The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 19, 2002
Filed:
Apr. 21, 2000
Taiyo Yuden, Co., Ltd., Tokyo, JP;
Abstract
It is an object of the present invention to provide a method and an apparatus for driving a piezoelectric transformer capable of always driving with maximum conversion efficiency regardless of changes in the input voltage level, load and temperature, etc. The method and apparatus for driving a piezoelectric transformer of the present invention generate a time-varying sweep voltage through a sweep circuit at predetermined regular intervals, thereby changing the frequency of a drive signal output from a voltage control oscillator, at this time detect a phase difference between the voltage and current generated on the primary side of the piezoelectric transformer by a phase difference detector, and hold the sweep voltage corresponding to the timing at which a maximum value detector detects the maximum value by a sample-and-hold circuit, thereby controlling the frequency of the drive signal so that the phase difference between the voltage and current on the primary side of the piezoelectric transformer always becomes a maximum value.