IEEE SSCS-2007 HAPPY LUNAR NEW YEAR ☺ 1
IEEE SSCS-2007 Portable Power Management Challenges and Solutions Jinrong Qian Portable Power Management Applications Feb 16, 2007 2
IEEE SSCS-2007 Portable Device Market Cellular Phone Unit (Million) Notebook PC Unit (Million) 70 900 800 60 700 50 Others Others 600 LGE Lenovo 40 S Ericsson 500 Acer Siemens Toshiba 400 30 Samsung HP Motorola 300 Dell Nokia 20 200 10 100 0 0 Y Y Y Y Y C C C C C Y Y Y Y Y 2002 2003 2004 2005 2006 2 3 4 5 6 C C C C C 0 0 0 0 0 2002 2003 2004 2005 2006 2 3 4 5 6 0 0 0 0 0 Digital Camcorder Unit (Million) DSC Unit (Million) 90 20 80 70 15 Others 60 Fujifilm Nikon 50 Others Olympus 10 Hitachi 40 Kodak Samsung Sony 30 Canon Canon JVC 5 20 Pana Sony 10 0 0 Y Y Y Y Y Y Y Y Y Y C C C C C C C C C C 2002 2003 2004 2005 2006 2002 2003 2004 2005 2006 2 3 4 5 6 2 3 4 5 6 3 0 0 0 0 0 0 0 0 0 0
IEEE SSCS-2007 Portable Power Design Challenges � 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 4
IEEE SSCS-2007 Total Portable Power Management for Battery-Driven Electronics... Portfolio strength in... � Battery management � Low-dropout regulators Longer Battery Life � Low-power DC/DC � White-light and RGB, LED drivers Smaller Size � Power supervisors & Weight � LCD bias power 5
IEEE SSCS-2007 Battery Chemical Capacity Voltage, V Battery Capacity: 1C 4.5 Discharge rate 1C: Current to completely discharge a Load current: 0.2C 4.0 battery in one hour 3.6V (Battery rated voltage) Example: 3.5 2200mAh battery, 1C discharge rate: 2200mA, 1 hr EDV=3.0V/cell 0.5C rate: 1100mA, 2hrs 3.0 C BAT R BAT 0 1 2 3 4 5 6 Q max Capacity, Ah • 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. 6
IEEE SSCS-2007 Battery Chemistry Development Li ion battery � NiCd, NiMH, Li-Ion Rechargeable Battery Battery Capacity Increase by 7% per year � 18650-2,6Ah (2005 ) Gravimetric Energy Density (wh/kg) 200 Polymer 4 2 3 4 5 6 -7 8 0 m Ah 3 8 3 5 6 2 -8 0 0 m Ah 18650-2.4Ah 4 2 3 0 4 8 -L2 6 3 3 4 5 0 -L3 5 2 3 4 5 0 -L2 3 2 3 4 5 6 -5 4 0 m Ah 18650-2.2Ah 4 2 3 4 5 0 -L1 5 2 3 4 5 0 -L1 18650-1.8Ah 4 2 3 0 4 8 -L1 6 3 3 4 5 0 -L2 6 3 3 0 4 8 -L4 8 6 3 4 4 8 -M3 6 3 3 0 4 8 -L3 150 Cylindrical 6 3 3 0 4 8 -L1 6 3 3 4 5 0 -L1 18650-1.3Ah (1997) 6 3 3 0 4 8 -L2 8 6 3 4 4 8 -M1 Prismatic 100 500 250 400 450 600 350 Volumetric Energy Density (wh/liter) 7
IEEE SSCS-2007 Long Battery Run-time and Cycle Life Battery Charging 8
IEEE SSCS-2007 Li-Ion Charge CC-CV Profile Constant Current: 20-30% charging time, 70-80% capacity Constant Voltage: 70-80% charging time, 20-30% capacity Pre-charge Fast-charge Constant Voltage Battery Voltage 4.2V/Cell I CHARGE Taper Current 3.0V/Cell I TERMINATION I PRECHARGE Pre-charge Timer Safety Timer 9
IEEE SSCS-2007 Charge Voltage Affects Battery Cycle Life 4.2V 4.3V 4.25V 4.35V The higher the cell voltage, the higher the capacity • Over charging shortens battery cycle life • Requirements: High accuracy battery charge voltage <1% • 10
IEEE SSCS-2007 Charge Current vs Battery Cycle Life 1.0C 1.1C 1.3C 1.5C 2.0C “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 • Charging Current ≤ 1C rate to prevent overheating, degradation. • The higher charge current will not short the charge time too much! 11
Charging with an Active System Load IEEE SSCS-2007 I CHG I SYS + I BAT Adapter System or USB Charger Charger output current is shared: I CHG = I BAT + I SYS Design Challenges: � Charger and System Interaction � Safety Timer � Charge Termination Detection 12
IEEE SSCS-2007 Challenge: Pre-charge and Safety Timer Fault I CHG I SYS + 100mA 80mA Adapter I BAT System or USB Charger 20mA 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 13
IEEE SSCS-2007 Power Path Management Battery Charge Architecture Powering System Adapter Q1 Q2 + C1 System Controller Charging - Battery • 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 14
