WO2010108551A1

WO2010108551A1 - Power management

Info

Publication number: WO2010108551A1
Application number: PCT/EP2009/053697
Authority: WO
Inventors: Pertti Vihtori Saarinen
Original assignee: Nokia Corporation
Priority date: 2009-03-27
Filing date: 2009-03-27
Publication date: 2010-09-30

Abstract

First and second apparatuses, first and second methods and a computer program are provided. The first apparatus comprises: power supply circuitry configured to supply power to the second apparatus; monitoring circuitry configured to monitor an input impedance at the second apparatus, and configured, in response to a change in the input impedance at the second apparatus being detected by the monitoring circuitry, to control the power supply circuitry to supply power to the second apparatus.

Description

TITLE

Power Management

TECHNICAL FIELD

Embodiments of the present invention relate to power management. In particular, they relate to power management in serial bus compliant apparatuses.

BACKGROUND

The Universal Serial Bus (USB) On-The-Go (OTG) Supplement is a supplement to the USB standard. USB OTG defines, in conjunction with the USB standard, a wired interface that supports data exchange between a host and a peripheral.

In USB OTG, the role of host and peripheral is initially defined by which end of the cable an apparatus is connected to. A USB OTG cable may comprise a micro A-plug and a micro B-plug. A micro A-plug has a grounded identification pin, whereas a micro B-plug has a floating identification pin.

If an apparatus is connected to a micro A-plug of the cable, it is an A-device and initially operates as the host of the bus. If an apparatus is connected to a micro B-plug, it is a B-device and initially operates as a peripheral of the bus.

A USB OTG bus includes a power supply line (Vbus) which enables an A- device to provide power to a B-device. The A-device may, for example, comprise a power source (such as a battery) which it uses to provide power to the B-device. However, if Vbus is left on for long periods of time (for example, while the bus is not being used to transfer data) the battery may run out of power prematurely. BRIEF DESCRIPTION OF VARIOUS EXEMPLARY EMBODIMENTS OF THE INVENTION

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: power supply circuitry configured to supply power to a further apparatus; monitoring circuitry configured to monitor an input impedance at the further apparatus, and configured, in response to a change in the input impedance at the further apparatus being detected by the monitoring circuitry, to control the power supply circuitry to supply power to the further apparatus.

The monitoring circuitry may be configured, after controlling the power supply circuitry to supply power to the further apparatus, to continue to monitor the input impedance at the further apparatus for a further change in the input impedance.

The change in the input impedance may be from a first impedance to a second impedance. The further change in the input impedance may be from the second impedance to the first impedance. The monitoring circuitry may be configured, in response to the further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to continue supplying power to the further apparatus.

The further change in the input impedance may be from the second impedance to a third impedance. The monitoring circuitry may be configured, in response to the further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to cease supplying power to the further apparatus.

The monitoring circuitry may be configured, in the absence of a further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to cease supplying power to the further apparatus.

The monitoring circuitry may be configured to monitor the input impedance at the further apparatus by monitoring an input impedance at one of a plurality of pins of a connector of the further apparatus.

The connector may be a universal serial bus connector. The monitoring circuit may be configured to monitor an identification pin of the connector.

According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: monitoring an input impedance at an apparatus; detecting a change in the input impedance at the apparatus; and supplying, in response to detecting the change in input impedance, power to the apparatus.

The method may further comprise continuing to monitor the input impedance at the apparatus after supplying power to the apparatus, for a further change in the input impedance.

The change in the input impedance may be from a first impedance to a second impedance. The further change in the input impedance may be from the second impedance to the first impedance. The method may further comprise continuing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

The further change in the input impedance may be from the second impedance to a third impedance. The method may further comprise ceasing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected. The method may further comprise: ceasing to supply power to the apparatus if a further change in the input impedance at the apparatus is not detected.

The input impedance at the apparatus may be monitored by monitoring the input impedance at one of a plurality of pins of a connector of the apparatus.

The connector may be a universal serial bus connector and the input impedance at an identification pin of the connector may be monitored.

According to various, but not necessarily all, embodiments of the invention there is provided a computer program comprising instructions which, when executed by a processor, enable: monitoring an input impedance at an apparatus; detecting a change in the input impedance at the apparatus; and supplying, in response to detecting the change in input impedance, power to the apparatus.

The instructions may further enable: continuing to monitor the input impedance at the apparatus, after supplying power to the apparatus, for a further change in the input impedance.

