Research And Design Of Charge Pump For TFT-LCD Gate Drive

In recent years, TFT-LCD flat panel display technology has developed rapidly, TFT-LCD flat panel power management products develope towards the direction of a complete power supply and small volume. The paper originates from the scientific research item in Xidian University"the power source management class integrated circuit key technologies fundamental research and design". A complete power supply solution realized by charge pump circuits is analyzed and designed according to the requirements of TFT-LCD gate driving systems.This paper analyses and studies the principles of TFT-LCD driver and charge pump converter which are the theory guidance of the design and implementation. The system adopts charge-pump structure, making the chip have two work modes including 3x and-1x. A stable output voltage is achieved by controlling the size of equivalent on-resistance on the charge-discharge circuit, that is, to control the current of the charge and discharge. 3x positive charge pump and -1x negative charge pump are used in step-up and step-down circuit system, so that the voltage conversion circuit can use the same mode of control and the symmetrical structure of the circuit, greatly simplifies the design process, in particular shortening the back-end circuit design, and have great value in project. Besides, this chip has built in the functions such as over-voltage protection, under-voltage protection and soft start.After the analysis of circuit principles and design, the function performance and key characteristics of the chip and its sub-block are simulated based on the 0.6μm BiCMOS process using Cadence software.The simulation results verify the correctness of theory and the feasibility of design method, and it meet the prospective specifications.