Piezoelectric transformer showing a reduced input impedance and step-up/step-down operation for a wide range of load resistance

Claim 2

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said second a.c. current; said first electrode means comprising a pair of opposing electrodes each having a first area and provided on the substrate to oppose with each other across substrate; said second electrode means comprising a pair of opposing electrodes each having a second area and provided on the piezoelectric substrate to oppose with each across the piezoelectric substrate, said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means including a plurality of electrodes each extending in the first direction with a first length, and said second electrode means including a plurality of electrodes each extending in the first direction with a second length that is different from the first length, said first electrode means exciting the elastic wave with a wavelength, and said piezoelectric substrate extending in the first direction with a length corresponding to one half the wavelength of said elastic wave.

Claim 3

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said second a.c. current; said first electrode means comprising a pair of opposing electrodes each having a first area and provided on the substrate to oppose with each other across substrate; said second electrode means comprising a pair of opposing electrodes each having a second area and provided on the piezoelectric substrate to oppose with each across the piezoelectric substrate, said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means including a plurality of electrodes each extending in the first direction with a first length, and said second electrode means including a plurality of electrodes each extending in the first direction with a second length that is different from the first length, said first electrode means exciting the elastic wave with a wavelength, and said piezoelectric substrate extending in the first direction with a length corresponding to one full wavelength of said elastic wave.

Claim 4

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said second a.c. current; said first electrode means comprising a pair of opposing electrodes each having a first area and provided on the substrate to oppose with each other across substrate; said second electrode means comprising a pair of opposing electrodes each having a second area and provided on the piezoelectric substrate to oppose with each across the piezoelectric substrate, said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means including a plurality of electrodes each extending in the first direction with a first length, and said second electrode means including a plurality of electrodes each extending in the first direction with a second length that is different from the first length, said first electrode means exciting the elastic wave with a wavelength, and said piezoelectric substrate extending in the first direction with a length corresponding to one full wavelength of said elastic wave.

Claim 5

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said second a.c. current; said first electrode means comprising a pair of opposing electrodes each having a first area and provided on the substrate to oppose with each other across substrate; said second electrode means comprising a pair of opposing electrodes each having a second area and provided on the piezoelectric substrate to oppose with each across the piezoelectric substrate, said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means including a plurality of electrodes each extending in the first direction with a first length, and said second electrode means including a plurality of electrodes each extending in the first direction with a second length that is different from the first length, said piezoelectric substrate including a 140° rotated-Y cut single crystal of LiNbO 3 .

Claim 6

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said second a.c. current; said first electrode means comprising a pair of opposing electrodes each having a first area and provided on the substrate to oppose with each other across substrate; said second electrode means comprising a pair of opposing electrodes each having a second area and provided on the piezoelectric substrate to oppose with each across the piezoelectric substrate, said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means including a plurality of electrodes each extending in the first direction with a first length, and said second electrode means including a plurality of electrodes each extending in the first direction with a second length that is different from the first length, said piezoelectric substrate including a 140° rotated-Y cut single crystal of LiNbO 3 .

Claim 7

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having upper and lower major surfaces, and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said secondary a.c. current; said first electrode means including a pair of opposing electrodes each having a first area and provided on the piezoelectric substrate to oppose with each other across the piezoelectric substrate; said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means extending in a second direction that is perpendicular to said first direction and disposed on the upper and lower major surfaces of the piezoelectric substrate, with a first length, and said second electrode means extending in said second direction with a second length that is different from said first length, said piezoelectric substrate having an uniform polarization inclined with respect to the first direction and with respect to the upper and lower major surfaces of the piezoelectric substrate, and third electrode means including first and second electrodes provided on said piezoelectric substrate such that the first and second electrodes are provided respectively on said upper and lower major surfaces of the substrate substantially in alignment in said second direction with the electrodes that form the second electrode means.