The change in the input impedance may be from a first impedance to a second impedance. The further change in the input impedance may be from the second impedance to the first impedance. The instructions may further enable: continuing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

The further change in the input impedance may be from the second impedance to a third impedance. The instructions may further enable: ceasing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected. The instructions may further enable: ceasing to supply power to the apparatus if a further change in the input impedance at the apparatus is not detected.

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: power supply means for supplying power to a further apparatus; monitoring means for monitoring an input impedance at the further apparatus, and for controlling, in response to a change in the input impedance at the further apparatus being detected by the monitoring means, the power supply means to supply power to the further apparatus.

The monitoring means may be for continuing to monitor the input impedance at the further apparatus, after controlling the power supply circuitry to supply power to the further apparatus, for a further change in the input impedance.

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: an unpowered circuitry arrangement comprising at least one user input device configured to enable a user to change, by actuating the at least one user input device, the unpowered circuitry arrangement from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry arrangement is configured to provide a first impedance to another apparatus and, in the second state, the unpowered circuitry arrangement is configured to provide a second impedance to the another apparatus, the second impedance signaling the another apparatus to supply power to the apparatus.

The apparatus may further comprise a connector configured to electrically connect the apparatus to the another apparatus. The unpowered circuitry arrangement may be configured to provide the first and second impedances at the connector. The unpowered circuitry arrangement may be configured, following user actuation of the at least one user input device, to automatically return the unpowered circuitry arrangement to the first state, without further user intervention.

The unpowered circuitry arrangement may comprise a switch electrically coupled to a power supply line. The switch may be configured, in response to power being supplied on the power supply line by the another apparatus, to automatically return the unpowered circuitry arrangement to the first state.

The at least one user input device may comprise a resiliently biased switch that is configured, following user actuation, to automatically return the unpowered circuitry arrangement to the first state.

According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: enabling a user to change, by actuating at least one user input device, an unpowered circuitry arrangement from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry arrangement provides a first impedance to an apparatus and, in the second state, the unpowered circuitry arrangement provides a second impedance to the apparatus, the second impedance signaling the another apparatus to supply power to the circuitry arrangement.

Following user actuation of the at least one user input device, the unpowered circuitry arrangement may automatically return the unpowered circuitry arrangement to the first state, without further user intervention.

The unpowered circuitry arrangement may comprise a switch electrically coupled to a power supply line. In response to power being supplied on the power supply line by the apparatus, the switch may automatically return the unpowered circuitry arrangement to the first state. The at least one user input device may comprise a resiliency biased switch that, following user actuation of the at least one user input device, automatically returns the unpowered circuitry arrangement to the first state.

According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: unpowered circuitry means comprising at least one user input means for enabling a user to change, by actuating the at least one user input means, the unpowered circuitry means from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry means provides a first impedance to another apparatus and, in the second state, the unpowered circuitry means provides a second impedance to the another apparatus, the second impedance signaling the another apparatus to supply power to the apparatus.

The unpowered circuitry means may be for automatically returning the unpowered circuitry means to the first state, following user actuation of the at least one user input device.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of various examples of embodiments of the present invention reference will now be made by way of example only to the accompanying drawings in which:

Fig. 1 illustrates a first apparatus and a second apparatus; Fig. 2 illustrates a first apparatus and a second apparatus;

Fig. 3 illustrates a first universal serial bus apparatus connected to a second universal serial bus apparatus;

Fig. 4 illustrates a method; and

Fig. 5 illustrates a first universal serial bus apparatus connected to a second universal serial bus apparatus. DETAILED DESCRIPTION OF VARIOUS EXEMPLARY EMBODIMENTS OF THE INVENTION

The exemplary Figures illustrate a first apparatus 100, comprising: power supply circuitry 120 configured to supply power to a second apparatus 200; monitoring circuitry 130 configured to monitor an input impedance at the second apparatus 200, and configured, in response to a change in the input impedance at the second apparatus 200 being detected by the monitoring circuitry 130, to control the power supply circuitry 120 to supply power to the second apparatus 200.

The exemplary Figures also illustrate a second apparatus 200, comprising: an unpowered circuitry arrangement 205 comprising a user input device 210 configured to enable a user to change, by actuating the user input device 210, the unpowered circuitry arrangement 205 from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry arrangement 205 is configured to provide a first impedance to a first apparatus 100 and, in the second state, the unpowered circuitry arrangement 205 is configured to provide a second impedance to the first apparatus 100, the second impedance signaling the first apparatus 100 to supply power to the second apparatus 200.

