(12) United States Patent
`(10) Patent N0.:
`US 6,507,172 B2
`
`Sherman
`(45) Date of Patent:
`Jan. 14, 2003
`
`US006507172B2
`
`(54) UNIVERSAL SERIAL BUS POWERED
`BATTERY CHARGER
`
`............ 361/939
`2/2002 Ouyang et a1.
`6,347,029 B1 *
`FOREIGN PATENT DOCUMENTS
`
`(75)
`
`Inventor: Leonard Harris Sherman, Los Altos,
`CA (US)
`
`(73) Assignee: Maxim Integrated Products, Inc.,
`S
`1 CA US
`unnyVa e,
`(
`)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`( * ) Notice:
`
`(21) Appl. N0.: 09/813,040
`
`(22)
`
`Filed:
`
`Mar. 19, 2001
`
`(65)
`
`Pfior Publication Data
`
`US ”OZ/0130638 A1 Sep. 19’ 2002
`Int. Cl.7 ................................................... H02J 7/00
`(51)
`(52) US. Cl.
`........................................ 320/134; 320/128
`(58) Field of Search ................................. 320/134 128
`‘
`‘
`2
`320/149’ 130’ 323/ 73’ 277
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`6,184,652 B1 *
`2/2001 Yang .......................... 320/110
`6,211,649 B1 *
`4/2001 Matsuda .
`320/115
`
`6/2001 Kang ......................... 713/300
`6,253,329 B1 *
`
`EP
`0889659
`EP
`1198049
`W0
`W0 9621900
`W0
`W0 0217460
`* cited by examiner
`
`1/1999
`4/2002
`7/1996
`2/2002
`
`Primary Examiner—Edward H. Tso
`Assistant Examiner—Lawrence Luk
`(74) Attorney, Agent, 0r Firm—Blakely, Sokoloff, Taylor &
`Zafman LLP
`
`(57)
`
`ABSTRACT
`
`Universal serial bus powered battery charger primarily
`intended for use in battery powered hand-held and other
`portable devices to charge the battery or batteries within the
`batterypowered device when the same is connected toahost
`(Mm Powered hub or a bus Powered hub through a
`“nwersalsmalbus(USB)P°“~The battery Chargermd‘ldes
`one or more current limits to conform to the universal serial
`.
`.
`.
`.
`.
`bus current supply lumt set 111 the USB spec1ficat10n. Any of
`the universal serial bus .voltage and current limits. may be
`used to charge batterles 1n the battery powered dev1ce, such
`as single cell
`lithium-ion batteries. Various features are
`dISClosed'
`
`26 Claims, 2 Drawing Sheets
`
`22
`
`20
`
`24
`
`SYSTEM
`
`1040
`
`CHARGER
`
`.
`
`1
`
`APPLE 1012
`
`APPLE 1012
`
`1
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`

`

`US. Patent
`
`Jan.14,2003
`
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`US 6,507,172 B2
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`US. Patent
`
`Jan. 14, 2003
`
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`US 6,507,172 B2
`
`1
`UNIVERSAL SERIAL BUS POWERED
`BATTERY CHARGER
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to the field of power storage
`unit charging devices.
`2. Prior Art
`
`Many battery powered devices such as hand-held and
`other portable devices currently include a universal serial
`bus (USB) port for connecting to other devices having a
`universal serial bus port, such as hosts, powered hubs and
`bus powered hubs, for communication with a host or local
`area network. Being battery powered, these hand-held and
`other portable devices require their batteries to be charged
`periodically,
`typically through an AC to DC converter
`plugged into an AC source. Such battery chargers work well,
`though are inconvenient to carry around with the battery
`powered device, particularly as the battery powered devices
`themselves become smaller and smaller and easily carried
`on ones person.
