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Wireless Charging Concepts
Wireless power transfer is, essentially, a transformer. Power is provided to a primary coil which produces an
electromagnetic (EM) field. In this field, a secondary coil is placed. The EM field induces a current into the
secondary coil, providing power to whatever it is connected to.
However, unlike a conventional power transformer that operates at line frequencies and requires an iron core for
efficiency, wireless power systems are designed to operate in the 100 kHz range, and thus can perform efficiently
with an air core. As such, the primary and secondary windings, if closely spaced, can be in separate devices, the
primary being part of a transmitter and the secondary within a receiver. This implementation can also be described
as a radio broadcast process, and as such, these transformer coils can also be seen as antennas with equal validity,
and the two terms will be used interchangeably in this text.
Receiver
End
Equipment
Transmitter
Power
Supply
Wireless power systems differ in another major aspect from conventional transformers, in that they are
intelligently managed. A transmitter will only provide power when a receiver is present, and only produce the
amount of power requested by the receiver. In addition, the system is capable of recognizing when the
electromagnetic field has been interrupted by an unintended element, a 'foreign object', and will shut down the
transfer to prevent any significant amount of power being absorbed by anything but a proper receiver. The
intelligent management of the wireless power transmission process is achieved though the programming of the
TS81000. When introduced to a compliant transmitter, the TSDMRX-19V20W-EVM receiver informs the
transmitter of its power requirements, and transmission begins. The receiver then verifies the right amount of
power is being sent, and that none is being lost to foreign objects. The receiver continually provides ongoing
requests for power to maintain the transaction. If these requests cease, the transaction terminates. Via this
protocol, even complex charging patterns can be supported, as the transmitter can provide varying amounts of
power at different times, as requested by the TSDMRX-19V20W-EVM. Should the TSDMRX-19V20W-EVM require
no further power, such as when a battery charge is completed, it can request no further power be sent, and the
transmitter will reduce its output accordingly.
Wireless power systems have been broken into three basic power categories. "Wearable" devices, such as
headsets, wrist-band devices, medical sensors, and so forth - all operate in the low power range, up to 5 watts.
Medium power devices, in the 5- to 15-watt range, include most handheld devices, such as cell phones, tablets,
and medical electronics. High power wireless systems are intended to support devices such as power tools, radio
controlled ("RC") devices such as drones, and other equipment requiring 15 to 100 watts of power.
Wireless Charging
User Guide
TSDMRX-19V20W-EVM
Supply
Rectifier
Regulation
Controller
FET Array
Electromagnetic
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