NZ715493A - Inductive power transfer in an electrical outlet - Google Patents

Abstract

Disclosed is an inductive power transfer system for use in a surface-mounted electrical switch or power outlet system. A primary side is provided in a base unit of the electrical system to convert mains or supply power into an output power for use by a cover unit. The cover unit is provided with a secondary side of the inductive power transfer system to receive the output power from the base unit inductively. In some embodiments, data is also able to be inductively transferred between the base unit and the cover unit. econdary side of the inductive power transfer system to receive the output power from the base unit inductively. In some embodiments, data is also able to be inductively transferred between the base unit and the cover unit.

Description

INDUCTIVE POWER TRANSFER IN AN ELECTRICAL OUTLET INCORPORATION BY REFERENCE The following publications are referred to in the present application: PCT/AU12014/000545 entitled “Connection System and Method For Electrical Outlets” PCT/AU12014/000544 entitled “Batten Holder, Connector, System and Method” PCT/AU12011/001675 entitled “Touch Switch” entitled “General Power Outlet and Remote Switch Module” Co-pending Australian Provisional Patent Application entitled “Electrical System, Apparatus and Method” Co-pending Australian Provisional Patent Application entitled “Connection System and Method for Electrical Outlets” Co-pending Australian Provisional Patent Application entitled “Switch Assembly, System and Method” Co-pending Australian Provisional Patent Application entitled “Push Button Switch Assembly” Co-pending Australian Provisional Patent Application entitled “Switch Assembly with Rotatable Operational Part” The entire content of each of these documents is hereby incorporated by reference.

PRIORITY The present application claims priority from the following applications: Australian Provisional Patent Application No 2014905210 entitled “Electrical System, Apparatus and Method” Australian Provisional Patent Application No 2014905212 entitled “Inductive Power Transfer In an Electrical Outlet” Australian Provisional Patent Application No 2014905211 entitled “Connection System and Method for Electrical Outlets” Australian Provisional Patent Application No 2014905209 entitled “Switch Assembly, System and Method” Australian Provisional Patent Application No 2014905213 entitled “Push Button Switch Assembly” Australian Provisional Patent Application No 2014905203 entitled “Switch Assembly with Rotatable Operational Part” Chinese Patent Application No 201410795485.8 entitled ”Hybrid Switch Mechanism” Chinese Patent Application No 201410795482.4 entitled “Switch Assembly With Rotatable Operational Part” Chinese Patent Application No 201410795430.7 entitled “Push-Button Switch Assembly and Operational Part”.

The entire content of each of these documents is hereby incorporated by reference.

TECHNICAL FIELD The present application relates to electrical outlets and switch plates.

SUMMARY According to one aspect, there is provided a primary side of an induction power transfer system, the primary side comprising; a power input for inputting mains or supply power; a rectifier for receiving an electrical signal from the power input and for rectifying the electrical signal; and a transmitting coil for receiving a rectified signal from the rectifier and for transmitting the rectified signal.

In one embodiment, the power input is an AC/DC flyback power converter.

In one embodiment, the primary side further comprises a primary side data input for receiving data.

In one form, the primary side further comprises a controller for generating a control signal for controlling the transmitting coil to transmit the input data.

In one form, the control signal controls the transmitting coil by frequency modulation of the excitation frequency of the transmitting coil.

According to a second aspect, there is provided a secondary side of an inductive power transfer system, the secondary side comprising; a receiver coil for receiving an electromagnetic signal from a transmitter coil of a primary side of the inductive power transfer system; a voltage rectifier for rectifying an output signal from the receiver coil; and a voltage regulator for regulating the rectified signal received from the voltage rectifier and for outputting a regulated voltage.

In one embodiment, the secondary side further comprises a signal demodulator for demodulating data in the received electromagnetic signal output from the receiver coil.

In one form, the secondary side further comprises a data input for receiving data input to the secondary side.

In one form, the secondary side further comprises a modulator for modulating the amplitude of a signal transmitted by the receiver coil.

According to a third aspect, there is provided a base unit for installation in a cavity in a surface, the base unit comprising; an input terminal for receiving mains or supply power; and a primary side of an inductive power transfer system according to the first aspect.

