AU3515801A - Universal serial bus powered battery charging - Google Patents

Description

S&FRef: 546917

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant Actual Inventor(s): Address for Service: Invention Title: Canon Kabushiki Kaisha 30-2, Shimomaruko 3-chome, Ohta-ku Tokyo 146 Japan Timothy Merrick Long and Mark Pulver Spruson Ferguson St Martins Tower,Level 31 Market Street Sydney NSW 2000 Universal Serial Bus Powered Battery Charging ASSOCIATED PROVISIONAL APPLICATION DETAILS [33] Country [31] Applic. No(s) AU PQ6822 [32] Application Date 11 Apr 2000 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815c UNIVERSAL SERIAL BUS POWERED BATTERY CHARGING Technical Field of the Invention The present invention relates generally to peripheral networks, wherein power is supplied to peripherals from the network. In particular, the present invention relates to a Universal Serial Bus (USB) network and the use of power from the USB network to supply power to USB peripherals wherein the instantaneous power requirements of the peripherals exceeds a power supply capacity of the network.

Background Art Known systems exist wherein a peripheral connected to a host takes its power :supply from a physical connection between the host and the peripheral. Power "stealing" from RS-232 connection is a very common technique whereby signals on data and controls lines of the RS-232 connection are rectified to from a continuous power supply •se.

oe to the peripheral. Some systems use this technique and augment it with power storage.

Power storage can overcome supply current limits of the RS-232 connection, as RS-232 was never designed to supply power to peripherals.

Universal Serial Bus (USB) is a peripheral network standard for connecting peripherals to host personal computers (PC) and is designed to supply power to peripherals. Power supply is allocated to each peripheral on the network at a different current rating according to a request by the peripheral during initialisation. If insufficient power supply is available to fulfil the request from the peripheral, the request will be refused by the host PC on the network. Advantages of the USB include that it is inexpensive, and easy to use.

A USB cable contain only 4 wires, 2 for the data, and 2 for power supply. The bus may be expanded to hold many peripherals by inserting a USB hub, which can allow up to another 8 peripherals to be connected to the host PC. Again, any one of these peripherals may be another USB hub, allowing the network to grow in a star shaped network. USB peripherals (peripheral connected to the USB) may be classed as self- 546917.doc powered or bus-powered. Self-powered peripherals have their own power supply, whereas bus-powered peripherals draw their power from power supplied from the USB cable.

The USB standard provides for strict limits on the design of bus powered peripherals. Bus powered peripherals may have high or low power requirements. Low power requirement peripherals may draw no more than 100 mA, whereas high power requirement peripherals may draw up to 500 mA. High powered requirement peripherals may not always be used on the USB, such as when not enough supply remains to be allocated to the peripheral. This is often the case if the peripheral is connected after a bus 10 powered USB hub.

The above presents several difficulties during the design of commercial peripherals, which include: S Bus powered peripherals are more attractive to consumers because less cable connections are required. However, many peripherals, such as scanners and printers, require more peak current during operation than low power requirement peripherals are allowed to draw.

-Peripherals may even require more current than high power requirement buspowered peripherals are allowed to draw. Furthermore, high power requirement ••oso bus-powered peripherals are not always desirable to the consumer as they may not always work on a USB that includes many other high power requirement buspowered peripherals or is to be used downstream from a bus-powered hub.

Disclosure of the Invention It is an object of the present invention to substantially overcome, or at least ameliorate, one or more disadvantages of existing arrangements.

According to a first aspect of the invention, there is provided a network peripheral for connecting to a network including a host computer, wherein a network connection for connecting said network peripheral to said network includes a data 546917.doc communication line and a power supply line for providing limited power to said network peripheral, said network peripheral comprising: a peripheral engine; an internal power storage means for powering said peripheral engine, said internal power storage means being charged by said power supply line of said network connection; and a controller for controlling said peripheral engine between a low power idle mode and a normal power operating mode, whereby said controller places said peripheral engine in said low power idle mode while said internal power storage means has insufficient stored power to supply said peripheral engine in said normal power operating mode.

o Brief Description of the Drawings One or more embodiment of the present invention will now be described with 15 reference to the drawings, in which: Fig. 1 is a block diagram of a typical self powered USB peripheral; Fig. 2 is a block diagram of a USB peripheral according to the preferred implementation; and Fig. 3 shows processing steps within a USB controller.

Detailed Description including Best Mode Where reference is made in any one or more of the accompanying drawings to features, which have the same reference numerals, those features have for the purposes of this description the same operation(s), unless the contrary intention appears.