Fig. 1 is an exemplary schematic illustrating the first apparatus 100 and the second apparatus 200. The first apparatus comprises power supply circuitry 120 and monitoring circuitry 130.

The second apparatus 200 may comprise an unpowered circuitry arrangement 205 that comprises a user input device 210. The unpowered circuitry arrangement 205 is "unpowered" in the sense that it has no need for the second apparatus 200 to have its own source of power. For example, the unpowered circuitry arrangement 205 has no need for the second apparatus 200 to comprise a battery or a connector for connecting the second apparatus 200 to mains electricity. While the unpowered circuitry arrangement 205 may allow current/voltage signals to pass, it does not need a power source for generating current/voltage signals. The second apparatus 200 may, however, include a battery for powering some further functional circuitry in the second apparatus 200.

User actuation of the user input device 210 causes the unpowered circuitry arrangement 205 to change from being in a first state to being in a second state. In the first state, the unpowered circuitry arrangement 205 may be configured to provide a first impedance Zi to the first apparatus 100. In the second state, the unpowered circuitry arrangement 205 may be configured to provide a second impedance Z₂ to the first apparatus 100.

The monitoring circuitry 130 is configured to monitor the input impedance at the unpowered circuitry arrangement 205. A change in the input impedance at the unpowered circuitry arrangement 205 signals the first apparatus 100 to supply power to the second apparatus 200.

The first apparatus 100 may comprise its own internal power source, such as a battery. Alternatively, the first apparatus 100 may not have its own internal power source and may derive power from an external power source, such as mains electricity. In response to detecting a change in the input impedance at the unpowered circuitry arrangement 205, the monitoring circuitry 130 may control the power supply circuitry 120 to supply power (derived from an internal or external power source) to the second apparatus 200.

The unpowered circuitry arrangement 205 may be configured to automatically return the input impedance of the unpowered circuitry arrangement 205 to the first impedance, following actuation of the user input device 210. After controlling the power supply circuitry 120 to supply power to the second apparatus 200, the monitoring circuitry 130 may continue to monitor the input impedance of the unpowered circuitry arrangement 205 for a time period.

If the monitoring circuitry 130 does not detect a change in the input impedance at the unpowered circuitry arrangement 205 from the second impedance Z₂ to the first impedance Zi within the time period, it controls the power supply circuitry 120 to cease supplying power to the second apparatus 200. For example, the input impedance at the unpowered circuitry arrangement 205 may not return to the first impedance Zi within the time period if the first apparatus 100 and the second apparatus 200 are disconnected.

If the monitoring circuitry 130 may detect a change in the input impedance of the unpowered circuitry arrangement 205 from the second impedance Z₂ to the first impedance Zi within the time period, it may control the power supply circuitry 120 to continue supplying power to the second apparatus 200.

In some embodiments of the invention, the monitoring circuitry 130 may comprise one or more specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other devices. Alternatively or additionally, the monitoring circuitry 130 may comprise a processor that operates using computer program instructions

180. The monitoring circuitry 130 may, for example, comprise a memory that stores a computer program comprising the computer program instructions

180.

Fig. 2 illustrates an embodiment of the invention in which the monitoring circuitry 130 comprises a processor 132 and a memory 134. The memory 134 stores the computer program instructions 180. The computer program instructions 180 may control the operation of the first apparatus 100 when loaded into the processor 132. The computer program instructions 180 may provide the logic and routines that enables the first apparatus to perform the methods illustrated in Fig 4. The processor 132, by reading the memory 134, may be able to load and execute the computer program.

The computer program may arrive at the first apparatus 100 via any suitable delivery mechanism 70. The delivery mechanism 70 may be, for example, a computer-readable storage medium, a computer program product, a memory device, a record medium such as a CD-ROM or DVD, an article of manufacture that tangibly embodies the computer program. The delivery mechanism 70 may be a signal configured to reliably transfer the computer program. The first apparatus 100 may propagate or transmit the computer program as a computer data signal.

Fig. 3 illustrates an exemplary embodiment in which a first USB apparatus 100 is connected to a second USB apparatus 200. The first apparatus 100 may, for example, be a hand portable electronic apparatus such as a mobile telephone, mobile terminal, mobile device, a personal music player or a personal digital assistant. The first apparatus 100 comprises a transceiver 110, power supply circuitry 120, monitoring circuitry 130 and a first connector 135.

