(12) United States Patent
`(10) Patent N0.:
`US 6,178,514 B1
`
`Wood
`(45) Date of Patent:
`Jan. 23, 2001
`
`U8006178514B1
`
`(54) METHOD AND APPARATUS FOR
`CONNECTING A DEVICE TO A BUS
`CARRYING POWER AND A SIGNAL
`
`(76)
`
`Inventor: Bradley C. Wood, 6738 Independence
`Ave. Apt. 102, Canoga Park, CA (US)
`91303
`
`(*) Notice:
`
`Under 35 U.S.C. 154(b), the term of this
`patent shall be extended for 0 days.
`
`(21) Appl, No.: 09/127,642
`
`1.11.0.7
`(51)
`('52) U.S.Cl.
`
`(22)
`
`Filed:
`
`Jul. 31, 1998
`
`G06F1/26
`
`.. 713/300, 713/340, 713/320,
`710/129
`713/300, 320,
`(58) Field of Search
`713/340, 310, 330, 322—24; 710/126, 129
`
`(56)
`
`References Cited
`U.S. PA'I'EN'I‘ DOCUMENTS
`
`8/1997 Kikinis
`5,655,138 *
`5,675,813 * 10/1997 Holmdahl.
`5,799,196 *
`8/1998 Flanneiy ..
`5,841,268 * 11/1998 Mednik
`
`.. 395/800
`713/300
`713/300
`
`.. 323/222
`
`* cited by examiner
`
`Primary ExaminerflArio Etienne
`
`(57)
`
`ABSTRACT
`
`The object of the invention is to interface a device to a bus
`carrying power and a signal While simultaneously comply—
`ing with bus-standard current draw limits, storing power for
`the device in an energy storage device located in the
`interface apparatus, and conditioning the bus signal as a
`function of the energy level of the signal received by the
`interface device from the bus and the level of energy
`measured in the energy storage device in the interface
`apparatus. As shown in FIG. 29, according to one aspect of
`the invention the interface apparatus (472) includes an input
`filter (480), a current limiter (482), a power converter (483),
`an energy storage device (484), a signal decoder/controller
`(486) and a signal conditioner (488). In operation, power
`flows from the bus through input filter (480) through the
`current limiter (482) to the power converter (483), which
`converts the power to a form suitable for charging the energy
`storage device (484). The output of the energy storage
`device provides power to the device. The bus signal
`is
`received by the signal decoder/controller (486), which per-
`forms any necessary decoding before sending the signal onto
`the signal conditioner (488). Signal decoder/controller (486)
`also is connected to and controls power converter 483.
`Signal conditioner (488) measures the level of energy stored
`in energy storage device (484) then generates and conveys
`to the signal input of the device an output signal that is a
`function of the energy level of the bus signal and the
`measured level of energy in the energy storage device (484).
`23 Claims, 19 Drawing Sheets
`
`
`
` 302
`PRE-READ NEXT SAMPLE OF
`
`
`DlGlTlZED AUDIO SIGNAL (DAS)
`
`
`DETERMINE POWER LEVEL OF DAS
`
`
`
`RECEIVE ENERGY STORAGE
`
`DEVICE (ESD) POWER LEVEL
`
`
`FROM USB SPEAKER CIRCUITRY
`
`
`
`NEW DAS =
` 308
`
`l(Power Level of Old DAS, Power Level of ESD)
`
`/300
`
`304
`
`306
`
`
`
`
` 310
`SEND NEW DAS TO
`
`
`USB SPEAKER CIRCUITRY
`
`
`Huawei V. Exhibit No. 1017 - 1/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 1 0f 19
`
`US 6,178,514 B1
`
`
`
`USBSPKR
`
`50
`
`52
`
`
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`DDFWE w
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`
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`FIG. 2
`
`Huawei V. Exhibit No. 1017 - 2/3 8
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 2 0f 19
