Energy efficiency of error correcting mechanisms for wireless
Measuring Wireless Charging Efficiency In the Real …...Power for a Wireless World Conclusions 1....
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Measuring Wireless Charging Efficiency In the Real World WPC Trade Conference Taipei 16 June, 2016
Transcript of Measuring Wireless Charging Efficiency In the Real …...Power for a Wireless World Conclusions 1....
Power for a Wireless World
Measuring Wireless Charging EfficiencyIn the Real World
WPC Trade ConferenceTaipei16 June, 2016
Power for a Wireless WorldEfficiency
Matters
• Who cares about efficiency?• IKEA• McDonald’s• EPA/EU/ Gov’t agencies• Auto makers• Consumers• Who doesn’t care?
Power for a Wireless WorldPower for a Wireless World
Industry-Wide Problem:
There is no Standardized test methodology for specifying power-
transfer efficiency of a wireless charging system
Power for a Wireless World
Two
Architectures
Rezence perimeter coil Qi planar coil
Loosely Coupled Closely Coupled
Power for a Wireless WorldArchitecture
Comparison
Architecture Representative Standards
OperatingFrequency
AntennaStructure
Benefits
Loosely Coupled
• Rezence• Qi
• 6.78 MHz• 100 ~ 205 kHz
• Perimeter• Planar
Extended Z-distance
CloselyCoupled
• Qi • 100 ~ 205 kHz Planar • Highly efficient• Low cost
Question: Why not use resonant architecture for all applications?Answer: Efficiency and cost tradeoffs make it inappropriate to do so.
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Use-Case
Examples
Resonant: Under-surface mount
Inductive: Automotive
Inductive: Charging Stand
Inductive: Charging Plate
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Efficiency
Experiment
1. Loosely-coupled, high-frequency wireless charger
– EPC-9112
– Similar to A4WP/Rezence Class 3
– 6.78 MHz operation
2. Closely-coupled, low-frequency wireless charger
– BQ500212
– Qi spec 1.1.2, Type A11
– 110 ~ 210 kHz
Power for a Wireless WorldWhere is Efficiency
Measured?
Li+
Sync
hron
ous
DC
-DC
Buc
k Re
gula
tor
Bat
tery
Ch
arge
r
DC In
AC Adapter
Wireless Transmitter
Wireless Receiver
Efficiency Measurement
Taken at the optimal spatial position and load power (5W, 4.2V @ 1.2A)
DC out
AC
DC
h
Power for a Wireless WorldBattery Model:
2100 mA hr.
Model determines load resistance, voltage
and current test conditions
Power for a Wireless WorldTotal Energy
27 kJ
Energy required for typical (90%) charge-cycle of a 2100 mA hr. battery
Power for a Wireless World
Step 1
Map the Flux Field
Rezence perimeter coil
Loosely Coupled
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Texas InstrumentsEvaluation Kit bq500212
• 100 ~200 kHz operation• CMOS switches• Würth antenna compliant to
Qi A11
Qi
Flux Field (A11)
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Efficiency Test
Results
• Qi is the most efficient system by design
• Efficiency is impacted by:• Switching frequency• Antenna design• Spatial position / Coil-
coupling coefficient• Maximum Power-
Point Transfer
Power for a Wireless WorldBattery Model:
2100 mA hr.
Total energy over 5% to 95% charge cycle:
27 k Joules
Power for a Wireless World
Ideal Definition of Efficiency
Efficiency should be calculated a as spatial average:
“Total joules into the battery divided by total joules into the transmitter averaged over the charge area/volume for a charge
cycle”
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Real-World Energy Use
Qi system used 33% less energy to charge a battery
27 kJBattery
43.8 kJQi
65.7 kJRezence
Power for a Wireless World Conclusions
1. Real-world conditions must be used to measure efficiency (voltage, current, resistance to simulate a battery being charged)
2. Efficiency should be defined as a spatial average
“Total joules into the battery divided by total joules into the transmitter over one charge cycle”
3. There are tradeoffs between different approaches; why not use the most efficient approach?
Power for a Wireless WorldPower for a Wireless World
Thank You