Claim 8

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having upper and lower major surfaces, and extending in a first direction; first electrode means provided on said piezoelectric substrate for exciting an elastic wave propagating through the piezoelectric substrate in the first direction in response to an electric excitation caused by the primary a.c. current; and second electrode means provided on said piezoelectric substrate at a location offset from said first electrode means in said first direction for converting the elastic wave to an electric voltage to produce said secondary a.c. current; said first electrode means including a pair of opposing electrodes each having a first area and provided on the piezoelectric substrate to oppose with each other across the piezoelectric substrate; said first electrode means and said second electrode means being formed such that the first area and the second area are different from each other, said first electrode means extending in a second direction that is perpendicular to said first direction and disposed on the upper and lower major surfaces of the piezoelectric substrate, with a first length, and said second electrode means extending in said second direction with a second length that is different from said first length, said piezoelectric substrate having an uniform polarization inclined with respect to the first direction and with respect to the upper and lower major surfaces of the piezoelectric substrate, and third electrode means including first and second electrodes provided on said piezoelectric substrate such that the first and second electrodes are provided respectively on said upper and lower major surfaces of the substrate substantially in alignment in said second direction with the electrodes that form the second electrode means.

Claim 9

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, said input a.c. current and said output a.c. current having a predetermined frequency, comprising: a piezoelectric substrate extending in a first direction with first and second opposing ends separated with each other by a predetermined longitudinal length; first electrode means provided on said piezoelectric substrate along said first direction to cover the piezoelectric substrate with a first area, said first electrode means being supplied with said input a.c. current for exciting a resonant elastic wave in the piezoelectric substrate with a wavelength determined by the frequency of said input a.c. current; and second electrode means provided on said substrate along said first direction to cover the piezoelectric substrate with a second area that is different from the first area, said second electrode means converting the resonant elastic wave to an electric voltage to produce said output a.c. current, said predetermined longitudinal length of said piezoelectric substrate being set to be equal to an integer multiple of one-half of said wavelength such that there are formed a plurality of nodes in the piezoelectric substrate along said first direction; said first and second electrode means having a synchronization in phase with said elastic wave, and said first and second electrode means including a plurality of electrodes each extending in a second direction that is a direction perpendicular to said first direction within a principal surface of the substrate, each electrode of said first and second electrodes means being provided in correspondence to each node formed in the substrate.

Claim 10

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, said input a.c. current and said output a.c. current having a predetermined frequency, comprising: a piezoelectric substrate extending in a first direction with first and second opposing ends separated with each other by a predetermined longitudinal length; first electrode means provided on said piezoelectric substrate along said first direction to cover the piezoelectric substrate with a first area, said first electrode means being supplied with said input a.c. current for exciting a resonant elastic wave in the piezoelectric substrate with a wavelength determined by the frequency of said input a.c. current; and second electrode means provided on said substrate along said first direction to cover the piezoelectric substrate with a second area that is different from the first area, said second electrode means converting the resonant elastic wave to an electric voltage to produce said output a.c. current, said predetermined longitudinal length of said piezoelectric substrate being set to be equal to an integer multiple of one-half of said wavelength such that there are formed a plurality of nodes in the piezoelectric substrate along said first direction; said first and second electrode means having a synchronization in phase with said elastic wave, and said first and second electrode means including a plurality of electrodes each extending in a second direction that is a direction perpendicular to said first direction within a principal surface of the substrate, each electrode of said first and second electrodes means being provided in correspondence to each node formed in the substrate.

Claim 11

A piezoelectric transformer as claimed in claim 5 in which each electrode forming the first electrode means has a first length in said first direction, each electrode forming the second electrode means has a second length in said first direction, wherein said first length is set different from said second length.

Claim 12

A piezoelectric transformer as claimed in claim 5 in which each electrode forming the first electrode means and each electrode forming the second electrode means have a same length in said first direction, wherein said first electrode means include the electrodes with a number that is different from a number of the electrodes included in said second electrode means.

Claim 13

A piezoelectric transformer as claimed in claim 7 in which the electrodes forming the first electrode means are connected in series, and the electrodes forming the second electrode means are connected in series.

