FIELD OF THE INVENTION

This application relates to circuitry for detecting at least partial removal and/or insertion of an audio jack plug from or into a corresponding socket and, in particular, to circuitry for detecting disconnection of an accessory device from and/or connection of an accessory device to a connector of an extension cable, splitter or the like that is connected to a connector of a host device.

BACKGROUND

Many electronic devices include a suitable connector for removably connecting an accessory device to the electronic device. For example many electronic devices have a connector to connect audio accessories to the electronic device. Mobile telephones, tablets, laptop computers and the like are examples of electronic devices, also referred to as “host devices”, that are operable with audio accessory devices such as headphones, earphones, earbuds and headsets, for example, that are external to and distinct from the electronic device. Such audio accessories typically comprise mono or stereo speakers for audio playback and some audio accessories may also have a microphone for voice communication.

Such external accessory devices are often connected to the host electronic device via a mating connector arrangement such as a plug and socket. For instance, many audio accessories have a jack plug for connection to a suitable jack socket of the host electronic device. A well-known arrangement for a jack plug and its associated socket is the 3.5 mm 4-pole TRRS (Tip-Ring-Ring-Sleeve) configuration, which has four contacts, one contact for each of left audio, right audio, microphone, and ground.

In many devices it is desirable for the host electronic device to be able to detect when an accessory is connected to and/or disconnected from the host device. Thus commonly the host device may comprise circuitry such as a “jack detect” circuit to allow the host device to determine when a suitable accessory device connector has been connected to the host device (e.g. when a plug of an accessory device has been inserted into a socket of the host device). Various different types of jack detect arrangement are known. For instance, the presence of a suitable jack plug inserted fully into a socket may operate a mechanical switch to complete or disconnect a circuit coupled to a jack detect signal line. Monitoring the jack detect signal line, e.g. by comparing a voltage of the jack detect signal line with a known threshold voltage, gives an indication of whether a jack plug is inserted or not. In other arrangements the jack plug itself may form part of a jack detect circuit when inserted. Upon detection of the presence of a connector (e.g. a plug) of the audio accessory device in the connector (e.g. a socket) of an electronic device, the circuitry of the electronic device will be configured appropriately for operation with the accessory device e.g. to supply audio to the accessory device.

The detection circuitry also provides an indication of when the connector of the accessory device has been disconnected or removed from the connector of the host electronic device. This indication can cause the electronic device to react appropriately e.g. by suspending the generation and output of audio signals, thereby reducing power consumption of the electronic device, since audio output signals are not generated unnecessarily.

Some users may connect an accessory device such as a set of headphones, earphones, earbuds, a headset or the like to a host electronic device via a suitable extension cable. The extension cable may be formed of a suitable 3.5 mm TRRS jack plug at one end, with a corresponding TRRS jack socket at the other end. The plug of an accessory device can be received in the socket of the extension cable.

When an extension cable is used in this way, the jack detection circuitry of the host device will detect that a connector is received in the connector of the host electronic device, even when there is no accessory device connected to the extension cable. Thus audio signals may still be generated and output by the electronic device even when the accessory device is not connected to the connector of the extension cable, which can lead to unnecessary power consumption by the host electronic device.

Similarly, a splitter cable having a single jack plug at one end coupled to two or more parallel jack sockets at the other end may be used to connect two or more accessory devices to a host electronic device. The jack plug of the splitter cable is received in the socket of the host electronic device. Each socket of the splitter cable can receive the plug of a different accessory device.

When a splitter cable is used in this way, the jack detection circuitry of the host device will detect that a connector is received in the connector of the host electronic device, even when there is no accessory device connected to the splitter cable. Thus audio signals may still be generated and output by the electronic device even when no accessory device is connected to a connector of the splitter cable, which can lead to unnecessary power consumption by the host electronic device.

Also, when an extension cable or splitter cable is used in this way, the jack detection circuitry of the host device will not detect that a connector is removed from the far end of the extension or splitter cable (e.g. that a plug of an accessory device has been removed from a socket of the extension cable or splitter cable). Thus, audio signals may still be generated and output by the electronic device even when the accessory device is not connected to the connector of the extension cable or splitter cable, which can lead to unnecessary power consumption by the host electronic device.

