GB2584814A

GB2584814A - Multiband wireless charging apparatus

Info

Publication number: GB2584814A
Application number: GB1903921.3A
Authority: GB
Inventors: Mhand Mohamed Cheikh; Ren Daqian
Original assignee: Planck Ltd
Current assignee: Planck Ltd
Priority date: 2019-03-21
Filing date: 2019-03-21
Publication date: 2020-12-23
Also published as: GB201903921D0

Abstract

Wireless charging apparatus comprising a wireless power transmitter (figure 2) and a wireless power receiver (figure 3). The receiver comprises an active receiving antenna (Lr figure 3) electrically coupled to a rectifier (14, figure 3) and rechargeable battery, and a passive receiving antenna (Lr2, figure 3). Up to four inductively coupled passive receiving antennae may be provided, wirelessly coupled to the active antenna. The power transmitter comprises a transmitter circuit comprising two high frequency power sources, at least one high frequency amplifier 6, optionally a MOSFET, and at least one high frequency multiplier 8 electrically connected to the sources. An active transmitting antenna is electrically connected to the transmitter circuit, and first and second passive transmitting antennae are inductively coupled to the active antenna, thereby generating first and second transmitter resonant frequencies. Both transmitter and receiver antennae may be substantially 2D and may be formed concentrically. The apparatus may operate at ISM frequencies and may be adapted to transmit and receive at multiple frequencies. Electronic devices, optionally wearable devices, comprising the apparatus are also claimed.

Description

Multiband Wireless Charging Apparatus The present invention relates to multiband wireless charging apparatus for use with electronic devices, especially mobile electronic devices. More particularly, the present invention relates to multiband wireless charging transmitter devices and multiband wireless charging receiver devices. The invention also relates to use of such apparatus for wirelessly charging electronic devices, more particularly wearable electronic devices.

Wireless power transmission uses a transmitter device to generate and transmit an electromagnetic signal through space to a receiver that extracts electrical power from the signal. Wireless power transmission is useful where physical connections are inconvenient or difficult.

Wireless power transmission may be radiative or non-radiative. Radiative wireless power transmission may be used over relatively long distances. In near field or non-radiative wireless power transmission, power is transferred over short distances by magnetic fields using inductive coupling or by electric fields using capacitive coupling. Inductive coupling is currently the more widely used wireless power transmission method and is used in inductive heating including in electric hobs and industrial heaters and to wirelessly charge mobile electronic devices including mobile telephones, implantable medical devices and electric vehicles.

Wireless power transfer using inductive coupling between wire coils has a relatively short range, with the power transmitted decreasing exponentially with distance and depends on the size and shape of the antennas. More sophisticated methods of inductive coupling using resonance increase power transfer and useable range between the transmitter and receiver antennas.

Wireless charging of mobile electronic devices may use a number of standards including the Qi standard, an open interface standard developed by the Wireless Power Consortium. The Qi system uses a charging pad transmitter and a compatible device with a receiver coil, which is placed on top of the pad, charging via inductive coupling. Power may pass between the transmitter and receiver coil placed closely together, usually only separated by the outer casing of the two devices (< 10 mm). The coils must be aligned to make the connection. Resonant inductive coupling charges at greater distance (up to 45mm). The Qi standard uses a low frequency of 100kHz.

There have been attempts to provide wireless charging systems.

US-A-2011/0101788 discloses a system for wireless transfer of energy, in particular to a wireless energy transfer units and cells employed thereby, that allow energy, such as RF energy, to be transferred wirelessly using nonradiative resonant coupling for power transfer and/or data communications purposes.

WO-A-2013/074533 relates generally to wireless power. More specifically, the disclosure is directed to power transmit antennas configured to operate in multiple frequency bands.

