3
Functional description
WPC Wireless charging system is shown in the below diagram.
The TX is responsible for controlling the transmitting coil and generating the correct amount
of power requested by the RX.
The RX continuously provides the transmitter with the correct power level requested, by modulating the
transmitter carrier through the controlled resistive or capacitive load. Generating the correct amount of power
ensures the highest level of end to-end efficiency due to reduced energy losses. It also helps maintaining a lower
operational temperature.
The TX can adapt to the amount of energy transferred by the coil by modulating the frequency, duty cycle or
amplitude of the PWM voltage on the transmitting coil.
Figure 6.
Functional description
3.1
Power conversion
The power transmitter design uses a full bridge inverter to drive the primary coil and series capacitance. The
power transmitted to the coil is regulated by varying the switching frequency of bridge, higher the operating
frequency (example 200 kHz) for lower power transmission , lower operating frequency (example 110 kHz) for
Higher power transfer.
The coil used in the current design has self-inductance of 6.8 uH, the value of series capacitor 347 nF. The input
voltage to the Full bridge inverter is 5 V.
The LC resonant circuit optimization to be done based on power transfer requirements.
UM2901
Functional description
UM2901
-
Rev 1
page 7/18