Abstract:
A computer system typically includes a central computer and several peripherals, such as a mouse and a printer, which communicate with the computer via a communications channel known as a serial bus. The serial bus may also supply a limited amount of power to some peripherals. Unfortunately, the power limit compels high-power peripherals to include independent power supplies, an arrangement which increase their complexity and cost. Accordingly, one embodiment of the present invention provides a bus-powered peripheral that includes a controller, a rechargeable battery, and a voltage regulator or recharge circuit. The recharge circuit monitors data on a serial bus, recharges the battery during inactive periods, and allows the battery to supplement bus power during active periods, thereby overcoming the power limit of the serial bus.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention concerns computer systems and computer peripherals, particularly a system that recharges a battery-powered peripheral through a serial bus.  
         BACKGROUND OF THE INVENTION  
         [0002]    Computer systems, particularly personal computers, typically include a central processing unit and a number of peripherals, or auxiliary devices, such as monitors, keyboards, mice, disc drives, printers, scanners, and even cameras, which communicate with the central processing unit. The central processing unit and the peripheral devices are usually connected via a two-way communications channel, known as a serial bus, which carries a stream of electrical pulses representing a sequence of ones and zeros. The serial bus may also carry electrical power for operating one or more peripherals.  
           [0003]    Serial bus parameters, or specifications, are usually standardized not only to reduce the number of communications protocols, or procedures, a computer must understand, but also to simplify matching of computers and peripherals. Examples of serial bus specifications include Apple desktop bus (ADB), Access.bus (A.b), Institute of Electrical and Electronic Engineers (IEEE) P1394, Concentration Highway Interface (CHI), and GeoPort.  
           [0004]    Within the past few years, a new serial bus specification, called the Universal Serial Bus (USB) Specification, has been developed to work with peripherals that require higher data rates, more flexibility, or less complexity than previously available in standard serial busses. A Universal Serial Bus, a serial bus that operates according to the USB Specification, has a maximum data rate of 12 million bits per second (12 Mbps), and carries as much as 2.5 watts of electric power to operate USB peripherals (that is, USB-compliant peripherals).  
           [0005]    One problem with the USB and other serial bus specifications are the power limits they impose on bus-powered peripherals, peripherals that operate almost entirely on power carried by a serial bus. Because of the power limits, high-power peripherals, such as printers or speakers, that require more than the power limit for a particular serial bus must use separate, external power supplies. Unfortunately, external power supplies add expense and complexity to peripherals.  
           [0006]    Accordingly, there is a need for a better way of powering high-power computer peripherals.  
         SUMMARY OF THE INVENTION  
         [0007]    To address this and other needs, the present invention provides a peripheral with a rechargeable battery that stores energy during inactive periods for use during active periods. In one exemplary embodiment, the peripheral includes a voltage regulator for coupling to a pair of bus power lines; a controller coupled between the voltage regulator and one or more bus data lines; and a rechargeable battery coupled to the voltage regulator. In operation, the controller switches the battery between a charge mode and a supply mode according to signals received through the bus data lines. The charged battery supplements the power available through the bus power lines, thereby providing more power for operating the peripheral than otherwise available over the bus power lines alone.  
           [0008]    Another embodiment packages the supplemental power capabilities as a power-extension or power-enhancement peripheral for connection between a computer and another peripheral. And, yet another embodiment, which lacks a controller, relies on rechargeable battery coupled in parallel with a primary-function module of the peripheral. The rechargeable battery responds automatically to power demands of the primary-function module to supply supplemental power during high-power-demand periods and to store excess power during low-power-demand periods.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a block diagram of a first computer system including a computer peripheral with rechargeable battery;  
         [0010]    [0010]FIG. 2 is a block diagram of a second computer system including a power-extension peripheral connected between a computer and a USB bus-powered peripheral;  
         [0011]    [0011]FIG. 3 is a block diagram of another embodiment of a computer peripheral having a rechargeable battery; and  
         [0012]    [0012]FIG. 4 is a block diagram of another embodiment of a computer peripheral having a rechargeable battery.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    The following detailed description, which references and incorporates FIGS.  1 - 4 , describes and illustrates specific preferred embodiments, or versions, of the invention. These embodiments, offered not to limit but only to exemplify and teach the invention, are shown and described in sufficient detail to enable those skilled in the art to practice the invention. Thus, where appropriate to avoid obscuring the invention, the description may omit certain information known to those of skill in the art.  
