Providing An Electrical Circuit

Field of the Invention

The present invention relates to a system for providing an electrical circuit. The invention relates also to apparatus for use in a system for providing an electrical circuit with a mobile device, and to a mobile device for use in a system for providing an electrical circuit with an external device.

Background of the Invention Portable electronic devices, such as mobile or cellular telephones, personal music players, digital cameras and personal digital assistants (PDAs) are normally powered by an internal power supply, for instance an integrated or removable battery. Even though technology relating to battery reliability and longevity has improved, batteries usually need to be replaced or recharged relatively frequently.

It is known to recharge a battery by connecting the portable device to a charger, thereby avoiding the need to remove the battery from the device itself. The charger typically includes a plug for connection to a mains socket, transforming and rectifying circuitry, a cable and a connector suitable for connection to the portable device to be charged. However, a user normally has to locate the charger, untangle any cables that have become knotted and connect the charger both to a power source and to the portable device. This can be burdensome and time-consuming for the user. It also relies on the connectors of the charger and the mobile device being intact, although the fact that these connectors need to engage and disengage with one another means that one or both of the connectors can become damaged through repeated use.

WO 03/075416 discloses an electrical coupling device. The coupling includes a contactor device and a plurality of electrical contacts which close an electrical circuit between the contactor device and an adaptor device when the adaptor device is brought into physical contact with the contactor device, there being no need for aligning for the electrical contacts of the contactor device with contacts of the adaptor device. This is convenient since it allows a portable device to be charged by

simply placing it on a base unit, and does not require mating and de-mating of connectors. However, one variant of the system is complicated in that it requires a sensing unit and power switching circuitry. Another variant is simpler but requires a particular alignment of the portable device and the base unit.

The present invention seeks to ameliorate problems associated with the described prior art.

Summary of the Invention According to a first aspect of the invention there is provided a system for providing an electrical circuit, the system comprising: a first device comprising a first array of at least two first device contact pads separated from one another by a minimum first device contact pad separation distance, adjacent contact pads forming different terminals of the electrical circuit; and a mobile device comprising a second, non-linear array of at least four mobile device contact pads, the separation between adjacent mobile device contact pads being less than the smallest dimension of the first device contact pads through a centre point thereof, and the footprint of the mobile device contact pads having a largest dimension smaller than the minimum first device contact pad separation distance, whereby each of the adjacent first device contact pads contacts with a different one of the mobile device contact pads, thereby to include the mobile device in the electrical circuit.

Since the separation between adjacent mobile device contact pads is less than the smallest dimension of the first device contact pads, it can be assured that at least one mobile device contact pad will contact each first device contact pad that underlies part of the mobile device that has mobile device contact pads on it. Also, since the footprint of the mobile device contact pads has a largest dimension smaller than the minimum first device contact pad separation distance, it can be assured that no mobile device contact pad will contact two first device contact pads simultaneously, so it is not necessary to provide the first device with sensing or

power switching circuitry when operating to charge the mobile device, or with corresponding means when communicating data.

According to a second aspect of the invention, there is provided apparatus for use in a system for providing an electrical circuit with a mobile device, wherein the apparatus comprises a first array of at least two contact pads separated from one another by a minimum contact pad separation distance, adjacent contact pads of the first array being for forming different terminals of the electrical circuit; and the apparatus being connectable with a mobile device comprising a second, non-linear array of at least four mobile device contact pads, the separation between adjacent contact pads of the second array being less than the smallest dimension of the contact pads of the first array through a centre point thereof, and the footprint of the contact pads of the second array have a largest dimension smaller than the minimum separation distance of the contact pads of the first array, whereby each of the adjacent contact pads of the first array is contactable with a different one of the contact pads of the second array, thereby to allow the mobile device to be included in the electrical circuit.

According to a third aspect of the invention, there is provided mobile device for use in a system for providing an electrical circuit with an external device, wherein the mobile device comprises a first, non-linear array of at least four contact pads, the external device comprising a second array of at least two external device contact pads separated from one another by a minimum external device contact pad separation distance, wherein the separation between adjacent contact pads of the first array is less than the smallest dimension of the contact pads of the second array through a centre point thereof, and the footprint of the contact pads of the first array have a largest dimension smaller than the minimum separation distance of the contact pads of the second array, whereby each of the mobile device contact pads is contactable with a different one of adjacent external device contact pads, which are operable to form different terminals of the electrical circuit, thereby to include the mobile device in an electrical circuit with the external device.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic drawing illustrating first to third embodiments of a system in accordance with, and including components in accordance with, the present invention;

