基于低温多晶硅薄膜晶体管的AMOLED交流像素电路

This work presents a new voltage programmed pixel circuit for an active-matrix organic light-emitting diode(AMOLED) display.The proposed pixel circuit consists of six low temperature polycrystalline silicon thinfilm transistors(LTPS TFTs),one storage capacitor,and one OLED,and is verified by simulation work using HSPICE software.Besides effectively compensating for the threshold voltage variation of the driving TFT and OLED,the proposed pixel circuit offers an AC driving mode for the OLED,which can suppress the degradation of the OLED.Moreover,a high contrast ratio can be achieved by the proposed pixel circuit since the OLED does not emit any light except for the emission period.     

一种基于低温多晶硅薄膜晶体管的交流AMOLED像素补偿电路

This paper presents a new poly-Si pixel circuit employing AC driving mode for active matrix organic light-emitting diode （AMOLED） displays. The proposed pixel circuit, which consists of one driving thin-film tran- sistor （TFT）, three switching TFTs, and one storage capacitor, can effectively compensate for the threshold voltage variation in poly-Si and the OLED degradation. As there is no light emission, except for during the emitting period, and a small number of devices used in the proposed pixel circuit, a high contrast ratio and a high pixel aperture ratio can be easily achieved. Simulation results by SMART-SPICE software show that the non-uniformity of the OLED current for the proposed pixel circuit is significantly decreased （〈 10%） with an average value of 2.63%, while that of the conventional 2T1C is 103%. Thus the brightness uniformity of AMOLED displays can be improved by using the proposed pixel circuit.     

Design of a 16 gray scales 320×240 pixels OLED-on-silicon driving circuit

A 320×240 pixel organic-light-emitfing-diode-on-silicon （OLEDoS） driving circuit is implemented using the standard 0.5μm CMOS process of CSMC. It gives 16 gray scales with integrated 4 bit D/A converters. A three- transistor voltage-programmed OLED pixel driver is proposed, which can realize the very small current driving required for the OLEDoS microdisplay. Both the D/A converter and the pixel driver are implemented with pMOS devices. The pass-transistor and capacitance in the OLED pixel driver can be used to sample the output of the D/A converter. An additional pMOS is added to OLED pixel driver, which is used to control the D/A converter operating only when one row is on. This can reduce the circuit＇s power consumption. This driving circuit can work properly in a frame frequency of 50 Hz, and the final layout of this circuit is given. The pixel area is 28.4 × 28.4μm^2 and the display area is 10.7 × 8.0 mm^2 （the diagonal is about 13 mm）. The measured pixel gray scale voltage shows that the function of the driver circuit is correct, and the power consumption of the chip is about 350 mW.     

一种用于高压降压型转换器的高精度强驱动能力驱动电路

This paper presents a novel driving circuit for the high-side switch of high voltage buck regulators.A 40 V P-channel lateral double-diffused metal–oxide–semiconductor device whose drain–source and drain–gate can resist high voltage, but whose source–gate must be less than 5 V, is used as the high-side switch. The proposed driving circuit provides a stable and accurate 5 V driving voltage for protecting the high-side switch from breakdown and achieving low on-resistance and simple loop stability design. Furthermore, the driving circuit with excellent driving capability decreases the switching loss and dead time is also developed to reduce the shoot-through current loss. Therefore, power efficiency is greatly improved. An asynchronous buck regulator with the proposed technique has been successfully fabricated by a 0.35 m CDMOS technology. From the results, compared with the accuracy of16.38% of the driving voltage in conventional design, a high accuracy of 1.38% is achieved in this work. Moreover,power efficiency is up to 95% at 12 V input and 5 V output.     

通用可编程多量子阱空间光调制器驱动电路

A universal programmable multi-quantum-well（MQW） spatial light modulator（SLM） driving circuit is developed.With a twice scanning, it can generate programmable signals to drive a non-linear MQW SLM by using a software preprocessing unit.By adjusting the switching network of the driving circuit, this circuit can reduce the switching noise and improve the output precision.The chip test results show that the driving voltage can swing from 0 to VDD, and its resolution could be close to 256 with a pixel area of only 65 × 65 μm2.     

一种用于半桥功率IC的新型高压电平位移电路

In order to reduce the chip area and improve the reliability of HVICs,a new high-voltage level-shifting circuit with an integrated low-voltage power supply,two PMOS active resistors and a current mirror is proposed.The integrated low-voltage power supply not only provides energy for the level-shifting circuit and the logic circuit,but also provides voltage signals for the gates and sources of the PMOS active resistors to ensure that they are normally-on.The normally-on PMOS transistors do not,therefore,need to be fabricated in the depletion process.The current mirror ensures that the level-shifting circuit has a constant current,which can reduce the process error of the high-voltage devices of the circuit.Moreover,an improved RS trigger is also proposed to improve the reliability of the circuit.The proposed level-shifting circuit is analyzed and confirmed by simulation with MEDICI,and the simulation results show that the function is achieved well.     

