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IEEE SSCS-2007
HAPPY LUNAR NEW YEAR ☺
2
Portable Power Management Challenges and Solutions
Jinrong QianPortable Power Management Applications
Feb 16, 2007
IEEE SSCS-2007
3
IEEE SSCS-2007Portable Device Market
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90002
CY
03CY
04CY
05CY
06CY
OthersLGES EricssonSiemensSamsungMotorolaNokia
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40
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70
02CY
03CY
04CY
05CY
06CY
OthersLenovoAcerToshibaHPDell
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40
50
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02CY
03CY
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05CY
06CY
OthersFujifilmNikonOlympusKodakSonyCanon
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5
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02CY
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05CY
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OthersHitachiSamsungCanonJVCPanaSony
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 managementSafety• Li-Ion cell battery• Battery pack electronics• AuthenticationSmall 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 managementLow-dropout regulatorsLow-power DC/DCWhite-light and RGB, LED driversPower supervisorsLCD 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 canbe 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: 1CDischarge rate 1C:Current to completely discharge a battery in one hourExample:2200mAh battery, 1C discharge rate: 2200mA, 1 hr0.5C 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)
Gra
vim
etric
Ene
rgy
Den
sity
(wh/
kg) 18650-2,6Ah (2005)
250 500450 600100
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-L3423048-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 DevelopmentNiCd, NiMH, Li-Ion Rechargeable BatteryBattery Capacity Increase by 7% per year
8
IEEE SSCS-2007
Long Battery Run-time and Cycle Life
Battery Charging
9
IEEE SSCS-2007Li-Ion Charge CC-CV Profile
IPRECHARGE
3.0V/Cell
Pre-charge
ICHARGE
4.2V/CellFast-charge
ITERMINATION
Taper Current
Battery Voltage
Constant Current: 20-30% charging time, 70-80% capacityConstant 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 <1%
Charge Voltage Affects Battery Cycle Life
4.35V
4.3V4.25V
4.2V
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
1.0C1.1C1.3C1.5C
2.0C
12
IEEE SSCS-2007
Charger output current is shared:ICHG = IBAT + ISYS
Design Challenges:Charger and System InteractionSafety TimerCharge Termination Detection
Charging with an Active System Load
System
ISYS+
Adapteror 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 WarningBattery 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 modeDrawback: Can not operate the system while charging a deeply discharged battery simultaneously
100mA 80mA+
Adapteror USB System
ICHG ISYS
IBATCharger 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 ManagementAvoid 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
+
-
Adapteror USB
System
Q2CurrentControl
OutputControl
ICHG
IADP ISYS
Time
ICHG
System Voltage
VDPPM
IADP AC adapter current limit
ISYSDPPMMode
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
LDOOr 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
C10uF
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: 500mALow: 100mA R1
R2High: ACLow: USB
3.3V/20mA
HighEnable
System LoadAC AdapterUSB
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 modeled as V=V0CV-I*RBATHigher Voltage with light load, Lower voltage under heavy load IssueDisplay Remaining Capacity Error: 50-100%Unexpected Shutdown
Qmax
0 1 2 3 4 6
3.0
3.5
4.0
4.5
Capacity, Ah
Voltage, V CBAT RBAT
VOCV+ - I
+ -V=V0CV - I*RBAT
5
3.6VLight Load
+
I*RBAT
Heavy load
22
IEEE SSCS-2007Voltage Based Gauging with Aging
Cycle 1 Cycle 100 Cycle 200 Cycle 300
Cycle 400Cycle 500
Cell Voltage (V)4.2
4.0
3.8
3.6
3.4
3.2
3.00 0.4 0.8 1.2 1.6 2.0
• Same Voltage, Different State of Charge
23
IEEE SSCS-2007
Battery is fully chargedDuring discharge capacity is integrated Qmax is updated every time full discharge occurs
∫= dt iQ
Coulomb Counting Based Gauging
Q
0 1 2 3 4 5 63.0
3.5
4.0
4.5
Capacity, Ah
Li-Ion Battery Cell Voltage
EDV (end of discharge voltage)
QmaxDisadvantages
Learning cycle needed to update Qmax
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
24
IEEE SSCS-2007
Combine advantages of voltage and current based methodsUse voltage based method where no load is applied to battery, todetermine starting SOC and no-load capacity degradationUse current integration based method when under loadUpdate impedance at every cycle using voltage and current information
BATOCV RIVV ×= -
Impedance TrackTM : Handling of Battery Aging
0.06 0.1 0.14 0.18 0.22 0.26 0.30R(Z) - Ω
0.12
0.08
0.04
0
Im(Z
) -Ω
Cycle 1
Cycle 100
Battery Impedance with AgingBattery DC impedance
Fully charged Deeply discharged
25
IEEE SSCS-2007How to Measure and Update Impedance
BATOCV RIVV ×= -
• Data flash contains a fixed table for open circuit voltage as a function of remaining capacity OCV = f (SOC)This is true for all standard Li-ion cells, regardless of manufacturer
• The IT algorithm performs real-time measurements and calculationsduring charge and discharge cycles.
