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  • 1

    IEEE SSCS-2007

    HAPPY LUNAR NEW YEAR ☺

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    Portable Power Management Challenges and Solutions

    Jinrong Qian Portable Power Management Applications

    Feb 16, 2007

    IEEE SSCS-2007

  • 3

    IEEE SSCS-2007Portable Device Market

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    900 02

    C Y

    03 C Y

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    Others LGE S Ericsson Siemens Samsung Motorola Nokia

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    Others Lenovo Acer Toshiba HP Dell

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    Others Fujifilm Nikon Olympus Kodak Sony Canon

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    Others Hitachi Samsung Canon JVC Pana Sony

    Cellular Phone Unit (Million) Notebook PC Unit (Million)

    DSC Unit (Million) 2002 2003 2004 2005 2006 2002 2003 2004 2005 2006

    2002 2003 2004 2005 2006 2002 2003 2004 2005 2006

    Digital Camcorder Unit (Million)

  • 4

    IEEE SSCS-2007

    Long Battery Run-time and Cycle Life • High capacity battery chemistry • Battery Charging • Accurate gas gauge • System power management Safety • Li-Ion cell battery • Battery pack electronics • Authentication Small Size • High component integration • High switching frequency

    Portable Power Design Challenges

  • 5

    IEEE SSCS-2007Total Portable Power Management for Battery-Driven Electronics...

    Longer Battery Life

    Smaller Size & Weight

    Portfolio strength in... Battery management Low-dropout regulators Low-power DC/DC White-light and RGB, LED drivers Power supervisors LCD bias power

  • 6

    IEEE SSCS-2007Battery Chemical Capacity

    EDV=3.0V/cell

    Qmax

    Load current: 0.2C

    • Battery capacity (Qmax) is defined as amount of charge which can be extracted from the fully charged cell until its voltage drops below end of discharge voltage (EDV).

    • EDV is minimal voltage acceptable for the application or for battery chemistry, whichever is higher.

    CBAT RBAT

    Battery Capacity: 1C Discharge rate 1C: Current to completely discharge a battery in one hour Example: 2200mAh battery, 1C discharge rate: 2200mA, 1 hr 0.5C rate: 1100mA, 2hrs

    3.6V (Battery rated voltage)

    1 2 3 4 5 60

    3.0

    3.5

    4.0

    4.5

    Capacity, Ah

    Voltage, V

  • 7

    IEEE SSCS-2007

    Volumetric Energy Density (wh/liter)

    G ra

    vi m

    et ric

    E ne

    rg y

    D en

    si ty

    (w h/

    kg ) 18650-2,6Ah (2005)

    250 500450 600 100

    150

    200

    350 400

    423048-L1

    863448-M1

    863448-M3

    633048-L1

    633048-L2

    18650-2.2Ah

    633450-L1

    523450-L1

    633048-L3

    633048-L4633450-L2

    633450-L3 423048-L2

    523450-L2

    18650-2.4Ah

    423450-L1

    383562-800mAh

    323456-540mAh

    423456-780mAh

    Cylindrical

    Prismatic

    Polymer

    Li ion battery

    18650-1.3Ah (1997)

    18650-1.8Ah

    Battery Chemistry Development NiCd, NiMH, Li-Ion Rechargeable Battery Battery Capacity Increase by 7% per year

  • 8

    IEEE SSCS-2007

    Long Battery Run-time and Cycle Life

    Battery Charging

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    IEEE SSCS-2007Li-Ion Charge CC-CV Profile

    IPRECHARGE

    3.0V/Cell

    Pre-charge

    ICHARGE

    4.2V/Cell Fast-charge

    ITERMINATION

    Taper Current

    Battery Voltage

    Constant Current: 20-30% charging time, 70-80% capacity Constant Voltage: 70-80% charging time, 20-30% capacity

    Constant Voltage

    Pre-charge Timer Safety Timer

  • 10

    IEEE SSCS-2007

    • The higher the cell voltage, the higher the capacity • Over charging shortens battery cycle life • Requirements: High accuracy battery charge voltage

  • 11

    IEEE SSCS-2007

    • Charging Current ≤ 1C rate to prevent overheating, degradation. • The higher charge current will not short the charge time too much!