`
`US 6,178,514 B1
`
`MASTER _-->1--‘D--
`
`USB DEVICE
`
`GND -_'-_
`“TIE:
`
`Vcc
`
`FIG. 3
`
`
`
`
`SECONDARY HUB
`
`64
`
`PORT1
`
`PORT2 PORTS
`
`
`
`FIG. 4
`
`Huawei V. Exhibit No. 1017 - 3/3 8
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 3 0f 19
`
`US 6,178,514 B1
`
`
`
`USB SPKR
`CIRCUITRY
`
`
`
`AMPLIFIER
`
`21
`
`84
`FIG. 6
`
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`284
`284
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`
`FIG. 19
`
`Huawei V. Exhibit No. 1017 - 4/3 8
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 4 0f 19
`
`US 6,178,514 B1
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`Huawei V. Exhibit No. 1017 - 5/3 8
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`US. Patent
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`Jan.23,2001
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`Huawei V. Exhibit No. 1017 - 6/3 8
`
`
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`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 6 0f 19
`
`US 6,178,514 B1
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`Huawei V. Exhibit No. 1017 - 7/3 8
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`

`

`US. Patent
`
`Jan.23,2001
`
`Shcct7 0f19
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`US 6,178,514 B1
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`Huawei V. Exhibit No. 1017 - 8/3 8
`
`
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`
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`

`

`US. Patent
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`Huawei V. Exhibit No. 1017 - 9/3 8
`
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 9 0f 19
`
`US 6,178,514 B1
`
`DATA/
`
`...01001
`
`DECODER
`
`256
`
`253
`
`READ SIGNAL
`
`LEVEL (SL)
`
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`FIG. 14
`
`
`240
`
`246
`
`250
`
`252
`
`Huawei V. Exhibit No. 1017 - 10/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Shcct10 0f19
`
`US 6,178,514 B1
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`Huawei V. Exhibit No. 1017 - 11/38
`
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`

`

`US. Patent
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`Huawei V. Exhibit No. 1017 - 12/38
`
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 12 0f 19
`
`US 6,178,514 B1
`
`
`
`
`PRE-READ NEXT SAMPLE OF
`DIGITIZED AUDIO SIGNAL (DAS)
`
`
`302
`
`foo
`
`DETERMINE POWER LEVEL OF DAS
`
`304
`
`RECEIVE ENERGY STORAGE
`DEVICE (ESD) POWER LEVEL
`
`
`FROM USB SPEAKER CIRCUITRY
`
`
`
`NEW DAS =
`
`f(Power Level of Old DAS, Power Level of ESD)
`
`
`
`
`
`306
`
`308
`
`
`
`310
`
`SEND NEW DAS TO
`USB SPEAKER CIRCUITRY
`
`DRIVER
`
`USB SPEAKER
`
`
`
`258
`
`OO0
`
`FIG. 18
`
`Huawei V. Exhibit No. 1017 - 13/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 13 0f 19
`
`US 6,178,514 B1
`
`500 \
`
`508
`/
`..010110...
`
`SB SPEAKER /
`
`‘x— 96
`FROM USB
`DECODER/DAC
`
`FIG. 20
`
`ENERGY STORAGE
`
`DEVICE
`
`Huawei V. Exhibit No. 1017 - 14/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 14 0f 19
`
`US 6,178,514 B1
`
`HOT PLUG OR INITIAL POWER ON
`
`
`
`402
`
`
`
`DETERMINE AVAILABLE POWER
`FROM MASTER BUS HUB
`
`404
`
`
`
`
`
`AS LOW POWER DEV.
`
`
`
`/400
`
`CONFIGURE DEVICE
`
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`AS HIGH POWER DEV.
