Advanced Battery Charger Considerations for Portable Devices Jinrong Qian Richard Stair Battery Charge Management Texas Instruments Battery Power 2012 1
Li-Ion Charge CC-CV Profile Constant Current Pre-charge Fast-charge 4.2 V/Cell I CHARGE Constant Voltage Battery Voltage Capacity 3.0 V/Cell Taper Current I PRECHARGE Pre-charge Timer Safety Timer I TERMINATION Constant Current: 20-30% charging time, 70-80% capacity Constant Voltage: 70-80% charging time, 20-30% capacity Battery Power 2012 2
Battery Charger Topologies Battery Power 2012 3
Charger Requirements for Portable Devices Input Power Source Adapter: 5V, 9V, and 12V up to 2A (24W) USB2.0: 5V@100mA/500mA (many systems) USB3.0: 5V@150mA/900mA/1.5A Battery System Performance: Support dynamic system pulsating power Fast and high efficiency charging Supporting all kinds of battery chemistry Thermal management Battery Power 2012 4
Charging with an Active System Load + Adapter or USB Charger I CHG I SYS I BAT System Charger output current is shared: I CHG = I BAT + I SYS Issues: Operate system and charging simultaneously Safety Timer Termination Battery Power 2012 5
Linear Charger with DPM Architecture Adapter Powering System + - Q1 Controller Q2 Charging Battery C1 System Separate charge current path from system current path Charge current controlled by Q2 Powering System from adapter through Q1 Simultaneously powering system and charging battery Linear Charger Battery Power 2012 6
Switch-Mode Battery Charger with DPM I IN Q2 A2 - Control + Loops Q3 I CHG Q4 VBUS I SYS I SYS I IN I SYS1 I SYS2 DPM Mode Adapter Limit I REF + - BAT I CHG Input Current Regulation V REF Maximize use of the input current Current sharing between system & charger Minimize the AC adapter size and power rating How to avoid adapter crash if its current is NOT Known? Battery Power 2012 7 t1 t2
Consideration 1: How to Support unknown Adapter? Input Voltage Regulation DPM V IN I IN Q1 Q2 VBUS A2 - Control + Loops Q3 I CHG Q4 I SYS VINDPM + - BAT V REF If VIN < VINDPM; D ICHG IIN VIN = VINDPM Automatically Track Adapter s Max Current. Perfect for third party adapter Battery Power 2012 8
Consideration 2: How to Support Pulsating Load? Supplement Mode Operation VIN/USB Q1 Q2 L VBUS Q4 Q3 ICHG System VBAT 3.0V 3.4V VBUS VBAT 4.2V Time Pre-charge: Q4 -- Linear Mode, Fast Charge: Q4 = ON ICHG t1 Pre-Charge t2 t3 Fast-Charge Battery Power 2012 9
Consideration 3: How To Reduce the Battery Charging? High Current Charging IR Compensation 1. Extending the Constant Current mode 2. Reducing the Constant Voltage charging time Battery Power 2012 10
Battery Charging Time VREG CC Mode ONLY ICHG 4.2V VREG I CHG C + - CC: t1 CC/CV + - VREG R C + - OCV 4.2V I CHG I R CC: t1 VREG OCV R C CV: t2 Goal: VREG = 4.2V + IR (R = Rdson + Rsense+ Trace resistance) Battery Power 2012 11
Battery Charging Profile with IR Compensation Longer constant current phase and shorter constant voltage phase reduces total charge time. Battery Power 2012 12
Consideration 4: How To Support USB OTG? Boost 5V@ 0.1A 0.5A 0.9A Q1 Q2 Q3 Q4 ICHG VBUS VBAT System Bidirectional Synchronous Buck: a. Charge in Buck b. Discharge in Boost for USB OTG Save an additional Boost converter Battery Power 2012 13
Design Examples Battery Power 2012 14
4A I2C Single Cell Battery Charger Support DC Adaptor, USB2.0 and USB 3.0 up to 3A USB Input 3.9V 17V VREF D+/D- Detection I2C Interface REGN VBUS Q1 4x4mm^2 QFN-24Pin Package PMID D+ D- STAT Q2 Q3 Q4 SW BOOT REGN PGND SYS BAT SYS: 3.4V-4.4V Integration of power path and switching MOSFETs Up to 4A Charge Current and 6A Discharge Current Host USB On-The-Go Default USB Current SDA SCL INT OTG /CE ILIM bq24190 Thermal PAD TS1 TS2 REGN Input Current Setting Dual battery Pack Thermistor Monitoring Battery Power 2012 15
Thermal Performance (IC Case Temperature) bq24190 PG10 Case Temperature 80 Case Temperature (C) 70 60 50 40 VBUS=5V, VBAT=3.8V VBUS=9V,VBAT=3.8V VBUS=12V,VBAT=3.8V 30 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ICHG (A) VBAT=3.8V, Ta= 31ºC Battery Power 2012
System Efficiency Measured on EVM 96.00% 94.00% 92.00% VBUS 5V VBUS 9V VBUS 12V Efficiency 90.00% 88.00% 86.00% 84.00% 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Charge Current ((A) VBAT=3.8V with 2.2uH inductor Battery Power 2012
Summary Charger Topology: Linear vs Switching Mode charger How to Support all kinds of Power Source and USB? Fast Charging: high charge current and IR Compensation Design Examples Battery Power 2012 18