Impedance RBAT = OCV – VBATI
100 75 50 25 0SOC %
4.2
3.93
3.67
3.4
Open Circuit Voltage Profile
OCV
VBAT2SOC1SOC
QΔQmax -
=
26
IEEE SSCS-2007System Test Results
0 20 40 60 80 1003000
3200
3400
3600
3800
4000
4200
Vol
tage
1.5
1
0.5
0
0.5
1
RSO
C e
rror
True vs Reported RSOC RSOC Accuracy (%)
0 20 40 60 80 100RSOC(%)
True SOC (%)SMbus Reported SOC (%)
0 20 40 60 80 100RSOC (%)
4.2
3.8
3.4
3.0
1.00.5
0-0.5-1.0-1.5
Test conditions: bq27350 gas gauge with Impedance Track technology• Single Li-Ion battery• DSC-like load discharge profile• 1% accuracy
27
IEEE SSCS-2007
System Power Management
• Challenge: Higher power demand vs Battery Run-time• Solution: Dynamic Power Management
Long Battery Run-time
28
IEEE SSCS-2007
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
200 300 400 500 600 7000
20
40
60
80
100
120
CPU Frequency (MHz)
Core
Vol
tage
(V)
Power Consumption (%
)
Core Voltage
Power Consumption
Voltage Scaling or Positioning Reduces Power Dissipation
VINEN_1EN_2MODEGND
TPS62401
10μF
VOUT1SW1FB1
DFE_1SW2
ADJ2 10μF
VOUT2
Vcore
Vcore_SelVI/O
μP
• Applications: Laptop CPU, portable device CPU• The Lower Core voltage, the lower CPU speed and Power Dissipation• Voltage Identification (VID) through communication lines
t: 100μs/div
VOUT1=1.1V
IL: 500mA/div
DEF_1: 2V/div
VOUT1=1.575V
s2CPUCPU fCV
21
P =
29
IEEE SSCS-2007
• Synchronous Rectification• Discontinuous Conduction Mode
• Lower conduction loss • Lower Switching frequency
• Lower switching loss• Lower gate drive loss
• Lower quiescent current (<20μA)
PWM ModeVI=3.6V
Power SaveMode
High Efficiency Power Converters
+
L
Co R VO
+
-VIN
Q1
Q2
Most circuits: offLower IQ
iLIavg
t
Comp HighComp Low
Vo0.8%1.6%
PWM ModePower Save Mode
30
IEEE SSCS-2007
Battery Powered Device Safety
Very Active Battery Materials (Lithium=Bomb)
Battery Management Electronics: Protection
Battery Pack Authentication
31
IEEE SSCS-2007Battery Safety
Conference on June 21th, 2006 in Japan
Safety!!!
32
IEEE SSCS-2007How many cases are there ?
• More than 43 cases of events on the Notebook PC was reported during 2001~2003according to the US Consumer Product Safety Commission.
• Nokia announced that 3 –40 cases of battery explosion occurred in 2004.• Verizon announced that they had more than 24 cases in 2004.
Safety
33
IEEE SSCS-2007Safety and Thermal Stability
Safety event: Thermal runawayDevice malfunctions possibly leading to safety event:
short circuits:• cell internal• pack internal• pack externaloverchargeoverheatingoverdischarge
Thermal Runaway
OCV=4.3VScan Rate= 3oC/min
34
IEEE SSCS-2007
Temp Sensing
Pack+
Pack-
Voltage ADC
Over VoltageUnder Voltage
Gas Gauge IC
I2C
Chemical Fuse Q2Q1
SenseResistor
bq20z90
Second safetyOver Voltage Protection IC
bq29412
AFE IC
RT
Current ADC Rs
SMBusSMDSMC
Li-Ion Battery Pack
bq29330
Over currentCell balancing
LDO
Battery Pack Electronics
Over Charge (or over-voltage)1st : Gas gauge IC firmware2nd: Protection IC
Over CurrentGas gauge IC firmware
1st level (chg or dsg)2nd level, Safety
AFE hardware3rd level, discharge only
Short Circuit – AFE hardware.Over-Discharge Over temperature
Chipset: bq20z90-bq29330: Gas gauge accuracy 1% over battery life
35
IEEE SSCS-2007
Counterfeit Battery
• Cheap Replacement Battery
• Functionality Removal
• Without Safety Circuit
• No Protection Circuit
• OEM Lose Business and Reputation
• Loss of public confidence as safety compromised
PACK+
PACK-
Battery Pack
TSRT: 103AT
Protector
GasGaugeHDQ
Battery Authentication/Security Development
36
IEEE SSCS-2007
In General: A simple and cost effective method to identify and validate identity.
