Maximum efficiency control of a system composed of a piezoelectric transformer and cold cathode tube driven by inverter, and its characteristics

This paper concerns a control method in which cold cathode tube used for liquid crystal display, etc. is made to light at maximum efficiency. In the system composed of inverter, LC circuit, piezoelectric transformer, and cold cathode tube, tube current is controlled at the height of inverter output voltage, and the efficiency is controlled at the frequency. In this way, maximum efficiency control which does not depend on tube current is realized by carrying out tube current control and efficiency control separate. Maximum efficiency control method is deduced, after the characteristics of piezoelectric transformer and cold cathode tube are well examined, and the performance of the control has been confirmed by simulation and experiment. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 82– 93, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20567