WO2008026162A2

WO2008026162A2 - Audio system and method for managing power

Info

Publication number: WO2008026162A2
Application number: PCT/IB2007/053455
Authority: WO
Inventors: Lambertus F. M. De Koning; Dirk W. J. Groeneveld
Original assignee: Nxp B.V.
Priority date: 2006-08-30
Filing date: 2007-08-28
Publication date: 2008-03-06
Also published as: WO2008026162A3

Abstract

An audio system monitors the presence/absence of a headphone that can be connected to a portable audio player device and controls the on and off state of the device. It is logical to switch on the audio player device when the headphone is inserted in the headphone jack. The design results in minimal power consumption, because the audio player device remains in a power-off condition as long as no headphone is present. As soon as a headphone is inserted into the audio player device, the device switches to a power-on state. This makes the audio player device easy to use.

Description

AUDIO SYSTEM AND METHOD FOR MANAGING POWER

FIELD OF THE INVENTION

The invention relates to an audio system comprising an audio player device, a headphone, and a headphone connector for connecting the headphone to the audio player device, wherein the headphone connector is arranged to be removably inserted into the audio player device. The invention also relates to a method for managing power in such an audio system.

BACKGROUND OF THE INVENTION

Mobile audio players, such as MP3 players and mobile phones, have become very popular. There are many flavors and types of mobile audio player devices. For example, the Apple iPod player is nowadays very popular.

US2003/0187654 discloses an example of a mobile audio player. Music files are downloaded to a card-type hard disk using a personal computer in which a dedicated application program is installed. A battery operated hand-held mobile audio player, to which the hard disk card is removably inserted, reproduces the music file to play music. There are many other types of mobile audio players. Nowadays mobile phones are often equipped with the functionality of an audio player, for example the Apple iTunes application running on Motorola mobile phones.

An important factor in the design of mobile audio players is the power consumption of the devices. The battery life and the time in which uninterrupted listening is possible heavily depend on the power consumption of the audio players. It is important to create smart designs with regard to power management. However, mobile audio players often consume too much power.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an audio system of the kind set forth, which is easy to use and which has a relatively low power consumption. This object is achieved by the audio system according to claim 1. It is another object to provide a method for managing power in an audio system of the kind set forth, resulting in an audio system which is easy to use and which has a relatively low power consumption. This object is achieved by the method according to claim 7. The audio system according to the invention monitors the presence/absence of a headphone that can be connected to a portable audio player device and controls the on and off state of the device. It is logical to switch on the audio player device when the headphone is inserted in the headphone jack. The design results in minimal power consumption, because the audio player device remains in a power-off condition as long as no headphone is present. As soon as a headphone is inserted into the audio player device, the device switches to a power-on state. This makes the audio player device easy to use.

In an embodiment of the invention, the audio system further comprises a headphone presence measurement unit (HP detection) being arranged to detect the presence of the headphone connector. In a further embodiment of the invention, the audio system further comprises a state control unit (control) connected to the headphone presence measurement unit (HP detection), the state control unit being arranged to switch the audio player device into the power-on condition in response to a wake-up signal (wake-up) from the headphone presence measurement unit. In yet a further embodiment of the invention, the state control unit (control) is arranged to switch the audio player device into the power-on condition by controlling a power management unit (PMU) comprised in the audio player device.

In another embodiment of the invention, the headphone presence measurement unit (HP detection) is further arranged to detect the presence of the headphone connector while the audio player device is in the power-on condition.

In yet another embodiment of the invention, the audio player device is further arranged to switch back to the power-off condition when the headphone presence measurement unit (HP detection) detects that the headphone connector is not present.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in more detail with reference to the drawings, in which:

Fig. 1 illustrates an audio system according to the invention; Fig. 2 illustrates a headphone driver according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 illustrates an audio system according to the invention. It depicts the general supply arrangement for a power management unit PMU, which cooperates with a headphone detection part comprised in an audio codec. There is an internal supply from the PMU, which is always available provided that at least a valid supply source (battery, USB, adapter) is present. Next there is an internal control signal that enables the HP detection to autonomously start the PMU and sequentially the other functions. The headphone presence measurement distinguishes two different conditions:

1) In the first condition the headphone amplifier is switched off. Here power consumption is a very important parameter, since this condition can exist virtually forever. The system can be in off mode, which means there is hardly any other power consumption in the system. Any additional current consumption will reduce the off-state battery lifetime. 2) In the second condition the headphone amplifier is active. Audio signals are fed to the headphone. Since the application is now active, the power consumption is less important. The way of presence measurement is different since there are (random) audio signals present.

The headphone presence measurement in the power-off state is performed as follows. A separate circuit part, next to the headphone driver, generates a low amplitude, out of audio band test signal. The signal is fed to a filter section where the headphone impedance takes part in. Now depending on the present impedance (thus the presence of a headphone) the amplitude will be smaller or larger. This is detected by means of a comparator. The signal is repeated with a time interval T_mtitest- The state of presence will only change when 2 consecutive tests show the same result. In this way a debounce time is applied, to stabilize the result. The amplitude and pulse width are chosen such that this causes no audible disturbance.

