GB2480850A - A battery bypass arrangement for a portable headphone amplifier - Google Patents
A battery bypass arrangement for a portable headphone amplifier Download PDFInfo
- Publication number
- GB2480850A GB2480850A GB1009314A GB201009314A GB2480850A GB 2480850 A GB2480850 A GB 2480850A GB 1009314 A GB1009314 A GB 1009314A GB 201009314 A GB201009314 A GB 201009314A GB 2480850 A GB2480850 A GB 2480850A
- Authority
- GB
- United Kingdom
- Prior art keywords
- amplifier
- power source
- external power
- power
- voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000005236 sound signal Effects 0.000 claims description 7
- 230000003750 conditioning effect Effects 0.000 abstract description 3
- 230000003321 amplification Effects 0.000 description 12
- 238000003199 nucleic acid amplification method Methods 0.000 description 12
- 230000008901 benefit Effects 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/181—Low-frequency amplifiers, e.g. audio preamplifiers
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
- H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
- H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
- H03F1/0211—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers with control of the supply voltage or current
- H03F1/0244—Stepped control
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/03—Indexing scheme relating to amplifiers the amplifier being designed for audio applications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/507—A switch being used for switching on or off a supply or supplying circuit in an IC-block amplifier circuit
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F2200/00—Indexing scheme relating to amplifiers
- H03F2200/511—Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Multimedia (AREA)
- Amplifiers (AREA)
Abstract
When a standalone portable headphone amplifier 10 for use with a portable audio source is connected to a USB power socket 60, the voltage available from the USB supply, which is higher than the battery voltage 50, can be fed directly to the amplifier power supply circuit 80 to improve available output audio power and linearity. The supply source for the amplifier may be selected 70 by a user. Alternatively, the USB voltage may be selected automatically upon connection of the USB power source. To reduce charging time, no power may be drawn from the battery 50 while it is being recharged. The optional power conditioning circuit 80 may step-up the voltage supplied to the amplifier 20 by use of a boost converter and/or a voltage inverter. The technique may be applied also to portable devices having an internal audio source.
Description
TITLE: PORTABLE AUDIO DEVICE
DESCRIPTION
The present invention relates to the field of portable audio devices, and particularly but not exclusively to the field of rechargeable portable headphone amplifiers.
Rechargeable portable headphone amplifiers for use with portable audio sources (e.g. portable media players such as mp3 or mp4 players or any other portable electronic device capable of providing an audio signal) are well known in the art. Typically, such rechargeable portable headphone amplifiers are used to improve sound quality by amplifying audio signals produced by low-quality internal amplification included in a portable audio source in order to more accurately drive a pair of headphones. A rechargeable portable headphone amplifier is typically connected to a portable audio source via a headphone connector (e.g. 3.5 mm headphone jack) or "line out" connector provided in the portable audio source. Recharging of the portable headphone amplifier is typically achieved by connecting the amplifier to an external power supply via a USB connection or AC mains adapter.
Despite the advantages provided by portable headphone amplifiers developed to date, the present applicant has identified the need for an improved portable headphone amplifier for providing enhanced driving of headphones.
Tn accordance with the present invention, there is provided a portable audio device comprising: an amplifier for amplifying an audio signal received from a source; a headphone connector for connecting a set of headphones to the amplifier; and a power supply comprising: an internal battery power source for powering the amplifier; an external power source connector; and a selector for selectively connecting the amplifier to the external power source connector; wherein the power supply is configured to direct a higher supply voltage to the amplifier when the amplifier is selectively connected to the external power source connector than when the amplifier is not selectively connected to the external power source connector.
In this way, a portable audio device may be provided which is configured to provide a relatively low voltage power supply to the amplifier when powered by the internal battery power source and a relatively high voltage power supply to the amplifier when connected to a relatively high power external supply. Advantageously, this allows the device to provide even higher quality amplification whilst an external power supply is available (e.g. at a user's home or office) thereby allowing high-performance, high-impedance headphones to be driven more effectively than would otherwise be possible with a conventional re-chargeable portable headphone amplifier of limited voltage.
In contrast to the present invention, the normal convention in portable headphone amplifiers fitted with a rechargeable battery is to power the amplifier from the battery even when connected to an external relatively high voltage power supply. However, since battery voltage ultimately limits the amount the output of an amplifier can "swing" in response to a received audio signal and the output power of an amplifier is a function of the square of the output voltage, any steps that increase the voltage supply to an amplifier has been found to significantly improve output power and performance even for a small change in supply voltage. Furthermore, given that amplifiers become less linear as the output approaches the supply rails, another benefit of extra voltage headroom is that distortion performance can be farther improved. This is of particular significance when driving high impedance headphones which require a larger voltage swing in order to be driven at the same power output level as lower impedance headphones.