Claim 14

A piezoelectric transformer as claimed in claim 7 in which the electrodes forming the first electrode means are connected in parallel, and the electrodes forming the second electrode means are connected in parallel.

Claim 15

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with second voltage, the input and output a.c. currents having a predetermined frequency, comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction with first and second opposing ends separated from each other by a predetermined longitudinal length; first electrode means, including a plurality of electrodes grouped into first and second groups in a first area on said piezoelectric substrate, for receiving the input a.c. current and for exciting a resonant longitudinal elastic wave in said piezoelectric substrate with a wavelength determined by the frequency of the input a.c. current, the predetermined longitudinal length of said piezoelectric substrate being equal to an integer multiple of one-half of the wavelength, thereby forming a plurality of nodes along the first direction in said piezoelectric substrate, said electrodes of the first group being provided on said upper major surface of said piezoelectric substrate along the first direction and said electrodes of the second group being provided on said lower major surface of said piezoelectric substrate opposing said electrodes of the first group across said piezoelectric substrate to produce the resonant longitudinal elastic wave propagating in the first direction; and second electrode means, including a plurality of electrodes grouped into third and fourth groups, for converting the resonant longitudinal elastic wave to an electric voltage to produce the output a.c. current, said electrodes of the third group and the fourth group being provided on said piezoelectric substrate along the first direction in a second area different from the first area and opposing each other across said piezoelectric substrate, said first and second electrode means having a synchronization in phase with the resonant longitudinal elastic wave.

Claim 16

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with second voltage, the input and output a.c. currents having a predetermined frequency, comprising: a piezoelectric substrate having upper and lower major surfaces and extending in a first direction with first and second opposing ends separated from each other by a predetermined longitudinal length; first electrode means, including a plurality of electrodes grouped into first and second groups in a first area on said piezoelectric substrate, for receiving the input a.c. current and for exciting a resonant longitudinal elastic wave in said piezoelectric substrate with a wavelength determined by the frequency of the input a.c. current, the predetermined longitudinal length of said piezoelectric substrate being equal to an integer multiple of one-half of the wavelength, thereby forming a plurality of nodes along the first direction in said piezoelectric substrate, said electrodes of the first group being provided on said upper major surface of said piezoelectric substrate along the first direction and said electrodes of the second group being provided on said lower major surface of said piezoelectric substrate opposing said electrodes of the first group across said piezoelectric substrate to produce the resonant longitudinal elastic wave propagating in the first direction; and second electrode means, including a plurality of electrodes grouped into third and fourth groups, for converting the resonant longitudinal elastic wave to an electric voltage to produce the output a.c. current, said electrodes of the third group and the fourth group being provided on said piezoelectric substrate along the first direction in a second area different from the first area and opposing each other across said piezoelectric substrate, said first and second electrode means having a synchronization in phase with the resonant longitudinal elastic wave.

Claim 17

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, the input and output a.c. currents having a predetermined frequency, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with first and second opposing ends separated from each other by a predetermined longitudinal length; first electrode means, including a plurality of first electrodes provided on the principal surface along the first direction in a first area on said piezoelectric substrate, for receiving the input a.c. current at each pair of adjacent electrodes and for producing width-shear vibration by exciting a resonant longitudinal elastic wave in said piezoelectric substrate with a wavelength determined by the frequency of the input a.c. current, the predetermined longitudinal length of said piezoelectric substrate being equal to an integer multiple of one-half of the wavelength, thereby forming a plurality of nodes in said piezoelectric substrate along the first direction; and second electrode means, including a plurality of second electrodes provided on the principal surface of said piezoelectric substrate along the first direction in a second area different from the first area, for converting the resonant longitudinal elastic wave to an electric voltage to produce the output a.c. current, said first and second electrode means having a synchronization in phase with the resonant longitudinal elastic wave.