Figure 2A shows a perspective view of a rear face of a first mobile device in accordance with the present invention;

Figure 2B shows a perspective view of a rear face of a second mobile device in accordance with the present invention;

Figure 3 is a schematic cross-sectional view of the first embodiment of the system shown in Figure 1 taken along the line A-A';

Figure 4 is a schematic cross-sectional view of the second embodiment of the system shown in Figure 1 taken along the line A-A'; Figure 5 is a schematic cross-sectional view of the third embodiment of the system shown in Figure 1 taken along the line A-A';

Figure 6 is a schematic diagram of circuitry of a mobile device in accordance with the present invention; and

Figure 7 is a schematic diagram of circuitry for data transfer between a first device and a mobile device in accordance with the present invention.

Detailed Description of the Embodiments

Referring to Figure 1 , a system for providing an electrical circuit is shown. The system includes a first device 1 and a mobile device 2.

The first device 1 is a charging pad or tray. The charging pad 1 is rigid, i.e. it is not flexible. The charging pad 1 is connectable to an external device (not shown), such as a laptop or a desktop PC, and to a source of mains electricity.

The charging pad 1 includes a first array of at least two charging pad contact pads 3. In this example, there are sixteen charging pad contact pads, namely pads 3j to 3 ₁₆ , in a matrix of four pads by four pads, although a different number of charging pad contact pads 3 may be used instead. The charging pad contact pads 3 are arranged

in a regular repeating pattern and are each rectangular. In this example, the charging pad contact pads 3 are arranged in a rectangular array in the X ₁ -V ₁ plane so that the centre point of any given charging pad contact pad 3 _k generally has coordinates (x _lk ,y _lk ) = (x ₁₁ +na, y^+mb), where (X ₁₁₅ Y ₁₁ ) is the centre point of an origin charging pad contact pad 3 _l5 "n" and "m" are integers and "a" and "b" represent the distance between the centre points of adjacent pads in the X ₁ and J ₁ directions respectively. When the charging pad contact pads 3 are square in shape, the values of "a" and "b" are equal.

The charging pad contact pads 3 comprise or are coated with a material having a sufficiently high electrical conductivity, for instance copper, silver, a silver-cadmium alloy and/or gold.

A charging pad contact pad 3 is separated from an adjacent pad by a minimum charging pad contact pad separation distance (I ₁ . This distance d _t is typically in the range of 2 to 5 millimetres, and defines the gap between adjacent pads.

In use, adjacent charging pad contact pads 3 form different terminals of an electrical circuit. In this example, charging pad contact pads 3,, where "i" is an odd integer between one and fifteen, form positive terminals of an electrical circuit. Similarly, the remaining charging pad contact pads 3 _j , where "j" is an even integer between two and sixteen, form negative terminals of an electrical circuit. The resulting arrangement is like that of a chess board, with what would be black squares having one polarity and what would be white squares having the opposite polarity. One significant difference is that, unlike on a chess board, adjacent charging pad contact pads 3 do not contact one another.

The mobile device 2 is a portable electronic device, for example a mobile or cellular telephone, a personal music player, a digital camera or a PDA. Alternatively, the mobile device 2 may be any other rechargeable device, for instance a battery- powered toy, such as a toy car, battery-powered headphones, a wireless mouse or a robot.

The mobile device 2 includes a second array of at least four mobile device contact pads 4. In this example, there are thirty-five mobile device contact pads 4 in a matrix of five pads by seven pads. For the sake of clarity, only eight mobile device contact pads, referenced A ₁ to 4 ₈ , are described herein. The mobile device contact pads 4 each have a circular contact surface and are arranged in a regular repeating pattern in the (x ₂ ,y ₂ ) plane. The contact surface of a mobile device contact pad 4 is also referred to herein as the "footprint" thereof and both terms relate generally to the surface or region of a given mobile device contact pad 4 which are able to touch the charging pad 1 , when the mobile device 2 is placed thereupon. The mobile device contact pads 4 comprise or are coated with a sufficiently electrically conductive material.

The separation distance d ₂ between adjacent mobile device contact pads 4 is less than a smallest dimension d ₃ of the charging pad contact pads 3 through a centre point thereof. For example, if a charging pad contact pad 3 is rectangular, then its smallest dimension d ₃ is the length of the shortest sides of that rectangle. If a charging pad contact pad 3 is circular, then its smallest dimension d ₃ is the diameter of that circle.