In one embodiment, the internal battery power source comprises a rechargeable battery and charger; and the power supply is configured to direct at least a component of power from the external power source connector to the amplifier without passing through the charger.
Since the power source voltage used to charge a rechargeable battery is generally higher than the working voltage of the rechargeable battery in order to ensure that the battery is charged correctly, direct connection of the amplifier to the external power source (i.e. bypassing the charger) allows a higher supply voltage to be directed to the amplifier than the supply voltage provided to the amplifier by the rechargeable battery.
In one embodiment, the power supply is configured to direct a component of power from the external power source connector to the charger for recharging the rechargeable battery in parallel to directing power to the amplifier. In this way, the rechargeable battery may be recharged whilst the device is operated using the external power supply.
Furthermore, in one embodiment the power supply may be configured so that no power is transferred from the rechargeable battery to the amplifier whilst the rechargeable battery is being charged (e.g. no power is transferred from the rechargeable battery to the amplifier whilst the amplifier is selectively connected to the external power source connector).
Advantageously, such a configuration may reduce recharging time when compared to prior art devices since use of the amplifier during charging will not drain the battery.
The selector may comprise a user-operated selector control (e.g. a switch) for allowing a user to manually connect the amplifier to the external power source connector. In another embodiment, the selector may automatically connect the amplifier to the external power source connector upon connection of the external power source connector to an external power source. For example, the selector may comprise a relay configured to switch the amplifier power source to receive an external power source when the relay is energised (e.g. with power for the relay being provided by the external power source so that the internal battery power source is not unnecessarily drained).
In one embodiment, the power supply further comprises means for increasing the voltage supplied to the amplifier. For example, the means for increasing the voltage may comprise a step-up (or boost) converter and or a voltage inverter. In one embodiment, the means for increasing the voltage is provided between the selector and the amplifier. In this way. the voltage increase provided by the external power supply may be maximised to allow significantly increased voltage swing to assist driving high impedance headphones.
In one embodiment, the device is a standalone portable headphone amplifier.
However, it is conceivable that the device may include an internal audio source for supplying an audio signal to the amplifier.
An embodiment of the invention will now be described by way of example with reference to the accompanying Figure 1 which shows a block diagram of a portable headphone amplifier embodying the present invention.
Figure 1 shows a portable headphone amplifier 10 comprising: an amplification circuit 20 for amplifying an audio signal received from a source (not shown); a headphone connector 30 for connecting a set of headphones (again not shown) to amplification circuit 20; and a power supply 40. Power supply 40 comprising: an internal battery power source 50 including a 3.6V lithium-ion rechargeable battery 52 for powering amplification circuit 20 and a battery charging circuit 54; an USB power socket 60 for connecting headphone amplifier 10 to a standard USB 5V external power supply; a power source selector switch 70 for selectively connecting the amplification circuit 20 to USB power socket 60; and a power conditioning circuit 80 including a step-up converter.
When power source selector switch 70 is manually set by a user to a first "battery operated" (or internal power) position, portable headphone amplifier 10 operates in battery-powered mode with amplification circuit 20 being powered exclusively by rechargeable battery 52. The battery voltage is around 4.2V maximum when fully charged and will decrease as the battery discharges. This ultimately limits the amount the output of amplification circuit 20 can "swing" resulting in limited volume andlor potentially limited output quality.
When power source selector switch 70 is manually set by a user to a second "external power" position and USB power socket 60 is connected to an external USB power source (e.g. USB port in a desktop computer or laptop or a 5.2V USB mains adaptor), portable headphone amplifier 10 operates in a high voltage mode with amplification circuit 20 being powered exclusively by a component of power provided by the external USB power source via USB power socket 60 with a connection being fomied between USB power socket 60 and amplification circuit 20 bypassing battery charging circuit 54. At the same time, a component of power provided by the external USB power source is directed to recharger 54 to charge battery 52.
Power conditioning circuit 80 (which effectively doubles the voltage supplied to the amplification circuit 20 in both modes of operation) acts to accentuate the voltage increase provided in the external powered mode of operation. Assuming: Power = Vrms2/Rload; and Vrms (sine wave) = Vpeak/v2 and assuming amplification circuit 20 comfortably provides a 3V sinusoidal peak voltage at its output for full power low distortion operation, Vmis=2.l2V;and the power dissipation (output) into a resistive 300 ohm load impedance will be 15mW.
Given that the output power is a function of the square of the output voltage, if an increase in output power is required the most effective way to do this is to increase the output voltage. The load impedance is determined by the headphones which typically having an impedance range from 32 ohms to 300 ohms (or even higher for high-performance headphones).
For a S.2V close tolerance USB power adapter of the type commonly available, then a lv increase in supply voltage translates into a 4V peak voltage which means that the output power increases by up to 27mW (equivalent to an approximate 80% increase in output power).
