Low Flicker Research Articles

P‐246: Late‐News Poster: Effective flicker reduction through luminance compensation between pixels in the fringe field switching mode using positive dielectric liquid crystals

We develop the positive dielectric liquid crystals for flicker free that saves the power consumption and improves the image quality. The dielectric constant was optimized for a low flexoelectric effect and flicker is advanced by adding the LC component which reduces the luminance difference between frames. We confirmed that the a‐Si TFT LCD Panel incorporating the developed LC operates without flicker at the driving frequency of 40Hz.

A 0.65 V 4 dB NF 2.4 GHz Sub-Passive RF Down-Converter With Trans-Frequency Current-Reusing Scheme Achieving Low Flicker Noise and High Linearity

A 0.65 V 4 dB NF 2.4 GHz Sub-Passive RF Down-Converter With Trans-Frequency Current-Reusing Scheme Achieving Low Flicker Noise and High Linearity

Electrical characteristics assessment and noise analysis of pocket-doped multi source T-shaped gate tunnel FET

A detailed analysis of a novel multi-source T-shaped gate Tunnel FET (MS-TTFET) is presented in this study in order to address the main issues with conventional TFETs. Due to its exceptionally low off-state current (IOFF) and remarkable sub-threshold properties, the tunnel field effect transistor has received a great deal of interest for low standby power applications. The MSR's integration into the SOI platform increases the device's on current, which increases the effective tunnelling area in the middle of the source-channel junctions. An isolator oxide has been added to prevent the source and drain regions from being directly coupled. A SiGe pocket has been suggested at the source and channel junction; silicon-germanium, a low bandgap material which enhances the tunnelling of charge carriers. A T-shaped gate can increase the effectiveness of the tunnel junction in order to limit the lower value of the leakage current. The multi-source regions of the T-shaped gate tunnel field effect transistor can boost the on-state current (ION) by improving tunnel junction areas. The device's ION/IOFF ratio, which is 1013 for our suggested construction, is the standard measure of merit for any device. It is possible to achieve an increased ON current of the order of 10−5 A/μm with a negligible subthreshold swing (SS) of 42 mV/decade. Moreover, the effect of low frequency flicker noise on the device behavior has been investigated.

Integrated Isolated AC/DC Converter Using IOFL for LED Driver Applications

Power factor correction, voltage and current ripple reduction and eradicating short-life electrolytic capacitors are challenging issues in state-of-the-art ac/dc Light-Emitting-Diode (LED) drivers. Conventional single-stage drivers need an electrolytic capacitor to ensure low output current flicker. However, electrolyte capacitors having a high failure rate, reduce the life-span of the LED driver. To cover these challenges, in this paper an integrated LED driver is proposed. The proposed driver, is combined of three dc/dc converters with only one active switch. It features high power factor, low current flicker, and due to using only one active switch its cost, volume, complexity and power loss is low. The driver is analyzed step by step to show the operation principles based on duty cycle variations. Dynamic analysis and control design of the proposed driver is presented based on nonlinear control by Input-Output Feedback Linearization (IOFL). The simulation and experimental results have been provided to verify the versatility of the proposed driver.

A 30-GHz Class-F Quadrature DCO Using Phase Shifts Between Drain–Gate–Source for Low Flicker Phase Noise and I/Q Exactness

In this article, we present a low phase noise (PN) mm-wave quadrature digitally controlled oscillator (DCO) exploiting transformers for class-F operation and harmonic extraction. A third transformer coil is added for the inter-core coupling with the source terminals of the switching transistors. We identify that the inter-core coupling in quadrature oscillators causes an asymmetric flicker noise current, thus degrading flicker PN. As a remedy, we propose a deliberate drain-to-gate phase shift of the switching transistors by means of capacitive loading to fix this asymmetry. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> I/Q mode ambiguity is also resolved by introducing another phase shift in the source-coupling; it is explained by a simplified analysis with phasor diagrams. Fabricated in the TSMC 28-nm LP CMOS, the prototype achieves PN of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 112 dBc/Hz and figure-of-merit (FoM) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 185 dB at 1-MHz offset of 25.7 GHz. The measured flicker PN corner is 140–250 kHz and image rejection ratio (IRR) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 47 dB over the whole 18% tuning range (TR). To the best of the authors’ knowledge, it is the best reported PN and IRR for a mm-wave quadrature oscillator.