Electromagnetic compatibility (EMC) is a branch of electrical engineering concerned with the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage in operational equipment. EMC regulations define a maximum emission for a series of allowed frequency bands which reduce the chance of unintentional EMI or physical damage to electronic devices. The allowed frequency bands are often referred to as the industrial, scientific, and medical radio bands (ISM bands) and are internationally reserved for the use of radio frequency (RF) energy intended for scientific, medical and industrial requirements rather than for communications. ISM bands are generally open frequency bands, which vary according to different regions and permits.

Wireless power transmission may occur using one of the ISM bands (e.g. A4WP using 6.78N1Hz) however there is a limit to the amount of power that may be transmitted using a single high frequency because of the wireless regulations and electrical saturation, heating, or safety concerns. There is nevertheless a need to provide more power to electronic devices wirelessly, especially to provide wireless power transmitting or receiving apparatus for wearable electronic devices for consumer, military or medical purposes. There is additionally a need that such wireless power apparatus should be light, efficient and compact.

It is an aim of the present invention to address these needs.

The present invention accordingly provides, in a first aspect, wireless charging apparatus comprising a wireless power receiver, the receiver comprising, an active receiving antenna, a first passive receiving antenna, a rectifier in electrical connection with the active receiving antenna, and a rechargeable battery in electrical connection with the rectifier.

Preferably, the apparatus further comprises at least a second passive receiving antenna. More preferably the apparatus further comprises at least a third passive receiving antenna, and optionally, a fourth passive receiving antenna and further passive receiving antennas.

Preferably, the first passive receiving antenna is (and, if present the second, third, fourth and any further passive receiving antennas are each) inductively coupled to the active receiving antenna thereby, in use, receiving at least a first receiver resonant frequency.

Preferably, the or each passive receiving antenna is in parallel electrical connection with a capacitor.

The first, or each, passive receiving antenna is preferably not in direct electrical connection (i.e. not in wired electrical connection) with the active receiving antenna.

Power received by the passive receiving antenna(s) may be transferred to the active receiving antenna, and/or to the circuit or to the rechargeable battery, by coupling, usually inductive and/or magnetic coupling. This is advantageous because it enables a smaller and less complex wireless power receiver whilst still achieving the advantage of receiving power using two or more bands.

Preferably, the first passive receiving antenna, and the active receiving antenna each comprise substantially 2D antennas. For compactness, the substantially 2D first passive receiving antenna and the 2D active receiving antenna may be arranged so that they are substantially concentric. If present, the second passive receiving antenna, the third passive receiving antenna, (and the fourth passive receiving antenna and/or any other passive receiving antennas, if present) may also comprise substantially 2D antennas, and/or may be arranged so that they are substantially concentric with the 2D first passive receiving antenna and the 2D active receiving antenna.

Usually, the or each passive receiving antenna is a high frequency antenna adapted to receive a frequency selected from an ISM frequency.

Four or more different frequencies may be used during the wireless charging in ISM band for example 6.765 to 6.795 MHz, 13.553 to 13.567 MHz, 26.957 to 27.283 MHz and 40.66 to 40.70 MHz. The 6.78MHz, 13.56MHz and 27.12MHz are in the EIF bands and can be used for wireless power transfer, the magnetic behaviour and appropriate antenna design at 40.78MHz are close to those of the ELF bands and can also be used for multi-band charging. Use of multiple bands allows higher energy transfer within EMC regulations.

In a second aspect the present invention provides wireless charging apparatus comprising a wireless power transmitter, the transmitter comprising, a transmitter circuit comprising a first, high frequency source and a second, high frequency source, at least a first high frequency power amplifier, and at least one high frequency multiplier electrically connected to the first and second high frequency sources, an active transmitter antenna electrically connected to the transmitter circuit, a first passive transmitting antenna and a second passive transmitting antenna, wherein the first passive transmitting antenna and the second passive transmitting antenna are each inductively coupled to the active transmitter antenna thereby, in use, generating a first transmitter resonant frequency and a second transmitter resonant frequency.

Preferably, the first passive transmitting antenna and the second passive transmitting antenna are in parallel electrical connection with a first capacitor and a second capacitor respectively.

