Electrical computers and digital processing systems: support – Computer power control
Reexamination Certificate
1998-07-31
2001-01-23
Etienne, Ario (Department: 2781)
Electrical computers and digital processing systems: support
Computer power control
C713S340000, C713S320000, C710S120000
Reexamination Certificate
active
06178514
ABSTRACT:
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 connecting 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 mA of 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 batteries 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 particular 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 dislodged from the wall. Wall 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 speakers. Speaker users are particularly sensitized to issues of speaker performance and ease of operation. Speakers typically 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 initially 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 complication.
One great appeal of USB peripherals, such as USB speakers, stems from their “Plug and Play” installation and their operational behavior. With Plug and Play, installing new peripherals does not require disassembly of the computer 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, infrared data links, scanners and other devices in which electromechanical 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 limiting 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 connected 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 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.
In another aspect of the present invention, the power converter further includes a linear current device, a buck converter, a boost converter or a flyback converter connected 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
LandOfFree
Method and apparatus for connecting a device to a bus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for connecting a device to a bus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for connecting a device to a bus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528241