P‐4.7: Wide Refresh Rate Display Technology

Realize 20~240Hz wide refresh rate display on 16.0 WUXGA Oxide platform, while meeting intel LPDT4.0 test standard, adding dynamic VCOM solution to optimize low frequency flicker. The experimental countermeasures are mainly to verify different panel parameters, dynamic VCOM, and different K‐value LCDs, which have been tested pass on the 16.0 WU platform.

SSVEP-based Brain-Computer Interface Controlled Robotic Platform with Velocity Modulation.

Steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs) have been extensively studied due to many benefits, such as non-invasiveness, high information transfer rate, and ease of use. SSVEP-based BCI has been investigated in various applications by projecting brain signals to robot control commands. However, the movement direction and speed are generally fixed and prescribed, neglecting the user's requirement for velocity changes during practical implementations. In this study, we proposed a velocity modulation method based on stimulus brightness for controlling the robotic arm in the SSVEP-based BCI system. A stimulation interface was designed, incorporating flickers, target and a cursor workspace. The synchronization of the cursor and robotic arm does not require the subject's eye switch between the stimuli and the robot. The feature vector consists of the characteristics of the signal and the classification result. Subsequently, the Gaussian mixture model (GMM) and Bayesian inference were used to calculate the posterior probabilities that the signal came from a high or low brightness flicker. A brain-actuated speed function was designed by incorporating the posterior probability difference. Finally, the historical velocity was considered to determine the final velocity. To demonstrate the effectiveness of the proposed method, online experiments, including single- and multi-target reaching tasks, were conducted. The extensive experimental results validated the feasibility of the proposed method in reducing reaching time and achieving proximity to the target.

Highly Stable Metal-Free Long-Persistent Luminescent Copolymer for Low Flicker AC-LEDs.

Organic room-temperature long-persistent luminescent materials are promising light-emitting materials for encryption, architectural decoration, organic solar cells, and biomedical applications. However, their unstable structures and thermal- and humidity-induced emission quenching have greatly limited their utility and reliability. Here, we report a metal-free nonconjugated copolymer that possesses stable photoluminescence at both high temperature and humidity. The room-temperature long-persistent luminescence (LPL) of this copolymer lasts for more than 15 s and can be recovered in high humidity conditions by heating to remove moisture. Copolymer LPL can be achieved with various excitation wavelengths, ranging from ultraviolet to near-infrared, and the LPL color can be adjusted accordingly. The high initial LPL intensity and ultrafast filling time of the copolymer makes it suitable for low flicker alternating current-driven light-emitting diodes (AC-LEDs).

Highly Stable Metal‐Free Long‐Persistent Luminescent Copolymer for Low Flicker AC‐LEDs

AbstractOrganic room‐temperature long‐persistent luminescent materials are promising light‐emitting materials for encryption, architectural decoration, organic solar cells, and biomedical applications. However, their unstable structures and thermal‐ and humidity‐induced emission quenching have greatly limited their utility and reliability. Here, we report a metal‐free nonconjugated copolymer that possesses stable photoluminescence at both high temperature and humidity. The room‐temperature long‐persistent luminescence (LPL) of this copolymer lasts for more than 15 s and can be recovered in high humidity conditions by heating to remove moisture. Copolymer LPL can be achieved with various excitation wavelengths, ranging from ultraviolet to near‐infrared, and the LPL color can be adjusted accordingly. The high initial LPL intensity and ultrafast filling time of the copolymer makes it suitable for low flicker alternating current‐driven light‐emitting diodes (AC‐LEDs).

