Study And Design Of Charge Pump Circuit In AMOLED Driver Chip

With the maturity and popularity of 4G network technology,the demand for portable devices has rapidly increased.AMOLED(Active Matrix Organic Light Emitting Diode)display technology has become more popular with its unique features such as self-illumination,low power consumption and wide viewing angle.It is widely used in mobile phones,tablet computers,etc.While the AMOLED screen market is getting hotter,the demand for driver chips for AMOLED screens is also growing.The function of the power manage ment system module in the driver chip is to convert the input voltage provided by the lithium battery into the gate drive voltage of the pixel circuit on the AMOLED screen and the power supply voltage required by each module inside the chip.The charge pump circuit is the preferred solution for power management systems in AMOLED driver chips due to its high integration and low power consumption.In this thesis,AMOLED screen,AMOLED driver chip and related concepts are studied first,then determines the system structure?the function of the AMOLED driver chip and the power system according to the requirements of the AMOLED screen.This thesis presents the design of charge pump circuit for VGH which is the positive voltage of the gate drive.The function of VGH is turning off the switching transistor of the pixel to prevent transmission of the source drive signal.The gate drive signal VGH of AMOLED screen pixel circuit requires a wide adjustable range and the capability of drive load.It also requires high efficiency and low ripple.In this thesis,a multi-mode boost charge pump is designed for a wide adjustable range.The voltage provided by the lithium battery and the output voltage obtained by other charge pumps are combined to be the input voltage of the char ge pump VGH to realize the wide adjustable range in different modes.The addition of the cross-cycle modulation circuit makes the output voltage stable and adjustable.The pump circuit in the multi-mode boost charge pump system uses a symmetrical bilateral mode to increase the load carrying capacity of the output voltage while also reducing the ripple of the output voltage.In addition,the problem of charge selection in mode selection and mode switching encountered in multi-mode charge pump design is solved by initializing circuit,voltage detector and substrate selection switch in this thesis,and these circuits also improve the voltage of multi-mode boost charge pump system conversion rateBased on the UMC80 nm process,the design of the charge pump circuit is simulated by Cadence's Spectre software.The simulation results show that when the load current is 4mA,the output voltage range is 9V?16V,and the voltage conversion rate in four working modes maintaining over 90% and voltage ripple ?1mV,these indicators meet the system requirements.