile device of claim 16, wherein the plurality of ribs are electrically conductive. The mobile device of claim 17, wherein the plurality of ribs are formed of the same material as the metal back cover forming the mobile device. The mobile device of claim 1, wherein the area of the conductive area is less than or equal to 150% of the area occupied by the receiving coil. The mobile device of claim 1, wherein the first conductive region has a thickness greater than 0.01 micrometers.