The contact surface or footprint of the mobile device contact pads 4 has a largest dimension d ₄ smaller than the minimum charging pad contact pad separation distance (I ₁ . In this example, the mobile device contact pads 4 comprise cylinders. Accordingly, the contact surface is a circle having a largest dimension d ₄ which is the diameter of that circle.

When the mobile device 2 is placed upon, or meets, the charging pad 1, a number of the adjacent charging pad contact pads 3 contact with different ones of the mobile device contact pads 4. In this example, charging pad contact pad 3 ₆ contacts with plural mobile device contact pads 4 including, inter alia, mobile device contact pads 4 ₃ , 4 ₄ , A ₆ , A ₁ . Similarly, charging pad contact pad 3 ₇ contacts with plural mobile device contact pads 4 including, inter alia, mobile device contact pads 4 _l5 4 ₂ . Charging pad contact pad 3 ₁₆ , however, does not contact any of the mobile device

contact pads 4. Thus, multiple mobile device contact pads 4 may contact the same charging pad contact pad 3. This can result in an increased connection reliability.

None of the mobile device contact pads 4 contact more than one charging pad contact pad 3. This avoids the possibility of inadvertently providing a short circuit. Thus, provided that the above-mentioned criteria are satisfied, the mobile device 3 may be positioned at any point and at any angle on the charging pad 1 to provide an electrical circuit, so that the mobile device 2 can be supplied with a charging current. Furthermore, multiple mobile devices 2 may be simultaneously placed upon and thus connected with the charging pad 1. Thus, a user may simultaneously charge two devices, such as a mobile phone and a music player using a single charging pad 1.

Referring to Figure 2A, a first mobile device 2' is shown. The first mobile device 2' includes a non-linear array 4' of thirty- five mobile device contact pads. The array 4' is non-linear in the sense that the contact pads do not all fall on a single straight line. Put another way, they are not co-linear. Put yet another way, a first contact pad is separated from a straight line connecting second and third contact pads by a positive distance. Since the array 4' is non-linear, the contact pads are spread over a two-dimensional area instead of being formed in a single dimensional line. The mobile device contact pads are arranged so that the separation between adjacent mobile device contact pads is less than the smallest dimension d ₃ of the charging pad contact pads 3 through a centre point thereof. Furthermore, the contact surface or footprint of the mobile device contact pads, which in this example is circular, has a diameter, and hence largest dimension d ₄ , smaller than the minimum charging pad contact pad separation distance (I ₁ .

The first mobile device 2' includes a raised portion 5 which extends approximately two millimetres in a direction normal to the reverse face 6' of the first mobile device 2'. This raised portion 5 provides protection for a component which contributes to providing the mobile device 2' with camera functionality. Some or all of the mobile device contact pads protrude from the general plane of the rear surface 6' of the mobile device 2'. This enables the first mobile device 2' to complete an electrical

circuit when placed upon the charging pad 1. The mobile device contact pads protrude by an amount approximately equal to that of the raised portion 5. This avoids the possibility that, if the raised portion 5 extends from the reverse face 6' by a distance greater than a certain critical value, an insufficient number of the mobile device contact pads are contactable with the charging pad contact pads 3. Without protruding contact pads, an electrical circuit may not be assured.

The first mobile device 2' includes a socket 7 for connecting the first mobile device 2' to a corresponding connector of an external power supply (not shown). Thus, a user may also recharge a mobile device 2 conventionally.

Referring to Figure 2B, a second mobile device 2" in accordance with the present invention is shown. The second mobile device 2" includes a non-linear array 4" of twenty-seven mobile device contact pads. The mobile device contact pads are arranged in substantially the same way as the mobile device contact pads of the first mobile device 2'. However, in contrast to the first mobile device 2', the second mobile device 2" does not include a raised portion 5 on its reverse face 6". Furthermore, the mobile device contact pads are not raised above the reverse face 6". Of course, the mobile device contact pads may be raised above the reverse face 6" if this is desirable. Also, the mobile device contact pads have an oval-shaped footprint.

Referring to Figure 3, a first embodiment of the system shown in Figure 1 is illustrated. The first device 1 is a charging pad. The charging pad 1 includes a power supply 8 which has positive and negative terminals. The power supply 8 is disposed internal to the charging pad 1. The power supply 8 includes a socket (not shown) for connection with another power-supplying device (not shown) such as a Nokia™ ACP-7 or ACP-12 charger.

