6.6.3 Startup of EPP
In the following image, you can see the Vin being switched to 12 V and the bridge switching to full bridge (AC2
active) as an EPP Rx is identified and EPP power transfer is started.
Figure 42. Startup of EPP
6.6.4 Efficiency and spatial freedom in the XY plane
Efficiency is one of the most important metrics of wireless charging performance evaluation. Spatial freedom, size
of the area in which a power receiver can be placed on the power transmitter, which still allows sufficient power to
be transmitted, is another important metric.
The efficiency and spatial freedom of the STEVAL-WBC2TX70 were measured with STEVAL-WLC99RX as the
receiver. The resulting efficiency is therefore affected by the efficiency of both devices. The efficiency was
measured at the pins of the board, so losses on the cables are not included in the result.
The measurement was done for 20 V input voltage and 20 V output voltage.
The test setup consisted of:
• Rohde&Schwarz HMP4040 power supply
• STEVAL-WBC2TX70 as the transmitter
• STEVAL-WLC99RX as the receiver
• Electronic load in CC mode, model Itech IT8512
UM3286
STEVAL-WBC2TX70 description
UM3286 - Rev 1
page 60/84