Phase Controlled Piezoelectric Backlight Inverter
Date Issued
2005
Date
2005
Author(s)
Lin, Po-Chen
DOI
zh-TW
Abstract
The backlight system is one of the most important parts in the liquid crystal display (LCD) TV. It consumes most of the power of the whole TV system. Furthermore, the power dissipated by the backlight system increases as the size of the LCD increases. To achieve higher power efficiency, piezoelectric transformers are utilized in the backlight systems.
A piezoelectric transformer can be a high-efficiency power converter. Compared with a traditional electromagnetic transformer, it has many advantages such as higher safety, lower electromagnetic interference (EMI) and smaller volume. However, a piezoelectric transformer has the highest efficiency and the highest voltage gain only when it is operated around its resonant frequency. As a result, it is very important to maintain the operating frequency of a piezoelectric transformer.
This thesis is focused on the application of the piezoelectric transformer in the LCD TV backlight system. The relations between the phase difference of the input voltage and the output current, operating frequency, and voltage gain are discussed. A phase control strategy is also proposed. The control strategy uses the phase of the output current as the feedback signal to maintain the operating frequency of the piezoelectric transformer. We implement the designed phase controlled circuit with piezoelectric transformer to ignite the CCFL and the EEFL.
Subjects
壓電變壓器
背光反流器
相位控制
Piezoelectric
Inverter
Phase Controlled
Type
thesis
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