`
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`
`Huawei V. Exhibit No. 1017 - 15/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 15 0f 19
`
`US 6,178,514 B1
`
`HOT PLUG 0R
`INITIAL POWER ON
`
`402
`
`,/401
`
`
`
`416
`
`
`
`
`
`
`SEARCH FOR EXTERNAL
`POWER SUPPLY (EPS)
`
`TO STEP 404
`IN FIG. 22
`
`NO
`
`
`
`TO STEP 404
`IN FIG. 22
`
`FIG. 23
`
`Huawei V. Exhibit No. 1017 - 16/38
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 16 0f 19
`
`US 6,178,514 B1
`
`
` SEND
`COMMAND
`
`
`TO ENTER
`
`
`SUSPEND
`
`
`432
`
`PLACE AMP IN FIRST
`SUSPEND MODE
`
`434
`
`START TIMING
`
`436
`
`Exw
`SUSPEND
`MODE
`
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`YES
`
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`
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`SUSPEND
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`
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`
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`446
`
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`448
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`SUSPEND MODE
`
`449
`
`YES
`
`
`Exn
`SUSPEND
`MODE
`
`
`447
`
`FIG. 24
`
`Huawei V. Exhibit No. 1017 - 17/38
`
`

`

`US. Patent
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`Huawei V. Exhibit No. 1017 - 19/38
`
`
`
`
`

`

`US. Patent
`
`Jan. 23, 2001
`
`Sheet 19 0f 19
`
`US 6,178,514 B1
`
`CONTROLLER
`
`DECODER/
`
`Huawei V. Exhibit No. 1017 - 20/38
`
`

`

`US 6,178,514 B1
`
`1
`METHOD AND APPARATUS FOR
`CONNECTING A DEVICE TO A BUS
`CARRYING POWER AND A SIGNAL
`BACKGROUND
`
`The present invention relates to a method and apparatus
`for connecting a device to a bus carrying power and a signal,
`and more particularly to a method and apparatus for con-
`necting a computer peripheral bus or a consumer electronics
`bus carrying power and a signal to a peripheral device, such
`as a speaker, that is powered in whole or in part by the bus
`and that uses the signal carried by the bus.
`The universal serial bus (“USB”) holds great promise for
`improving the ease with which computer peripherals, such
`as keyboards and speakers, can be attached to personal
`computers. The USB standard is specified in a series of
`documents available via the World Wide Web at
`http:\\www.usb.org.
`One important aspect of the USB standard is management
`of devices that draw power from the USB. The USB
`standard defines two types of devices, low power devices
`that draw 100 onf bus current and high power devices that
`draw 500 mA or less of the bus current.
`
`The USB standard supports attaching to a USB both
`devices that draw power from the USB and devices that are
`powered by other, external, sources of power such as bat-
`teries or line voltage transformers.
`The importance of power management and the relatively
`low power drain supported by the USB standard has led to
`two separate approaches for USB devices that may draw
`more than the permitted power. One is to create a “powered”
`hub that draws power from an external source to support
`more peripheral devices that the USB can power alone. The
`other is to provide an external power supply for the particu-
`lar USB device.
`
`While it is generally adequate to use powered hubs (with
`their external power supplies) with other USB peripheral
`devices (with their external power supplies), the need for
`external power supplies makes the connecting and the
`operating the devices more complex than if the device were
`powered from the USB alone. Moreover, with external
`power supplies such as batteries or wall transformers, there
`is the disadvantage of loss of power to the peripheral due to
`the battery draining or the wall transformer becoming dis—
`lodged from the wall. W'all
`transformers are also often
`unattractive (hence the nickname “wall wart”) and have
`cords that can become entangled. Batteries can be expensive
`to replace. Batteries can also be hassles to change.
`All of these disadvantages of external powered computer
`peripheral devices are particularly acute for users of speak-
`ers. Speaker users are particularly sensitized to issues of
`speaker performance and ease of operation. Speakers typi—
`cally operate in pairs (to provide for the option of stereo
`sound), so a speaker “problem” is usually a double problem.
`Computer speakers may be embedded in another computer
`peripheral (such as a desk top keyboard or monitor), in
`which case they are generally not usable with other
`computers, and may still require the use of external power
`supplies and additional cabling for operation with the ini-
`tially intended computer. Computer speakers may be
`attached to a personal computer via cables to allow wider
`separation for optimum stereo separation, in which case an
`extra cable for the wall transformer is an unwelcome com-
`plication.
`One great appeal of USB peripherals, such as USB
`speakers, stems from their “Plug and Play” installation and
`
`2
`their operational behavior. With Plug and Play, installing
`new peripherals does not require disassembly of the coni—
`puter case to install special cards or change jumper/switch
`settings of existing cards and does not require knowledge of
`interrupt request and DMA settings. The new peripheral
`identifies itself upon interrogation by the host computer
`system. The USB protocols, correctly implemented, assure
`absence of device conflicts.