IdentificationDriver licensePassport
Specific to Peripherals:A simple and cost effective method to ensure peripherals come from authorized vendors.• Form factors
Strength: Economies of scaleWeakness: Easy to duplicate
• LabelingStrength: CheapWeakness: Easily copied & moved around
• User InterventionStrength: Informed consentWeakness: Requires user motivation, difficult to enforce
What is authentication?
37
IEEE SSCS-2007Battery Authentication/Security Development
Solutions
• Identification (ID): bq2022
Fixed challenge, fixed response
• Random challenge-response
bq26150 and bq26100
• Bq20z70/z80/z90 include the SHA-1 based authentication
PACK+
PACK-
TS
Protector
GasGauge
HDQ AuthenticationICHost
38
IEEE SSCS-2007
System dependent• Battery Packs:
– Allow discharge only
• Chargers:– Reduced charging current rate, or lower voltage
• Other Peripherals– Reduced functionality
May choose to simply log that an unauthorized peripheral was used for warranty information.
What if not authenticated?
39
IEEE SSCS-2007
Small Size
• High Switching Frequency: Small inductor and capacitor
5 -10MHz DC-DC converter development
sIN
BAT
ripple
BATIN
f1
VV
IΔVV
L-
=
• High Integration: Power Management IC
40
IEEE SSCS-2007Power Management Challenge: Small Size
Innovation:- Long battery operation- Small solution size
Battery Management Supervision
Photo Flash
LED Backlight
TFT/OLEDDisplay
Memory
Audio Supply
Noise-SensitiveRF Circuit
Integration
Power Conversion
Battery Charging
USB
Li-Ion battery
Adapter
Gas Gauge
41
IEEE SSCS-2007
TPS658207x7mm
L1: 3.3μH
ADAPTER
CSM110μF
VIN CIN10μF
L1
SM1
L2
SM2
PGND2
VIN_SM2
AC
6
24
ANLG2
OU
T
23
2
3
19
21
SCLK
INT
TS
54
SM3
L3
34
VIN_SM1
PGND1
0.6V-1.8V600mA
L2: 3.3μH
CSM210μF
1.0V -3.4V600mA
OUT CIN1:10μF
OUT CIN2:10μF
46
44
45
47
51
49
52
50
D1OUT
L3:4.7μH
SM3SW
FB3
39
42
40
41
PGND338
D2-D7: White LEDs
D9
RED
GR
EEN
BLU
E
D11
OUT
D10
LDO0
LDO
1
3.3V/150mA
1.25-3.3V/150mA
LDO
2
LDO
3
LDO
4
LDO
5
VIN_LDO02
VIN_LDO35 C02.2μF
C12.2μF
C22.2μF
C32.2μF
C42.2μF
C52.2μF
C81.0μF
C61.0μF
DPPM
AG
ND
2
AG
ND
1
LED_PW
M
AG
ND
0
TMR
SIM
AD
C_R
EF
LDO
35_R
EF
C710nF
RTC
_OU
T
C9100mF
LDO
_PM
ISET
18
C101.0μF
11 10 4 22 30 5 26 27 28 33 37
32
HO
T_RST
TRSTPW
ON
BA
T
OU
T
COUT10μF
USBCUSB10μF
USB
9
12
BA
T
17
RT103AT
RT2442k1%
PACK+
PACK-RT1:
Li-IonBattery
SYS_IN
OUT
31
35
29
GPIO1
GPIO2
GPIOs(ADC_TRG)
43
53
RESPWRON
SDAT
ANLG1
PWM
OUT
R7-R10: 100k
HO
ST INTER
FAC
E
R1:10Ω
R539k
R649.9k
R16: 220k
R15100k
R41k
C11:1μF
C121μF
C130.1uF
OUT
Battery ID
R3200k
R2200k
OUTD8
55 56 1
R11-R13: 100k
R14:33ΩMotor(Buzz)
8 7
RGBLEDs
1425481636131520
CSM31μF
CIN31μF
μP
I/O
LEDS
ANALOG/DIGITALRTC
BATTERY CHARGER
RGB
BUZZ
I2C
USB
ADAPTER Keyboard Backlight
SIM
Complete Power Solution: Power Management IC
42
IEEE SSCS-2007Smart Phone
Power Management
43
IEEE SSCS-2007
• Longer battery run-time and cycle life• High capacity battery chemistry development• High efficiency DC-DC converter• High accurate gas gauge• Accurate battery charging
• Device miniaturization• High Integration• High frequency
• Safety• Multi-level Protection• Authentication
Summary
44
IEEE SSCS-2007
Thank you and Happy New Year ☺