Composite piezoelectric transformer

• US 6,366,006 B1
• Filed: 12/15/2000
• Issued: 04/02/2002
• Est. Priority Date: 12/15/2000
• Status: Expired due to Term

• Current Assignee: Face International Corp.
• Original Assignee: Face International Corp.
• Inventors: Boyd, Clark Davis
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US09/738,831
• Time in Patent Office: 473 Days
• Field of Search: 310/359, 310/366
• US Class Current: 310/359
• CPC Class Codes: H10N 30/40 with electrical input and electrical output, e.g. functioning as transformers

Abstract

A multi-layer piezoelectric transformer (PT) is provided that is capable of achieving high mechanical momentum and, therefore, is capable of high energy transmission. The PT has a plurality of layers arranged as a composite structure. The outermost portions of the PT comprise the input portions, which are bonded to the central output portion of the PT. The construction and anisotropic nature of the PT allows it to be driven at the longitudinal resonant frequency of the PT corresponding to its overall thickness, which increases the achievable gain and power density of the PT.

Claims

1. A piezoelectric transformer, comprising:

a first input portion having a first thickness, said first input portion further comprising;

a first input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to an axis normal to said first and second opposing major faces; and

a first input terminal adjacent said first major face of said first input ceramic layer;

a second input portion having a second thickness, said second input portion further comprising;

a second input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis; and

a second input terminal adjacent said first major face of said second input ceramic layer; and

an output portion having a third thickness, said output portion further comprising;

a first output ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

a second output ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

an output terminal adjacent said first major face of said first output ceramic layer and said first face of said second output ceramic layer;

a first common terminal adjacent said second major face of said first output ceramic layer and said second major face of said first input ceramic layer; and

a second common terminal adjacent said second major face of said second output ceramic layer and said second major face of said second input ceramic layer;

wherein upon application of a first oscillating voltage across said first input terminal and said first common terminal, said first input ceramic layer alternatingly expands and contracts in said direction parallel to said axis;

and wherein upon application of a second oscillating voltage across said second input terminal and said second common terminal, said second input ceramic layer alternatingly expands and contracts in said direction parallel to said axis;

and wherein said expansion and contraction of said first and second input ceramic layers in said direction parallel to said axis causes a first oscillating mechanical strain of said first and second output ceramic layers parallel to said axis;

and wherein said first oscillating mechanical strain of said first and second output ceramic layers piezoelectrically generates a third oscillating voltage between said first and second faces of each of said first and second output ceramic layers.

2. The piezoelectric transformer of claim 1, wherein said first input portion further comprises:

a third input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

said first major face of said third input ceramic layer being adjacent said first input terminal; and

a third input terminal;

said second major face of said third input ceramic layer being adjacent said third input terminal;

wherein upon application of said first oscillating voltage across said first input terminal and said third input terminal, said third input ceramic layer alternatingly expands and contracts in said direction parallel to said axis.

3. The piezoelectric transformer of claim 2, wherein said second input portion further comprises:

a fourth input ceramic layer having first and second opposing major faces and polarized in a direction parallel to said axis;

said first major face of said fourth input ceramic layer being adjacent said second input terminal; and

a fourth input terminal;

said second major face of said fourth input ceramic layer being adjacent said fourth input terminal;

wherein upon application of said second oscillating voltage across said second input terminal and said fourth input terminal, said fourth input ceramic layer alternatingly expands and contracts in said direction parallel to said axis.

4. The piezoelectric transformer of claim 3,

wherein said first input portion is bonded to said output portion with an adhesive;

and wherein said second input portion is bonded to said output portion with an adhesive.

5. The piezoelectric transformer of claim 4,

wherein said first common terminal further comprises a first bondline between said first face of first input ceramic layer and said first face of first output ceramic layer;

and wherein said mechanical strain in said first output ceramic layer is concentrated at said first bondline.

6. The piezoelectric transformer of claim 5,

wherein said second common terminal further comprises a second bondline between said first face of second input ceramic layer and said first face of second output ceramic layer;

and wherein said mechanical strain in said second output ceramic layer is concentrated at said second bondline.

