| With the rapid development of mobile devices such as mobile phones and tablet computers,more and more information can be obtained on mobile devices.As the main medium of human-computer interaction,the screen has also developed rapidly with this wave.The AMOLED(Active Matrix Organic Light Emitting Diode)screen has the ad vantages of self-illumination,low power consumption,wide viewing angle,etc.compared with the LCD(Liquid Crystal Display)screen,and has gradually become the most mobile device.The selected display schemes.In China,BOE,TCL Optoelectronics and other AMOLED display panel manufacturers have developed rapidly and can independently produce high-quality display panels.However,there is still a large gap between the display driver chip technology supporting the panel and South Korea and Taiwan.The function of the display driver chip is to convert the image data into gray-scale voltage,and then transmit the gray-scale voltage to the display panel to display the image.Since the driving chip needs a high voltage and a negative voltage higher than the power supply to realize the image display,the charge pump technology becomes an important part of the driving chip.The display driver chip is powered by a lithium battery,the supply voltage is 2.7 ～ 3.3V,and the positive voltage re quired for display is 6 ～ 16 V,and the negative voltage is-6 ～-16 V,so high voltage gain is important for driving the charge pump in the chip One of the design indicators.This article analyzes existing Dickson charge pumps,charge transfer switch charge pumps,fourphase clock charge pumps,cross-coupled charge pumps,Fibonacci charge pumps,and exponential charge pumps,and compares them in ter ms of voltage gain and design complexity.Based on this analysis,an exponential charge pump design with a higher voltage gain is selected.In addition to the voltage gain,the stability of the output voltage of the charge pump affects the display effect of the driver chip,so the output voltage ripple is also one of the important indicators in the design.Currently,the commonly used methods to reduce the output voltage ripple are hybrid modulation structure and multi-branch structure.Comprehensive voltag e ripple size and chip area consumption,this paper uses a dual branch structure for design.The charge pump design for the AMOLED display driver chip proposed in this paper uses a multi-stage exponential charge pump structure to increase the voltage gain,and the output stage charge pump uses a symmetrical double-branch structure to reduce the output voltage rippl e.In addition,the pump circuit is also designed with a substrate adjustment circuit to reduce energy consumption in the circuit and improve the power efficiency of the charge pump.Based on UMC80 nm DNW process,the charge pump system designed in this article by spectre software is used for simulation verification.The simulation results show that the positive voltage output range of the charge pu mp system is 6 ～ 16 V and the negative voltage output range is-6 ～-16 V.With a current load of 8m A,the minimum positive and negative voltage output voltage ripple is 0.7m V,the input stage charge pump efficiency is higher than 80%,and the output stage charge pump efficiency is higher than 70%,which can meet AMOLED display driver chip power supply requirements f or the charge pump system. |
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