Method and apparatus for high voltage gain using a magnetostrictive-piezoelectric composite

• US 7,256,532 B2
• Filed: 03/08/2005
• Issued: 08/14/2007
• Est. Priority Date: 03/08/2004
• Status: Expired due to Fees

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: Virginia Tech Intellectual Properties, Inc.
• Inventors: Dong, Shuxiang, Li, Jiefang, Viehland, Dwight Douglas
• Primary Examiner(s): Schuberg; Darren
• Assistant Examiner(s): ADDISON, KAREN B
• Application Number:
  US11/073,763
• Publication Number:
  US 20050194863A1
• Time in Patent Office: 889 Days
• Field of Search: 310/358, 310/328, 310/368, 310/26, 310331-332, 310/326, 310/357, 310/359, 324/260, 324/244, 331/157, 333/215
• US Class Current: 310/358
• CPC Class Codes: H10N 30/00 Piezoelectric or electrostrictive devices integrated devices or assemblies of multiple devices H10N39/00
• CPC Class Codes: H10N 35/00 Magnetostrictive devices integrated devices or assemblies of multiple devices H10N39/00

Abstract

A method and apparatus attains high voltage gain by using a composite structure of an elastic section of piezoelectric layers bonded between magnetic and electric sections of magnetostrictive layers, with a harmonic magnetic field being applied along the layers at a mechanical resonance frequency of the composite structure, through coils around the laminate carrying current, such as to produce a continuity of both magnetic and electric flux lines, and achieving a high voltage output.

Claims

1. A magneto-electric transformer, for receiving an external AC electric signal of a given voltage and outputting a stepped up output voltage in response, comprising:

a laminated composite core formed of parallel layers, including

a first magnetostrictive layer,

at least one piezoelectric layer extending substantially parallel to said top magnetostrictive layer, and

a second magnetostrictive layer extending substantially parallel to said piezoelectric layer,

wherein said piezoelectric layer is sandwiched with a mechanical bond between said first magnetostrictive layer and said second magnetostrictive layer electric section to form the composite core of parallel layers; and

output terminals connected to said piezoelectric layer; and

a winding having input terminals to receive the external AC electric signal, constructed and arranged with respect to said composite core to generate an alternating magnetic field in said laminated composite core in response to said external AC electric signal flowing though said winding, said arrangement being such that an alternating magnetic flux flows through and induces a magnetostrictive strain in said first and second magnetostrictive layers, wherein said magnetostrictive strain induces a vibration in said first and second magnetostrictive layers at a mechanical frequency,

wherein said mechanical bond is constructed and arranged such that said induced vibration of said first and second magnetostrictive layers urges a vibration of said piezoelectric layer, and

wherein laminated composite core and said winding are constructed and arranged such that said urged vibration in said piezoelectric layer causes said output voltage across said output terminals, wherein said output voltage is stepped up with respect to said external AC electric signal.

2. The magneto-electric transformer of claim 1, wherein said first layer, said piezoelectric layer and said second layer are rings forming a layered ring structure, and said winding is a toroid wound around said ring structure.

3. The magneto-electric transformer of claim 1,

wherein said layers are longitudinal and said composite core is a rectangular plate.

4. The magneto-electric transformer of claim 3,

wherein said magnetostrictive layers are longitudinally-magnetized Tarfenol-D layers and said piezoelectric layers are longitudinally poled Ob(Zr,Ti)O₀₃.

5. The magneto-electric transformer of claim 4,

wherein the piezoelectric layers are longer than the magnetostrictive layers.

6. The magneto-electric transformer of claim 1, further comprising means for applying a dc magnetic bias field to said ac magnetic field.

7. The magneto-electric transformer of claim 1, wherein the first magnetostrictive layer, the piezoelectric layer and the second magnetostrictive layer are constructed and arranged such that the laminated composite core has a given mechanical resonance frequency.

8. The magneto-electric transformer of claim 1, wherein he laminated composite core further comprises an electrically insulating layer located between the first magnetostrictive layer and the piezoelectric layer, and an electrically insulating layer located between the second magnetostrictive layer and the piezoelectric layer.