`
`BRIEF SUMMARY OF THE INVENTION
`
`Universal serial bus powered battery charger primarily
`intended for use in battery powered hand-held and other
`portable devices to charge the battery or batteries within the
`battery powered device when the same is connected to a host
`device, powered hub or a bus powered hub through a
`universal serial bus (USB) port. The battery charger includes
`one or more current limits to conform to the universal serial
`
`bus current supply limit set in the USB specification. Any of
`the universal serial bus voltage and current limits may be
`used to charge batteries in the battery powered device, such
`as single cell lithium-ion batteries. Various features are
`disclosed.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrating a typical system
`utilizing the present invention.
`FIG. 2 is an illustration showing the pinouts used with an
`exemplary embodiment of the present invention.
`FIG. 3 is a block diagram illustrating the circuitry within
`the exemplary charger of FIGS. 1 and 2.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The universal serial bus powered battery charger of the
`preferred embodiment is intended for charging a single cell
`lithium-ion battery, or a single cell of a multi-cell lithium-
`ion battery system at any one time in battery powered
`devices through a universal serial port connection with a
`non-battery powered host or network hub. Accordingly, the
`preferred embodiment will be described in that context,
`though the invention itself is not to be so limited.
`Referring now to FIG. 1, a block diagram illustrating a
`typical use of the present invention may be seen. The charger
`20 of the present invention is used in a battery powered
`portable device between a USB port 22 on the device and the
`battery powered system load 24, which load may be any of
`various types of devices using USB ports to enable the
`devices to be connected to a host, a host powered hub or a
`bus powered hub. The preferred embodiment of the inven-
`tion is adapted for charging a single lithium-ion cell 26,
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`though could be adapted for charging other types of
`batteries, including charging of multiple lithium-ion cells,
`one at a time, or other rechargeable batteries as desired.
`Further or course, while charging the battery in the battery
`powered device is the primary intended use for the charger
`20, it should be noted that the charger 20 may also be used
`in conjunction with other power sources, such as by way of
`example, a conventional AC adapter converting 115 volts
`AC power to an appropriate DC voltage for battery charging
`purposes.
`A preferred embodiment of the charger 20 in integrated
`circuit form for charging a single cell lithium-ion battery is
`illustrated in FIG. 2. As shown therein, the charger includes
`an input terminal IN for connection to the power line on the
`USB port, and a ground connection GND for connecting to
`the ground line of the USB port, the ground for the system
`load 24 and the low side of battery or cell 26 (see FIG. 1).
`The charger further includes a battery connection BATT to
`connect to the battery 26, with a capacitor 28 typically being
`used for noise reduction purposes. The embodiment illus—
`trated in FIG. 2 also includes a logical enable signal EN for
`turning the charger on and off, a charging voltage select line
`VSEL for selecting between charging to a regulated voltage
`of 4.1 volts or 4.2 volts. Finally, the preferred embodiment
`of FIG. 2 includes an output CHG that is an open drain
`output going low when charging by the charger begins. CHG
`goes high impedance when the battery voltage reaches the
`battery regulation voltage, at which voltage the charger
`transitions from a constant current mode to a fixed voltage
`mode. The signal on terminal CHG may be used for such
`purposes as turning on a light emitting diode 30, as illus-
`trated in FIG. 2, when CHG goes low. The signal ISEL is a
`current sclcct, sclccting between a current of 100 milliamps
`and a current of 500 milliamps. In that regard, hosts or
`powered hubs can supply up to 500 milliamps from a
`minimum of 4.5 volts at the end of the cable, whereas bus
`powered hubs can supply to the 100 milliamps to low power
`functions from a minimum of 4.35 volts at the cable end. In
`use,
`the charger 20 of the present invention normally is
`incorporated into a system which will itself determine the
`current capability by polling the USB host to determine if
`the USB is capable of providing 500 milliamps or only 100
`milliamps, and controlling the SELI logic level accordingly.
`Now referring to FIG. 3, a block diagram of a preferred
`embodiment of charger 20 may be seen. The charger
`includes a linear regulator 32 that controls the output ter-
`minal BATT based on one of various conditions.