Ideal USB peripherals for consumers are low power requirement bus-powered peripherals, as they only require a single cable for connecting the peripheral to a host PC.

However, a large class of peripherals can not directly be implemented as low power requirement bus-powered USB peripherals as they require peak current supply beyond the 546917.doc specified limits of the USB standard. Often, these peripherals have a low duty cycle being idle for the majority of the time.

Fig. 1 illustrates a typical self-powered USB peripheral 101, which is connected to a USB Network 100 by means of a USB cable 102. The USB Network 100 may be a host PC, or alternatively a USB hub. The USB cable 102 comprises 4 wires. Two of these wires are data wires, which are for bi-directional data.

The peripheral end of the USB cable 102 connects to a USB connector 103 of the self-powered USB peripheral 101. The USB connector 103 provides through connections for the data wires of the USB cable 102 to data wires 104, which are connected from the connector 103 to a USB controller 105. The other two wires of the cable 102 are for power, having 5 Volts and 0 Volts potential respectively. These wires do not exit the :connector 103. The USB controller 105 negotiates with the host (not illustrated) on the USB Network 100 for the power resources the peripheral 101 requires, and initialises the peripheral 101 as required.

The USB controller 105 is also connected to a peripheral engine 107 through connection 106. During normal operation, the USB controller 105 will transfer data between the peripheral engine 107 and the USB Network 100 according to the USB standard. The peripheral engine 107 is typically a printer or a scanner, and includes any oo..oi peripheral that requires more than 100 mA peak current or more than 500 mA peak current.

Therefore, in order to meet these high power requirements, power is supplied to the peripheral engine 107 from a power regulator 112, connected by a power harness or power bus 113 which includes all necessary voltages required for the operation of the peripheral engine 107. The power harness 113 typically includes a 3.3V and 5V supply for system logic, and a 12V or 20V supply for motors and light source (for scanner). The power regulator 112 is supplied with a single DC voltage from a rectified and filtered output of transformer 110 through connection 111. The transformer 110 is supplied from mains power 108 at 110V AC -230V AC through connection 109. The transformer 110 is often implemented as an external power pack (not illustrated). However, these external 546917.doc power packs made the problems of having addition power wiring even more inconvenient to users.

Fig. 2 illustrates a preferred implementation in which a low-power requirement bus-powered USB peripheral 201 is connected to the USB Network 100 by means of the USB cable 102. The peripheral end of the USB cable 102 is received by a USB connector 203 of the low power requirement bus-powered USB peripheral 201.

The data cables of the USB cable are through connected by the USB connector 203 to data wires 104 to a USB controller 205. The USB controller 205 is also connected to the peripheral engine 107 through connection 106. During normal operation, the USB a controller 205 transfers data between the peripheral engine 107 and the USB Network 100 according to the USB standard.

:Also referring to Fig. 3 wherein processing steps within the USB controller 205 a. a.

S is shown, upon initiation, the USB controller 205 negotiates with the host (not illustrated) on the USB Network 100 for the power resources the peripheral 201 requires in step 301.

The USB controller also initialises the peripheral 201 as required in step 303.

The two-powered wires of the USB cable 102 are connected through USB connector 203 to a battery charger 207 by means of connection 214. The battery charger 207 is connected to rechargeable batteries in a battery pack 210 through connection 209, :oo i and constantly trickle charge the batteries from the power supplied from the network 100.

Power is supplied to the peripheral engine 107 from a power regulator 212, connect by the power harness or power bus 113, which includes all necessary voltages required for the operation of the peripheral engine 107. The power regulator 212 is supplied by a single DC voltage over connection 211 from the battery pack 210. This allows the battery pack 210 to meet the high current requirement of the peripheral engine 107, while the USB power is constantly used to charge the batteries in the battery pack 210.

The battery pack 210 is made from rechargeable battery cells, and in the preferred implementation are either Nickel Cadmium (NiCd), Nickel Metal-Hydride (NiMH), or Lithium Ion cells. These battery cell families all have the ability to supply 546917.doc high currents, while being trickle charged with much lower currents. As the voltage supplied to the battery charger 207 from the USB network 100 may be as low as 4.4V instead of the 5V specified in the USB specification, in the preferred implementation the battery pack 210 is 3.6V. This is typically created by placing 3 battery cells in series.

A cost tradeoff can be made in choosing the capacity of the battery pack 210, versus the run time of the peripheral engine 107. If the peripheral engine 107 draws an average current of 500mA while in operation, and the battery pack has a rating of then the peripheral engine 107 should be able to operate for an hour before the battery pack 210 is completely discharged. Preferably, the peripheral engine 107 should be specified to have about half this operation time in order to account for capacity loss of the batteries over time.