IEEE SSCS-2007 Challenge for Power Path Management Charger I ADP I SYS System Current System Current Adapter V OUT I CHG Q1 I SYS Q2 + System I CHG I ADP Controller C1 Charging Adapter current limit - Battery I ADP = I SYS + I CHG V OUT High AC adapter Current • May crash the system for high pulse current System Crash • V OUT-MIN Designing the AC adapter with peak power • • Higher cost Time • Larger size Avoid System Crash Power Regulation: Dynamic Power Path Management 15
IEEE SSCS-2007 Dynamic Power Path Management (DPPM) I ADP I SYS DPPM I SYS Mode + Output Control Q2 Adapter Current I CHG Control or USB C1 System I ADP AC adapter current limit - Charging Current I CHG � System voltage drops if (I SYS + I CHG ) > I AC_LIMIT � DPPM function : � Reduces the charge current when the System Voltage system voltage is below V DPPM VDPPM VBAT � “Finds” maximum adapter power !!! � Battery Supplement Mode Time 16
Functional Block Diagram IEEE SSCS-2007 Regulation Loop OUT • Battery Voltage AC LDO • Charge Current Or Mini USB • USB Current • System Bus Voltage (DPPM) • Junction Temperature BAT USB ISET1 USB Control Protection • Battery Temp Detection TMR • System Short Circuit • Battery Short Circuit • Safety Timer Charge Control DPPM TS Protection 17
IEEE SSCS-2007 System Solution Example: DPPM Battery Charger System Load Q1 AC Adapter AC OUT USB USB OUT C D1 D2 D3 10uF OUT STAT1 High D4 CE STAT2 103AT Q3 Q2 Enable D5 BAT USBPG BAT D6 RT1 ACPG TS High: 500mA ISET2 R1 3.3V/20mA Low: 100mA LDO ISET1 High: AC PSEL TMR RT2 Low: USB R2 bq2403x DPPM VSS R3 • 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 18
IEEE SSCS-2007 Long Battery Run-time High Accurate Battery Gas Gauging 19
IEEE SSCS-2007 Full Use of Available Battery Capacity + Charging Voltage Tolerance 100% 80% 60% Actual Useful Capacity 40% 20% Shutdown Uncertainty 0% due to inaccurate gauging Capacity • Only 80-90% of Available Capacity may actually be used! • High Accuracy Gas Gauge Increase the Battery Run-time 20
IEEE SSCS-2007 Voltage Based Gas Gauge C BAT R BAT Voltage, V 4.5 + - I Light Load 4.0 V OCV I*R BAT 3.6V - V =V 0CV - I*R BAT + 3.5 Heavy load + 3.0 0 1 2 3 4 6 5 Q max Capacity, Ah External battery voltage can be roughly modeled as V=V 0CV -I*R BAT � Higher Voltage with light load, Lower voltage under heavy load Issue � Display Remaining Capacity Error: 50-100% � Unexpected Shutdown � 21
Voltage Based Gauging with Aging IEEE SSCS-2007 Cell Voltage (V) 4.2 4.0 3.8 Cycle 1 Cycle 100 Cycle 200 3.6 Cycle 300 3.4 Cycle 400 3.2 Cycle 500 3.0 0 0.4 0.8 1.2 1.6 2.0 Same Voltage, Different State of Charge • 22
Coulomb Counting Based Gauging IEEE SSCS-2007 Li-Ion Battery Cell Voltage � Battery is fully charged 4.5 = ∫ Q i dt � During discharge capacity is integrated 4.0 Q � Q max is updated every 3.5 time full discharge EDV (end of discharge voltage) occurs 3.0 0 1 2 3 4 5 6 Disadvantages Capacity, Ah Q max � Learning cycle needed to update Q max � Battery capacity degradation with aging (Qmax: 3-5% with 100-cycles) � Gauging error increase 1% for every 10-cycle with learning � Self-discharge has to be modeled: Not accurate 23
Impedance Track TM : Handling of Battery Aging IEEE SSCS-2007 � Combine advantages of voltage and current based methods � Use voltage based method where no load is applied to battery, to determine starting SOC and no-load capacity degradation � Use current integration based method when under load � Update impedance at every cycle using voltage and current information V V I R = - × OCV BAT Battery DC impedance Battery Impedance with Aging 0.12 Im (Z) - Ω 0.08 Cycle 100 0.04 Cycle 1 0.06 0.1 0.14 0.18 0.22 0.26 0.30 Fully charged Deeply discharged R(Z) - Ω 24 0
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