Use of transmitter-side electrical information to estimate mutual inductance and regulate receiver-side power in wireless inductive link

It is well-known that the power transfer efficiency and the power transmitted over a wireless inductive link are significantly affected by the strength of the magnetic coupling and the spatial displacement between the transmitting and receiving coils. Misalignment between the transmitting and receiving coils is practically unavoidable. In order to control and regulate the receiver-side power, on-the-spot measurement of electrical quantities and establishment of communication link between the transmitter and receiver are typically required. This paper will present an investigation into the use of the transmitter-side electrical information to estimate the mutual inductance and regulate the power consumption of the receiver side. The nonlinear input voltage-current characteristics of the diode-bridge rectifier, which causes current distortions in the system, are taken into account in the mathematical formulations. The proposed technique is successfully implemented on a 4-W wireless-powered LED driver prototype. Experimental results reveal that the LED power can be regulated within ±25% spatial misalignment over the operating zone. The estimated mutual inductance is also found to be in close agreement with the theoretical predictions.