`In
`particular,
`the voltage on terminal BATT is coupled to a
`battery over-voltage detector 34, which in the preferred
`embodiment compares the battery voltage with a voltage
`limit of 4.7 volts, providing a signal to the regulator 32 to
`turn the same off if the battery voltage exceeds a 4.7 volt
`reference voltage. Also,
`the regulator 32 will sense the
`output voltage on the BATT terminal
`to detect battery
`voltages of less then 2.5 volts in the exemplary embodiment,
`with the regulator limiting the output current to the BATT
`terminal to 40 milliamps for a battery preconditioning mode
`for fairly thoroughly discharged batteries. Under these
`conditions, the CHG signal output from comparator 36 will
`be high (high impedance), switching to a low state when a
`2.5 volt battery voltage is reached, indicating to regulator 32
`that it is no longer limited to the 40 milliamp charging
`current.
`
`Once out of the preconditioning mode, the charger of the
`exemplary embodiment will charge a battery connected to
`the BATT terminal to 4.1 or 4.2 volts, as determined by the
`signal on the voltage select terminal SELV at a current of
`
`4
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`

`

`US 6,507,172 B2
`
`3
`100 milliarnps or 500 milliarnps, dependent upon the logic
`signal connected to the current select terminal SELI. Once
`the battery is charged, the selected voltage regulator 32 will
`maintain that voltage using a current which will depend on
`the load on the battery, if any, with an upper current limit of
`100 milliamps or 500 milliamps, as set by the current select
`signal SELI.
`When the state of the SELI terminal is set, the current
`selector 38 sets a current limit output for the current loop
`amplifier 40, providing an output to the maximum detector
`circuit 42. The actual current is sensed by current sense
`circuit 44 associated with regulator 32, providing an input
`signal to the current loop amplifier 40 and to an over-current
`detector 46, also limiting the output of the current loop
`amplifier 40. Also provided is a thermal loop 48 comprising
`a temperature sensitive device, also providing a limit to
`current loop amplifier 40. In particular,
`in the preferred
`embodiment the thermal loop 48 provides an overriding
`current limit to the current loop 40 to further limit the current
`in the current loop, if necessary,
`to limit the maximum
`temperature of the integrated circuit.
`In the preferred
`embodiment, normally the thermal
`loop will not be
`activated, as the combination of the typical power dissipa-
`tion in the integrated circuit and a reasonable ambient
`temperature will keep the temperature of the integrated
`circuit well below its design limit. However, given the size
`limitations normally encountered in battery operated
`devices,
`integrated circuits of the present invention will
`normally be made available in small package configurations,
`limiting their ability to dissipate heat. This, in combination
`with a substantial upper charging current value (500 milli-
`amps in the preferred embodiment) and a particularly high
`input voltage IN, whcthcr from a particularly high USB
`supply voltage or from some other supply voltage source for
`which the present invention is being used, may cause the
`temperature limit to be reached and the thermal loop 48 to
`become active to control (limit) the charging current as
`necessary to limit
`the integrated circuit
`temperature as
`desired. Other factors, of course, which affect whether the
`thermal loop is active include the ambient temperature as
`well as the proximity of the integrated circuit to other heat
`sources within the portable device and the ability of the
`portable device to dissipate such heat.
`As stated before,
`the voltage on the voltage select pin
`SELV selects between a regulated voltage of 4.1 volts and
`4.2 volts in the exemplary embodiment. Depending upon
`this input,
`the voltage selector 50 compares the output
`voltage of the regulator 32 on the BATT terminal with the
`regulated voltage selected to control a voltage loop 52, also
`providing a limit signal to the detector circuit 42. If the
`output voltage is less than the voltage selected, the detector
`circuit 42 will be controlled by the current loop, with a 100
`milliamp or 500 milliamp current limit in the exemplary
`embodiment unless further limited by the thermal loop 48.