28-nm CMOS 공정을 이용한 Ka-Band 수신기 설계

This study presents a Ka-band direct-conversion receiver using a 28-nm CMOS (Complimentary Metal Oxide Semiconductor) process for radar applications. The designed receiver includes a LNA (Low-Noise Amplifier), Mixer, and Baseband amplifier. The LNA adopts a two-stage cascode amplifier structure. Then, the mixer is a single-balanced passive mixer with low flicker noise. At the end, the baseband amplifier is a transimpedance amplifier with fat FET (Field-Effect-transistor) for low flicker noise and current-mode operation of the mixer. The LO (Local Oscillator) signal for driving the mixer is supplied externally. The performance of the receiver is tested using on-wafer probing and an air test is performed by integrating a microstrip antenna. The total conversion gain, noise figure, and 3 dB bandwidth are 28 dB, 6.1 dB, and 6 GHz, respectively. The chip size is 0.320 mm2.

Optics-Free Chip-Scale Intraoperative Imaging Using NIR-Excited Upconverting Nanoparticles.

We present an optics-free CMOS image sensor that incorporates a novel time-gated dual-photodiode pixel design to allow filter- and lens-less image acquisition of near-infrared-excited (NIR-excited) upconverting nanoparticles. Recent biomedical advances have highlighted the benefits of NIR excitation, but NIR interaction with silicon has remained a challenge, even with high-performance optical blocking filters. Using a secondary diode and a dual-photodiode design, this sensor is able to remove the 100s of mV of NIR background on pixels and bring it down to single-digit mV level, nearing its noise floor of 2.2 mV rms, not achievable with any optical filter. Non-linear effects of background cancellation using the diode pair has been mitigated using an initial one-time pixel-level curve fitting and calibration in a post-processing setting. This imager comprises a highly linear 11 fF metal-oxide-metal (MOM) capacitor and includes integrated angle-selective gratings to reject oblique light and enhance sharpness. Each pixel also includes two distinct correlated double sampling schemes, to remove low frequency flicker noise and systematic offset in the datapath. We demonstrate the performance of this imager using pulsed NIR-excited upconverting nanoparticles on standard United-States-Air-Force (USAF) resolution targets and achieve an SNR of 15 dB, while keeping NIR background below 6 mV. This 36-by-80-pixel array measures only 2.3 mm by 4.8 mm and can be thinned down to 25 µm, allowing it to become surgically compatible with intraoperative instruments and equipment, while remaining optics-free.

GÜÇ FAKTÖRÜ VE FLICKERI DİKKATE ALAN BİR TEPE AKIM MODU KONTROLLÜ SEPİC LED SÜRÜCÜ TASARIMI

In this paper, a peak current mode controlled single ended primary inductor converter (SEPIC) LED driver is proposed to control the brightness of the LED. One string of 37 series connected LEDs is adopted as output of the circuit. The proposed control strategy is based on measuring MOSFET peak current value using a shunt resistor. When this voltage reaches peak threshold value, controller turns off MOSFET. The output current is adjusted to desired levels by changing this peak threshold value. The power factor in the AC power supply side is low because of the full wave bridge rectifier with capacitor filter at the input of the converter. The proposed control strategy is applied with power factor correction (PFC) circuit where input voltage is multiplied by control voltage to achieve high power factor. In PFC circuit, although the line current waveform is slightly distorted due to voltage limitations in integrated circuit (IC) chip used for the proposed control strategy, power factor is kept above 0.9 for operation region between 100mA-300mA. In addition, flicker on LED string is measured for operating current region and flicker limits are revealed. Adjustable output current levels, low flicker on LED string, MOSFET peak current control at each cycle, fast output dynamics, and high power factor are acquired by the proposed control strategy.

Effects of phase flicker in digitally driven phase-only LCOS devices on holographic reconstructed images.

Phase flicker can degrade the performance of holographic applications at the device and application levels. On the device side, the meaningful phase modulation resolution is proved to be limited by the overlapping between adjacent phase levels caused by flicker. Here, the tolerance of the overlapping for different modulation levels is provided. The frame rate of the device is also constrained by the phase flicker. The balance between low flicker and fast LC response for fast frame rate is quantitatively analyzed. On the application side, the effects of real phase flicker on the performance of blazed gratings and image holograms are investigated using the temporal phase flicker profiles measured from a phase-only liquid crystal on silicon (LCOS) device; they are shown to be comparable with that introduced by quantization level and amplitude noise, respectively.

