Magnetoelectric coil-free voltage transformer based on monolithic ferrite-piezoelectric heterostructure

Abstract

Low-power voltage transformers using magnetoelectric (ME) effect in ferromagnetic-piezoelectric heterostructures occupy an intermediate position between electromagnetic and piezoelectric transformers. They have low input and high output impedance, their transformation ratio is controlled by magnetic field. The paper describes design and manufacturing technology of monolithic ME transformers based on the nickel-zinc ferrite - lead zirconate-titanate structure. A prototype of the transformer is fabricated, in which a bulk electromagnetic coil in the input circuit is replaced with a planar electrode, deposited directly on the ferrite layer. This results in simplification of the design and reduction in the size of the transformer. At operating frequency of 70 kHz, the input impedance of the transformer is 0.1 Ω, the output impedance depends on the direction of the piezoelectric polarization and is 6–300 kΩ, the transformation ratio is tuned in the range 0–43 by magnetic field up to 60 Oe. The coil-free magnetoelectric transformers are promising to match circuits with very different impedances.