Patent ID: 6040654
Filing Date: 2000-03-21
Classification: H01L

Abstract:
A piezoelectric transformer including:a body made of piezoelectric material having a first and a second face and an outer lateral surface;a plurality of primary electrodes arranged on said body to cause said body to vibrate in response to a primary alternative voltage; anda plurality of secondary electrodes arranged on said body to generate a secondary voltage in response to said vibration;said outer surface having, in the absence of said vibration, the shape of a first circular cylinder having a circular axis of symmetry and said faces each having an outer portion situated on the side of said outer lateral surface and an inner portion surrounded by said outer portion,wherein said primary electrodes are arranged so that, when said primary voltage has a frequency at least substantially equal to a determined frequency, said outer lateral surface alternately takes the shape of a first elliptical cylinder and the shape of a second elliptical cylinder, said first elliptical cylinder having a major axis and a minor axis perpendicular to said circular axis of symmetry and respectively situated in a first plane of symmetry including said circular axis of symmetry and a second plane of symmetry perpendicular to said first plane of symmetry and also including said circular axis of symmetry, said second elliptical cylinder having a major axis and a minor axis perpendicular to said circular axis of symmetry and respectively situated in said second plane of symmetry and said first plane of symmetry, and, when said outer lateral surface has the shape of one of said first and second elliptical cylinders, the respective major axis having a length which varies regularly increasing from a minimum value equal to the diameter of said circular cylinder to a maximum value then decreasing from said maximum value to said minimum value, said outer lateral surface then taking the shape of the other of said first and second elliptical cylinders.