A Design Of Temperature Compensation System Based On Bandgap Reference For AMOLED Display Pannel

Recently, because of the advantages that wider visual angle, better display quality, higher response speed than LCD displayers, and without back light and low power dissipation, AMOLED displayers are widely employed in many mobile terminals, and as AMOLED is flexible,it can be used in more different application domain. According to displayresearch’s reports, OLED product’s permeability has been rising year by year, it can be predicted that AMOLED panels is going to take over the present position of LCD. However, some problem that the luminance will degrade and start up lighting delay will be longer with the temperature decreasing. Therefore, it is very necessary to design a temperature compensation system to guarantee the high display quality.In this thesis, a kind of circuit architecture is designed to compensate the problem mentioned above. The architecture mainly includes a sensor circuit to detect the panel temperature and a compensation circuit to compensate the luminance changing by modifying the response voltage, and also a structure for converting the detector signals to compensation controlling signals is designed. This design is different from the commercial method. It is entirely integrated on one display driver chip to adjust the GAMMA curve by controlling the BGR output voltage.Because the compensation temperature range is from-30 ℃ to 10 ℃, and compensate once per ten degrees, so it’s no need to design a very high accurate sensor, and consider the area and power dissipation, then designed a frequency output sensor, and the frequency is PTAT, the frequency difference between two degrees is about 117 KHz, in 1℃ accuracy, and 152μW dissipation; signal converter is consist of a 9-bit counter, some logic gate. By setting a suitable counting threshold time then a binary number is got, and be converted to the controlling signal; compensation circuit is based on the bandgap reference, and the output voltage is adjustable, there are 6 different optional values, so that the circuit can compensate the changing temperature condition. The BGR’s temperature coefficient is 10ppm/℃, the PSRR is-75.4dB, the error is in ±2.3mV. The simulation results show that the proposed design is able to achieve the desired function very well.