In one form, the base unit further comprises a base connector for connecting to a cover unit.

In one form, the base unit further comprises a base supply power output for providing supply or mains power to a device.

According to a fourth aspect, there is provided a cover unit for connection to a base unit, the cover unit comprising: a cover connector for connecting to a base connector of the base unit; and a secondary side of an inductive power transfer system according to the third aspect.

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the various aspects described herein will be detailed with reference to the accompanying drawings in which: Figure 1A – shows a front perspective view of a base unit according to one aspect; Figure 1B – shows a rear view of the base unit of Figure 1A; Figure 2A – shows a side view of the base unit with power input; Figure 2B – shows a front perspective view of the base unit with an embodiment of a transmitter coil; Figure 2C – shows a front perspective view of the base unit with another embodiment of the transmitter coil; Figure 3 – shows a system block diagram of a first side of an inductive power transfer system according to one embodiment; Figure 4 - shows a system block diagram of a first side of an inductive power transfer system according to another embodiment; Figure 5 – shows a base unit according to another embodiment, including a base supply power output; Figure 6 – shows a perspective rear view of a cover unit according to one embodiment; Figure 7A – shows a perspective rear view of a cover unit according to another embodiment; Figure 7B - shows a perspective rear view of a cover unit according to another embodiment; Figure 8 – shows a systems block diagram of a second side of the inductive power transfer according to one embodiment; Figure 9 – shows a systems block diagram of a second side of the inductive power transfer according to another embodiment with communications functionality; Figure 10 – shows a side view of cover unit 200 connected to base unit 100 to allow power and/or data to be transferred between the two units inductively; Figure 11 – shows a systems block diagram of the first side and the second side of the inductive power transfer system according to one aspect; Figure 12 – shows a graph of transmitting losses vs output power for different gap sizes between the transmitting and receiving coils; Figure 13 – shows a graph of system efficiency as a function of the gap size; Figure 14 – shows a graph of regulated output voltage vs output current for varying gap sizes; Figure 15A - shows a circuit diagram of circuitry for the primary side of the inductive power transfer system; Figure 15B - shows a circuit diagram of further circuitry for the primary side of the inductive power transfer system; Figure 15C - shows a circuit diagram of further circuitry for the primary side of the inductive power transfer system; Figure 16 - shows a circuit diagram of circuitry for the secondary side of the inductive power transfer system; Figure 17A – shows an implementation of the circuitry of Figures 15A to 15C and 16 on PCBs; Figure 17B – shows the arrangement of Figure 17A from below; Figure 18A - shows an assembled first side using three of the PCBs of Figures 17A and 17B; and Figure 18B shows an assembled second side using two of the PCBs of Figures 17A and 17B.

DESCRIPTION In one aspect described herein, there is provided a base unit 100 for mounting to a surface and for electrical connection to a mains or supply power and for connection to a cover unit 200. Figure 1A shows a front perspective view of a general embodiment of base unit 100 and Figure 1B shows a rear perspective view of the base unit 100 of Figure 1A. In one aspect, the base unit 100 comprises a mounting region 110 for mounting the base unit 100 to the surface. In some embodiments, the surface is a wall. In some other embodiments, the surface is a floor. In some other embodiments, the surface is a wall of a box or other enclosure.

In some embodiments, the mounting region 110 is itself a surface which will come into contact with the surface to which the base unit 100 is to be mounted. In one such embodiment, this mounting region surface is a border running around at least a portion of the periphery of base unit 100 for connection to the surface. In other embodiments, the mounting region 110 is a pin, tab or other connector.

As shown in Figure 1A, base unit 100 also comprises a base connector 120 for connecting the base unit to a cover unit 200 as will be described in more detail below. The base connector 120 is shown generically in Figure 1A but can take on any form that allows connection of the cover unit 200 (see Figure 6) to the base unit 100. Such forms include a recess for receiving a protrusion from the cover unit 200, a protrusion for being received in a corresponding recess in the cover unit 200, a clipping arrangement, or a magnet for attracting and retaining a region of the cover unit. In other embodiments, the base connector is an adhesive, or a loop-hook connector such as a product sold under the trade mark Velcro® by Velcro Industries B.V. In this embodiment, base connector 120 can be either the loop component of the connector or the hook component.