7. The piezoelectric transformer of claim 6, further comprising:

means for applying an oscillating voltage of a first frequency across said first or second input ceramic layers.

8. The piezoelectric transformer of claim 7,

wherein said first frequency is a resonant frequency of oscillation parallel to said axis;

and wherein a sum of said first, second and third thicknesses equals an integral multiple of half-wavelengths of said resonant frequency.

9. The piezoelectric transformer of claim 1,

wherein said first output ceramic layer and said second output ceramic layer are polarized in opposite directions parallel to said axis.

10. The piezoelectric transformer of claim 3,

wherein said first input ceramic layer and said third input ceramic layer are polarized in opposite directions parallel to said axis.

11. The piezoelectric transformer of claim 3,

wherein said second input ceramic layer and said fourth input ceramic layer are polarized in opposite directions parallel to said axis.

12. The piezoelectric transformer of claim 7,

wherein said first thickness does not equal an integral multiple of half-wavelengths of said resonant frequency;

and wherein said second thickness does not equal an integral multiple of half-wavelengths of said resonant frequency;

and wherein said third thickness does not equal an integral multiple of half-wavelengths of said resonant frequency.

13. A piezoelectric transformer, comprising:

a first input portion having a first thickness, said first input portion further comprising;

a first input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to an axis normal to said first and second opposing major faces;

a first input terminal adjacent said first major face of said first input ceramic layer; and

a second input terminal adjacent said second major face of said first input ceramic layer

a second input portion having a second thickness, said second input portion further comprising;

a second input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

a third input terminal adjacent said first major face of said second input ceramic layer; and

a fourth input terminal adjacent said second major face of said second input ceramic layer;

a first isolation layer having first and second opposing major faces;

said first major face of said first isolation layer being adjacent said second input terminal;

a second isolation layer having first and second opposing major faces;

said first major face of said second isolation layer being adjacent said fourth input terminal;

an output portion having a third thickness, said output portion further comprising;

a first output ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

a second output ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

a first output terminal adjacent said first major face of said first output ceramic layer and said first face of said second output ceramic layer;

a second output terminal adjacent said second major face of said first output ceramic layer and said second major face of said first isolation layer; and

a third output terminal adjacent said second major face of said second output ceramic layer and said second major face of said second isolation layer;

wherein upon application of a first oscillating voltage across said first and second input terminals, said first input ceramic layer alternatingly expands and contracts in said direction parallel to said axis;

and wherein upon application of a second oscillating voltage across said third and fourth input terminals, said second input ceramic layer alternatingly expands and contracts in said direction parallel to said axis;

and wherein said expansion and contraction of said first and second input ceramic layers in said direction parallel to said axis causes a first oscillating mechanical strain of said first and second output ceramic layers parallel to said axis;

and wherein said first oscillating mechanical strain of said first and second output ceramic layers piezoelectrically generates a third oscillating voltage between said first and second faces of each of said first and second output ceramic layers.

14. The piezoelectric transformer of claim 13, wherein said first input portion further comprises:

a third input ceramic layer having first and second opposing electroded major faces and polarized in a direction parallel to said axis;

said first major face of said third input ceramic layer being adjacent said first input terminal; and

a fifth input terminal;

said second major face of said third input ceramic layer being adjacent said fifth input terminal;

wherein upon application of said first oscillating voltage across said first input terminal and said fifth input terminal, said third input ceramic layer alternatingly expands and contracts in said direction parallel to said axis.

15. The piezoelectric transformer of claim 14, wherein said second input portion further comprises:

a fourth input ceramic layer having first and second opposing major faces and polarized in a direction parallel to said axis;

said first major face of said fourth input ceramic layer being adjacent said third input terminal; and

a sixth input terminal;

said second major face of said fourth input ceramic layer being adjacent said sixth input terminal;

wherein upon application of said second oscillating voltage across said third input terminal and said sixth input terminal, said fourth input ceramic layer alternatingly expands and contracts in said direction parallel to said axis.