Piezoelectric transformer and power converting apparatus employing the same

• US 5,751,092 A
• Filed: 07/05/1996
• Issued: 05/12/1998
• Est. Priority Date: 07/06/1995
• Status: Expired due to Fees

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Abe, Tooru
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US08/675,880
• Time in Patent Office: 676 Days
• Field of Search: 310/316, 310/317, 310/358, 310/359, 310/366, 310/328
• US Class Current: 310/359
• CPC Class Codes: H10N 30/40 with electrical input and electrical output, e.g. functioning as transformers
• CPC Class Codes: H10N 30/804 for piezoelectric transformers conversion of DC or AC power H02M; for operating discharge lamps H05B41/282

Abstract

A piezoelectric transformer has a driving section area which is provided with input electrodes at the central portion of a long-plate-shaped piezoelectric element and which is polarized in the direction of the thickness thereof; and power generating section areas which are provided with output electrodes on the ends surfaces in the direction of the length thereof, which are polarized in the opposite directions from each other with the driving section area between them, and which are disposed on both ends of the piezoelectric element. The piezoelectric transformer is excited in the half wavelength mode to obtain an output between the output electrodes and the input electrodes. A ratio L2/L1 of the length L2 of the driving section to the overall length L1 in the direction of the length of the piezoelectric transformer ranges from 0.3 to 0.6.

Claims

1. A piezoelectric transformer comprising:

a long-plate-shaped piezoelectric element;

input electrodes coupled to the long-plate-shaped piezoelectric element;

output electrodes coupled to the long-plate-shaped piezoelectric element;

a driving section area of the long-plate-shaped piezoelectric element being polarized in the direction of thickness and including the input electrodes positioned at the central part of the piezoelectric element;

first and second power generating section areas including the output electrodes provided on end surfaces of said piezoelectric element in the direction of the length thereof, the first and second power generating sections being polarized in opposite directions from each other and disposed on opposite sides of said driving section area;

wherein said piezoelectric element is excited in a half wavelength mode to obtain an output between said output electrodes and said input electrodes and a ratio L2/L1 of a length L2 of said driving section area to an overall length L1 in the direction of the length of said piezoelectric element ranges from 0.3 to 0.6 and

wherein a ratio L1/W of the overall length L1 to a width W of said piezoelectric element ranges from 4.10 to 4.77.

3. A power converting apparatus comprising:

a piezoelectric transformer described in one of claims 1 or 2;

inductance means constituting a resonance circuit with an input capacitance of said piezoelectric transformer;

switching means connected between a DC input power supply for supplying power to said piezoelectric transformer and said inductance means; and

driving/oscillating means for generating a driving voltage of a predetermined frequency by the switching function of said switching means.

4. A power converting apparatus according to claim 3, further comprising a frequency changing section for controlling said driving/oscillating means.

5. A power converting apparatus according to claim 3, further comprising rectifying/smoothing means which is connected to the output of said piezoelectric transformer.

2. A piezoelectric transformer comprising:

a long-plate-shaped piezoelectric element;

input electrodes coupled to the long-plate-shaped piezoelectric element;

output electrodes coupled to the long-plate-shaped piezoelectric element;

a driving section area of the long-plate-shaped piezoelectric element being polarized in the direction of thickness and including the input electrodes positioned at the central part of the piezoelectric element;

first and second power generating section areas including the output electrodes provided on end surfaces of said piezoelectric element in the direction of the length thereof, the first and second power generating sections being polarized in opposite directions from each other and disposed on opposite sides of said driving section area;

wherein said piezoelectric element is excited in a half wavelength mode to obtain an output between said output electrodes and said input electrodes;

and wherein a ratio L2/L1 of a length L2 of said driving section area to an overall length L1 in the direction of the length of said piezoelectric element ranges from 0.3 to 0.6 and wherein said driving section area is comprised of said piezoelectric element and said input electrodes are alternately laminated and are connected with external electrodes at every other layer.