This chart shows the overall efficiency breakdown of the WPC – Qi system as implemented in TI’s bqTESLA chipset. The overall efficiency at peak loads is in the mid-70-percent range. This efficiency is the end-to-end efficiency of the system, starting with the DC input to the transmitter pad all the way to the regulated DC out of the receiver stage that feeds directly into the powered device. There are three basic stages where the efficiency is characterized: first, the transmitter stage itself (DC-to-AC); secondly, the magnetic coupling from TX coil to RX coil (AC-to-AC), and finally the receiver’s rectifier and regulator stage (AC to DC).  Each of these component efficiencies is in the 90+ percent range. The total efficiency is the product of the three stages, or about 73% peak.