The first connector 135 may, for example, be a micro A-receptacle for receiving a micro A-plug. Alternatively, the first connector 135 may be a dual mode receptacle that is configured to receive a micro A-plug or a micro B- plug. In other embodiments of the invention, other types of connector may be used, for example, standard A, standard B or mini B.

The first connector 135 comprises a D⁺ connector pin 140, a D^" connector pin 150, a Vbus connector pin 160 and an identification (ID) connector pin 170. The first connector 135 may also include a ground (GND) connector pin.

However, the ground connector pin is not illustrated in Fig. 3 for clarity.

The transceiver 110 may be configured to transfer data to and from the second apparatus 200 on first and second data lines D⁺ 10 and D^" 20 via the D⁺ and D^" connector pins 140 and 150.

The power supply circuitry 120 may be configured to supply power to the second apparatus 200 on a power supply line Vbus 30, via the Vbus connector pin 160. The power supplied by the power supply circuitry 120 may be derived from a power source that is internal to or external from the first apparatus 100, as explained above.

The monitoring circuitry 130 may be configured to monitor an identification (ID) line 40 for changes in input impedance at an ID pin 260 of the second apparatus 200. The monitoring circuitry 130 may be also configured to control the power supply circuitry 120 in dependence upon changes in input impedance detected using the ID line 40.

The second apparatus 200 may, for example, be a headset, any other type of accessory device or any other type of mobile apparatus. In case the second apparatus is a headset it may be used for listening to music. If the first apparatus 100 has telephone functionality, the second apparatus 200 may be for conducting telephone calls. The second apparatus 200 may comprise a second connector 235, functional circuitry 240, first and second resistors 230, 250, a transistor 220 and a user actuable switch 210.

In this example, the second connector 235 may be a micro A-plug. The second connector 235 may comprise a D⁺ connector pin 290, a D^" connector pin 280, a Vbus connector pin 270, an ID connector pin 260. The second connector 235 may also comprise a ground connector pin. However, the ground connector pin is not illustrated in Fig. 3 for clarity. In some embodiments of the invention, a cable comprising the D+ line 10, the D- line 20, the Vbus line 30, ID line 40 and the ground line may connect the second connector 235 and the functional circuitry 240. In these embodiments, the first resistor 230, the second resistor 250, the transistor 220 and/or the switch 210 may be located adjacent the second connector 235, in the cable, or adjacent the functional circuitry 240.

When the first connector 135 is electrically connected to the second connector, the D⁺, D^", Vbus and ID pins 140, 150, 160, 170 are electrically connected to the D⁺' D^", Vbus and ID pins 290, 280, 270, 260 of the second apparatus 200 respectively.

If the second connector 235 is a micro A-plug, the first apparatus 100 becomes the default host of the USB connection between the first apparatus 100 and the second apparatus 200, and the second apparatus 200 becomes the default peripheral.

The functional circuitry 240 may be configured to transfer data to and from the first apparatus 100 on the first and second data lines D⁺ and D^" 10, 20, via D⁺ and D^" connector pins 290, 280. If the second apparatus 200 is for example a headset, the functional circuitry 240 may comprise one or two earphones. It may also comprise a microphone.

The user actuable switch 210 may be in one of two positions. When the user actuable switch 210 is in a first position (illustrated in Fig. 3), it connects the ID line 40 to ground and is not connected to the functional circuitry 240. When the user actuable switch 210 is in a second position, it connects the functional circuitry 240 to ground and is not connected to the ID line 40. The user actuable switch 210 may be resiliently biased, so that its natural position (in the absence of user applied force) is the first position. One end of the first resistor 230 is connected to the ID line 40 and another end is connected to ground. When the first apparatus 100 is electrically connected to the second apparatus 200, the first resistor 230 may be connected to the monitoring circuitry 130 of the first apparatus 100 in parallel.

One end of the second resistor 250 may be connected to the Vbus line 30 and the other end of the resistor 250 may be connected to the transistor 220. The transistor 220 may be connected to the Vbus line 30 (via the resistor 250) in such a way that if power is supplied on the Vbus line 30, the transistor 220 allows current to be passed between the ID line 40 and ground. The transistor 220 may be any type of transistor. In the illustrated example, the transistor 220 is a field effect transistor. The gate of the transistor 220 may be connected to the Vbus line 30 via the second resistor 250.