DCM Boost PFC for High Brightness LED Driver Applications

This paper is concerned with the derivation of a discontinuous conduction mode boost PFC rectifier as a driver for high-power LED lighting applications. The proposed driver is operated in the current mode regime while emulating a resistance towards the line, thus attaining a near unity power factor and low total harmonic distortion of the line current. Theoretical analysis is reported and conditions for the low LED flicker are derived. A method of design for minimum THD is also suggested. Simulation and experimental results are reported.

A Pseudo-Pseudo-Differential ADC Achieving 105dB SNDR in 10kHz Bandwidth Using Ring Amplifier Based Integrators

This brief presents a high-resolution ADC which makes use of the pseudo-pseudo-differential noise filtering technique in an oversampling ADC architecture with ring amplifier based integrators. The pseudo-pseudo-differential noise filtering technique utilizes single-ended circuits while maintaining the even-order rejection found in fully-differential structures which alleviates, in the active analog blocks, the need for differential matching and circuit overhead such as common-mode feedback. Additionally, pseudo-pseudo-differential provides a cancellation of low frequency flicker noise without the need for traditional techniques such as auto-zero, correlated-double-sampling, or chopping and mitigates double-sampling thermal noise penalties by processing input signal twice. In this prototype, the flicker corner is maintained below 50Hz with measured ADC performance achieving a peak SNDR of 105.0dB and a dynamic range of 106.5dB while consuming 1.17mW from a 1.8V supply.

Intercross scanning control with double driver for micro-LED display

This paper proposes a control chip for micro-light emitting diode (μLED) applied on real-time display system. TheμLED control system has the video transmitter and the LED display matrix. The transmitter includes interface control, memory management, image format conversion. For LED display unit, we present the intercross scanning, memory management, PWM output controller, gamma correction for LED brightness control. TheμLED display is controlled by the intercross drivers to reduce the flicker and promote the sweeping speed with two FPGA controllers, where two parallel SPI data is adopted. The micro LED components are mounted on a PCB with mass-transfer techniques successfully. The FPGA controller can drive about 10 k light-emitting diodes with 12-bit colors for displaying system with PWM method. The passive-matrix micro LED (PMLED) driving can achieve 384 refresh rates with 50 MHz clocking frequency. The experiments result low flicker achieved, which the SVM index is only 1.5 with a photometer measurement.

(Invited) Recent Advances in Ion Sensitive Graphene Field Effect Transistors

I will summarize recent advances [1-3] in large-area graphene based ion sensitive field effect transistors (ISFETs), including the achievement of record potentiometric ion concentration resolution. Sensor resolution, the smallest measurable change in analyte concentration, is a critical parameter in the assessment of sensor performance. Notably, the absence of a bandgap in graphene is frequently perceived as prohibiting competitive graphene FET performance. A graphene FET cannot be driven into saturation, limiting intrinsic gain and high-frequency performance. The graphene FET cannot be turned off, severely limiting the on/off current ratio for switching applications. In contrast, in the case of graphene ISFETs, the graphene FET functions as an analog pre-amplifier directly integrated with a sensing layer, enabling record sensor resolution to be achieved.Large-area graphene ISFETs combine high mobility charge transport, low flicker noise, facile integration with a variety of ion sensitive layers. The advent of wafer-scale graphene processing methods facilitates reproducible production of graphene ISFETs. Field effect mobilities in graphene ISFETs can reach μ = 5000 cm2 V-1 s-1, contributing to high gain gm = ∂Id /∂Vg ∝ μVDS. In particular, high mobility allows for the reduction of bias voltage VDS , which improves potentiometric uniformity across the sensor channel. We further find that low-frequency (1/f) noise, which ultimately determines sensor resolution, decreases approximately inversely with graphene FET channel area, in accord with 1/f scaling in Si MOSFETs. In other words, large transistors are quiet transistors. Scaling graphene FETs up to a 5 mm x 5 mm channel area, we observe a normalized 1/f noise parameter K = f <Δv 2>/v0 2 = 5×10-13, the lowest reported to date for a graphene FET at room temperature. Facile integration of graphene FETs with ion sensitive layers, such as metal oxides and ionophore polymer membranes, enables sensitization to a wide range of ions including H+, K+, Na+, NH4 +, Cl-, NO3 -, HPO4 2- and SO4 2-. Combining the Nernstian limited sensitivity with low 1/f noise enables record ion concentration resolution as low as r ~ 0.003 log M.Beyond sensor resolution, specificity is another important sensor parameter. Ionophores suffer cross-sensitivity to ionic species other than their target ion. The combined stability and resolution of graphene ISEFTs allows simultaneous, real-time measurement of multiple ionic analytes through the use of an array of graphene ISFETs, with each graphene ISFET element sensitized to a particular ion. Measurement of the cross-sensitivity within the array allows the application of Nikolskii-Eisenmann analysis to quantitatively account for cross-sensitivity, and achieve selective response with the graphene ISFET array that would otherwise not be possible with graphene ISFETs operated in isolation. I will conclude with a discussion of challenges and prospects for the future development of graphene FET based sensors. REFERENCES [1] Tran et al., Nanotechnology 32, 045502 (2020).[2] Fakih et al., Nature Communications 11, 3226, (2020).[3] Fakih et al., Sensors and Actuators B 291 89 (2019).