Polling of the impedance of signal paths coupled to the left (L) and right (R) contacts of the socket of the host device can be employed in order to determine if such an accessory device is subsequently connected to the connector of the extension cable or splitter cable. Such polling typically involves temporarily connecting a DC voltage source to the relevant socket contact and measuring a parameter (e.g. a current) indicative of the impedance of the signal path. Whilst this approach is acceptable when audio signals are not being output to the connected accessory device, it is not viable when audio signals are being output, as the injection of DC voltages would give rise to unacceptable audio artefacts such as clicks and pops.

There is thus a desire for a way to detect the disconnection of an accessory device from a host electronic device that can be used without degrading audio signals being output to the accessory device, even when the accessory device is connected to the host electronic device via an extension cable or splitter cable.

According to a first aspect the invention provides circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket, comprising:a monitoring unit comprising:a first terminal configured to be electrically connected to a first socket contact of the socket that is in electrical contact with a first plug contact of the plug when the plug is fully received in the socket,wherein the monitoring unit is configured to monitor a first impedance of a first signal path coupled to the first terminal, andwherein the circuitry is configured to output a signal indicative of detection of at least partial removal of the plug from the socket in response to detection by the monitoring unit of a first predetermined sequence of impedance states of the first signal path.

The circuitry may further comprise:a second terminal configured to be electrically connected to a second socket contact of the electrical socket that is in contact with a second plug contact of the electrical plug when the electrical plug is fully received in the socket,wherein the monitoring unit is configured to monitor a second impedance of a second signal path coupled to the first terminal, andwherein the circuitry is configured to output a signal indicative of detection of at least partial removal of the electrical plug from the electrical socket in response to detection by the monitoring unit of a first predetermined sequence of impedance states of the first and second signal paths.

The first predetermined sequence may comprise impedance states corresponding to a first removal state and a second removal state of the plug, for example.

The first removal state may correspond to the electrical plug being fully received in the electrical socket and the second removal state may correspond to a partial removal of the electrical plug from the electrical socket.

The first predetermined sequence may further comprise an impedance state corresponding to a third removal state of the plug.

The third removal state may corresponds to at least partial removal of the jack plug from the socket.

The first predetermined sequence may further comprises an impedance state corresponding to a fourth removal state corresponding to a full removal of the jack plug from the socket.

The signal may be indicative of a full removal of the jack plug from the socket in response to detection by the monitoring unit of the first predetermined sequence of impedance states within a first predetermined time period.

The first predetermined time period may be started upon a detection by the monitoring unit of a trigger.

The trigger may comprise the first impedance state transitioning from a first value to a second value.

The signal may be indicative of a partial removal of the electrical plug from the electrical socket in response to the monitoring unit detecting an impedance state corresponding to one of the removal states of the plug and not detecting impedance states corresponding to all of the removal states of the plug within the first predetermined time period.

The circuitry may further comprise a third terminal configured to be electrically connected to a third socket contact of the electrical socket that is in contact with a third plug contact of the electrical plug when the electrical plug is fully received in the socket and the monitoring unit may be further configured to monitor a third impedance of a third signal path coupled to the third terminal.

The first predetermined sequence of impedance states may further comprise impedance states of the third signal path.

In response to detection by the monitoring unit of the first predetermined sequence of impedance states, the monitoring unit may be further configured to monitor the third impedance to determine whether the at least partial removal of the electrical plug from the electrical socket is a partial removal or a full removal.

The monitoring unit may be configured not to monitor the third impedance during the first removal state and the second removal state.

The circuitry may be configured to output a signal indicative of full removal of the electrical plug from the electrical socket in response to detection by the monitoring unit of a second predetermined sequence of impedance states of the first, second and third signal paths.

The signal may be indicative of full removal of the electrical plug from the electrical socket in response to detection by the monitoring unit of the second predetermined sequence of impedance states within a second predetermined time period.

The signal may be indicative of partial removal of the electrical plug from the electrical socket in response to the monitoring unit not detecting the second predetermined sequence of impedance states within the second predetermined time period.

The first impedance state and the second impedance state may comprise impedance measurements.

The first impedance state and the second impedance state may comprise one of a high impedance state or a low impedance state.