    “Factors that affect cycle-life and possible degradation mechanisms of a Li-ion cell based on LiCoO2”, Journal of Power Sources 111 (2002) 130-136

    Charge Current vs Battery Cycle Life

    1.0C1.1C 1.3C 1.5C

    2.0C

  • 12

    IEEE SSCS-2007

    Charger output current is shared: ICHG = IBAT + ISYS

    Design Challenges: Charger and System Interaction Safety Timer Charge Termination Detection

    Charging with an Active System Load

    System

    ISYS +

    Adapter or USB

    ICHG

    IBAT Charger

  • 13

    IEEE SSCS-2007Challenge: Pre-charge and Safety Timer Fault

    Pre-Charge Mode: Battery voltage may NOT reach the fast charge voltage threshold

    Pre-charge Timer False Warning Battery may NOT fully charged when the safety time expires • Safety Timer False Warning

    Solution: Keep system off or in low-power mode in pre-charge mode Drawback: Can not operate the system while charging a deeply discharged battery simultaneously

    100mA 80mA +

    Adapter or USB System

    ICHG ISYS

    IBAT Charger 20mA

  • 14

    IEEE SSCS-2007Power Path Management Battery Charge Architecture

    • Decoupling charge current path from system current path • Charge current controlled by Q2 • Powering System from adapter through Q1 • Simultaneously powering system and charging battery • No interaction between charge current and system current

    C1 +

    -

    Adapter

    System

    Q1 Q2

    Powering System

    Charging Battery

    Controller

  • 15

    IEEE SSCS-2007Challenge for Power Path Management Charger

    Time

    ICHG

    VOUT

    IADP

    Adapter current limit

    ISYS System Current

    System Crash

    IADP= ISYS + ICHG • High AC adapter Current • May crash the system for high pulse current • Designing the AC adapter with peak power

    • Higher cost • Larger size

    Power Regulation: Dynamic Power Path Management Avoid System Crash

    IADP

    C1

    +

    -

    Adapter

    System

    Q1 Q2

    System Current

    Charging Battery

    Controller ICHG

    ISYS

    VOUT

    VOUT-MIN

  • 16

    IEEE SSCS-2007Dynamic Power Path Management (DPPM)

    C1

    +

    -

    Adapter or USB

    System

    Q2 Current Control

    Output Control

    ICHG

    IADP ISYS

    Time

    ICHG

    System Voltage

    VDPPM

    IADP AC adapter current limit

    ISYS DPPM Mode

    System voltage drops if (ISYS + ICHG) > IAC_LIMIT DPPM function :

    Reduces the charge current when the system voltage is below VDPPM

    “Finds” maximum adapter power !!! Battery Supplement Mode

    VBAT

    Charging Current

  • 17

    IEEE SSCS-2007Functional Block Diagram

    Protection

    Regulation Loop • Battery Voltage • Charge Current • USB Current • System Bus Voltage (DPPM) • Junction Temperature

    Protection • Battery Temp Detection • System Short Circuit • Battery Short Circuit • Safety Timer

    USB Control

    Charge Control

    AC

    USB

    TMR

    DPPM

    TS

    OUT

    BAT

    ISET1

    LDO Or Mini USB

  • 18

    IEEE SSCS-2007

    • AC adapter or USB can power the system and charge the battery simultaneously • Dynamically reduces charge rate to supply sufficient system current • Selectable USB charge current limits of 100/500mA and up to 1.5A from AC adapter • Thermal regulation and Battery temperature monitoring

    System Solution Example: DPPM Battery Charger

    C 10uF

    AC

    USB

    STAT1

    STAT2

    USBPG

    ACPG

    ISET2

    ISET1

    TMR

    VSS

    OUT

    OUT

    OUT

    CE

    BAT

    BAT

    TS

    LDO

    PSEL

    DPPM

    103AT

    RT2

    bq2403x

    D1 D2

    D4

    D3

    D6

    D5

    High: 500mA Low: 100mA R1

    R2 High: AC Low: USB

    3.3V/20mA

    High Enable

    System LoadAC Adapter USB

    RT1

    R3

    Q1

    Q2Q3

  • 19

    IEEE SSCS-2007

    High Accurate Battery Gas Gauging

    Long Battery Run-time

  • 20

    IEEE SSCS-2007Full Use of Available Battery Capacity

    +

    0%

    20%

    40%

    60%

    80%

    100%

    Capacity

    Charging Voltage Tolerance

    Actual Useful Capacity

    Shutdown Uncertainty due to inaccurate gauging

    • Only 80-90% of Available Capacity may actually be used! • High Accuracy Gas Gauge Increase the Battery Run-time

  • 21

    IEEE SSCS-2007Voltage Based Gas Gauge

    External battery voltage can be roughly mode