A Multi-mode Charge Pump System Applied In AMOLED Driver Chip

In the advancement of the display technology, AMOLED(Active Matrix Organic Light Emitting Diode) as the new display technology, has been recognized as the next generation display technology, which AM(Active Matrix body) refered to the pixels behind addressing technology and OLED refered to the use of Organic semiconductor materials and light-emitting materials under the electric driving, through the carrier injection and compound resulted in light-emitting Diode. At present, more and more applied in electronic instrument such as cellphones, computers and TVs.The requirements of AMOLED driver chip were very large.In the paper, after studying and researching the charge pump system theory in-depth, it completed the design of charge pump system and applied two kinds of feedback system and modulation technology. Contraposing the different characteristics of the gate and the source driver circuit at power supply voltage in this AMOLED driver chip, it designed different feedback system, which made it in the view of improving the performance of the output voltage and improved the conversion efficiency and stability of the charge pump system.Meanwhile it improved secondary booster system, which only used a new multi-mode charge pump circuit and it can offer positive and negative two voltage simultaneously.The voltage can adjust, which greatly simplifyed the circuit structure and reduced the cost.The voltage VSOUT of booster charge pump system provided power supply voltage for the source driver in the AMOLED driver chip.It designed a kind of hybrid modulation mode which had a high efficiency and low ripple combining the linear modulation and cross modulation for the system. It can improve the conversion efficiency of booster charge pump system at the same time of reducing the output voltage ripple.The new multi-mode charge pump system only used one circuit, which can provided the power supply voltage VGHO and VGLO at the same time for the positive and negative gate driver system in AMOLED driver chip.And the request of gate drive system power supply voltage was not as good as source drive system, so in the new multi-mode charge pump system it only used the cross modulation mode, which made the new multi-mode charge pump system have a higher conversion efficiency.After finishing the function introducing, principle analysising and circuit designing, it carried on the simulation on the basis of mixed high and low voltage CMOS process, in condition of 0.18 um 32V with Cadence Spectre for the whole charge pump system.In the tt process corner, T=25℃, VCI=2.65 V, the simulation results showed that the set-up time of the output voltage VSOUT was 287 us, stable output voltage was 5.285 V after work and ripple was 7m V;Output voltage VGLO and VGHO had four kinds of working mode, which were 7.793 V and-7.791 V, 7.793 V and-10.391 V, 10.393 V and-7.791 V, 10.393 V and-10.391 V.The set up time of voltage was in less than 2ms and voltage ripple was less than 20 m V.The charge pump system average conversion efficiency was 91% in the range of input voltage, which met the needs of the whole system.