Preferably, the apparatus further comprises at least a third passive transmitting antenna in parallel electrical connection with a third capacitor, and optionally a fourth passive transmitting antenna in parallel electrical connection with a fourth capacitor.

Preferably, the first passive transmitting antenna and the active transmitter antenna each comprise substantially 2D antennas. Preferably, the substantially 2D first passive transmitting antenna and the 2D active transmitting antenna are substantially concentric.

If present, the second passive transmitting antenna, the third passive transmitting antenna, (and the fourth passive transmitting antenna and/or any other passive transmitting antennas, if present) may also comprise substantially 2D antennas and/or may be arranged so that they are substantially concentric with the 2D first passive transmitting antenna and the 2D active transmitter antenna.

The apparatus may further comprise a second-high frequency power amplifier, optionally a third high frequency power amplifier, and further optionally a fourth high frequency power amplifier.

Preferably, the or each high frequency power amplifier comprises at least one

MOSFET

The multiplier may be digital or analogue.

Preferably, the or each passive transmitting antenna is a high frequency antenna adapted to transmit a frequency selected from an ISM frequency.

The active transmitting antennas is preferably adapted to transmit a plurality of ISM frequencies. The active antenna is preferably able to transmit all high frequency ISM frequencies.

In order to provide a wide HF band antenna, the self-frequency resonance (i.e. that of the antenna alone without any external components) may be higher than the maximum 25 frequency within the HF ISM band (more preferably higher than 40.7 MHz).

Preferably, the self-resonance may be at least 5 MHz higher than the maximum HF band (e.g. higher than 45.71\TElz) to reduce or avoid possible interference between the self-resonance of the active and the passive antennas.

The ISM frequencies or frequency may be selected from an ISM band of 6.765 to 6.795 MHz, 13.553 to 13.567 MHz, 26.957 to 27.283 MHz or 40.66 to 40.70 MHz.

Preferably the apparatus may further comprise a control circuit, the control circuit controlling the power management of the apparatus thus providing a smart receiver system, using a miniaturised, combined electronic device.

The control unit may provide for smart charging by providing an adaptable power charging procedure (e.g. at different power levels) that may be compatible with electronic devices, for example, smartphones, headphones, smartwatches, key fobs, medical devices and/or other wearable electronic devices. A communication link between the transmitter and receivers may be established by using a BLE (Bluetooth Low energy at 2.45 GHz) to ensure a safer power charging protocol.

A great advantage of the invention is that of frequency diversity: the antenna parameters and magnetic environment are different for each frequency and using different frequencies increases the charging performance.

The charging system may be optimized at limited power.

Such an apparatus as in the receiving and transmitting apparatus of the invention is advantageous because it provides for multiband wireless charging and reduces or eliminates heating and interference problems and avoids saturation and regulatory difficulties that may occur at a single frequency. Thus, greater power may be transferred wirelessly. The use of a passive antenna allows the apparatus to be light and compact. A wireless charging apparatus as in the present invention is beneficial because it may be used with many different types of electronic device of different shapes and configurations. Wireless charging apparatus of the present invention allows more efficient, safe and convenient wireless charging of electronic devices.

In further aspects the invention provides an electronic device comprising a wireless charging apparatus, a wearable electronic device comprising a wireless power receiver and a method for wireless charging of an electronic device.

Examples of devices that may incorporate wireless charging apparatus of the invention include smart watches, fitness bands, headphones, key-fobs, medical devices and other portable electronic devices.

Embodiments of the present invention will now be described with reference to the following figures, in which: FIG. 1 shows a graph of efficiency vs battery current and illustrates typical efficiency of wireless charging at a single frequency.

FIG. 2 is a schematic of an embodiment of a power transmitter apparatus of the present invention.

FIG. 3 is a schematic of a power receiver apparatus of the present invention.

FIG. 4 (a) is a graph of the time response of the transmitted signals at two separated transmitters 6.78 MHz (dark curve) and 13.56 MHz (grey curve); (b) is a graph of the time response of the transmitted signal at the transmitting active antenna of an embodiment of the invention with dual simultaneous transmission at 13.56 MHz and 6.78 MHz.