`It is therefore unfortunate that existing implementations
`of USB speakers and many other USB peripheral devices
`require the devices to be “self-powered” (i.e., not powered
`by the USB) due to the limited power available from USB
`ports. Self powered USB devices, by definition, have the
`added complication of batteries or transformers or other
`means of supplying external power to their associated USB
`device. Yet most of these self—powered USB devices do not
`require average power in excess of the continuous power
`available from low-power or high-power USB ports. In
`particular, while speakers reproducing music,
`typical
`speech, or game sound effects require large peak powers,
`they require far less average power, even if their power
`requirements are averaged over a time scale of the order of
`a few tenths of a second. Other peripheral devices with
`similar power demand characteristics include printers, infra-
`red data links, scanners and other devices in which electro—
`mechanical or electro—optical
`transduction is, or can be,
`discontinuous and of a low duty cycle.
`There is therefore a need for a device that provides a high
`intermittent peak power output while simultaneously limit-
`ing its current input to an amount at or below the maximum
`current
`input allowed by the USB standard or by the
`standard of any other bus (such as other serial buses, like the
`serial bus defined by IEEE—1394, or parallel buses, like the
`Small Computer Systems Interface or SCSI bus).
`SUMMARY OF THE INVENTION
`
`The present invention relates to an apparatus and method
`for interfacing a bus to a device. The bus includes a power
`line carrying power and a signal line carrying a signal. The
`device including a power input and a signal input. The
`interface includes a power output connected to the device
`power input; a power input connected to the bus power line;
`a signal input connected to the bus signal line; a signal
`output connected to the device signal
`input; an energy
`storage device having an input and an output, the energy
`storage device output connected to the interface apparatus
`power output; and a power converter having a power input
`connected to the interface apparatus power input and a
`power output connected to the energy storage device input,
`whereby the power converter receives power from the bus
`power line and converts it to a form suitable for charging the
`energy storage device. The power converter further includes
`a current sensor and a current limiter. The current sensor is
`connected in series with the power converter power input
`and output and has an output carrying a signal representative
`of the current flowing through the current sensor. The
`current limiter has a predetermined current
`limit and is
`operably connected to the power converter power input and
`power output. The current limiter also has an input con-
`nected to the current sensor output for receiving the current
`sensor signal representative of the current flowing through
`the current sensor, whereby the current limiter limits the
`current drawn by the device and the interface apparatus to
`the predetermined current limit. The interface also includes
`a signal conditioner that has a first input connected to the
`energy storage device output, a second input connected to
`interface apparatus signal input or the interface apparatus
`
`m
`
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`
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`
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`
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`
`Huawei V. Exhibit No. 1017 - 21/38
`
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`signal output, and an output connected to the interface
`apparatus signal output. The signal conditioner includes a
`transfer function that produces a signal conditioner output
`signal at the signal conditioner output. This transfer function
`is a function of the level of energy in the energy storage
`device and the level of energy of the bus signal or the signal
`conditioner output signal.
`the power
`In another aspect of the present invention,
`converter further includes a linear current device, a buck
`converter, a boost converter or a flyback converter con—
`nected to the power converter power input and to the energy
`storage device input, whereby the device or the converter
`converts power from the bus power line into a form suitable
`for charging the energy storage device.
`In yet another aspect of the present invention, the energy
`storage device includes a capacitor connected between the
`energy storage device input and output.
`In another aspect of the present invention, the energy
`storage device includes a first capacitor; a second capacitor;
`a first switch having an open and a closed position; and an
`energy storage device controller. The energy storage device
`input further includes a first line and a second line. The first
`and second lines are capable of being at different voltage
`potentials with respect to each other. The first capacitor is
`connected across the first and second energy storage device
`lines. The second capacitor is connected in series with the
`first switch, and the series combination of the first switch
`and the second capacitor is connected across the first and
`second energy storage lines and in parallel with the first
`capacitor. When the first switch is closed the first and second
`capacitors are connected in parallel across the energy stor-
`age device input and when the first switch is open only the
`first capacitor is connected across the energy storage device
`input.