The headphone presence measurement in the power-on state is performed as follows. The measurement circuit in the on state is implemented as part of the output driver stage for the headphone. A current mirror is situated in parallel to the output stage and will represent a proportional fraction of the current that is delivered to the headphone load. The current from the mirror is compared against the input signal. When no headphone is connected the current from the mirror approaches zero. And when the headphone is connected, the current mirror output follows the input signal. One additional condition has to be taken into account. When there is no audio signal (mute or silent music passages) the detection circuit will conclude that there is no headphone connected. When this occurs for a time longer than T_wait, then an inaudible test signal will be injected to verify the absence of a headphone.

Any state change can be signaled by the hosting microprocessor. This can be done through reading an I²C status and interrupt-registers and/or through monitoring of an interrupt signal. Next to this, there is a dedicated wake-up signal that allows for starting up through the PMU, because in the off mode the microprocessor is in power down mode and cannot receive any interrupt or I²C command. The combination of the headphone detection circuitry with the PMU functionality takes care that the whole system can be started just based on the insertion of the headphone. The headphone detection circuitry can be enabled or disabled from the hosting software, to tune the system performance to the user requirements. Also the interrupt signal can be masked.

The audio system according to the invention monitors the presence/absence of a headphone that can be connected to a portable audio application and controls the on and off state of the application. As the headphone is essential to be connected to the device's usage it is logical to switch on the application when the headphone is inserted in the headphone jack and subsequently switch off the application when it is removed. This gives the user a logical way of switching on and off his mobile audio player. The smart design results in minimal power consumption (long battery playtime). The invention is to be regarded as an interesting feature in mobile audio player applications like MP3 players and mobile phones. It enables the system or functions to be controlled On/Off by only inserting or removing the headphone connector from the application. The presence detection is fully electronic and requires no additional components, neither electronic, nor mechanical. The circuit is integrated into the audio codec chip, which already provides the connections to the headphone. The detection circuit is also active during power-off conditions of the application. An internal connection to the power management unit chip (PMU) makes it possible that the system will be activated when a headphone is inserted. The audio codec and PMU function may be integrated in a single package. The audio codec function is also available as a single function. In that case only two wire connections between a PMU and the codec are required to enable this function.

In short, the advantages of the invention are as follows. It provides a sophisticated way of switching on/off the application. Furthermore, it reduces the battery usage, because the application (or the associated parts) is only active when required. It doesn't need additional components; therefore it has a relatively low cost. The additional power consumption is minimal (~ 15 μW). The insertion status can be read through an interface such as I²C. The status change can be programmed to generate an interrupt signal. Insertion can be programmed to generate a wake-up signal to the PMU to activate the application from the off mode. The circuit does not cause audible sounds in the headphone. It is compatible with both AC and DC connected headphones.

The main application areas are portable music players (MP3, Flash and hard disk based). Secondly, also mobile phones and multimedia players (with movie capabilities) could make use of the invention. The headphone presence information can also be used to switch on/off the associated driver circuits and e.g. the playback function of MP3 decoding or a FM radio receiver.

It is remarked that the scope of protection of the invention is not restricted to the embodiments described herein. Neither is the scope of protection of the invention restricted by the reference symbols in the claims. The word 'comprising' does not exclude other parts than those mentioned in a claim. The word 'a(n)' preceding an element does not exclude a plurality of those elements. Means forming part of the invention may both be implemented in the form of dedicated hardware or in the form of a programmed general- purpose processor. The invention resides in each new feature or combination of features.

Claims

CLAIMS:

1. An audio system comprising: an audio player device; a headphone; a headphone connector for connecting the headphone to the audio player device, wherein the headphone connector is arranged to be removably inserted into the audio player device; characterized in that: when the audio player device is in a power-off condition, the audio player device is arranged to detect the presence of the headphone connector, - and wherein the audio player device is arranged to switch to a power-on condition when the headphone connector is present.

2. An audio system as claimed in claim 1, further comprising a headphone presence measurement unit (HP detection) being arranged to detect the presence of the headphone connector.

3. An audio system as claimed in claim 2, further comprising a state control unit (control) connected to the headphone presence measurement unit (HP detection), the state control unit being arranged to switch the audio player device into the power-on condition in response to a wake-up signal (wake-up) from the headphone presence measurement unit.

4. An audio system as claimed in claim 3, wherein the state control unit (control) is arranged to switch the audio player device into the power-on condition by controlling a power management unit (PMU) comprised in the audio player device.

5. An audio system as claimed in claim 2, 3 or 4, wherein the headphone presence measurement unit (HP detection) is further arranged to detect the presence of the headphone connector while the audio player device is in the power-on condition.

6. An audio system as claimed in claim 5, wherein the audio player device is further arranged to switch back to the power-off condition when the headphone presence measurement unit (HP detection) detects that the headphone connector is not present.

7. A method for managing power in an audio system comprising: - an audio player device; a headphone; a headphone connector for connecting the headphone to the audio player device, wherein the headphone connector is arranged to be removably inserted into the audio player device; characterized in that the method comprises the following steps: detecting the presence of the headphone connector when the audio player device is in a power-off condition; switching to a power-on condition when the headphone connector is present.