         [0014]    [0014]FIG. 1 shows a personal computer system  10 , which includes a personal computer  20 , a Universal Serial Bus (USB)  30 , and a USB peripheral  40 . Computer  20 , preferably a Gateway 2000 personal computer from Gateway 2000, Inc. of North Sioux City, S. Dak., includes a processor  22 ; a memory  24 , which includes Universal Serial Bus (USB) communications software  241 ; a power supply  26 , which converts 110 VAC to 5 volts DC; and a USB port  28 , which follows the USB Specification 1.0 (Final Revision of Nov. 13, 1995) or an earlier or subsequent version. The USB. Specification is incorporated herein by reference.  
         [0015]    USB port  28  connects to USB serial bus  30 . USB serial bus  30  includes a USB cable  32  which terminates at one end (computer end) with USB connector  34  and at its other end (peripheral end) with USB connector  36 . In accord with the USB Specification, cable  32 , which has 90 ohm impedance, includes four insulated wires  321 - 324 . Wires  321  and  322  provide respective nominal voltages of 5 volts and return ground, and carry a maximum of 2.5 watts of power. Wires  323  and  324  are differential data lines that carry differential data signals as well as an NRZI-encoded clock signal. Connector  34 , at the computer end of cable  32 , mates with USB port  26 , and connector  36 , at the peripheral end, mates with USB port  42  of USB peripheral  40 .  
         [0016]    Port  42  includes not only power terminals  421  and  422  which connect respectively to wires  321  and  322 , but also data terminals  423  and  424  which connect respectively to wires  323  and  324 . USB peripheral  40  additionally includes an interface-controller module  44 , a voltage regulator (or recharge circuit)  46 , a rechargeable battery  48 , and a primary-function module  49 . Interface-controller module  44  is connected to data terminals  423  and  424  of USB port  42 . Power terminals  421  and  422  (of port  42 ) connect to voltage regulator  46 . Voltage regulator  46  connects to battery (or energy-storage device)  48 , which includes one or more energy-storage cells (not shown), preferably long-life rechargeable lithium, nickel-cadmium, zinc-bromine, or alkaline-manganese cells with minimum charging hysteresis. In addition, voltage regulator  46  includes output terminals  461  and  462  which are connected to primary-function module  49 .  
         [0017]    Primary-function module  49  includes the primary circuits and components necessary for the USB peripheral to perform its intended function. For example, USB peripheral  40  may be a printer, and module  49  would thus include the buffers, print heads, motors, etc. for a complete printer. Alternatively, USB peripheral  40  may also be a pair of speakers, with each speaker including a digital-to-analog converter, an amplifier, volume controls, and an audio transducer. Ultimately, the invention encompasses any type of computer peripheral, including high-power peripherals that require more power than available through bus  30 .  
         [0018]    In operation, interface-controller module  44  monitors and decodes data received at data terminals  423  and  424 . If it receives data indicating or invoking an inactive period, for example, data instructing that the peripheral be turned off, it sends a control signal to voltage regulator  46 . The control signal invokes a charge mode in voltage regulator  46 . In the charge mode, voltage regulator  46  diverts power away from primary-function module  49  to battery  48 , thereby charging battery  48 .  
         [0019]    On the other hand, if interface-controller module  44  receives data indicating or invoking an active period, such as data instructing that the peripheral be turned on, it sends a different control signal to voltage regulator  44 . The different control signal invokes a supply mode during which module  44  couples battery  48  to primary function module  49 , allowing battery  48  to provide supplemental power to primary-function module  48 . Thus, during the supply mode, primary-function module  48  receives power not only from computer  20  (via bus  30 ), but also from battery  48 , thereby overcoming the 2.5 watt power limit of bus  30 .  
         [0020]    In another embodiment, voltage regulator  46  monitors power drawn by primary-function module  49  against that available through serial bus  30 . If excess power is available, that is, if more power is available than power being drawn, voltage regulator  46  invokes a variable-trickle-charge mode which charges battery  49  at a rate proportionate to, or at least dependent on, the amount of excess power. Consequently, battery  49  keeps a charge sufficient to consistently satisfy the peak power demands of primary-function module  48 .  