FIG. 5 (a) is a graph of the frequency response of the received signals at two separated receivers 6.78 MHz (left curve) and 13.56 MHz (right curve); (b) is a graph of the frequency response of the received signal at the receiving active antenna of an embodiment of the invention with dual simultaneous reception at 13.56 MHz and 6.78 MHz.

FIG. 6 shows in (a) and (b) graphs of power received at single band receiving antenna against time for two transmitted frequencies, in each graph the horizontal line indicates average power received at that frequency: (a) single band 6.78 MHz 5 Watts average power; (b) single band 13.56 MHz 4.5 Watts average power; (c) simultaneous multiband 6.78 MHz and 13.56 MHz at a receiving active antenna of an embodiment of the invention 8 Watts average power.

FIG. 7 shows schematic plan views of (a) a concentric arrangement of a 2D active (drive) receiving or transmitting antenna, and passive antenna adapted to receive or transmit at 6.78 MHz, 13.56 MHz and 27.12 MHz; (b) a schematic showing the top view of a PCB design (layer 1); and (c) the bottom view of the PCB design (layer 4).

FIG. 8 shows a schematic side view of an embodiment of the multi-band antenna (transmitting or receiving).

FIG. 9 shows an embodiment of the present invention in the form of key fob incorporating a multi-band antenna (a) is a partially exploded view of the key fob; (b) is a plan view inside the bottom cover of the key fob; and (c) is a plan view inside the top cover of the key fob.

Figure 1 illustrates a graph showing that the efficiency of a wireless charging systems generally reduces as power increases, this may be owing to saturation.

In Figure 2 a schematic of a transmitter 2 of the present invention is shown with four passive antennas and a single active antenna. A DC power supply 4 supplies four sources of high frequency signals (oscillators) for power transmission at the frequencies: 6.78 MHz, 13.56 MHz, 27.12 MHz, and 40.68 MHz all frequencies in the ISM band. The sources are electrically connected (via serial capacitors 9) to high frequency amplifiers 6 (e.g. MOSFETs) and then I-IF frequency multipliers 8 (that may be analogue or digital). An active antenna (Lt) that transmits at all of the frequencies is electrically connected to the output of the multipliers 8.

Four passive antennas Ltl (6.78 MHz) , Lt2 (13.56 MHz), Lt3 (27.12 MHz) and Lt4 (40.68 MHz) (there may be two, three, four or more passive antennas in other embodiments) are each connected in parallel to a respective parallel capacitor for the passive resonators 10 but not directly electrically connected to the rest of the circuit. Instead the passive antennas are coupled inductively / magnetically with the active antenna in order to generate the four resonance frequencies. The coupling factors between the active and passive antennas are Ktl (between Lt and Ltl), Kt2 (between Lt and Lt2), Kt3 (between Lt and Lt3) and Kt4 (between Lt and Lt4). The coupling factors are affected by the distance between the antennas, the ratio between the size of antennas, and the ratio between the number of turns in the antennas.

Figure 3 shows a schematic of a receiver 12 of the present invention with four passive antennas Lrl. Lr2, Lr3, Lr4 (corresponding to the frequencies of the passive transmitter antennas of Fig 2 in this case but there may of course be fewer or more passive antennas) and a single active antenna Lr.

An active receiver antenna Lr receives all bands (directly or by inductive resonance with the passive receiver antennas) and is electrically connected to an AC to DC rectifier 14 and the output of the rectifier is (with capacitor for DC filtering 16 in parallel) electrically connected to a rechargeable battery. The receiver apparatus 12 may be incorporated in a wearable electronic device for consumer, military or medical purposes.