As explained above, the contact surfaces of the mobile device contact pads 4 have a largest dimension d ₄ smaller than the minimum charging pad contact pad separation distance (I ₁ . This helps to avoid the possibility of providing a short circuit when the mobile device 2 is placed upon the charging pad 1. The power supply 8 and/or the

other power- supplying device (not shown) includes integrated electronics for short circuit protection.

The positive terminal of the power supply 8 is electrically connected to charging pad contact pads 3 ₅ , 3 ₇ by means of an electrical connector 9 _t . The negative terminal of the power supply 8 is electrically connected to charging pad contact pads 3 ₆ , 3 ₈ by means of an electrical connector 9 ₂ . The electrical connectors 9 _l5 9 ₂ comprise conductive wires, conductive tracks and/or conductive paint. Although the power supply 8 is shown as being connected only to four of the charging pad contact pads, referenced 3 ₅ , 3 ₆ , 3 ₇ , 3 ₈ , it is also connected to the other ones of the charging pad contact pads 3j to 3 ₄ , 3 ₉ to 3 ₁₆ .

The mobile device 2 is placed upon the charging pad 1, as shown in Figure 1. In this example, the mobile device contact pads 4 are raised with respect to the reverse face 6 of the mobile device 2, for example as shown in Fig. 2 A. The mobile device contact pads 4 are cylinders.

Mobile device contact pads 4 _l5 4 ₂ contact a charging pad contact pad 3 ₇ , which forms a positive terminal of an electrical circuit. Mobile device contact pads 4 ₃ , 4 ₄ contact a different charging pad contact pad 3 ₆ , which forms a negative terminal of an electrical circuit. Mobile device contact pad 4 ₅ does not contact any of the charging pad contact pads 3. In this way, an electrical circuit is provided between the charging pad 1 and the mobile device 2 and including both of those devices.

Referring to Figure 4, a second embodiment of the system shown in Figure 1 is illustrated. This embodiment corresponds to the first embodiment, except in that the mobile device contact pads 4 are pins comprising a cylindrical base portion and a semi-hemispherical head portion, the head portion being in contact with the charging pad 1.

Referring to Figure 5, a third embodiment of the system shown in Figure 1 is illustrated. This embodiment is different to the first and second embodiments in that the mobile device contact pads 4 are not raised with respect to the reverse face

6 of the mobile device 2. The charging pad 1 is thus provided with an arrangement of high electrical conductivity brushes 10, for creating an electrical connection between the charging pad contact pads 3 and corresponding ones of the mobile device contact pads 4 comprises. The brushes 10 are resiliently deformable. Thus, the mobile device contact pads 4 do not need to protrude from the reverse face 6 of the mobile device 2. However, the brushes 10 are sufficiently rigid that neighbouring fields of brushes cannot electrically contact each other, thereby avoiding the possibility of providing a short circuit. The brushes 10 may be in the form of nanograss.

Referring to Figure 6, a schematic diagram of circuitry of a mobile device 2 in accordance with the present invention is shown. For simplicity, only those mobile device contact pads A ₆ , A ₁ , 4 ₈ that intersect an imaginary reference line B-B' in Figure 1 are illustrated.

The mobile device contact pads 4 are electrically connected to a recharging circuit 12 via diodes 11. The recharging circuit 12 is for charging a battery 13. Each mobile device contact pad 4 is connected to both a positive and negative terminal of the recharging circuit 12. A first positive path IA ₁ connecting mobile device contact pad A ₆ to the positive terminal of the recharging circuit 12 includes a first battery- facing diode H ₁ . The diode H ₁ is battery- facing in the sense that it is arranged to allow current flow from the mobile device contact pad A ₆ towards the positive terminal of the recharging circuit 12, and thus the battery 13, but not in the opposite direction. A first negative path 14 ₂ connecting the mobile device contact pad A ₆ to the negative terminal of the recharging circuit 12 includes a first pad- oriented diode H ₂ . The diode H ₂ is pad- facing in the sense that it is arranged to allow current flow from the negative terminal of the recharging circuit 12, and thus the battery 13, toward the mobile device contact pad A ₆ but not in the opposite direction. Second and third, positive and negative paths 14 ₃ , 14 ₅ and 14 ₄ , 14 ₆ are defined in a similar way.