Advantageously, portable headphone amplifier 10 has been found to provide significantly increased output power, improved headroom allowing more output swing before the onset of output device non-linearity and eventual clipping distortion, and potentially reduced battery charging time since charging is not extended by amplifier operation during charging.
Claims (8)
- Claims: 1. A portable audio device comprising: an amplifier fbr ampli1E'ing an audio signal received from a source; a headphone connector for connecting a set of headphones to the amplifier; and a power suppiy comprising: an internal battery power source for powering the amplifier; an external power source connector; and a selector for selectively connecting the amplifier to the external power source connector; wherein the power supply is configured to direct a higher supply voltage to the amplifier when the amplifier is selectively connected to the external power source connector than when the amplifier is not selectively connected to the external power source connector.
- 2. A portable audio device according to claim 1, wherein: the internal battery power source comprises a rechargeable battery and charger; and the power supply is configured to direct at least a component of power from the external power source connector to the amplifier without passing through the charger.
- 3. A portable audio device according to claim 2, wherein the power supply is configured to direct a component of power from the external power source connector to the charger for recharging the rechargeable battery in parallel to directing power to the amplifier.
- 4, A portable audio device according to claim 3, wherein the power supply is configured so that no power is transferred from the rechargeable battery to the amplifier whilst the rechargeable battery is being charged.
- 5, A portable audio device according to any of the preceding claims, wherein the selector comprises a useroperated selector control for allowing a user to manually connect the amplifier to the external power source connector.
- 6. A portable audio device according to any of claims 1-4, wherein the selector is configured to automatically connect the amplifier to the external power source connector upon connection of the external power source connector to an external power source.
- 7. A portable audio device according to any of the preceding claims, wherein the power supply thrther comprises means fhr increasing the voltage supplied to the amplifier.
- 8. A portable audio device according to any of the preceding claims, wherein the device is a standalone portable headphone amplifier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1009314A GB2480850A (en) | 2010-06-03 | 2010-06-03 | A battery bypass arrangement for a portable headphone amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1009314A GB2480850A (en) | 2010-06-03 | 2010-06-03 | A battery bypass arrangement for a portable headphone amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB201009314D0 GB201009314D0 (en) | 2010-07-21 |
| GB2480850A true GB2480850A (en) | 2011-12-07 |
Family
ID=42471114
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1009314A Withdrawn GB2480850A (en) | 2010-06-03 | 2010-06-03 | A battery bypass arrangement for a portable headphone amplifier |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2480850A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102543151A (en) * | 2011-12-21 | 2012-07-04 | 边仿 | MP3 player with headphone amplifier card capable of being replaced |
| US9231543B2 (en) | 2014-01-13 | 2016-01-05 | Apple Inc. | Audio power amplification with reduced input power supply crest factor |
| CN106535022A (en) * | 2016-12-07 | 2017-03-22 | 北京工业大学 | Earphone noise reduction circuit with balancer and power amplification function |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03150909A (en) * | 1989-11-07 | 1991-06-27 | Matsushita Electric Ind Co Ltd | Low frequency amplifier circuit |
| US5834977A (en) * | 1995-10-31 | 1998-11-10 | Sanyo Electric Co., Ltd. | Amplifying circuit with power supply switching circuit |
| US20060280314A1 (en) * | 2005-03-16 | 2006-12-14 | Taiyo Yuden Co., Ltd. | Digital amplifier and switching power supply |
| US20090180638A1 (en) * | 2008-01-11 | 2009-07-16 | David Hsu | Method and system for wireless headset instant on capability during battery charging |
-
2010
- 2010-06-03 GB GB1009314A patent/GB2480850A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03150909A (en) * | 1989-11-07 | 1991-06-27 | Matsushita Electric Ind Co Ltd | Low frequency amplifier circuit |
| US5834977A (en) * | 1995-10-31 | 1998-11-10 | Sanyo Electric Co., Ltd. | Amplifying circuit with power supply switching circuit |
| US20060280314A1 (en) * | 2005-03-16 | 2006-12-14 | Taiyo Yuden Co., Ltd. | Digital amplifier and switching power supply |
| US20090180638A1 (en) * | 2008-01-11 | 2009-07-16 | David Hsu | Method and system for wireless headset instant on capability during battery charging |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102543151A (en) * | 2011-12-21 | 2012-07-04 | 边仿 | MP3 player with headphone amplifier card capable of being replaced |
| US9231543B2 (en) | 2014-01-13 | 2016-01-05 | Apple Inc. | Audio power amplification with reduced input power supply crest factor |
| CN106535022A (en) * | 2016-12-07 | 2017-03-22 | 北京工业大学 | Earphone noise reduction circuit with balancer and power amplification function |
Also Published As
| Publication number | Publication date |
|---|---|
| GB201009314D0 (en) | 2010-07-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |