Design of analog circuits for column driver ICs and backlight inverters of LCD TVs

Abstract

This thesis contains the suggestions and improvements of the core analog circuits of the LCD system to answer to the requirements of the next-generation flat panel display systems. Firstly, a differential algorithmic DAC and a differential-to-single switched-capacitor buffer amplifier for column drivers of the next generation TFT-LCD were proposed and designed. The capacitor mismatch problem, charge injection, and clock feedthrough of the conventional algorithmic DAC were investigated and a differential algorithmic DAC was suggested to resolve those problems. The clock frequency, switch size, and the capacitors for DAC were selected for 10-bit column driver for the UXGA (Ultra Extended Graphics Adaptor) LCD. The designed differential algorithmic DAC and differential-to-single buffer amplifier were verified using a 0.35 um CMOS process. Although, the firstly fabricated chip has some issues of revision, the possibilities of the proposed circuits were verified through the experiments. Secondly, a new low-power, high-slew-rate buffer amplifier for the LCD column driver was proposed, analyzed, designed and measured. This buffer rapidly increases the input tail current through recursive loops when the output voltage swings whereas it consumes a very low current in the static state. The designed buffer amplifier has the slew rate over 10 V/us for the load of 1 nF whereas it consumes a static current of 1~2 uA. Thirdly, a new low-cost, efficient CCFL inverter for the backlight units of wide LCD monitors and TVs was proposed. By using a modified class E-type resonant inverter, the inverter obtained the features of the low cost and a low-ripple input current. The newly proposed sensing circuit can accurately measure the lamp current and the transformer``s voltage with the floating condition of the secondary side, thereby significantly increasing the efficacy of the lamp. The control circuits including functions such as analog dimming through the current control loop, ...