`However, when the output voltage on the BATT terminal
`reaches the regulated voltage selected by the control signal
`on the SELV terminal, the voltage loop 52 will control the
`detector circuit 42, and thus regulator 32, to maintain the
`regulated voltage, decreasing the output current below any
`limit set by the current loop 40 as may be required to not
`overshoot the commanded regulated output voltage.
`The entire integrated circuit is controlled by an enable
`signal on the EN terminal that controls power to the rest of
`the circuits and establishes bias voltages as required. In the
`powerdown mode (the voltage on the EN terminal being
`low), various circuits shown in FIG. 3 are in a powerdown
`condition. In the exemplary embodiment,
`the circuits are
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`designed so that the leakage from a battery charged by the
`battery charger of the present invention back through the
`charger when powered down is on the order of microamps,
`preferably less than approximately 2 microamps. Similarly,
`when the device in which the present invention charger is
`used is not plugged into a USB connection, the input voltage
`IN to the charger will be zero. In this condition, it is also
`desired to keep the leakage current low, preferably less than
`approximately 5 microamps in the exemplary embodiment.
`There has been described herein a new and unique battery
`charger, the preferred embodiment being intended for the
`automatic charging of a battery in a battery operated device
`when plugged into a USB connection. While a preferred
`embodiment of the invention has been disclosed and
`described in detail herein,
`it has been so described for
`purposes of illustration and not for purposes of limitation.
`Accordingly various changes in form and detail may be
`made in the invention without departing from the scope and
`spirit thereof.
`What is claimed is:
`
`1. The improvement comprising:
`in a battery operated device having a Universal Serial
`Buss (USB) port, a linear voltage regulator coupled
`between a power line of the USB port and a battery in
`the battery operated device, the voltage regulator hav-
`ing a current limit input, the voltage regulator limiting
`the current delivered from the power line of the USB
`port to the battery responsive to a control signal on the
`current limit input.
`2. The improvement of claim 1 wherein the voltage
`regulator further having a regulation voltage input,
`the
`voltage regulator limiting the voltage to the battery to a
`regulated voltage responsive to a control signal on the
`regulation voltage input.
`3. The improvement of claim 1 wherein the voltage
`regulator includes an output indicating whether the charger
`is operating.
`4. The improvement of claim 1 wherein the charger
`includes an enable control for enabling and disabling the
`voltage regulator.
`5. The improvement of claim 1 wherein the battery
`chargcr furthcr includcs circuitry rcsponsivc to the battcry
`voltage to limit the current delivered from a power line of
`the USB port to the battery below the limits set by the
`control signal on the current limit input when the battery
`voltage is below a predetermined voltage.
`6. The improvement of claim 1 wherein the battery
`charger further includes circuitry responsive to the battery
`voltage to limit the current delivered from the power line of
`the USB port to the battery to a value below the limits
`settable by the control signal on the current limit input when
`the battery voltage is below a predetermined voltage.
`7. The improvement of claim 1 wherein the voltage
`regulator further comprises a thermal control for limiting the
`current delivered to the battery to limit the temperature of
`the voltage regulator.
`8. The improvement comprising:
`in a battery operated device powered by a lithium-ion
`battery having a Universal Serial Buss (USB) port, a
`linear voltage regulator coupled between a power line
`of the USB port and a cell of the lithium-ion battery in
`the battery operated device, the voltage regulator hav-
`ing a current limit input, the voltage regulator limiting
`the current delivered from the power line of the USB
`port to the battery to approximately 100 milliamps or
`500 milliamps responsive to a control signal on the
`current limit input.
`
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`

`US 6,507,172 B2
`
`5
`9. The improvement of claim 8 wherein the voltage
`regulator further having a regulation voltage input,
`the
`voltage regulator limiting the voltage to the battery cell to a
`regulated voltage of approximately 4.1 or 4.2 volts respon-
`sive to a control signal on the regulation voltage input.
`10. The improvement of claim 8 wherein the voltage
`regulator includes an output indicating whether the charger
`is operating.