Claim 18

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, the input and output a.c. currents having a predetermined frequency, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with first and second opposing ends separated from each other by a predetermined longitudinal length; first electrode means, including a plurality of first electrodes provided on the principal surface along the first direction in a first area on said piezoelectric substrate, for receiving the input a.c. current at each pair of adjacent electrodes and for producing width-shear vibration by exciting a resonant longitudinal elastic wave in said piezoelectric substrate with a wavelength determined by the frequency of the input a.c. current, the predetermined longitudinal length of said piezoelectric substrate being equal to an integer multiple of one-half of the wavelength, thereby forming a plurality of nodes in said piezoelectric substrate along the first direction; and second electrode means, including a plurality of second electrodes provided on the principal surface of said piezoelectric substrate along the first direction in a second area different from the first area, for converting the resonant longitudinal elastic wave to an electric voltage to produce the output a.c. current, said first and second electrode means having a synchronization in phase with the resonant longitudinal elastic wave.

Claim 19

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a pair of lateral boundaries that extend generally in the first direction while being separated from each other in a second direction that is defined as a direction perpendicular to said first direction in a plane of said principal surface, the piezoelectric substrate having a channel region extending in said first direction, and having a pair of marginal regions at both lateral sides of said channel region extending generally in the first direction, said channel region being separated from both lateral boundaries by said marginal regions; energy confinement means provided on the piezoelectric substrate in correspondence to said channel region for reducing a velocity of elastic waves propagating through the piezoelectric substrate along the channel region in said first direction; first electrode means provided on the principal surface of the piezoelectric substrate in correspondence to the channel region with a first area; and second electrode means provided on the principal surface of the piezoelectric substrate in correspondence to the channel region with a second area, said first and second electrode means being formed such that the first area and the second area are different from each other.

Claim 20

A piezoelectric transformer supplied with a primary a.c. current with a first voltage for producing a secondary a.c. current with a second voltage, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a pair of lateral boundaries that extend generally in the first direction while being separated from each other in a second direction that is defined as a direction perpendicular to said first direction in a plane of said principal surface, the piezoelectric substrate having a channel region extending in said first direction, and having a pair of marginal regions at both lateral sides of said channel region extending generally in the first direction, said channel region being separated from both lateral boundaries by said marginal regions; energy confinement means provided on the piezoelectric substrate in correspondence to said channel region for reducing a velocity of elastic waves propagating through the piezoelectric substrate along the channel region in said first direction; first electrode means provided on the principal surface of the piezoelectric substrate in correspondence to the channel region with a first area; and second electrode means provided on the principal surface of the piezoelectric substrate in correspondence to the channel region with a second area, said first and second electrode means being formed such that the first area and the second area are different from each other.

Claim 21

A piezoelectric transformer as claimed in claim 12 in which said energy confinement means comprises said first and second electrode means.

Claim 22

A piezoelectric transformer as claimed in claim 12 in which said energy confinement means comprises a material layer that is provided on said piezoelectric substrate in correspondence with said channel region.

Claim 23

A piezoelectric transformer as claimed in claim 14 in which said first and second electrode means are provided on said material layer.

Claim 24

A piezoelectric transformer as claimed in claim 14 in which said energy confinement means comprises a material layer that buries said first and second electrode means.

Claim 25

A piezoelectric transformer as claimed in claim 12 in which each of said marginal regions has a size in the second direction that is set at least four times as large as a wavelength of the elastic wave that is excited in the piezoelectric substrate.

Claim 26

A piezoelectric transformer as claimed in claim 12 in which each of said marginal regions has a size measured in the first direction such that the size is different from a size of said channel region measured in said first direction.

Claim 27

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a first length, said piezoelectric substrate having an orientation for preferential excitation of a width-shear vibration; first electrode means provided on said principal surface of the piezoelectric substrate along said first direction, said first electrode means comprising a plurality of electrodes each provided on said principal surface and extending in a direction substantially perpendicular to said first direction, each pair of said electrodes being supplied with said input a.c. current for inducing a shear wave in said piezoelectric substrate such that the shear wave propagates in said first direction with a direction of elastic displacement parallel to said principal surface of the piezoelectric substrate; and second electrode means provided on said principal surface of the piezoelectric substrate along said first direction, said second electrode means comprising a plurality of electrodes each provided on said principal surface and extending in a direction substantially perpendicular to said first direction, said second electrode means converting said shear vibration to an electric voltage to produce said output a.c. current, said piezoelectric substrate including a Y-rotated X-cut single crystal of LiNbO 3 with an angle of rotation of 163±10°.