A method according to exemplary embodiments of the invention will now be described using Fig. 4. The left hand side of Fig. 4 illustrates actions may be performed at the first apparatus 100 and the right hand side indicates an action may be performed at the second apparatus 200.

The first and second apparatuses 100, 200 are initially connected to one another. According to the USB OTG supplement (On-The-Go Supplement to the USB 2.0 Specification; Revision 1.3; December 5, 2006), in order for the first apparatus 100 to become an A-device, the ID pin 260 of the connector 235 of the second apparatus 200 has to be grounded.

When the first and second apparatuses 100, 200 are initially connected to one another, the first apparatus 100 becomes an A-device because the user actuable switch 210 is in the first position (as illustrated in Fig. 3), providing a connection between the ID line 40 and ground at the second apparatus 200. The power supply circuitry 120 of the first apparatus 100 subsequently supplies power to the second apparatus 200. Enumeration then takes place. Enumeration is a process described in the Universal Serial Bus Specification

(Revision 2.0, April 27, 2000) by which the second apparatus 200 is allocated an address and data is sent from the second apparatus 200 (the default peripheral) to the first apparatus 100 (the default host) that identifies the capabilities of the second apparatus 200 and enables communications between the first apparatus 100 and the second apparatus 200.

During enumeration, the second apparatus 200 indicates to the first apparatus 100 that is it a "zero-power apparatus". That is, the second apparatus 200 indicates to the first apparatus 100 that it does not have its own power source. It may also indicate that the first apparatus 100 is allowed to switch off the power being supplied on the Vbus line 30, if desired.

At a later point in time, the first apparatus 100 switches off the power being supplied to the second apparatus 200 on the Vbus line 30.

At block 300 of Fig. 4, after the power supply on the Vbus line 30 has been switched off, the first apparatus 100 monitors an input impedance at the second apparatus 200. In this example, the monitoring circuitry 130 continually monitors the input impedance at the ID connector pin 260 of the second apparatus 200.

The monitoring circuitry 130 may, for example, monitor the input impedance at the ID connector pin 260 by passing a current along the ID line 40. The resistor 230 and the user actuable switch 210 (currently situated in the first position) connect the monitoring circuitry 130 to ground. No power is being supplied on the Vbus line 30, so the gate of the transistor 220 is not open. Consequently, the transistor 220 does not pass (any significant) current between the ID line 40 and ground.

At this stage, the input impedance detected by the first apparatus 100 may be zero, or close to zero, because the switch 210 provides a very low impedance path between the ID line 40 and ground. This roughly zero value of the input impedance may be considered to be a "first impedance".

At block 310, a user actuates the switch 210, causing it to move from the first position to the second position. When the switch 210 is in the second position, it no longer provides a very low impedance path between the ID line 40 and ground. The path having the lowest impedance between the ID line 40 and ground at the second apparatus 200 is that through the first resistor 230.

Thus, the input impedance of the ID pin 260 of the second apparatus 200 becomes roughly equal to the resistance of the first resistor 230. This value of the input impedance may be considered to be a "second impedance".

The change in the input impedance from the first impedance to the second impedance signals to the first apparatus 100 to begin supplying power to the second apparatus 200. Also, detection of an input impedance that is roughly equal to the impedance of the first resistor 230 may indicate to the monitoring circuitry 130 that the second apparatus 200 remains electrically connected to the first apparatus 100. For example, if the user had disconnected the second apparatus 200 and the first apparatus 100, the monitoring circuitry 130 would have detected a higher impedance than that provided by the first resistor 230.

At block 320 of Fig. 4, the monitoring circuitry 130 of the first apparatus 100 detects the change in input impedance from the first impedance to the second impedance. At block 330, in response to detecting the change in the input impedance, the monitoring circuitry 130 controls the power supply circuitry 120 to supply power to the second apparatus 200 on the Vbus line 30.

Once power is supplied on the Vbus line 30, the gate of the transistor 220 is opened. The transistor 220 effectively acts as a switch, allowing current to pass freely between the ID line 40 and ground when the gate is opened. This may cause a further change in the input impedance at the ID pin 260 of the second apparatus 200. The input impedance may change from a value that is roughly equivalent to the impedance of the first resistor 230 to roughly zero. The input impedance at the ID pin 260 therefore returns to the "first impedance" value after power is supplied on the Vbus line 30.

After the controlling the power supply circuitry 130 to supply power on the Vbus line 30, the monitoring circuitry 130 may continue to monitor the input impedance of the ID pin 260 of the second apparatus 200. In this example, the monitoring circuitry 130 detects a change in the input impedance from the second impedance to the first impedance. This change in impedance signals to the monitoring circuitry 130 that power it is supplying on the Vbus line 30 is being received by the second apparatus 200. The monitoring circuitry 130 may therefore control the power supply circuitry 120 to continue supplying power to the second apparatus 200.

In a situation where the monitoring circuitry 130 does not detect a change in the input impedance from the second impedance to the first impedance, it may control the power supply circuitry 120 to cease supplying power on the Vbus line 30, because it has not received confirmation from the second apparatus 200 that power is being received.

Following initial user actuation of the switch 210, the switch 210 remains in the second position for a period of time, electrically connecting the functional circuitry 240 to ground. The switch 210 may, for example, be configured to remain momentarily in the second position after user actuation has ceased, before returning to the first position. Alternatively, the switch 210 may remain in the second position because the user is holding it in the second position.

After power is supplied to the functional circuitry 240 on the Vbus line 30, the functional circuitry 240 may detect that the switch 210 is in the second position. The powered-up functional circuitry 240 may execute a function associated with actuation of the switch 210. For example, if the first apparatus 100 has telephone functionality, the function may relate to making or receiving a telephone call. The switch 210 later may return to the first position. In some embodi merits of the invention, a second enumeration process may take place prior to execution of the function of the associated with the switch 210. This may take place, for example, if data relating to the first enumeration process was lost by the second apparatus 200 when the power on the Vbus line 30 was turned off.

Fig. 5 illustrates a further exemplary embodiment of the invention. The only illustrated difference between the Fig. 5 embodiment of the invention and the Fig. 3 embodiment of the invention is that the second apparatus 200 comprises multiple user actuable devices 210, 215. While Fig. 5 illustrates two user actuable devices 210, 215, the second apparatus 200 may comprise any number of user actuable devices. In illustrated example, the user actuable devices 210, 215 are user actuable switches.

The first switch 210 is connected in series to the second switch 215. The second switch 215 is connected to ground. When both the first switch 210 and the second switch 215 are in their leftmost positions (as shown in Fig. 5), they electrically connect the ID line 40 to ground. If a user actuates either the first switch 210 or the second switch 215, the functional circuitry 240 is connected to ground and ID line's connection to ground is broken. Consequently, a user may actuate either of the switches 210, 215 to change the impedance provided on the ID line 40 by the second apparatus 200. A change in the impedance provided on the ID line 40 may cause the first apparatus 100 to supply power to the second apparatus 200, as described above in relation to Figs 3 and 4.

Each of the switches 210, 215 may be resiliently biased, so that their natural positions (in the absence of user applied force) are the leftmost positions as shown in Fig. 5. The exemplary embodi merits of the invention provide a method of signaling a first apparatus 100 to supply power to a second apparatus 200 without requiring the second apparatus 200 to have its own source of power. This means that the first apparatus 100 need only supply power to the second apparatus 200 if and when it is needed by the second apparatus 200.

The blocks illustrated in Fig 4 may represent steps in a method and/or sections of code in the computer program. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, while embodiments of the invention have been explained in the context of USB in relation to Fig. 3 and 5, those skilled in the art will appreciate that embodiments of the invention are equally applicable to other standards and protocols.

In Figs. 3 and 5, the second apparatus 200 is illustrated as comprising a first resistor 230 connected to the ID line 40 and a transistor 220 connected to the Vbus line 30 via a second resistor 250. However, in other embodiments of the invention, the first resistor 230, the second resistor 250 and the transistor 220 may not be present. In the embodiments of the invention described above, the "second impedance" is roughly equal to the resistance of the first resistor 230. In embodiments of the invention not including the first resistor 230, the "second impedance" may, for example, be equal to an open circuit.

In the embodiments of the invention described above, the second resistor 250 and the transistor 220 are used to return the input impedance of the ID pin 260 to the first impedance (of roughly zero) when power is supplied on the Vbus line 30. In the embodiments of the invention where the transistor 220 and the resistor 250 are not present, restoration of an actuated switch 210, 215 to its leftmost position (its natural position) returns the input impedance of the ID pin 260 to the first impedance.