The four passive antennas Lrl (6.78 NIEL) , Lr2 (13.56 MHz), Lr3 (27.12 MHz) and Lr4 (40.68 MHz) (there may be two, three, four or more passive antennas in other embodiments) are each connected in parallel to a respective capacitor but not directly electrically connected to the rest of the circuit. Instead the passive antennas are coupled inductively / magnetically with the active antenna in order to receive the four resonance frequencies. The coupling factors between the active and passive antennas are Kt] (between Lt and LH), Kt2 (between Lt and Lt2), Kt3 (between Lt and Lt3) and Kt4 (between Lt and Lt4).

The design of the transmitter and receiver apparatus of the invention with two or 20 more passive antennas is much more compact than would be achievable if each frequency had its own active antennas and associated electronics, with the efficiency of transmission and reception still being excellent.

Figures 4 to 6 show graphs relating to the transmitter and receiver signals (two frequencies only 6.78 MHz and 13.56 MHz) indicating that the generated signals are mixed without losing the energy (i.e. amplitude) of the transmitter power at the active antennas (see Fig. 4). The frequency response shows a double peak of received energy (Fig. 5) obtained with the single active antenna which generates equivalent energy to two independent active apparatus. Figure 6 shows that the combined power for the apparatus of the invention (Fig 6 (c)) is only slightly less than the sum of two separate active systems (Fig 6 (a) and (b)) but with significant advantages in compactness, weight and simplicity and cost of manufacture.

FIG. 7 shows schematic plan views of (a) a concentric arrangement of a 2D active (drive) receiving or transmitting antenna 20, with an active antenna 22 and passive antennas 24, 26, 28 adapted to receive or transmit at 6.78 MHz (24), 13.56 MHz (26) and 27.12 MHz (28); (b) a schematic showing the top view of a PCB design (layer 1); and (c) a bottom view of the PCB design (layer 4).

The number of turns in each antenna varies the coupling factor between the active and passive antennas.

FIG. 8 shows a schematic side view of an embodiment of the multi-band antenna (transmitting or receiving) according to the invention. The antenna 20 comprises a PCB dielectric 40 with layers of PCB etched copper 38. The layers are as follows: PCB layer 1 (30) forms the passive antenna (6.78 MHz); PCB layer 2 (32) forms the passive antenna (27.12 MHz); PCB layer 3 (34) forms the passive antenna (13.56 MHz); and PCB layer 4 (36) forms the active antenna.

FIG. 9 shows an embodiment of the present invention in the form of a wirelessly chargeable key fob 50 incorporating a multi-band antenna. In (a) there is shown a partially exploded view of the key fob 50 incorporating a multi-band antenna. The key fob 50 has a top cover 52 with flexible parts and a bottom cover 54. The bottom cover 54 holds the electronic circuit 56 which incorporates the associated circuitry and the rechargeable battery 58. In (b) a plan view of the bottom cover 54 of the key fob 50 shows the rechargeable battery 58, the electronic circuit 56 and active antenna 22 electrically connected to the electronic circuit. In (c) an inner plan view of the top cover 52 of the key fob 50 shows the arrangement of the passive antennas 24, 26, 28, specifically the passive antenna (6.78 MHz), 24; the passive antenna (13.56 MHz), 26; and the passive antenna (27.12 MHz), 28.

Reference Numerals 2 transmitter 4 DC power supply 6 high frequency amplifier (e.g. MOSFET) 8 HE frequency multiplier 9 serial capacitor 10 parallel capacitor for passive resonator 12 receiver 14 AC to DC rectifier 16 capacitor for DC filtering antenna 22 active antenna 24 passive antenna (6.78 MHz) 26 passive antenna (13.56 MHz) 28 passive antenna (27.12 MHz) PCB layer 1 passive antenna (6.78 MHz) 32 PCB layer 2 passive antenna (27.12 MHz) 34 PCB Layer 3 passive antenna (13.56 MHz) 36 PCB layer 4 active antenna 38 PCB etched copper PCB dielectric 50 wirelessly chargeable key fob 52 key fob top cover 54 key fob bottom cover 56 electronic circuit 58 rechargeable battery

