Design and Development of a Test Rig for 13.56 MHz IPT Systems with Synchronous Rectification and Bidirectional Capability

This paper presents the development of a test rig for bidirectional 13.56 MHz wireless power using identical back-to-back Class EF converters. Theoretical principles of bi-directional wireless power are described and an operating chart representing the range of admissible complex voltages induced on the active transmit side is introduced. The implementation is achieved by driving the gate signals of two Class EF coil-drivers from a signal generator, allowing the relative phase of the currents in each coil to be controlled. The rig sets a constant input voltage for each of the two coil-drivers by implementing a source-sink configuration, emulating a bidirectional DC-DC conversion stage at each side. This setup can also be used to test for tuning mismatches and different loading conditions in the back-to-back Class EF configuration. Experimental results include bidirectional wireless power transmission of 20 W across a 13.56 MHz link with 6.56% coupling. The combination of low coupling factors and moderate power levels enables new classes of applications that require large air gaps and tolerance to misalignment such as in micro e-mobility. High efficiency can be maintained despite changes in coupling factors and load since active rectification ensures operation at the resonant point in both tanks.