The first predetermined sequence may be determined based on a contact configuration of the jack plug.

The socket may comprise a tip-ring-ring-sleeve (TRRS) socket and the jack plug may comprise a TRRS plug.

Detection by the monitoring unit of the first predetermined sequence is indicative of at least partial removal of one of a plurality of different types of TRRS plugs from the TRRS socket.

The circuitry may further comprise:a detection unit configured to detect a type of TRRS plug received in the TRRS socket;a memory configured to store a plurality of predetermined sequences of impedance states for detecting at least partial removal of a plurality of types of TRRS plugs from the TRRS socket; anda processor configured to select the first predetermined sequence of impedance states from the plurality of predetermined sequences of impedance states based on the type of TRRS plug received in the electrical socket.

The plug may be part of an accessory apparatus and the socket may be part of an extension cable connected to a host device.

Alternatively, the plug may be part of an accessory apparatus and the socket may be part of a splitter cable connected to a host device.

The circuitry may be implemented as an integrated circuit.

According to a second aspect the invention provides an electronic device comprising circuitry according to the first aspect.

According to a third aspect the invention provides a method of detecting at least partial removal of an audio accessory plug from a corresponding socket, comprising:monitoring a first impedance of a first signal path coupled to a first socket contact of the socket that is in electrical contact with a first plug contact of the plug when the plug is fully received in the socket;detecting a first predetermined sequence of impedance states of the signal path indicative of at least partial removal of the plug from the socket; andoutputting a signal indicative of detection of at least partial removal of the plug from the socket in response to detecting the predetermined sequence of impedance states.

According to a fourth aspect the invention provides circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket, comprising:a first terminal configured to be electrically connected to a microphone contact of the socket that is in electrical contact with a microphone contact of the plug when the plug is fully received in the socket;a monitoring unit configured to monitor an impedance state of a signal path coupled to the microphone contact at the first terminal,wherein the circuitry is configured to output a signal indicative of detection of at least partial removal of the plug from the electrical socket in response to detection by the monitoring unit of a predetermined sequence of impedance states of the signal path.

According to a fifth aspect the invention provides circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket, comprising:current mirror circuitry configured to mirror a proportion of a current through a load of the audio accessory when an audio signal is being supplied to the audio accessory to a dummy resistance; andvoltage detection circuitry configured to:detect a voltage across the dummy resistance due to the mirrored current; andoutput a signal indicative of an impedance of the load of the audio accessory based on the detected voltage.

The voltage detection circuitry may comprise a comparator.

The voltage detection circuitry may comprise an analog to digital converter.

According to a sixth aspect the invention provides circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket during output of an audio signal to the audio accessory via the socket, the circuitry comprising:a monitoring unit comprising:a first terminal configured to be electrically connected to a first socket contact of the socket that is in electrical contact with a first plug contact of the plug when the plug is fully received in the socket,wherein the monitoring unit is configured to monitor a first impedance of a first signal path coupled to the first terminal, andwherein the circuitry is configured to output a signal indicative of detection of at least partial removal of the plug from the socket in response to detection by the monitoring unit of a first predetermined sequence of impedance states of the first signal path.

According to a seventh aspect the invention provides circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket during output of an audio signal to the audio accessory via the socket, the circuitry comprising:a first terminal configured to be electrically connected to a microphone contact of the socket that is in electrical contact with a microphone contact of the plug when the plug is fully received in the socket;a monitoring unit configured to monitor an impedance state of a signal path coupled to the microphone contact at the first terminal,wherein the circuitry is configured to output a signal indicative of detection of at least partial removal of the plug from the electrical socket in response to detection by the monitoring unit of a predetermined sequence of impedance states of the signal path.

According to an eighth aspect the invention provides Circuitry for detecting at least partial removal of an audio accessory plug from a corresponding socket during output of an audio signal to the audio accessory via the socket, the circuitry comprising:current mirror circuitry configured to mirror a proportion of a current through a load of the audio accessory when an audio signal is being supplied to the audio accessory to a dummy resistance; andvoltage detection circuitry configured to:detect a voltage across the dummy resistance due to the mirrored current; andoutput a signal indicative of an impedance of the load of the audio accessory based on the detected voltage.

