Table of Contents
Advertisement
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-5W-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-
5W-EVM. Should the TSDMRX-5W-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
Rev 2.0
TSDMRX-5W-EVM
Jun 2016
Supply
Regulation
Controller
Rectifier
FET Array
Electromagnetic
Flux
www.semtech.com
2 of15
Semtech
Advertisement
Table of Contents