Base unit 100 also comprises a base supply power input 130 for electrically connecting the base unit 100 to a supply or mains power supply. In some countries, the mains, or supply power is provided as an alternating current (AC) electrical signal of about 240V (for example between about 220V and 260V) and about 50Hz frequency. In other countries, mains or supply power is provided as an AC signal of between about 100V and 130V. Some systems use a frequency of about 50Hz while others use a frequency of about 60Hz. Some supply power systems are single phase and others may be three-phase. It will be understood that any electrical power that would be considered to be supply or mains power can be used.

In some embodiments, base supply power input 130 is an electrical terminal block, to which electrical conductors or wires carrying the supply power may be connected. In some embodiments, each of active, earth and neutral conductors is connected to respective terminals of the electrical terminal block as will be understood by the person skilled in the art. In other embodiments, only active and earth conductors are connected.

In some embodiments, base unit 100 also comprises a base power output 150 for providing output power to the cover unit 200 when cover unit 200 is connected to base unit 100.

According to one aspect described herein, base power output 150 is provided by an inductive power transfer system 400 as will be described in detail further below.

Figure 2A shows a side view of a base unit 100 for mounting to a surface, and for connection to a source of power, such as mains or supply power. In this aspect, the base unit 100 comprises base supply power input 130 provided by an input terminal block for receiving mains or supply power 50, a first side 410 of an induction power transfer system 400 connected to the base supply power input 130 for receiving power from the supply power 50 and for radiating energy from a coil of the first side. In this arrangement, first side 410 also acts as power converter 140 in that it receives mains or supply power at its input and outputs power in a different form as will be described in more detail below.

In this embodiment, base power output 150 is provided by a coil 414 disposed, in one embodiment, around the periphery of base unit 100 as shown in Figure 2B, which shows a perspective front view of the base unit 100. In other embodiments, coil 414 is provided in a smaller region as shown in Figure 2C. In one embodiment, coil 414 is provided as a printed coil on a Printed Circuit Board (PCB). This implementation ensures high reproducibility and reduces costs. In other embodiments, coil 414 is provided by physical windings of wire around a ferrite core.

Figure 3 shows a system block diagram of one embodiment of first side 410. In this embodiment, first side 410 comprises a power input 411 for receiving power (e.g. from a mains or supply source via input terminal block or other source). In one embodiment, power input 411 is a 5W isolated AC/DC flyback converter. Input 411 is connected to a rectifier 412, in one embodiment a half bridge rectifier, and in a more specific embodiment, a half bridge rectifier constructed of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs).

Rectifier 412 is connected to a resonant network 413. The output of resonant network 413 is connected to transmitting coil 414 for radiating the energy as output power.

In one embodiment, there is also provided a magnetic flux concentrator 415 such as a ferrite core.

The input power to the AC/DC flyback stage can be between about 110V to about 240V AC, and about 50Hz to 60Hz. The output of this stage is about 12V DC between about 6W and about 10W. The other role of this power stage is to provide electrical isolation between the mains or supply power network input to the power stage and the data input stage (see Figure 4 and related description below).

Figure 4 shows another embodiment of first side 410, which provides data communication capabilities. In this embodiment, a data input 416 (for example a digital data input) for receiving data from an external source such as another device communicating with input 416 wirelessly by any suitable protocol such as IEEE 802.15.1 ( Bluetooth®), Bluetooth Low Energy (BLE®) or IEEE 802.15.4 (ZigBee®), or for receiving data directly from the mains power source 50 using modulation of the current carried by the mains power conductors.

The output of data modulator 416 is applied to the input of controller 417 which generates modulating signals to modulate the output of transmitter coil 414 in accordance with the data, as will be described in more detail below. This allows data to be transmitted by modulating the energy radiated by transmitting coil 414. All other elements in Figure 4 are as previously described in Figure 3.

