Multivariable optimization method for inductive power transfer in wireless sensors nodes

Abstract

Wireless power transfer has been employed in several applications where the use of cables for powering remote devices are not suitable or even feasible. For instance, in biomedical applications health monitoring sensors can be powered without the need of implantable batteries, which is safer for the patient. As the transferred power is highly dependent on the relative position between the transmitter and receiver coils, the use of an adaptive matching network in a wireless power transfer system allows to track the changes in the magnetic coupling between the coils. As a consequence, the output power can be approximately constant over a large range of magnetic coupling. This paper presents a multivariable method for maximizing the output power in a wireless power transfer system. The proposed method uses the concept of voltage-controlled capacitor and variable frequency to optimize the power transferred to the load. The experimental results have shown that for magnetic coupling coefficient k > 0.3 the output power can remain constant, offering more degree of freedom for coils positioning in wireless sensor nodes.