In this example, mobile device contact pads A ₆ , A ₁ are in electrical contact with a negative charging pad contact pad 3 ₆ and mobile device contact pad 4 ₈ is in

electrical contact with a positive charging pad contact pad 3 _π . The diodes 11 are arranged so that if any mobile device contact pad 4 contacts a positive charging pad contact pad 3, current flows along only a respective positive path from the respective positive charging pad contact pad 3 to the positive terminal of the recharging circuit 12, as indicated by arrows along the path 14 ₅ . Moreover, this diode arrangement 11 also allows the same mobile device contact pad 4 alternatively to be connected to a negative charging pad contact pad 3, in which case current is drawn from the negative terminal of the recharging circuit 12 to that negative charging pad contact pad 3, as indicated by arrows along paths 14 ₂ , 14 ₄ . In this way, an electrical circuit is provided between the charging pad 1 and the mobile device 2 regardless of the position or orientation of the mobile device 2 on the charging pad 1.

The invention can be expanded to any application where a device, in particular a stationary or fixed device, needs to be connected to one or more mobile devices 2. For example, the invention may alternatively or in addition be used to transfer data between the charging pad 1 and the mobile device 2, as will now be described with reference to Figure 7, which illustrates an additional embodiment of the invention.

Referring to Figure 7, a schematic diagram of a system including circuitry for data transfer between the charging pad 1 and the mobile device 2 is shown. The charging pad 1 and the mobile device 2 include respective modems 15, 16 for modulating and demodulating signals. Data may be transferred between the charging pad 1, also referred to herein as a data transfer pad 1, and the mobile device 2 by modulating data onto a carrier signal. Thus, data may be transferred from the charging pad 1 to the mobile device 2 by modulating, at the modem 15, the data onto the carrier signal and superimposing the result onto the charging voltage provided by the power supply 8. The modulated signal is then applied to the charging pad contact pads 3 and accordingly results in a potential difference across corresponding mobile device contact pads 4 and thus the modem 16. The signal is demodulated at the modem 16 to reconstruct the transmitted data. In some implementations a carrier signal may not be needed. In a bidirectional arrangement,

data is transmitted from the mobile device 2 to the data transfer pad 1 in a similar way.

Such data transfer capability may be in addition to, or instead of, data transfer by way of Bluetooth™, Infrared Data Association (IrDA) and/or serial connectivity. Therefore, data can be conveniently transferred between the charging pad 1 and the mobile device 2 without the need to connect the devices by means of a cable and without utilising Bluetooth, IrDA or other wireless transceivers or the mating of corresponding physical connectors. The invention may also be used to synchronise a mobile device 2 to a host computer (not shown) connected to the charging pad 1, i.e. automatically to back up or transfer data from the mobile device 2 onto the host computer (not shown) and to transfer information from the host computer onto the mobile device 2.

In an alternative embodiment, the data transfer pad 1 may solely be a data transfer device and not have the capability to provide a charging voltage.

It will be apparent that many modifications may be made to the embodiments described above.

The charging pad 1 may be flexible, i.e. deformable, so as to allow easy transportation thereof, to facilitate storage and/or to enable it to be used in a confined space. Alternatively, it may be integrated into a desk or other surface. The charging pad 1 may be part of a modular system, wherein corresponding devices are electrically connectable with the charging pad 1 so as to provide an increased charging surface area. Alternatively or additionally, the charging pad 1 may be capable of disassembly, in the sense that it can be separated into plural daughter devices, each daughter device having a smaller charging surface area than that of the parent charging pad 1.

When the charging pad contact pads are square rectangular, they are preferably arranged in an array having two axes. The axes preferably are orthogonal, although they could be skewed. The charging pad contact pads may be a different shape.

For instance, they could be triangular. In this embodiment, the charging pad contact pads preferably are arranged in a repeating pattern having three axes. The charging pad contact pads may alternatively be stripes, alternating in polarity.

The charging pad contact pads 3 may not be arranged in a regular repeating pattern, such as in concentric circles or such that the X ₁ and J ₁ and/or the x ₂ and y ₂ axes are not orthogonal. Some or all of the charging pad contact pads 3 may not be rectangular. Some or all of the charging pad contact pads 3 may be defined by transparent conductive areas resulting from deposition of Indium Tin Oxide (ITO) on the charging pad 1. The charging pad 1 may include a circuit breaker and/or a fuse so as provide short circuit protection. The electrical connectors 9 _l5 9 ₂ may be wholly or partly disposed on a surface of the charging pad 1.

In relation to the mobile device 2, the contact surfaces or footprints of the mobile device contact pads 4 may not be circular. For instance, some or all of them could be points, rectangles or other shapes. The charging pad 1 and/or the mobile device 2 may include means, such as an LED, a display or a buzzer, for indicating that an electrical circuit is provided.