         [0021]    FIGS.  2 - 4  show three other embodiments of the invention. In particular, FIG. 2 shows a system  100  in which USB peripheral  50  functions solely as an in-line power-extension (or power-enhancement) peripheral for a separate high-power peripheral  70 . The major difference between peripherals  40  and  50  is that peripheral  50  lacks primary-function module  49  and outputs power and data through a USB connector  64 . Connector  64  is connected via a USB cable  66  to another USB connector  68 . Connector  68  engages USB port  72  of peripheral  70 . Port  72 , substantially identical in structure and function to port  42 , has four output terminals  721 - 724  connected to a primary-function module  79 . Module  79  is substantially identical in structure and function to module  49 .  
         [0022]    In operation, the peripheral  50  operates much like peripheral  40 . More precisely, port  42  and controller  44  of power-extension peripheral  50  decode and monitor data on bus  30 . If controller  44  detects data indicating or invoking an inactive period for peripheral  70 , it directs regulator  46  to divert power away from connector  64  and thus away from peripheral  70  to charge battery  48 . On the other hand, if controller  44  detects data indicating or invoking an active period for peripheral  70 , it allows battery  48  to provide supplemental power through connector  64 , cable  66 , and connector  68  to peripheral  70 , thereby overcoming the 2.5 watt power limit of bus  30 . Furthermore, two or more substantially similar power-extension peripherals can be connected in parallel to provide even more supplemental power to a given high-power peripheral.  
         [0023]    [0023]FIG. 3 shows another embodiment of high-power peripheral  40 , designated  80 . Peripheral  80  includes many of the same or similar components as peripheral  40 , namely USB port  42 , voltage regulator  46 , battery  48 , and primary-function module  49 . Notably, peripheral  80  lacks controller  44  for monitoring and detecting bus data indicative of active or inactive operating periods. Instead, peripheral  80  has battery  48  connected in parallel with output terminals  461 - 462  of voltage regulator  46  to “sense” the current drawn by primary-function module  49 . During low power-demand periods, excess bus power (that is, bus current not drawn by module  49 ) charges battery  48  as necessary, and during high power-demand periods, battery  48  supplies supplemental power to primary-function module  49 . Thus, like peripherals  40  and  70 , peripheral  80  overcomes the 2.5 watt power limit of bus  30 .  
         [0024]    [0024]FIG. 4 shows another embodiment of high-power peripheral  40 , designated  90 . Peripheral  90  includes many of the same or similar components as peripheral  40 , specifically USB port  42 , voltage regulator  46 , battery  48 , and primary-function module  49 . However, primary-function module  49  has been divided, preferably according to power requirements, into two portions: a low-power portion  49   a  which receives power and data only from USB port  42 , and a high-power portion  49   b  which receives power from both USB port  42  and battery  48 .  
         [0025]    Low-power portion  49   a  preferably includes control logic and circuits for operating high-power portion  49   b,  and, high-power portion  49   b  includes one or more transducers for converting electrical energy into another form of energy essential to the function of the peripheral. For example, high-power portion  49   b  could include a motor which converts electrical energy to kinetic energy, or a light source which converts electrical energy to light, or a speaker which converts electrical energy to an acoustic energy. However, the scope of the invention encompasses any convenient division of a peripheral into first and second portions with the second portion connected to receive supplemental battery power.  
         [0026]    Peripheral  90  has battery  48  connected in parallel with output terminals  461 - 462  of voltage regulator  46  to sense the current load of only the high-power portion  49   b,  which is activated or deactivated via a control line from low-power portion  49   a.  Thus, when low-power portion  49   a  activates high-power portion  49   b,  battery  48  supplies supplemental power to primary-function module  49 , and when low-power portion  49   b  deactivates high-power portion  49   b,  excess bus power charges battery  48 . Therefore, like peripherals  40 ,  50 , and  80 , peripheral  90  overcomes the power limit of bus  30 .  
         [0027]    Conclusion  
         [0028]    The present invention provides several embodiments of bus-powered peripherals, including a power-extension peripheral, which overcome the 2.5 watt power limitation imposed by the USB Specification. Ultimately, the invention, applicable to any communications bus, eliminates the need to provide a separate external power supply in many high-power computer peripherals.  
         [0029]    The embodiments described above are intended only to illustrate and teach one or more ways of practicing or implementing the present invention, not to restrict its breadth or scope. The actual scope of the invention, which encompasses all ways of practicing or implementing the invention, is defined only by the following claims and their equivalents.