Claim 28

A piezoelectric transformer supplied with an input a.c. current with a first voltage for producing an output a.c. current with a second voltage, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a first length, said piezoelectric substrate having an orientation for preferential excitation of a width-shear vibration; first electrode means provided on said principal surface of the piezoelectric substrate along said first direction, said first electrode means comprising a plurality of electrodes each provided on said principal surface and extending in a direction substantially perpendicular to said first direction, each pair of said electrodes being supplied with said input a.c. current for inducing a shear wave in said piezoelectric substrate such that the shear wave propagates in said first direction with a direction of elastic displacement parallel to said principal surface of the piezoelectric substrate; and second electrode means provided on said principal surface of the piezoelectric substrate along said first direction, said second electrode means comprising a plurality of electrodes each provided on said principal surface and extending in a direction substantially perpendicular to said first direction, said second electrode means converting said shear vibration to an electric voltage to produce said output a.c. current, said piezoelectric substrate including a Y-rotated X-cut single crystal of LiNbO 3 with an angle of rotation of 163±10°.

Claim 29

A piezoelectric transformer as claimed in claim 19 in which said piezoelectric substrate comprises a piezoelectric crystal that is characterized by a maximum value for an electromechanical coupling coefficient k 15 .

Claim 30

A piezoelectric transformer as claimed in claim 19 in which said piezoelectric substrate comprises a rotated Y-cut single crystal of LiTaO 3 with an angle of rotation of -48±10°.

Claim 31

A piezoelectric transformer as claimed in claim 19 in which said piezoelectric substrate comprises a piezoelectric ceramic having a direction of polarization in said first direction.

Claim 32

A piezoelectric oscillator, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a first length, said piezoelectric substrate having an orientation for preferential excitation of a width-shear vibration; a plurality of first type electrodes provided on said principal surface of the piezoelectric substrate along said first direction, each electrode of said first type electrodes extending on said principal surface in a direction substantially perpendicular to said first direction for exciting the width-shear vibration; and a plurality of second type electrodes provided on said principal surface of the piezoelectric substrate along said first direction, each electrode of said second type electrodes extending on said principal surface in a direction substantially perpendicular to said first direction; each electrode of said first type electrodes and each electrode of said second type electrodes being provided alternately in said first direction; a first input terminal; and a second input terminal; said plurality of first type electrodes being connected commonly to said first input terminal and said plurality second type electrodes being connected commonly to said second input terminal; said piezoelectric substrate including a Y-rotated x-cut single crystal of LiNbO 3 with an angle of rotation of 163±10°.

Claim 33

A piezoelectric oscillator, comprising: a piezoelectric substrate having a principal surface and extending in a first direction with a first length, said piezoelectric substrate having an orientation for preferential excitation of a width-shear vibration; a plurality of first type electrodes provided on said principal surface of the piezoelectric substrate along said first direction, each electrode of said first type electrodes extending on said principal surface in a direction substantially perpendicular to said first direction for exciting the width-shear vibration; and a plurality of second type electrodes provided on said principal surface of the piezoelectric substrate along said first direction, each electrode of said second type electrodes extending on said principal surface in a direction substantially perpendicular to said first direction; each electrode of said first type electrodes and each electrode of said second type electrodes being provided alternately in said first direction; a first input terminal; and a second input terminal; said plurality of first type electrodes being connected commonly to said first input terminal and said plurality second type electrodes being connected commonly to said second input terminal; said piezoelectric substrate including a Y-rotated x-cut single crystal of LiNbO 3 with an angle of rotation of 163±10°.