However, a technical effect of including the transistor 220 may be that a user actuable switch 210, 215 need not be used to return the input impedance of the ID pin 260 to the first impedance. This means that a user actuable switch 210, 215 may remain in its rightmost position for a period of time that is long enough for power to be supplied to the functional circuitry 240 and for the functional circuitry 240 to recognize that a user actuable switch 210, 215 has been actuated, enabling the functional circuitry 240 to execute a function associated with the actuated switch 210, 215.

A further technical effect of including the transistor 220 may be that when power is being supplied to the functional circuitry 240 by the first apparatus 100, actuation of the switches 210, 215 does not cause a change in the impedance provided to the first apparatus 100 on the ID line 40. This means that, in this situation, user actuation of the switches 210, 215 need not cause an interrupt to be provided to the monitoring circuitry 130 which requires interpretation.

In the embodiments of the invention described above, the first apparatus 100 supplies power to the second apparatus 200, in response to the detecting a change in input impedance at the second apparatus 200. Alternatively or additionally, the first apparatus 100 may be configured to perform one or more other functions in response to detecting the change in input impedance at the second apparatus 200. The function(s) performed may depend upon the functionality provided by the first apparatus 100 and the current state of the first apparatus 100. For example, if the first apparatus 100 is configured to function as a telephone, the function performed in response to detecting the change in impedance may be answering an incoming telephone call. If the first apparatus 100 is configured to function as a music player, the performed function may relate to music playback.

A technical effect of using a change in input impedance at the second apparatus 200 as a prompt to perform a function at the first apparatus 100 may be that it is not necessary to wait for power to be provided to the functional circuitry 240 in order to initiate performance of the function. This may result in a better user experience.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

I/we claim:

Claims

1. An apparatus, comprising: power supply circuitry configured to supply power to a further apparatus; monitoring circuitry configured to monitor an input impedance at the further apparatus, and configured, in response to a change in the input impedance at the further apparatus being detected by the monitoring circuitry, to control the power supply circuitry to supply power to the further apparatus.

2. An apparatus as claimed in claim 1 , wherein the monitoring circuitry is configured, after controlling the power supply circuitry to supply power to the further apparatus, to continue to monitor the input impedance at the further apparatus for a further change in the input impedance.

3. An apparatus as claimed in claim 2, wherein the change in the input impedance is from a first impedance to a second impedance, and the further change in the input impedance is from the second impedance to the first impedance, and the monitoring circuitry is configured, in response to the further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to continue supplying power to the further apparatus.

4. An apparatus as claimed in claim 2, wherein the change in the input impedance is from a first impedance to a second impedance, and the further change in the input impedance is from the second impedance to a third impedance, and the monitoring circuitry is configured, in response to the further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to cease supplying power to the further apparatus.

5. An apparatus as claimed in claim 2 or 3, wherein the monitoring circuitry is configured, in the absence of a further change in the input impedance being detected by the monitoring circuitry, to control the power supply circuitry to cease supplying power to the further apparatus.

6. An apparatus as claimed in any of the preceding claims, wherein the monitoring circuitry is configured to monitor the input impedance at the further apparatus by monitoring an input impedance at one of a plurality of pins of a connector of the further apparatus.

7. An apparatus as claimed in claim 6, wherein the connector is a universal serial bus connector and the monitoring circuit is configured to monitor an identification pin of the connector.

8. A method, comprising: monitoring an input impedance at an apparatus; detecting a change in the input impedance at the apparatus; and supplying, in response to detecting the change in input impedance, power to the apparatus.

9. A method as claimed in claim 8, further comprising: continuing to monitor the input impedance at the apparatus, after supplying power to the apparatus, for a further change in the input impedance.

10. A method as claimed in claim 9, wherein the change in the input impedance is from a first impedance to a second impedance, the further change in the input impedance is from the second impedance to the first impedance, and the method further comprises continuing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

11. A method as claimed in claim 9, wherein the change in the input impedance is from a first impedance to a second impedance, the further change in the input impedance is from the second impedance to a third impedance, and the method further comprises ceasing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

12. A method as claimed in claim 9 or 10, further comprising: ceasing to supply power to the apparatus if a further change in the input impedance at the apparatus is not detected.

13. A method as claimed in any of claims 8 to 12, wherein the input impedance at the apparatus is monitored by monitoring the input impedance at one of a plurality of pins of a connector of the apparatus.

14. A method as claimed in claim 13, wherein the connector is a universal serial bus connector and the input impedance at an identification pin of the connector is monitored.