一种高可靠性、低功耗单节锂电池保护电路

A single lithium-ion battery protection circuit with high reliability and low power consumption is proposed.The protection circuit has high reliability because the voltage and current of the battery are controlled in a safe range.The protection circuit can immediately activate a protective function when the voltage and current of the battery are beyond the safe range.In order to reduce the circuit’s power consumption,a sleep state control circuit is developed.Additionally,the output frequency of the ring oscillation can be adjusted continuously and precisely by the charging capacitors and the constant-current source.The proposed protection circuit is fabricated in a 0.5 m mixed-signal CMOS process.The measured reference voltage is 1.19 V,the overvoltage is 4.2 V and the undervoltage is 2.2 V.The total power is about 9 W.     

A low-powerlow-voltage slew-rate enhancement circuit for two-stage operational amplifiers

正A novel circuit is presented in order to enhance the slew rate of two-stage operational amplifiers.The enhancer utilizes the class-AB input stage to improve current efficiency,while it works on an open loop with regard to the enhanced amplifier so that it has no effect on the stability of the amplifier.During the slewing period,the enhancer detects input differential voltage of the amplifier,and produces external enhancement currents for the amplifier,driving load capacitors to charge/discharge faster.Simulation results show that,fora large input step,the enhancerreduces settling time by nearly 50%.When the circuit is employed in a sample-and-hold circuit,it greatly improves the spur-free dynamic range by 44.6 dB and the total harmonic distortion by 43.9 dB.The proposed circuit is very suitable to operate under a low voltage(1.2 V or below) with a standby current of 200μA.     

Luminance uniformity compensation for OLED panels based on FPGA

Aiming at the problem of luminance uniformity for organic lighting-emitting diode （OLED） panels, a new brightness calculating method based on bilinear interpolation is proposed. The irradiance time of each pixel reaching the same lumi- nance is figured out by Matlab. Adopting the 64×32-pixel, single color and passive matrix OLED panel as adjusting luminance uniformity panel, a new circuit compensating scheme based on FPGA is designed. VH L is used to make each pixel＇s irradiance time in one flame period written in program. The irradiance brightness is controlled by changing its irradiance time, and finally, luminance compensation of the panel is realized. The simulation result indicates that the design is reasonable.     

电流模线性控制电荷泵的研究与设计

To meet the demands for a number of LEDs,a novel charge pump circuit with current mode control is proposed.Regulation is achieved by operating the current mirrors and the output current of the operational transconductance amplifier.In the steady state,the input current from power voltage retains constant,so reducing the noise induced on the input voltage source and improving the output voltage ripple.The charge pump small-signal model is used to describe the device’s dynamic behavior and stability.Analytical predictions were verified by Hspice simulation and testing.Load driving is up to 800 mA with a power voltage of 3.6 V,and the output voltage ripple is less than 45 mV.The output response time is less than 8μs,and the load current jumps from 400 to 800 mA.     

一种支持OLED亮度补偿的电流型PWM像素驱动电路

OLED(organic light-emitting diode,OLED)微显示器长时间工作在高对比度、高亮度的状态下,OLED像素衰退不一致,发光亮度衰退也不一致,会产生残影现象。因此,提出了一种改进的电流型PWM像素驱动电路,保持了对OLED像素衰退补偿效果,同时可以读出OLED阳极电压,计算得到OLED衰退信息,以便于对OLED亮度衰退进行有效的补偿。文章中分析了改进的电流型PWM驱动电路结构,及其对OLED衰退补偿和亮度补偿的原理。通过模拟仿真,得到几个影响OLED衰退补偿效果的关键参数。当OLED像素衰退电阻R_oled小于40 MΩ时,该电流型PWM驱动电路电流衰退度与传统2T1C驱动电路相比,只为其衰退度的50%。     

一种驱动MOS管工作在饱和区的硅基OLED微显示像素电路

硅基OLED微显示中为了在极小的像素面积内实现微小的OLED工作电流,其像素驱动电路的驱动MOS管一般工作在亚阈值区,存在OLED电流对驱动MOS管的阈值电压和栅源电压失配敏感、外围电路复杂等问题,如果驱动MOS管工作在饱和区则可避免这些问题,但为了获得微小的驱动电流,必须采用尺寸大的倒比MOS管,这又与极小的像素面积冲突。本文提出了一种采用脉宽调制(PWM)技术、驱动MOS管工作在饱和区的OLED微显示像素驱动电路,PWM信号减少了一帧内OLED的实际工作时间,OLED的脉冲电流变大,使驱动MOS倒比管的尺寸减小;由于PWM信号占空比小,同时实现了OLED微小的平均像素驱动电流和亮度。结果表明PWM信号占空比为3%时,实现的OLED驱动电流和像素亮度范围分别为27pA~2.635nA、2.19~225.1cd/m~2,同时采用双像素版图共用技术,在15μm×15μm的像素面积内实现了像素驱动电路的版图设计。     

