Jinrong Qian Intersil Corporation Most consumers today prefer not

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Method Minimizing Notebook Adapter Power Rating Battery Charging Time
Jinrong Qian Intersil Corporation
Most consumers today prefer notebook computers desktop computers because notebook computer compact size, light weight price continuously decreasing. Notebook computers have internal "silver box" power supplies like desktop computers. Instead, they rely either adapter, which typically provides from output voltage depending manufacturers, Li-Ion battery packs supply power notebook power system. shown Figure adapter output used only provide power system also charge Li-Ion battery.
100-240V
ADAPTER CURRENT SYSTEM LOAD CURRENT
Adapter
CHARGER INPUT CURRENT BATTERY CHARGE CURRENT
Notebook System Load: CPU, Chipset, Memory
Synchronous Buck Battery Charger
Li-Ion Battery
Figure Notebook Power Block Diagram Figure shows typical current waveforms notebook power system. power current drawn notebook system pulsating CPU's aggressive power management modes operation, which transitions from sleep mode active mode vice versa. resulting problem that adapter must designed worst case maximum system power plus power charging battery unless there active power control battery charger. This significantly increases adapter power rating adapter size, resulting more costly adapter since pulsating power could much twice average power. minimize adapter power rating while same time minimize battery charging time?
SYSTEM LOAD CURRENT
CHARGER INPUT CURRENT
ADAPTER CURRENT
Figure Current Waveforms Figure
05/07/2004
viable solution reduce battery charge current when pre-determined adapter current limit reached. This method avoids overloading adapter when supplying load battery charger simultaneously. Figure shows current waveforms with battery charging current regulated based adapter current limit. During t1-t2, system load current linearly increases adapter current remains less than current limit threshold ILIMIT. synchronous-buck battery charger still provides full-scale charging current IB1, maximizing adapter power while minimizing battery charging time. adapter current reaches ILIMIT, which point battery charge current automatically starts reduce adjusting duty cycle buck battery charger system load current continues increase. battery charge current reduced maintain constant adapter current when system load current reaches maximum value other hand, system load current reduced, indicated from battery charge current automatically increased, maintaining maximum adapter current until such time (t5) that system load current reaches level that does demand full adaptor current. this way, make full adapter power, ensure maximum Notebook performance, minimize battery charge time.
SYSTEM LOAD CURRENT
CHARGE CURRENT
ILIMIT
ADAPTER CURRENT
Figure Current Waveforms with Adapter Current Regulation adapter current monitoring limiting tolerance also very important. Poor adapter current monitoring accuracy restricts utilization adapter battery charging. example, adapter with ±10% adapter current limit accuracy only have maximum power available notebook use. notebook system draws 54W, there power available battery charging. battery charging However, adapter current limit accuracy when system draws same 54W, adapter available battery charging. This definitely reduces battery charging time. 58.2 58.2 battery charging other hand, adapter designed with maximum output power ±10% adapter current limit accuracy. Assuming adapter efficiency, adapter input power will 77.6 exceeding limit which requires adapter include power factor correction meet international harmonics requirements such 1000-3-2 61000-32. Having power factor correction typically adds more cost adapter.
77.6 However, maximum adapter input power only 72.7W adapter current limit accuracy, assuming same adapter efficiency. That means necessary include power factor correction function adapter. 61.8 61.8 72.7
Table shows relationship between current limit accuracy adapter power.
Table Current limit accuracy adapter power Current Limit Accuracy Adaptor Available Power ±10% 58.2W Adaptor Input Power Requirements 77.6W 72.7W
deliver higher efficiency cost savings, Intersil developed ISL6253 notebook battery charger provides industry's first accuracy adapter current limit maximize charging current minimize charging time under heavy system load conditions while eliminating need more expensive adapter. Figure shows block diagram this synchronous buck battery charger with typical application circuit. MOSFETs inductor form synchronous buck battery charger topology achieve high power conversion efficiency. power source selection MOSFET, which turned when adapter available. current sensing resistor used sense adapter current voltage drop across this sensing resistor amplified CA1. trans-conductance error amplifier employed regulate adapter current that never exceeds user-programmed limit. current sensing resistor used sense battery charging current trans-conductance amplifier used regulate battery charging current ensure that battery charging current never exceeds limit user through voltage CHLIM pin. Tight adapter current regulation battery charging current regulation accuracies make possible minimize adapter power rating shorten battery charging time. Figure shows waveforms from Intersil evaluation board ISL6253 evaluation board. shows that battery charging current reduced when system load current increased such that adapter current reaches current limit threshold adapter current loop very fast step load transient response (less than 100µs), which minimizes overloading adapter prevents system crashes heavy system loads. additional feature ISL6253 that world's first ±0.5% battery voltage regulation accuracy over wide temperature range from -100C 1000C. This accuracy critical improving battery capacity increasing battery service life. summary, accurate adapter current regulation avoids overloading adapter reduces adapter power requirements dynamic power system. high adapter current limit accuracy reduces adapter power ratings, potentially avoiding more costly power factor correction circuit minimizes battery charging time with heavy system load. Intersil's synchronous buck battery charger control ISL6253 significantly improves battery charging performance, potentially resulting significantly smaller lower cost adapters.
2004 Intersil Americas Inc. Rights Reserved.
05/07/2004
ADAPTOR
R2:20m SGATE CSIP CSIN DCSET DCPRN DCIN CSON Bias Regulator REF1 Adapter Current Limit BGATE
SYSTEM LOAD
C10: 0.1µF
DCIN
ACSET
ACPRN ACLIM VREF ICOMP
REF2 6.8nF VCOMP 10nF VADJ
Buffer kVCA2
Voltage Selector
3.1V/Cell
VCA2 CSOP CSON R10: C8:1µF
CELLS VDD=4S LOW=3S FLOAT=2S VREF
Reference
Trickle Charge Current
Charge Current
CHLIM VREF
Figure ISL6253 Battery Charger Schematic
SYSTEM LOAD CURRENT 5A/div ADAPTER CURRENT 5A/div CHARGE CURRENT 2A/div BATTERY VOLTAGE 2V/div
Figure experimental waveforms with adapter current regulation
REF1
VDDP BOOT
C7:1µF
0.1µF
UGATE PHASE VDDP LGATE
10µF 15µH BATTERY
10µF
PGND
1ms/div

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