Design criteria of transformer for LCD backlight inverter

Abstract

The paper presents the design methodology and results of a transformer for backlight inverter (TFBI) supplying a cold cathode fluorescent lamp (CCFL). The backlight inverter adopts resonant behavior and operates by high frequency, and contains resonant tank circuit in its topology. The transformer functions as not only voltage rise but also an inductance in resonance bank, in which the second leakage inductance is dominant. So, TFBI should be analyzed and designed in different scheme from general transformer. The circuit coupled analysis and design, especially considering resonance behavior and ZVS, should be applied to TFBI for performance improvement of inverter overall as well as transformer itself. the authors propose the design of TFBI operated at the maximum efficiency point considering the circuit coupled magnetic field analysis and inverter drive method for ZVS. The design variables are turn number of coils, gap and parameters including inductances of transformer.