`the energy storage
`In another aspect of the invention,
`device has a predetermined maximum energy storage level
`and the signal conditioner further includes a voltage con-
`trolled amplifier, first low pass filter network and a clip and
`detect limiter. The voltage controlled amplifier has a signal
`input connected to the interface apparatus signal input, a
`signal output connected to the signal conditioner signal
`output, and a control input. The voltage control amplifier
`amplifies the interface apparatus signal input to produce the
`signal conditioner signal output by an amount of arnplifica—
`lion controlled by the voltage controlled amplifier control
`input. The first low pass filter network has a predetermined
`filter characteristic, a signal
`input, and a signal output
`connected to the voltage controlled amplifier control input.
`The clip and detect limiter includes a voltage sealer and a
`comparator. The voltage sealer has a predetermined scaling
`factor and has an input and an output, The voltage scaler
`input is connected to the energy storage device output for
`receiving a signal representative of the level of energy stored
`in the energy storage device. The voltage scaler output
`conveys a signal proportional to the voltage scaler input by
`the predetermined scaling factor. The comparator has a first
`input connected to the voltage scaler output that receives the
`voltage scaler output signal, a second input connected to the
`voltage controlled amplifier signal output for receiving the
`voltage controlled amplifier output signal, an output con-
`nected to the input 01‘ the first filter network that conveys to
`the first filter network input a comparator output signal, and
`a predetermined comparator threshold level against which
`the signal received from the voltage scaler is compared.
`When the voltage scalcr output signal is above the prede-
`termined comparator threshold the comparator produces a
`comparator output signal that is substantially equivalent to
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`the voltage controlled amplifier output signal received at the
`comparator second input, and when the voltage scaler output
`signal
`is below the predetermined comparator threshold
`level the comparator produces a comparator output signal
`that is the voltage controlled amplifier output signal reduced
`in magnitude by an amount proportional to the amount by
`which the voltage sealer output signal is below the prede—
`termined comparator threshold level. The voltage controlled
`amplifier control
`input reduces the amplification ol‘
`the
`voltage controlled amplifier when the voltage sealer output
`signal
`is below the predetermined comparator threshold
`level.
`In other aspects of the invention, the first low pass filter
`network includes predetermined attack and decay profiles
`and the first low pass filter network is a resistor-capacitor
`network.
`In another aspect of the invention, the bus signal has a
`predetermined frequency range and the signal conditioner
`includes a summing amplifier, a plurality of frequency band
`filters, a frequency band variable amplifier associated with
`each frequency band filter and a signal conditioner control-
`ler. The summing amplifier has a plurality of inputs and an
`output, and the output connected to the signal conditioner
`signal output. Each frequency band filter is of predetermined
`bandwidth and occupies a predetermined portion of the bus
`signal frequency range. Each frequency band filter has an
`output and an input, and each input is connected to the signal
`conditioner signal
`input. Each frequency band variable
`amplifier has a control
`input
`to control
`its degree of
`amplification, a signal input connected to the output of its
`associated frequency band filter and has a signal
`input
`connected to one of the slimming amplifier inputs. The
`signal conditioner controller has a signal input connected to
`the signal conditioner signal input, an energy storage device
`energy level control input connected to the output ol‘ the
`energy storage device, and a plurality of control outputs, one
`connected to each of the frequency band variable amplifier
`control
`inputs. The signal conditioner controller further
`includes a transfer function for each frequency band variable
`amplifier that produces control signal to control the degree
`of amplification that is a function of the level of energy in
`the energy storage device, the level of energy in the signal
`received at
`the signal conditioner signal
`input, and the
`particular frequency band filter associated with the particular
`frequency band variable amplifier.