`11. The improvement of claim 8 wherein the charger
`includes an enable control for enabling and disabling the
`voltage regulator.
`12. The improvement of claim 8 wherein the battery
`charger further includes circuitry responsive to the battery
`cell voltage to limit the current delivered from a power line
`of the USB port to the battery cell to below the limit set by
`the control signal on the current limit input when the battery
`cell voltage is below a predetermined voltage.
`13. The improvement of claim 8 wherein the battery
`charger further includes circuitry responsive to the battery
`cell voltage to limit the current delivered from the power line
`of the USB port to the battery cell to a value below the limits
`settable by the control signal on the current limit input when
`the battery cell voltage is below a predetermined voltage.
`14. The improvement of claim 8 wherein the voltage
`regulator further comprises a thermal control for limiting the
`current delivered to the battery cell to limit the temperature
`of the voltage regulator.
`15. The improvement comprising:
`in a battery operated device having a Universal Serial
`Buss (USB) port, a linear voltage regulator coupled
`between a power line of the USB port and a battery in
`the battery operated device, the voltage regulator hav-
`ing a current limit input, the voltage regulator limiting
`the current delivered from the power line of the USB
`port to the battery responsive to a control signal on the
`current limit input, the voltage regulator further having
`a regulation voltage input, the voltage regulator limit-
`ing the voltage to the battery to a regulated voltage
`responsive to a control signal on the regulation voltage
`input.
`16. The improvement of claim 15 wherein the voltage
`regulator includes an output indicating whether the charger
`is operating.
`17. The improvement of claim 15 wherein the charger
`includes an enable control for enabling and disabling the
`voltage regulator.
`18. The improvement of claim 15 wherein the battery
`charger further includes circuitry responsive to the battery
`voltage to limit the current delivered from a power line of
`the USB port to the battery below the limits set by the
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`control signal on the current limit input when the battery
`voltage is below a predetermined voltage.
`19. The improvement of claim 15 wherein the battery
`charger further includes circuitry responsive to the battery
`voltage to limit the current delivered from the power line of
`the USB port
`to the battery to a value below the limits
`settable by the control signal on the current limit input when
`the battery voltage is below a predetermined voltage.
`20. The improvement of claim 15 wherein the voltage
`regulator further comprises a thermal control for limiting the
`current delivered to the battery to limit the temperature of
`the voltage regulator.
`21. The improvement comprising:
`in a battery operated device powered by a lithium-ion
`battery having a Universal Serial Buss (USB) port, a
`linear voltage regulator coupled between a power line
`of the USB port and a cell of the lithium-ion battery in
`the battery operated device, the voltage regulator hav-
`ing a current limit input, the voltage regulator limiting
`the current delivered from the power line of the USB
`port to the battery to approximately 100 milliamps or
`500 milliamps responsive to a control signal on the
`current limit input, the voltage regulator limiting the
`voltage to the battery cell to a regulated voltage of
`approximately 4.1 or 4.2 volts responsive to a control
`signal on the regulation voltage input.
`22. The improvement of claim 21 wherein the voltage
`regulator includes an output indicating whether the charger
`is operating.
`23. The improvement of claim 21 wherein the charger
`includes an enable control for enabling and disabling the
`voltage regulator.
`24. The improvement of claim 21 wherein the battery
`charger further includes circuitry responsive to the battery
`cell voltage to limit the current delivered from a power line
`of the USB port to the battery cell to below the limit set by
`the control signal on the current limit input when the battery
`cell voltage is below a predetermined voltage.
`25. The improvement of claim 21 wherein the battery
`charger further includes circuitry responsive to the battery
`cell voltage to limit the current delivered from the power line
`of the USB port to the battery cell to a value below the limits
`settable by the control signal on the current limit input when
`the battery cell voltage is below a predetermined voltage.
`26. The improvement of claim 21 wherein the voltage
`regulator further comprises a thermal control for limiting the
`current delivered to the battery cell to limit the temperature
`of the voltage regulator.
`*
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