Page 10 - PEN Ebook March 2021
P. 10
Cover Story - Design Cover Story - Design
formance of the standard Qi FOD method: actual This is possible due to a highly optimized power
voltage and current are used in the calculation system architecture. The inverter on the trans-
and not the inverter DC power. The solution is mitter side is driven by the wireless charging
more accurate and can detect smaller foreign driver WCDSC006 and powered by Infineon's
objects. It prevents over- (No foreign object de- high-performance OptiMOS™ MOSFET technolo-
tected) or underestimating losses (FOD fail with gy with low R DS(on) . A broad MOSFET portfolio is
no object present). The transmitter employs AI available to meet a wide range of system require-
and machine learning to determine if the charg- ments. On the receiver side, an active bridge rec-
ing environment is safe when metallic objects are tifier is used to optimize efficiency. The Minotaur
present. All of this runs on a microcontroller from solution reaches peak efficiency levels of ~95
the XMC™-SC Power Controller family, Infine- percent DC-DC efficiency at 45 W wireless power
on's microcontroller family dedicated for wireless transfer. It also maintains excellent efficiency
charging. across the entire power range up to 45 W.
Highest system efficiency of up to 95 INFINEON, TOGETHER WITH
percent ITS PREMIUM PARTNER SPARK
Figure 3: Temperature measurements on the transmitter and the receiver side after 45 minutes of wireless power operation at CONNECTED OFFERS A BROAD
45 W (Source: Spark Connected). In order to manage thermal limitations to guaran-
tee safe system operation, highest system effi- RANGE OF SOLUTIONS FOR
frequency and thus changing the AC waveform. and receiver. Bluetooth ICs, such as the Infineon ciency is required at higher power levels. During WIRELESS CHARGING
From the receiver to the transmitter-side ampli- CYW20719, are available in different packages operation, the Minotaur solution fully meets the
tude shift keying (ASK) is used by switching a re- and provide low-power and robust Bluetooth WPC Qi thermal limitations and complies with Spark Connected and Infineon already today offer
sistor to change the receiver side circuit's imped- communication facilitated by the easy-to-inte- the WPC Qi standards. a broad range of reference solutions (see Fig-
ance. By sensing the coil voltage and current on grate software environment ModusToolbox .
®
the transmitter side, the load change on the re-
ceiver side can be monitored and translated into Robust and reliable FOD
a communication signal. This operation principle Standard foreign object detection (FOD) methods
becomes increasingly difficult at higher power rely on the large primary coil winding for detect-
levels as a) the load change is becoming more ing foreign objects, which reduces sensitivity and
difficult to sense due to being smaller compared signal to noise ratio. Smaller objects are diffi-
to the overall power transmitted and b) harmonic cult to detect due to their small impact on the
distortions compromise the signal. much larger primary coil's magnetic field. Existing
transmitter solutions measure the parameters
The Minotaur solution of Spark Connected and needed for the power loss calculation (voltage
Infineon uses in-band communication complying and current) at the DC supply of the inverter. This
with the WPC Qi communication protocol which distorts the measurement when compared with
is applied in low-power wireless charging scenar- the actual values at the coil, causing an inaccu-
ios. In addition, the Minotaur solution is capa- rate transmitter loss calculation.
ble of switching to out-of-band communication
via Bluetooth in higher-power operating modes The Minotaur solution is Qi-certified and ful-
to guarantee a stable communication channel. ly meets Qi FOD functionality and performance
The high-bandwidth data throughput also en- requirements. The solution employs accurate
Figure 4: High peak efficiency (95 % tested and measured) of the 45 W laptop transmitter and receiver solution, a distance of 6
ables fast authentication between transmitter measurement techniques that improve the per- mm between transmitter and receiver (Source: Spark Connected).
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