`In accordance with other aspects of the invention, at least
`one frequency band variable amplifier is a voltage controlled
`amplifier and the signaler includes a low pass filter posi-
`tioned between the plurality of frequency band filters and the
`signal conditioner signal input,
`In accordance with another aspect of the invention, there
`is an apparatus for interfacing a bus powered amplifier to a
`universal serial bus. The bus power amplifier includes a
`power input that receives power to power the amplifier, a
`signal input that receives a signal to be amplified and a
`signal output that outputs the amplified signal. The universal
`serial bus includes a power line and a signal line. The signal
`line includes a data signal representative of an analog signal
`to be amplified by the bus powered amplifier. The interface
`apparatus includes a universal serial bus decoder, a current
`sensor, a current limiter, an energy storage device, a power
`converter, an energy storage device energy sensor and a
`signal conditioner. The universal serial bus decoder has a
`signal input operably connected to the universal serial bus
`signal line and has a signal output. The universal serial bus
`decoder decodes the data signal from the universal serial bus
`signal line into an equivalent first analog signal and makes
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`the first analog signal available at its signal output. The
`current sensor is connected in series with the universal serial
`bus power line. The current sensor senses the amount current
`drawn by the interface apparatus. The current
`limiter is
`connected in series with the universal serial bus power line
`and is operably connected to the current sensor. The current
`limiter limits the current drawn by the apparatus from the
`bus power line in response to the amount of current sensed
`by the current sensor. The energy storage device has a power
`input and a power output, and its power output is connected
`to the power input of the bus powered amplifier. The power
`converter is operably connected to the current sensor and is
`connected to the power input of the energy storage device
`and to the bus power line. The power converter converts
`power from the universal serial bus power line into a form
`suitable for storage by the energy storage device. The energy
`storage device energy sensor is connected to the power
`output of the energy storage device. The energy storage
`device energy sensor measures the amount of energy stored
`in the energy storage device. The signal conditioner has an
`input operably connected to the energy storage device
`energy sensor and an input operably connected to the
`universal serial bus decoder signal output. The signal con-
`ditioner has a transfer function that creates a signal condi-
`tioner output signal that is a function of its input signals. The
`signal conditioner receives the first analog signal and gen-
`erates signal conditioner output signal that is a function of
`the energy level stored in the energy storage device and the
`level of the first analog signal.
`In accordance with other aspects of the invention, the
`energy storage device is a capacitor and the current limiter
`limits the current drawn from the universal serial bus power
`line by the amplifier interface apparatus and the bus powered
`amplifier to 100 111A or less, or to 500 mA or less.
`In accordance with other aspects of the invention, the
`power converter further includes either a linear current
`device, buck converter, a boost converter or a flyback
`converter connected to the bus power line and to the energy
`storage device input, whereby the particular device or con-
`verter converts power from the bus power line into a form
`suitable for charging the energy storage device.
`In accordance with another aspect of the invention there
`is disclosed a method for interfacing a bus to a device. The
`bus includes a power line carrying power and a signal line
`carrying a bus signal. The device includes a power input and
`a signal input for receiving a device input signal. Under this
`method, power is drawn from the bus power line and stored
`in an energy storage device. Simultaneously with the draw-
`ing and storing power step, a device input signal is created
`that is a function of the level of energy stored in the energy
`storage device and the level of energy in the bus signal.
`Simultaneously with the drawing and storing power step and
`the creating a device input signal step, the current drawn
`from the bus power line by the device power input is limited
`to a predetermined current threshold.
`In accordance with another aspect of the invention, the
`step of drawing and storing power includes the step of
`converting the power drawn from the bus power line to a
`form suitable for storing in the energy storage device.
`In accordance with another aspect of the invention, the
`step of drawing and storing power includes the steps of
`determining the level of energy stored in the energy storage
`device; and drawing power from the bus power line and
`storing the drawn power in an energy storage device only
`when the level of energy stored in the energy storage device
`is less than a predetermined threshold.
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`In accordance with another aspect of the invention, the
`step of creating a device input signal includes the step of
`creating a device input signal that is the bus signal amplified
`by a constant, predetermined factor when the level of energy
`in the energy storage device is greater than a predetermined
`threshold, and otherwise creating a device input signal that
`is the bus inth signal amplified by a factor determined by
`reducing the predetermined factor by an amount that is a
`function of the degree to which the energy storage device is
`less than the predetermined factor.
`In accordance with yet another aspect of the present
`invention there is disclosed a method for interfacing a host
`computer containing a digitized sound signal that represents
`a substantially equivalent analog signal via a peripheral bus
`to a bus powered speaker to play the digitized sound signal.
