I
METHOD OF CHARGING BATTERIES IN ELECTRONIC DEVICES
The present invention relates to the field of electronic devices. More particularly, the invention relates to a method of charging batteries in electronic devices.
Recently it has become increasingly common for people to carry various electronic devices with them when out and about, such as mobile phones or tablet computers for example. Such devices are powered by a battery and typically the battery is charged by connecting the device to a trickle charger connected to mains electricity within the home or office. When out, such charging may not be possible and it can be frustrating if an electronic device runs out of battery power. The present technique seeks to address this problem.
Viewed from one aspect, the present invention provides a method of charging batteries of a plurality of electronic devices located within a confined public environment; the method comprising: transmitting radio frequency electromagnetic waves from at least one local transmitter provided in the confined public environment; and at each of the plurality of electronic devices: (i) receiving the radio frequency electromagnetic waves at a receiving antenna and generating an alternating voltage in response to the radio frequency electromagnetic waves; (ii) converting the alternating voltage into a direct voltage using a rectifier; and (iii) charging a battery of the electronic device using the direct voltage.
It is relatively common for many users of electronic devices to congregate within a confined public environment, such as a cinema or concert hall for example. Typically, while in the confined public environment, the users may not be using their electronic devices since they may be participating in some other activity such as watching a film. The present technique recognises that batteries of a plurality of electronic devices may conveniently be charged in such an environment by transmitting radio frequency electromagnetic waves from at least one local transmitter provided in the confined public environment. At each of the plurality of electronic devices, the device may receive the radio waves at a receiving antenna, generate an alternating voltage in response to the radio waves, convert the alternating voltage into a direct voltage using a rectifier, and charge a battery of an electronic device using the direct voltage. This avoids the need for trickle charging the battery of the electronic device and makes use of the down time while users are not using the electronic devices to charge the batteries so that when the users leave the confined public environment then the electronic devices will be available for use. A local transmitter of reasonably low power (for example 100 mW) may be sufficient to charge the batteries in many devices.
The system would be low cost to run and the system may provide the user with confidence that following a film or concert, say, their electronic device will be charged and ready for use, for example in calling a taxi or finding out a bus
timetable.
This technique differs from typical wireless charging methods in that a dedicated local transmitter provided in the confined public environment and is used to charge a plurality of devices. This is different from techniques which provide a dedicated local charger for charging a single device placed in close proximity to the charger, or techniques which harvest ambient radio waves from a long distance transmitter which is not a local transmitter provided within the same public space as the electronic device being charged (this method is usually used to charge a single device rather than multiple devices).
The confined public environment may be any public space of limited extent in which many users are expected to visit. For example, the confined public environment may comprise the inside or surroundings of a public building. The building may for example be a concert hall, a cinema, a theatre, a sports venue, a museum, a library, a conference venue, a supermarket, shop or shopping centre or a building in an airport, bus station or railway station. All of these types of buildings represent public places where a number of users are expected to congregate and the ability to wirelessly charge devices while in such buildings would be of use to the public and to the operator of the building.
For example, the local transmitter may be provided on a ceiling or interior wall of the public building. The ceiling would typically provide greatest coverage for the waves from the local transmitter. However, if mounting the device to the ceiling is not practical then a wall or other kind of support structure could be used to mount the local transmitter.
Alternatively, the confined public environment may comprise a confined outdoor space of limited extent. The limited outdoor space may be an outdoor venue which is operated under control of a single entity. For example, the confined outdoor space may be a park, a theme park, a playground, an outdoor sports venue such as a golf course, cricket pitch or tennis court, a courtyard adjacent a building, or a car park. The users of the confined outdoor space may have their devices simultaneously charged using the local transmitter.
In the outdoor environment, the local transmitter may be provided on a support structure (for example, a pole, pylon, overhead wire or scaffold) or may be mounted on the outside of a building within the confined outdoor space, such as a clubhouse or toilet block.
To cover a larger confined area, multiple local transmitters may be provided in the confined public environment. For example, a football stadium or other venue may be divided into smaller sectors and each sector may have a local transmitter for charging electronic devices in that sector.
The local transmitter may transmit radio waves using different kinds of radio transmission. Ultra wide band transmitters could be used if a wide frequency band is desired. However, if narrow-band radio transmission is used then the power generated may be more focused and there may be less loss of power in the transmission, making the charging more efficient.
Various radio frequency bands may be used for the local transmission.
Preferably, the radio waves may be transmitted in at least one ISM (industrial, scientific and medical) radio band. The ISM radio bands are bands of frequencies reserved for uses other than communication. For example, the ISM radio bands centred at a frequency of 434 MHz, 915 MHz, 2.45 GHz or 5.8 GHz may be used. The 2.45 GHz ISM band is particularly advantageous from a efficiency point of view and also, as this is the band at which wireless networks (e.g. WiFi ®) are typically operated, transmission in the 2.45 GHz ISM band enables existing wireless network antennas to be used for receiving the waves for charging the battery, avoiding the need for a specialised antenna.
The electronic devices located within the confined public environment need not always be charged using this method. The devices may have a user input for selecting whether the battery is charged in response to the radio frequency electromagnetic waves transmitted by the local transmitter. Hence, when the user visits the confined public environment then they can switch to the mode in which battery charging is enabled in order to allow the power to be harvested, or can opt out from battery charging if desired.
The electronic devices charged using this method may include, for example, a mobile phone, a tablet computer, music player, a video player, a camera, a gaming console (which may be a handheld console) or an electronic reading device (e-reader).
At least one of the electronic devices may be a mobile communications device capable of receiving mobile communication signals from a mobile base station. For example, a mobile telephone or a tablet computer with a SIM card may have a mobile communications antenna for this purpose. In some embodiments, the receiving antenna in the electronic device for receiving the radio waves from the local transmitter may be the same antenna as the mobile communications antenna used for mobile communication. This avoids duplicating the antenna and any increments in the overall size of the electronic device. The same antenna can be tuned to different frequencies depending on whether mobile communication signals or the locally transmitted battery charging waves are received, and the user may input a signal for selecting whether the device should operate in a mobile communications mode or a battery charging mode. The user input may be a hardware switch provided on the electronic device or a selecting function provided in software running on the electronic device.
Alternatively, the receiving antenna and the mobile communication antenna may be different antennas. For example, a device may already have a standalone mobile communication antenna which may not be capable of being adapted to receive the locally transmitted waves for charging the battery, and so a separate antenna may be provided for this purpose. For example, the receiving antenna may be implemented as an external antenna which is coupled to the at least one electronic device. The external antenna may be connected to the mobile device using a USB (Universal Serial Bus) connection for example.
Alternatively, the receiving antenna may be an internal antenna which is mounted in the casing of the electronic device for example.
The receiving antenna of the electronic device may have various forms.
One useful example is where the receiving antenna comprises a tn-polar antenna which can sense radio waves in any of three different polarisation types. For example, the antenna may sense radio waves with a horizontal polarisation, a vertical polarisation and a circular or elliptical polarisation. The ability to sense multiple polarisation types is useful, because the waves from the local transmitter may be reflected off surfaces in the confined public environment, changing the polarisation of the transmitted waves. By sensing multiple polarisation types, the antenna can harvest a greater proportion of the energy transmitted from the local transmitter, improving efficiency. Alternatively, a uni-polar or bi-polar antenna which can only sense one or two polarisation types can be provided.
Similarly, the local transmitter may comprise a tn-polar antenna, which can transmit radio waves with first, second and third polanisation types. As some of the electronic devices may only have a uni-polar or bi-polar antenna and different electronic devices could be sensing different polarisations, providing the local transmitter with an antenna for transmitting radio waves with several different polarisations increases the range of different electronic devices which can be charged using the local transmitter.
Another form of antenna may be a patch antenna, which is reasonably flat so that it can be mounted in the casing of the electronic device. A patch antenna is useful for a portable electronic device because it allows the device to be kept reasonably thin.
The rectifier for converting the alternating voltage received at the antenna into a direct voltage for charging the battery can be implemented in various ways.
Examples of rectifiers include a crystal rectifier, a diode bridge, and a rectifier multiplier. However, a Schottky diode is particularly useful since it is able to operate with zero biasing and so can operate at low power.
The electronic devices may comprise an impedance matching network coupled between the receiving antenna and the rectifier. For example, the impedance matching network may comprise a network of resistors provided between the antenna and the rectifier. The impedance matching network helps to reduce the transmission loss in the system and increase the input voltage of the rectifier, again improving charging efficiency.
Viewed from another aspect, the present invention provides a confined public environment comprising: at least one local transmitter provided within the confined public environment configured to transmit radio frequency electromagnetic waves; a plurality of electronic devices located within the confined public environment, each electronic device comprising: a receiving antenna configured to receive the radio frequency electromagnetic waves and generate an alternating voltage in response to the radio frequency electromagnetic waves; a rectifier configured to convert the alternating voltage into a direct voltage; and a battery configured to be charged using the direct voltage.
Viewed from a further aspect, the present invention provides a mobile communications device comprising: a mobile communications antenna for receiving mobile communications signals; a receiving antenna for receiving radio frequency electromagnetic waves from at least one local transmitter and generating an alternating voltage in response to the radio frequency electromagnetic waves; a rectifier configured to convert the alternating voltage into a direct voltage; a battery configured to be charged using the direct voltage; and a user input configured to select whether the battery is charged using energy provided by the radio frequency electromagnetic waves.
The above, and other objects, features and advantages of this invention will be apparent from the following detailed description of illustrative embodiments which is to be read in connection with the accompanying drawings.
in which: Figure 1 schematically illustrates a confined public environment in which a local transmitter is provided for wirelessly charging batteries in multiple electronic devices; Figure 2 shows an example of an outdoor confined public environment having the local transmitter; Figure 3 shows an example of an electronic device having an antenna and a rectifier to allow a battery to be charged using energy harvested from the radio waves sent from the local transmitter; Figure 4 shows in more detail a circuit example of the electronic device; Figure 5 shows an example of a mobile communications device having a single antenna which is shared for receiving both mobile communication signals and radio waves sent from the local transmitter for charging the battery; Figure 6 shows another example of a mobile communications device in which separate antennas for mobile communications and battery charging purposes are provided; and Figure 7 shows a method of charging batteries of a plurality of electronic devices.
Figure 1 shows a confined public environment 2 comprising a local transmitter 4 and a plurality of electronic devices 6. The confined public environment 2 in this example is the inside of a public building such as a concert hall, cinema, sports centre, theatre, museum, shopping centre, or other kind of building in which the public are likely to congregate. The local transmitter 4 comprises a radio antenna for transmitting radio frequency electromagnetic waves. The electronic devices 6 each comprise an antenna for receiving the electromagnetic waves and circuitry for charging the battery of the electronic device 6 using energy harvested from the radio waves. For example, the electronic devices 6 may include mobile telephones, tablet PCs, cameras or games devices. Radio waves may travel directly from the local transmitter 4 to the electronic devices 6 or via reflections 8 off walls or other surfaces within the building. To increase the efficiency of energy transfer, the antenna in the electronic devices 6 may be able to detect two or three different polarisation types, so that changes in polarisation caused by reflection do not affect the ability to receive the waves.
The confined public environment 2 is a type of building in which users are expected to arrive for some particular purpose, such as watching a film or playing a sport. While the users are active then they typically would not be using the electronic devices 6. This down time can be reused for charging the batteries in these devices so that when the user leaves the confined public environment or stops their other activity then their devices 6 are charged and ready for use, for example for making a phone call. While Figure 1 shows the local transmitter 4 being placed on the ceiling 10 of the confined public environment 2, it may also be provided on a wall or other support structure within the building.
Figure 2 shows another example of wirelessly charging batteries in an outdoor confined public environment 2. For example, the outdoor environment may be a golf course, park or other public space. In this example, the local transmitter 4 may be mounted on the outside of a building 12 within the outdoor space or on a dedicated support structure 14 such as a pylon or pole. Again, users of the public environment 2 can have their devices 6 wirelessly charged using the radio waves transmitted from the dedicated local transmitters 4.
Multiple local transmitters 4 may be provided if the confined public environment 2 is too large to be covered by one transmitter 4.
Figure 3 shows an example of an electronic device 6 for being charged using the present technique. The electronic device 6 has an antenna 20 for receiving the radio waves transmitted from the local transmitter 4. The radio waves cause electrons in the antenna to oscillate up and down, generating an alternating voltage. An impedance matching network 22 is provided to increase the voltage output from the antenna. A rectifier 24 converts the alternating voltage into a direct voltage, and the direct voltage is applied to a load 26 which comprises the battery to be charged.
Figure 4 shows in more detail an example circuit implementation of the electronic device 6. In this example, the impedance matching network 22 comprises a network of resistors or other devices having impedance. The rectifier 24 in this example comprises a Schottky diode 30 and a capacitor 32.
The Schottky diode 30 is used because it requires no bias voltage and so can operate at low power. The Schottky diode 30 converts the alternating voltage generated at the antenna into a direct voltage to be applied to the battery 26.
The capacitor 32 helps to smooth variation in the direct voltage. It will be appreciated that many other forms of rectifier may be provided, such as other types of diode, diode bridge networks or crystal rectifiers for example.
The radio waves transmitted from the local transmitter 4 to the electronic devices 6 to be charged may take various forms. Radio waves may be transmitted in various frequency bands as desired. It can be useful to avoid using frequency bands used for other forms of communication such as mobile communication and radio broadcast transmission. Therefore, an ISM radio band may be used which is reserved for non-communication use. There are a number of different ISM radio bands defined using international standards, but one preferred example is the ISM radio band centred at 2.45 0Hz (referred to in this application as the 2.45 GHz ISM band). The 2.45 GHz radio band is used for wireless network signals and so many electronic devices which already have an antenna for receiving wireless network signals can be adapted to charge their battery using the present technique.
Figure 5 shows a first example of a mobile communications device 60 which may be used as the electronic device 6 of the previous examples. The mobile communications device 60 comprises a single antenna 62 which functions as the antenna 20 for receiving the radio waves from the local transmitter 4 as described above. The single antenna 62 also receives mobile communication signals for receiving telephone calls or mobile data for example. A tuner 64 is provided to select which frequency band the antenna 62 is currently detecting. A user input 66 is provided for allowing the user to select whether the antenna 62 receives mobile communication signals or the signals from the local transmitter 4.
The user input 66 may be a hardware switch or a selection function provided in software, such as a selectable option within a menu. If a mobile communications mode is selected by the user, then the signals received at the antenna 62 are passed to a mobile communications system 68 which processes the mobile communications signals. The mobile communication system 68 may include any circuitry which is typically included in a mobile phone or tablet computer, for example. If the user selects a battery charging mode, then the locally transmitted waves from the local transmitter 4 are received by the antenna 62, and the alternating voltage is coupled to the rectifier 24 which generates the direct voltage for charging the battery 26.
Figure 6 shows a second example of a mobile communications device 80 in which separate antennas 82, 84 are provided for receiving mobile communication signals and for charging the battery respectively. The mobile communications antenna 82 is connected to a tuner 84 which supplies the received mobile communication signal to the mobile communication system 86 in the same way as described for Figure 5.
On the other hand, a separate battery-charging antenna 84 is provided for receiving the radio waves from the local transmitter 4. In this example, the battery-charging antenna 84 is provided as an external antenna located in a detachable dongle 88 which can be attached to the communications device 80 via an external port such as a USB port. The dongle 88 also includes a tuner 89.
A user input 90 is provided to select whether the alternating voltage generated at the antenna 84 is passed to the impedance matching network 22, rectifier 24 and battery 26. Therefore, the user can select whether the battery 26 is charged using the received radio waves. By providing an external antenna 84 for receiving the waves from the local transmitter, devices which do not already have an antenna capable of receiving the locally transmitted radio waves can be adapted so that the battery can be charged. If the electronic device 80 does not already have the rectifier 24 then this can also be provided on the detachable dongle 88.
In another example, the mobile communications device 80 may have separate antennas provided for mobile communication and for wireless charging of the battery, with both antennas mounted within the device.
The antenna 20, 62, 82 of the electronic device may be a tn-polar patch antenna. Tn-polar antennas are useful for detecting multiple polarisations of signals which can increase the efficiency with which energy is harvested from the radio waves. A patch antenna is useful because it is relatively flat and so it can help to reduce the thickness of the device.
Figure 7 shows a method of wirelessly charging batteries in multiple electronic devices located within a confined public environment 2. At step 100, a dedicated local transmitter 4 within the confined public environment 2 transmits radio waves. The power of the local transmitter may be reasonably low since the electronic devices 6 to be charged are nearby (for example, of the order of a hundred mW). At step 102, one of the electronic devices 6 within the local environment 2 determines whether wireless charging is enabled. For example, a user input 66, 90 may set whether charging is enabled. If wireless charging is enabled, then at step 104 the radio waves are received by the antenna 20, 62, 82 and at step 106 an alternating voltage is generated by the antenna. At step 108.
the alternating voltage converted to a direct voltage by the rectifier 24. At step 110, the direct voltage is used to charge the battery 26 of the electronic device 6.
Meanwhile, steps 102 to 110 are repeated for other electronic devices 6 in the confined local environment 2.
In this way, the present technique provides an efficient method of wirelessly charging batteries in many electronic devices using a single local transmitter. This ensures that users will be able to use their electronic devices when leaving the confined public environment and reduces the need for users to monitor whether devices are charged before going to the confined public environment.
Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope and spirit of the invention as defined by the appended claims.