NiCd and NiMH cells of a 500mA-hr rating can also supply very high currents and can supply a peak current of up to 5 amperes. Furthermore, batteries of this capacity can be trickle charged at 50mA, which is well below the limits of low power requirement *ooo bus-powered USB peripherals.

The battery charger 207 in the preferred implementation supplies a constant current supply of 50 mA. This current supply may be turned off by the USB controller 205 through connection 215. This may be implemented with a control transistor and ooooo series resistor, allowing for a very inexpensive implementation. More precise current control is possible to protect the batteries from overcharging by using devices such as a Benchmarq BQ2002. A cost trade off is made between these choices of implementation versus the life of the batteries and the speed for recharging.

The USB Controller 205 also monitors the charge level of the battery pack 210 through the battery charger 207. If the USB Controller 205 determines in step 305 that the charge level is sufficient for operating a complete cycle of operation of the peripheral engine 107, the USB controller instructs the peripheral device 107 to continue operation in step 307. However, if the USB Controller 205 determines in step 305 that the charge level is insufficient for operating a complete cycle of operation, then the controller 205 stalls operation of the peripheral engine 107 in step 309 and provides error feedback to 546917.doc the host in step 311. The error feedback to the host may include advising the host of the need for recharge and an estimation of the time required for recovery. The process continues to step 305. The Once the battery pack 210 has a sufficient charge, the USB controller instructs the peripheral device 107 to continue the stalled operation.

An alternative implementation allows the USB Controller 205 to request a 500mA current limit from the network 100, thereby requesting the host to configure the peripheral 201 as a high power requirement bus-powered peripheral. If the allocation is refused by the host, the USB controller 205 requests the lower 100mA limit from the host, thereby requesting the host to configure the peripheral 201 as a low power requirement bus-powered peripheral. In this manner, the peripheral 201 would thus have a faster recovery time between available active cycles, as the battery charger 207 would be :configured for a faster charge time if the higher current allocation was available.

The foregoing describes only some embodiments of the present invention, and S.modifications and/or changes can be made thereto without departing from the scope and spirit of the invention, the embodiments being illustrative and not restrictive.

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Claims (14)

1. A network peripheral for connecting to a network including a host computer, wherein a network connection for connecting said network peripheral to said network includes a data communication line and a power supply line for providing limited power to said network peripheral, said network peripheral comprising: a peripheral engine receiving data from said data communication line; and an internal power storage means for powering said peripheral engine, wherein said internal power storage means is charged by said power supply line of said network connection.

A network peripheral as claimed in claim 1 further comprising a controller for controlling said peripheral engine between a low power idle mode and a S.normal power operating mode, whereby said controller places said peripheral engine in o*oo said low power idle mode while said internal power storage means has insufficient stored power to supply said peripheral engine in said normal power operating mode.

3. A network peripheral as claimed in claim 1 or 2, wherein said limited ooooo power is allocated to said peripheral by said host computer.

4. A network peripheral as claimed in any one of claims 1 to 3, wherein said network is a Universal Serial Bus network.

A network peripheral as claimed in any one of claims 1 to 4, wherein said peripheral engine is a printer.

6. A network peripheral as claimed in any one of claims 1 to 4, wherein said peripheral engine is a scanner.

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7. A network peripheral as claimed in any one of claims 1 to 6, wherein said internal power storage means includes rechargeable batteries.

8. A network peripheral as claimed in claim 7, wherein said rechargeable batteries are Nickel Cadmium.

9. A network peripheral as claimed in claim 7, wherein said rechargeable batteries are Nickel Metal-Hydride.

10 10. A network peripheral as claimed in claim 7, wherein said rechargeable batteries are Lithium Ion.

11. A network peripheral as claimed in any one of claims 3 to 10, wherein said host computer allocates a highest allowable power limit to said peripheral.

12. A network peripheral as claimed in any one of claims 2 to 11, wherein said peripheral requests a power allocation from said host computer over said data communication line.

13. A network peripheral as claimed in claim 12, wherein said peripheral always requests a predetermined high current allocation, and in response to a failure of said host computer to allocate the requested power allocation, requests an allocation of a predetermined low current allocation from said host computer.

14. A network peripheral as claimed in claim 13, wherein said predetermined high current allocation is 500mA and said predetermined low current allocation is 100mA. 546917.doc A network peripheral substantially as described herein with reference to Fig. 2 of the drawings. DATED this eleventh Day of April 2000 Canon Kabushiki Kaisha Patent Attorneys for the Applicant SPRUSON FERGUSON *c SO *c U 0 546917.doc