Theory and Experiment of ZVS on Center-Driven Dual-Output Piezoelectric Transformer Based Inverters
Date Issued
2007
Date
2007
Author(s)
Chen, Yu-Yuan
DOI
zh-TW
Abstract
The main thrust of this thesis is to develop a single layer center-driven dual-output piezoelectric transformer based inverter for lighting CCFL (cold cathode fluorescent lamp) in LCD (liquid crystal display) backlight applications. Considering the basic mechanical properties of piezoelectric transformer, center-driven dual-output piezoelectric transformer were modeled and analyzed as vibrating at the 3/2λ mode. This thesis not only built the equivalent circuit of center-driven dual-output piezoelectric transformers but also derived the equivalent relationship between the electrical component model and the corresponding mechanical properties. All important properties of center-driven dual-output piezoelectric transformer which include the input impedance, voltage gain, resonant frequency, and optimal load condition are presented in this thesis. In practical applications, two typical configurations of center-driven dual-output piezoelectric transformer were used. The first configuration is two CCFLs connect onto the two output sections of the piezoelectric transformer and shows that the two CCFLs can be lit in sequence or simultaneously. The second configuration involves connecting the two output electrode to the two ends of a single extra-long CCFL for large size LCD TV backlight, where the floating connection configuration can provide larger driving voltage because two output sections was polarized along the same directions from the geometrical view in order to light the extra long CCFL. Combining mechanical analysis and equivalent electrical circuit with the notion of switching power supply, the optimum series inductance connected in series with piezoelectric transformer for ZVS (Zero-voltage-switching) and filtering was proposed in this thesis. The resonant tank composed of series inductance and the input static capacitance of piezoelectric transformer located between the first and the third resonance frequency of the piezoelectric transformer structure, where high-order current harmonic was used for ZVS in order to greatly reduce the value needed for the series inductance. By adjusting the deadtime of power switch and putting optimum series inductance, ZVS on center-driven dual-output piezoelectric transformer based inverter was then designed in this thesis. The final experiment measured the properties of center-driven dual-output piezoelectric transformer in high power condition, In addition, the power transfer efficiency that include the switching loss and piezoelectric transformer loss within the inverter composed of half bridge driver, series optimum inductance and center-driven dual-output piezoelectric transformer was also measured. The ZVS on center-driven piezoelectric dual-output transformer based inverter was successfully completed. Moreover, by using single transformer to light a U-type and two CCFLs (300mm or 500mm or 680mm) was also successful demonstrated while controlling the lamp current at arround 5mArms. This thesis successful verified that center-driven dual-output piezoelectric transformer can be used to light CCFL. In summary, combining all advantages of the center-driven dual-output piezoelectric transformer investigated in this thesis; the center-driven dual-output piezoelectric transformer possesses the potential to replace traditional electromagnetic transformer in the future.
Subjects
中央驅動
雙輸出
壓電變壓器
零電壓切換
換流器
液晶顯示器
冷陰極燈管
center-driven
dual-output
piezoelectric transformer
ZVS
inverter
LCD
CCFL
Type
thesis
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