Stable operation of a high-power piezoelectric transformer comprising two identical bolt-clamped Langevin-type transducers and a stepped horn

We previously developed a 100 W piezoelectric transformer comprising two identical bolt-clamped Langevin-type transducers (BLTs) and a stepped horn whose cross-sectional area ratio determines the specified step-up voltage transformation ratio. Unlike conventional piezoelectric transformers, this tra...

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Bibliographic Details
Published in:Japanese Journal of Applied Physics 2018-06, Vol.57 (6), p.66701, Article 1
Main Authors: Adachi, Kazunari, Suzuki, Kohei, Shibamata, Yuki
Format: Article
Language:English
Subjects:
Bolts
Disks
Electric fields
Electric potential
Energy dissipation
Linearity
Piezoelectricity
Power efficiency
Power transfer
Stability
Transducers
Transformers
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Summary:We previously developed a 100 W piezoelectric transformer comprising two identical bolt-clamped Langevin-type transducers (BLTs) and a stepped horn whose cross-sectional area ratio determines the specified step-up voltage transformation ratio. Unlike conventional piezoelectric transformers, this transformer is driven at a frequency quite near its mechanical resonance, and thus can be mechanically held firmly at its clearly identified vibratory node without mechanical energy loss. However, it has been revealed that the high-power operation of the transformer often becomes very unstable owing to the "jumping and dropping phenomena first found by Takahashi and Hirose [Jpn. J. Appl. Phys. 31, 3055 (1992)]. To avoid this instability, we have investigated the peculiar phenomena, and found that they can be attributed to a heavily distorted electric field inside the piezoelectric ceramic disks of the BLT on the primary side of the transformer being driven by a low-impedance voltage source near the mechanical resonance. The resultant concentration of the electric field leads to the local reversal of piezoelectric polarization in every half period of the vibration, viz., the instability. Consequently, we have developed a scheme for the steady high-power operation of this type of piezoelectric transformer and examined its validity experimentally. The method has eventually improved the linearity and power transfer efficiency of the transformer significantly.
ISSN:0021-4922
1347-4065
1347-4065
DOI:10.7567/JJAP.57.066701