`The bus includes a power line carrying power and a signal
`line carrying a bus signal. The bus powered speaker includes
`a power input, a signal input for receiving a speaker input
`signal, an amplifier for amplifying the speaker input signal
`and a speaker for converting the amplified speaker input
`signal to sound. According to this method, first the digitized
`sound signal is read and an equivalent analog signal level is
`determined for the substantially equivalent analog signal of
`one or more of the digitized sound samples contained in the
`digitized sound signal. Next for each equivalent analog
`signal level determined in the reading and determining step,
`a digitized representation is created for the equivalent analog
`signal level. Next for each digitized representation for the
`equivalent analog signal level, the digitized representation
`‘or
`the equivalent analog signal
`level
`is embedded in a
`digital data stream that includes the digitized sound signal
`Iom which the equivalent analog signal level was deter-
`mined in the previous step. Then the digital data stream is
`sent to the bus powered speaker signal input via the periph—
`eral bus signal line. Next power is drawn from the bus power
`ine and stored in an energy storage device in the bus
`oowered speaker. Simultaneously with the step of drawing
`and storing power, the current drawn from the bus power
`ine by the bus powered speaker is limited to a predeter-
`mined threshold. During the drawing and storing power step
`and the current
`limiting step,
`the digital data stream is
`decoded and received at the speaker signal input to recover
`he substantially equivalent analog signal and to recover the
`equivalent analog signal
`level, During the drawing and
`storing power step and the current limiting step, the equiva-
`ent analog speaker signal is amplified by a factor that is a
`‘imction of the equivalent analog signal level and the level
`of energy stored in the energy storage device.
`These and other features, aspects and advantages of the
`oresent invention will become better understood with regard
`o the following description, appended claims and accom—
`3anying drawings, where:
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`FIG. 1 is a pictorial representation of a desk top computer
`system and a lap top computer system embodying the
`present invention.
`FIG. 2 is a functional block diagram of the bus architec-
`ture of the desk top computer system of FIG. 1.
`FIG. 3 is a detailed functional diagram of the cable
`between the master USB hub resident in the desktop com-
`puter and a USB peripheral device connected to the desktop
`computer of FIG. 1.
`FIG. 4 is a functional block diagram of a secondary hub
`and associated USB peripheral devices.
`FIG. 5 is a pictorial representation of a laptop computer
`containing the secondary hub and associated peripheral
`devices of FIG. 4.
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`FIG. 6 is a functional block diagram of the USB speakers
`of FIG. 1.
`FIG. 7 is a functional block diagram of the USB speaker
`circuitry of the USB speakers of FIG. 6.
`FIG. 8 is a schematic diagram of a preferred embodiment
`of the USB speaker circuitry of FIG. 7.
`FIG. 9 is a schematic diagram of an alternate impleinen—
`tation of the power switch component of the USB speaker
`circuitry of FIG. 7 in which a Boost Converter is employed.
`FIG. 10 is a schematic diagram of another alternate
`implementation of the power switch component of the USB
`speaker circuitry of FIG. 7 in which a Buck Converter is
`employed.
`FIG. 11 is a functional block diagram of an alternative
`implelnentation of the limiter of FIG. 7.
`FIG. 12 is a functional block diagram of an implementa—
`tion of the USB decoder/DAC of FIG, 7,
`FIG. 13 is a flowchart of the software that can be used by
`the USB Decoder/DAC to control the VCAs of FIG. 11.
`FIG. 14 is a pictorial representation of USB speaker driver
`software, resident in host computer 12, for controlling the
`VCAs of FIG. 11.
`
`FIG. 15 is a schematic diagram of an alternate implemen-
`tation of the power switch component of the USB speaker
`circuitry of FIG. 7 in which a Linear Pass Element
`is
`employed.
`FIG. 16 is a functional block diagram of one implemen-
`tation of the Clip Detect and Filter of FIGS. 8, 9, 10 and 15.
`FIG. 17 is a llowchart of a software module that imple—
`ments in the host computer in software most of the functions
`of limiter 11 of FIG. 7.
`FIG. 18 is a pictorial representation of the software
`module of FIG. 17 resident in the USB Speaker Driver of
`FIG. 14.
`FIG. 19 is a pictorial representation of one of multiple
`data packets containing digitized audio signals and sent by
`the host computer to the USB speaker system of FIGS. 1, 2
`and 6.
`
`FIG. 2