In some embodiments as shown in Figure 5, base unit 200 comprises a base supply power output 190 for providing supply power directly to an electrical device such as a heater, fan, radio, television. In this embodiment, base 100 may have two power outputs, being base power output 150 for providing output power to the cover unit 200 and base supply power output 190 for providing supply power to an external device other than the cover unit 200. In this embodiment, base supply power output 190 is connected directly to base supply power input 130 to provide mains or supply power to the user. In one embodiment, base supply power output 190 is a socket for receiving a plug of an electrical device such as a vacuum cleaner. In some embodiments, cover unit 100 will have an aperture to allow direct access to base supply power output 190, or may have its own input for receiving a plug from an external device, such as a series of one, two or three or more apertures which receive a respective plug and which align with sockets of base supply power output 190.

In another aspect, there is provided a cover unit 200 as shown in Figure 6. In a broad embodiment, cover unit 200 comprises a cover connector 220 for connecting the cover unit 200 to the base unit 100. In some embodiments, cover connector 220 engages with base connector 120 to connect cover unit 200 to base unit 100.

The cover connector 220 is shown generically in Figure 6 but can take on any form that allows connection of the cover unit 200 to the base unit 100. Such forms include a recess for receiving a protrusion from the base unit 100, a protrusion for being received in a corresponding recess in the base unit 100, a clipping arrangement, or a magnet for attracting and retaining a region of the base unit 100.

Cover unit 200 further comprises a cover power input 210 for receiving power output from base unit 100. Cover unit 200 also comprises functional circuitry 280 which can receive power from cover power input 210.

According to another aspect described herein, cover power input 210 is a second side 420 of the inductive power transfer system 400. Figure 7A shows cover unit 200 with cover power input 210 provided by a receiving coil 424 of second side 420. Functional electronics 280 is connected to second side 420 to receive power to power any components of the functional circuitry.

It will be appreciated that functional circuitry 280 can be any of one or more electrical components which react to receiving power from cover power input 210. In one simple embodiment, functional circuitry 280 is a light or a light such as an incandescent light, fluorescent light, or light emitting diode (LED), which lights up upon receiving power from cover power input 210. These devices may also have supporting circuitry. In other embodiments, functional circuitry 280 comprises many components and may include integrated circuits, microcontrollers, memory devices and analog and digital circuitry, display units or screens, and electro-mechanical devices such as speakers or actuators, to perform any desired functions.

Figure 8 shows an embodiment of second side 420 of inductive power transfer system 400. In this embodiment, second side 420 comprises receiving coil 424 for receiving energy radiated by transmitting coil 414 of first side 410. The received energy is provided to the input of rectifier and filter block 422, which rectifies and filters the received signal and provides the rectified and filtered signal to the input of voltage regulator 421 to provide a regulated voltage as an output of second side 420. This output can then be connected to functional circuitry 280 to provide power to functional circuitry 280 to allow it to operate. In one embodiment, this output is 5V DC with 500mA current, providing 2.5W of power.

In another embodiment, second side 240 comprises communications functionality as shown in Figure 9. In this embodiment, which cooperates with the embodiment of the first side 410 as shown in Figure 4, receiving coil 424 receives the radiated energy from transmitting coil 414 of first side 410, upon which is modulated a data signal as previously described. The received signal at receiving coil 424 is applied to the input of rectifier and filter 422 to provide power processing as previously described, but is also provided at the input of signal demodulator 425 to extract the data signal from the received signal. The demodulated signal is provided at the output of signal demodulator 425 to be applied to functional circuitry 280. In this way, the operation of functional circuitry 280 can be controlled by data sent from base unit 100.

In one embodiment, the method of transmitting data from the primary side (i.e. base unit 100 to the secondary side (i.e. cover unit 200) is by way of modulation of the excitation frequency of the primary coil in accordance with the input data. This modulation may be done using analogue techniques in one embodiment, but may also be done via a microcontroller in other embodiments.

In one embodiment, the method of transmitting data from the secondary side (i.e., the cover unit 200) to the primary side (i.e. base unit 100) is by way of amplitude modulation by applying modulation signals on the LC resonant circuit in accordance with the data input to the cover unit 200. Such data may be input by any suitable means, including by the user actuating one or more user inputs such as a button on the cover unit, or by remote means which transmit data wirelessly to cover unit 200.

Figure 10 shows cover unit 200 connected to base unit 100 via base connector 120 and cover unit connector 220, to provide system 300. In this view, base unit 100 is mounted to surface 40, in this embodiment, a wall. In this arrangement, receiving coil 424 of second side associated with cover unit 200 is placed sufficiently close to the transmitting coil 414 of the first side 410 to provide the inductive power transfer system 400 as shown in Figure 11.

The distance between the receiving coil 424 and the transmitting coil 414 can range from substantially 0mm up to about 10mm or more, including 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm and 9mm and intervals therebetween. The operation of the inductive transfer system will vary depending upon the distance between the transmitting coil 414 and the receiving coil 424.

Figure 12 shows a graph of transmitting losses versus output power for different gap sizes. From this graph, it can be seen that transmitting losses begin to increase more rapidly as the gap exceeds about 1.5 mm.

Figure 13 shows a graph of efficiency of the system as a function of the gap size.

From this graph, it can be noted that efficiency also begins to reduce after a gap size of about 1.5mm.

Of course the system is still useable at these greater gap sizes.

Figure 14 shows a graph of regulated output voltage vs output current with varying gap sizes.

The details of one specific embodiment will now be described with reference to Figures 15A, 15B and 1C which shows an exemplary circuit layout of the various sections of the first side or primary side as discussed above, and with reference to Figure 16 which shows an exemplary circuit layout of the various sections of the secondary side. The function of the circuits will be understood by the person skilled in the art and the entire circuit will not be described in detail, however, details of some of the sections are provided below.

On the primary side 410 (as shown in Figure 15A), transmitter coil 414 (TX_ANTENNA A1) is in one embodiment, provided by a printed circuit of dimensions of about 20mm x 20mm, printed onto a PCB. The circuit comprises six copper layers, each of about 35µm thickness. One layer is used to carry the 12V power signal provided by the power stage and the other five layers comprise four turns, totalling 20 turns for the transmitter coil 414. The inductance provided by transmitter coil 414 in this embodiment is about 9µH (100kHz). A ferrite core (e.g.

PLT22/16/2.5 in 3C90 available from Ferroxcube International Holding B.V.) is attached to the rear of the coil with an inductance of about 13µH.

The control signal to control the coil 414 is provided in one embodiment, by a controller UCC25600 provided by Texas Instruments Incorporated. Control of the MOSFET half bridge 412 is provided by a high voltage gate driver such as the LM5101 provided by Texas Instruments Incorporated.

On the receiving side 420 (as shown in Figure 16), receiving coil 424 (RX_ANTENNA A2), is in one embodiment, printed onto a PCB, as in the embodiment described above for the primary or transmitting coil 414. To optimise the coupling between the two coils 414, 424, in one embodiment, their geometries (dimensions and shape) are substantially identical. In one embodiment however, the number of turns of the secondary or receiving coil 424 as a ration of the number of turns of the primary or transmitting coil 414 is 1.2. In one embodiment, the number of turns of secondary coil 424 is 24 and the number of turns of the primary coil is 20.

In one embodiment, the transmission frequency is about 180kHz.

In this embodiment, in order to minimise losses in the rectifier, use is made of a rectifier such as NMUL1210 available from Semiconductor Components Industries, LLC. The four- diode arrangement usually used in rectification are replaced by two MOSFETs coupled with two Schottky diodes, all integrated in a 4x4mm casing. The output of the rectifier is filtered and passed to a buck converter operating at 2MHz. This converts the filtered signal to a regulated voltage fixed at about 5V dc. The higher operating frequency of the buck converter allows the use of a low value inductor of 2µH with a height of less than 1mm. Each of these design elements allows the inductive power transfer system to be housed in a small volume, as is required in the present application.

The output of the receiving coil 424 is also used to extract data transmitted by the primary side as previously described. The first stage of the communications section comprises in one embodiment, an operational amplifier (U9) (e.g. LM393DMR2G) which discriminates and transforms the input signal into a rectangular signal of 0-5V having a frequency equal to the excitation frequency of the primary coil 414. This signal is then input to a monostable (U10:A) having a time period of 2.7µs. Since the time period of the monostable is fixed, when the frequency of the signal from the transmitter changes, the ratio of the cycle of the signal output from the monostable is accordingly modified.

The following stage (U11:B) provides a low pass filter at around 10kHz, which extracts the average value of the frequency of the signal output from the monostable. The output signal of U11 is therefore proportional to the excitation frequency of the transmitter coil 414. The final function provided by the comparator (U9:B) is as a differentiator. It compares the instantaneous value of the frequency of the signal output from the low pass filter with its average value.

In summary, rapid frequency changes change the output state of the comparator which are then filtered by the RC network R41/C35. This system allows the simple demodulation of frequency changes in the signal transmitted by the primary side.

To properly function, the frequency of the transmitted signals should be well above the cut-off frequency of the RC network (R41/C35), of 1Hz, and well below the cut-off frequency of the low pass filter at the output of the converter (10kHz).

To avoid oscillation of the comparator (U9:B), a small resistor (R46) is added to one of the inputs of the comparator. The LED (D9) at the output of the comparator allows the data exchanged between transmitter and receiver to be expressed visually.

Finally, the transmission of data from the receiver 420 to the transmitter 410 is provided by loading the receiving coil 424 in accordance with the data signal to be transmitted. This is performed by a resistor of 22 Ohms that is controlled by a MOSFET, which is itself controlled by the signal to be transmitted.

Data exchange between the transmitter and the receiver is performed in this embodiment non-simultaneously (i.e. half-duplex). In one embodiment, the also allows for a visual indication that data is being exchanged by the provision of an LED on each of the transmitter and receiver sides. In this example, information can be transmitted at a rate of up to about 500 bits/s.

It will be appreciated that the specific application of providing an inductive power transfer system within the physical constraints of an electrical plate system as described herein, provides significant obstacles. Some of the various electronic design elements described above, also can each contribute to allowing such a system to be implemented.

The physical construction can also contribute to allowing the system to be provided in a small volume. In one embodiment, the various functional blocks described above are provided on five separate PCBs.

Base Unit/Transmitter/Primary Side 1. Power stage – about 90V – about 240V ac input converted to about 12 V with power output about 10W 2. Electromagnetic transmission coil/antenna 3. Controller and modulation/demodulation sections Cover unit/Receiver/Secondary side 4. Electromagnetic receiving coil/antenna . Rectification, filtering, regulation and modulation/demodulation stages When fully assembled, in one embodiment, the transmitter/primary side is contained within a volume of about 23x20x42mm. In embodiments where the power output of the power stage is about 6W instead of about 10W, this volume can be even further reduced.

The receiving or secondary side 410 is provided on two PCBs in one embodiment.

One PCB is for the receiving coil 424 and the other is for the power regulation and modulation/demodulation of data. The functions performed by these components are reception and distribution of the received EM signal, rectification, DC/DC regulation to 5V, filtering and FM demodulation and AM modulation.

The receiving coil 424 is, in one embodiment, provided by a printed circuit on the PCB, having substantially the same dimensions as the transmitting coil 414, that is, about 20mm by 20mm. To compensate for the weak coupling between the two coils, the number of turns of the receiving coil 424 is slightly larger than the number of turns of the transmitting coil 414, and specifically in this embodiment, 24 turns (with the transmitting coil 414 having 20 turns). This is accomplished by using all six layers of the coil 424 as opposed to only five layers in the transmitting coil 414 as previously described. The inductance achieved of receiving coil 424 is about 13µH. A magnetic sheet 423 of the same thickness as the coil 424 is attached to the rear of the PCB opposite the coil 424, of inductance about 20.2µH. The output signal of the receiving coil 424 is then rectified as described above.

In one embodiment, the total surface area of the receiver/secondary side is about 40x20mm with a thickness of about 4.5mm (including PCB and components). In this embodiment, the components are mounted on both sides of the PCBs, but in other embodiments, components can be mounted on only one side, resulting in a thickness of about 2.5mm, resulting in an even smaller volume occupied by the electronics.

Figures 17A and 17B show a physical implementation of the circuits described above.

Figure 17A shows the circuit boards from a top view, with a coin placed in view to show scale.

Figure 17B shows the view of Figure 17A from below.

In one embodiment, the three boards of the transmitter 410 are assembled in a U- shape as shown in Figure 18A. The volume occupied by the transmitter side 424 is about 42x20x22mm, thus 18.5cm . Figure 18B shows the assembled receiver side 420 which is assembled in a plane.

It will be appreciated that the system 300 comprising base unit 100 and cover unit 200 allows easy connection of a cover unit 200 to base unit 100 by simply engaging the base connector 120 and cover connector 220. In this way, cover unit 200 can be easily installed, removed and replaced by any user without any need for electrical knowledge or certification.

Furthermore, the system 300 allows a plurality of different cover units 200 to be connected to base unit 100. This allows the user to replace the cover unit 200 with a cover unit 200 of a different functionality to thereby provide great flexibility to the user as the user’s needs change over time.

For example, in one embodiment, cover unit 200 is a power socket and switch arrangement to allow system 300 to act as a conventional power socket for allowing the user to power devices such as vacuum cleaners, televisions etc. If the user then enters a stage in life where the user has a baby, the user may easily remove cover unit 200 by simply disengaging the base connector and the cover connector, and can then replace this cover unit 200 with a different cover unit 200 that provides a different functionality such as a baby monitor or a night light.

Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

Claims (13)

1. A primary side of an induction power transfer system, the primary side comprising; a power input for inputting mains or supply power; a rectifier for receiving an electrical signal from the power input and for rectifying the electrical signal; and a transmitting coil for receiving a rectified signal from the rectifier and for transmitting the rectified signal.

2. A primary side as claimed in claim 1wherein the power input is an AC/DC flyback power converter.

3. A primary side as claimed in any one of claims 1 or 2 further comprising a primary side data input for receiving data.

4. A primary side as claimed in claim 3 further comprising a controller for generating a control signal for controlling the transmitting coil to transmit the input data.

5. A primary side as claimed in 4 wherein the control signal controls the transmitting coil by frequency modulation of the excitation frequency of the transmitting coil.

6. A secondary side of an inductive power transfer system, the secondary side comprising; a receiver coil for receiving an electromagnetic signal from a transmitter coil of a primary side of the inductive power transfer system; a voltage rectifier for rectifying an output signal from the receiver coil; and a voltage regulator for regulating the rectified signal received from the voltage rectifier and for outputting a regulated voltage.

7. A secondary side as claimed in claim 6 further comprising a signal demodulator for demodulating data in the received electromagnetic signal output from the receiver coil.

8. A secondary side as claimed in claim 7 further comprising a data input for receiving data input to the secondary side.

9. A secondary side as claimed in claim 8 further comprising a modulator for modulating the amplitude of a signal transmitted by the receiver coil.

10. A base unit for installation in a cavity in a surface, the base unit comprising; an input terminal for receiving mains or supply power; and a primary side of an inductive power transfer system as claimed in any one claims 1 to 5 connected to the input terminal.

11. A base unit as claimed in claim 10 further comprising a base connector for connecting to a cover unit.

12. A base unit as claimed in any one of claims 10 or 11 further comprising a base supply power output for providing supply or mains power to a device.

13. A cover unit for connection to a base unit, the cover unit comprising: a cover connector for connecting to a base connector of the base unit; and a secondary side of an inductive power transfer system as claimed in any one of claims 6 to 9. "&’()*+,#- ..(/"’0 "# 1" ,!,2 ! "# $!% $!% $!% $!% "&’ )*,!#..224 1" ,!,2 ! "# $!% $!% $!% $!% ..224 "&’ /, ! 1/ 1 ! 2 ,$! ! 6 7 $!% $!% $!% $!% ! 5/5