Claims

Claims 1. Wireless charging apparatus comprising a wireless power receiver, the receiver comprising, an active receiving antenna, a first passive receiving antenna, a rectifier in electrical connection with the active receiving antenna, and a rechargeable battery in electrical connection with the rectifier.
2. Wireless charging apparatus as claimed in claim 1, further comprising at least a second passive receiving antenna.
3. Wireless charging apparatus as claimed in claim 2, further comprising at least a third passive receiving antenna, and optionally, a fourth passive receiving antenna.
4. Wireless charging apparatus as claimed in any one of the preceding claims, wherein the or each passive receiving antenna is in parallel electrical connection with a capacitor.
5. Wireless charging apparatus as claimed in any one of the preceding claims, wherein the first passive receiving antenna, and the active receiving antenna each comprise substantially 2D antennas.
6. Wireless charging apparatus as claimed in claim 5, wherein the substantially 2D first passive receiving antenna and the 2D active receiving antenna are substantially concentric.
7. Wireless charging apparatus as claimed in any one of the preceding claims, wherein the or each passive receiving antenna is a high frequency antenna adapted to receive a frequency selected from an ISM frequency, preferably a high frequency ISM frequency.
8. Wireless charging apparatus comprising a wireless power transmitter, the transmitter comprising, a transmitter circuit comprising a first, high frequency source and a second, high frequency source, at least a first high frequency power amplifier, and at least one high frequency multiplier electrically connected to the first and second high frequency sources, an active transmitter antenna electrically connected to the transmitter circuit, a first passive transmitting antenna and a second passive transmitting antenna, wherein the first passive transmitting antenna and the second passive transmitting antenna are each inductively coupled to the active transmitter antenna thereby, in use, generating a first transmitter resonant frequency and a second transmitter resonant frequency.
9. Wireless charging apparatus as claimed in claim 8, wherein the first passive transmitting antenna and the second passive transmitting antenna are in parallel electrical connection with a first capacitor and a second capacitor respectively.
10. Wireless charging apparatus as claimed in either claim 8 or claim 9, further comprising at least a third passive transmitting antenna in parallel electrical connection with a third capacitor, and optionally a fourth passive transmitting antenna in parallel electrical connection with a fourth capacitor.
11. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 10, wherein the first passive transmitting antenna and the active transmitting antenna each comprise substantially 2D antennas.
12. Wireless charging apparatus as claimed in claim 11, wherein the substantially 2D first passive transmitting antenna and the 2D active transmitting antenna are substantially concentric 13. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 12, further comprising a second-high frequency power amplifier, optionally a third high frequency power amplifier, and further optionally a fourth high frequency power amplifier.14. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 13, 20 wherein the or each high frequency power amplifier comprises a MOSFET.15. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 14, wherein the multiplier is digital or analogue.16. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 15, wherein the or each passive transmitting antenna is a high frequency antenna adapted to transmit a frequency selected from an ISM frequency.17. Wireless charging apparatus as claimed in any one of the preceding claims 8 to 16, wherein the active transmitting antennas is adapted to transmit a plurality of ISM frequencies.18. Wireless charging apparatus as claimed in any one of the preceding claims, wherein the ISM frequencies or frequency is selected from an ISM band of 6.765 to 6.795 MHz, 13.553 to 13.567 MHz, 26.957 to 27.283 MHz or 40.66 to 40.70 MHz.19. Wireless charging apparatus as claimed in any one of the preceding claims, further comprising a control circuit, the control circuit controlling the power management of the apparatus.20. An electronic device comprising a wireless charging apparatus as claimed in any one of the preceding claims.2L A wearable electronic device comprising a wireless power receiver as claimed in any one of claims 1 to 7, 18 or 19.22. A method for wireless charging of an electronic device, the method comprising, providing an electronic device as claimed in claim 20, placing the electronic device in a varying electromagnetic field generated by a wireless power transmitter as claimed in any one of claims 8 to 19, whereby the wireless power receiver receives power from the electromagnetic field and charges the rechargeable battery of the electronic device.