Improvement of pixel electrode circuit for active-matrix OLED by application of reversed-biased voltage

In this paper, an improved ac pixel electrode circuit for active-matrix organic light-emitting display (AMOLED) has been proposed by adding a thin-film transistor. This circuit can provide an ac driving mode for AMOLED and makes the OLED in a reversed-biased voltage during the reverse cycle. And a circuit design for understanding ac driving mode was presented. The circuit simulation results indicate that this circuit is feasible. The circuit structure is practical for the AMOLED pixel driver; it can improve the performance of OLED.     

A new a-Si:H TFT pixel circuit compensating the threshold voltage shift of a-Si:H TFT and OLED for active matrix OLED

We propose a new hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) pixel circuit for an active matrix organic light-emitting diode (AMOLED) employing a voltage programming. The proposed a-Si:H TFT pixel circuit, which consists of five switching TFTs, one driving TFT, and one capacitor, successfully minimizes a decrease of OLED current caused by threshold voltage degradation of a-Si:H TFT and OLED. Our experimental results, based on the bias-temperature stress, exhibit that the output current for OLED is decreased by 7% in the proposed pixel, while it is decreased by 28% in the conventional 2-TFT pixel.     

Design of a 16 gray scales 320×240 pixels OLED-on-silicon driving circuit

A 320×240 pixel organic-light-emitting-diode-on-silicon (OLEDoS) driving circuit is implemented using the standard 0.5 μm CMOS process of CSMC. It gives 16 gray scales with integrated 4 bit D/A converters. A three-transistor voltage-programmed OLED pixel driver is proposed, which can realize the very small current driving required for the OLEDoS microdisplay. Both the D/A converter and the pixel driver are implemented with pMOS devices. The pass-transistor and capacitance in the OLED pixel driver can be used to sample the output of the D/A converter. An additional pMOS is added to OLED pixel driver, which is used to control the D/A converter operating only when one row is on. This can reduce the circuit's power consumption. This driving circuit can work properly in a frame frequency of 50 Hz, and the final layout of this circuit is given. The pixel area is 28.4×28.4 μm2 and the display area is 10.7×8.0 mm2 (the diagonal is about 13 mm). The measured pixel gray scale voltage shows that the function of the driver circuit is correct, and the power consumption of the chip is about 350 mW.     

A novel 3-TFT voltage driving method of compensating VTH shift for a-Si:H TFT and OLED degradation for AMOLED

This work demonstrates the feasibility of a novel pixel circuit by using three a-Si:H TFTs. The proposed circuit can stabilize the OLED current and provide an additional driving current to ameliorate the brightness degradation of the AMOLED. Measurement results indicate that the current degradation of the proposed circuit, caused by V_TH variations, is less than 5% over more than 50,000 s at 60 °C, whereas that of a conventional 2T1C pixel circuit is larger than 34%. Furthermore, to ameliorate the decrease in luminance owing to the OLED degradation, the OLED current can be increased by 10% by analyzing the current degradation and modulating the detected voltage appropriately.     

A Novel Voltage-Feedback Pixel Circuit for AMOLED Displays

This study presents a novel voltage-modulated pixel circuit for active-matrix organic light-emitting diode (AMOLED) consisting of five n-type thin-film transistors (TFTs), one additional control signal, and one storage capacitor. The proposed circuit, which can be implemented in all-n-type and all-p-type low temperature poly-silicon (LTPS) TFT technologies, successfully compensates for threshold voltage deviation of TFTs and facilitates correction of OLED degradation using a voltage feedback method. Simulation and experimental results for all-n-type TFTs indicate that the proposed pixel circuit reduced the nonuniformity brightness problem effectively by compensating for threshold voltage variation in TFTs and reduced the degradation of emission efficiency in OLEDs.     

一种新的有源硅基OLED象素驱动电路

提出了一种新的有源硅基有机发光二极管(OLED-on-Silicon)象素驱动电路.该电路解决了具有特定象素大小的OLED的极小象素电流(小于1μA)与传统MOS器件大的饱和驱动电流之间的不匹配问题.利用Synopsys公司的仿真软件H-spice,对该电路和传统的两管象素驱动电路进行了模拟,结果表明该电路作为OLED-on-Silicon的象素驱动更容易实现多级灰度.