9. The magneto-electric transformer of claim 7, wherein the first magnetostrictive layer, the piezoelectric layer and the second magnetostrictive layer are constructed and arranged such that, in response to the external AC electric signal at the input terminals of the winding having an electrical frequency substantially equal to said mechanical resonance frequency, the voltage gain of the stepped up AC electric voltage across the output terminals with respect to the external AC electric signal has a value in approximate accordance with the following formula:

$V_{\mathrm{gain}}=\frac{4<br><br>Q_{\mathrm{mech}}<br><br>{\mathrm{\varphi <br><br>}}_p}{\mathrm{\pi <br><br>}<br><br><br><br>{\mathrm{\omega <br><br>}}_s<br><br>C_0<br><br>Z_0}$

where Q_mech is a mechanical quality factor of the piezoelectric layer, φ

_p is an elasto-electric coupling factor of the laminate composite core, C₀ is the clamped capacitance of the piezoelectric layer, and Z₀ is the mechanical impedance of the laminated composite core.

10. The magneto-electric transformer of claim 7, wherein the laminated composite core further comprises an electrically insulating layer located between the first magnetostrictive layer and the piezoelectric layer and an electrically insulating layer located between the second magnetostrictive layer and the piezoelectric layer.

16. The magneto-electric transformer of claim 1, wherein the piezoelectric layer includes a planar first piezoelectric section and a planar second piezoelectric section that is co-planar with the first piezoelectric section, the first piezoelectric section having a first polarization and the second piezoelectric section having a second polarization opposite the first polarization direction.

11. A magneto-electric transformer, for receiving an external AC electric signal of a given voltage and outputting a stepped up output voltage in response, comprising:

a core having a magnetostrictive layer and a piezoelectric layer, sandwiched with a mechanical bond;

output terminals connected to said piezoelectric layer; and

a winding having input terminals to receive the external AC electric signal, constructed and arranged with respect to said core to generate an AC magnetic field in said core in response to said external AC electric signal flowing though said winding, said arrangement being such that said AC magnetic flux flows through and induces a magnetostrictive strain in said magnetostrictive layer, wherein said magnetostrictive strain induces a vibration in said magnetostrictive layer at a mechanical frequency,

wherein said mechanical bond is constructed and arranged such that said induced vibration of said magnetostrictive layer urges a vibration of said piezoelectric layer, and

wherein core and said winding are constructed and arranged such that said urged vibration in said piezoelectric layer causes said output voltage across said output terminals, wherein said output voltage is stepped up with respect to said external AC electric signal.

12. The magneto-electric transformer of claim 11, wherein the first magnetostrictive layer, the piezoelectric layer and the second magnetostrictive layer are constructed and arranged such that the laminated composite core has a given mechanical resonance frequency.

13. The magneto-electric transformer of claim 12, wherein the magnetostrictive layer and the piezoelectric layer are constructed and arranged such that, in response to the external AC electric signal having an electrical frequency substantially equal to the mechanical resonance frequency, the voltage gain of the stepped up AC electric voltage across said output terminals with respect to the external AC electric signal has a value in approximate accordance with the following formula:

$V_{\mathrm{gain}}=\frac{4<br><br>Q_{\mathrm{mech}}<br><br>{\mathrm{\varphi <br><br>}}_p}{\mathrm{\pi <br><br>}<br><br><br><br>{\mathrm{\omega <br><br>}}_s<br><br>C_0<br><br>Z_0}$

where Q_mech is a mechanical quality factor of the piezoelectric layer, φ

_p is an elasto-electric coupling factor of the laminated composite core, C₀ is the clamped capacitance of the piezoelectric layer, and Z₀ is the mechanical impedance of said laminated composite core.

14. The magneto-electric transformer of claim 11, wherein the magnetostrictive layer and the piezoelectric layer are planar and extend in a longitudinal direction.

15. The magneto-electric transformer of claim 14, wherein the piezoelectric layer is longer in the longitudinal direction than the magnetostrictive layer.

17. The magneto-electric transformer of claim 14, wherein the piezoelectric layer includes a planar first piezoelectric section and a planar second piezoelectric section that is co-planar with the first piezoelectric section, the first piezoelectric section having a first polarization and the second piezoelectric section having a second polarization opposite the first polarization direction.