15. A computer program comprising instructions which, when executed by a processor, enable: monitoring an input impedance at an apparatus; detecting a change in the input impedance at the apparatus; and supplying, in response to detecting the change in input impedance, power to the apparatus.

16. A computer program as claimed in claim 15, wherein the instructions further enable: continuing to monitor the input impedance at the apparatus, after supplying power to the apparatus, for a further change in the input impedance.

17. A computer program as claimed in claim 16, wherein the change in the input impedance is from a first impedance to a second impedance, the further change in the input impedance is from the second impedance to the first impedance, and the instructions further enable: continuing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

18. A computer program as claimed in claim 16, wherein the change in the input impedance is from a first impedance to a second impedance, the further change in the input impedance is from the second impedance to a third impedance, and the instructions further enable: ceasing to supply power to the apparatus if the further change in the input impedance at the apparatus is detected.

19. A computer program as claimed in claim 16 or 17, wherein the instructions further enable: ceasing to supply power to the apparatus if the further change in the input impedance at the apparatus is not detected.

20. A tangible computer-readable medium storing the computer program as claimed in any of claims 15 to 19.

21. An apparatus, comprising: power supply means for supplying power to a further apparatus; monitoring means for monitoring an input impedance at the further apparatus, and for controlling, in response to detecting a change in the input impedance at the further apparatus being detected by the monitoring means, the power supply means to supply power to the further apparatus.

22. An apparatus as claimed in claim 21 , wherein the monitoring means is for continuing to monitor the input impedance at the further apparatus, after controlling the power supply circuitry to supply power to the further apparatus, for a further change in the input impedance.

23. An apparatus, comprising: an unpowered circuitry arrangement comprising at least one user input device configured to enable a user to change, by actuating the at least one user input device, the unpowered circuitry arrangement from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry arrangement is configured to provide a first impedance to another apparatus and, in the second state, the unpowered circuitry arrangement is configured to provide a second impedance to the another apparatus, the second impedance signaling the another apparatus to supply power to the apparatus.

24. An apparatus claimed in claim 23, further comprising a connector configured to electrically connect the apparatus to the another apparatus, and wherein the unpowered circuitry arrangement is configured to provide the first and second impedances at the connector.

25. An apparatus as claimed in claim 23 or 24, wherein the unpowered circuitry arrangement is configured, following user actuation of the at least one user input device, to automatically return the unpowered circuitry arrangement to the first state.

26. An apparatus as claimed in claim 25, wherein the unpowered circuitry arrangement comprises a switch electrically coupled to a power supply line, and the switch is configured, in response to power being supplied on the power supply line by the another apparatus, to automatically return the unpowered circuitry arrangement to the first state.

27. An apparatus as claimed in claim 25 or 26, wherein the at least one user input device comprises a resiliently biased switch that is configured, following user actuation, to automatically return the unpowered circuitry arrangement to the first state.

28. A method, comprising: enabling a user to change, by actuating at least one user input device, an unpowered circuitry arrangement from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry arrangement provides a first impedance to an apparatus and, in the second state, the unpowered circuitry arrangement provides a second impedance to the apparatus, the second impedance signaling the apparatus to supply power to the circuitry arrangement.

29. A method as claimed in claim 28, wherein following user actuation of the at least one user input device, the unpowered circuitry arrangement automatically returns the unpowered circuitry arrangement to the first state.

30. A method as claimed in claim 29, wherein the unpowered circuitry arrangement comprises a switch electrically coupled to a power supply line, and in response to power being supplied on the power supply line by the apparatus, the switch automatically returns the unpowered circuitry arrangement to the first state.

31. A method as claimed in claim 29 or 30, wherein the at least one user input device comprises a resiliently biased switch that, following user actuation of the at least one user input device, automatically returns the unpowered circuitry arrangement to the first state.

32. An apparatus, comprising: unpowered circuitry means comprising at least one user input means for enabling a user to change, by actuating the at least one user input means, the unpowered circuitry means from being in a first state to being in a second state, wherein, in the first state, the unpowered circuitry means provides a first impedance to another apparatus and, in the second state, the unpowered circuitry means provides a second impedance to the another apparatus, the second impedance signaling the another apparatus to supply power to the apparatus.

33. An apparatus as claimed in claim 32, wherein the unpowered circuitry means is for automatically returning the unpowered circuitry means to the first state, following user actuation of the at least one user input device.