P‐2: High‐Performance LTPO TFT‐LCD Using Metal as Hydrogen Barrier Layer

Low‐Temperature Poly‐Si and Oxide (LTPO) thin‐film transistors (TFTs) have been successfully manufactured and adapted to 6.3 inch liquid crystal display (LCD) panels. To avoid the introducing of hydrogen (H) to oxide TFTs when passivating the Poly‐Si TFTs, the metal barriers are used to prevent the diffusion of hydrogen from the bottom layers. It is shown that those oxide TFTs built with metal barriers exhibit improved intrinsic resistance against hydrogen‐induced degradation. The optimum processes conditions have been used on the 6.3 inch LTPO LCD with ultra‐wide frame rate from 1 to 120 Hz. Further, the specifications of the prototype displays for 409‐ppi LCD with low power consumptions and superior flicker under 1‐Hz frame‐rate driving are reported.

A 24 GHz Direct Conversion Receiver for FMCW Ranging Radar Based on Low Flicker Noise Mixer

In this paper, a 24 GHz direct conversion receiver (DCR) for frequency-modulated continuous-wave (FMCW) ranging radar based on low flicker noise mixer in 90 nm silicon-on-insulator (SOI) CMOS technology is presented. A low-noise and low-power low-noise-amplifier (LNA) adopting simultaneous noise and input matching (SNIM) method is designed. Neutralized technology and boost inductor are introduced to improve performance. The measurement results of standalone LNA show that the peak gain is 17.2 dB at 23.8 GHz and the −3 dB bandwidth is around 2.2 GHz from 22.8 GHz to 25 GHz. The LNA achieves an average 3 dB NF within the 24 GHz band. A current-bleeding mixer is used to lower noise and the factors influencing flicker noise have been discussed. Proper element values and local oscillator (LO) power have been chosen to make the mixer low-noise. Measurement results illustrate that the receiver exhibits 20.3 dB peak gain, 7 dB SSB noise figure (NF) and −22 dBm IP1dB. Flicker noise of the mixer and the receiver are measured respectively and the noise knee-point of receiver is observed 60 kHz. The receiver consumes only 16 mW with chip area of 0.65 mm2 including pads. The results demonstrate that the proposed receiver can be a promising candidate for FMCW ranging radar.

Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup

The magnocellular-dorsal system is well isolated by high temporal frequency. However, temporal processing thresholds have seldom been explored in developmental dyslexia nor its subtypes. Hence, performances on two, four-alternative forced-choice achromatic flicker fusion threshold tasks modulated at low (5%) and high (75%) temporal contrast were compared in dyslexic and neurotypical children individually matched for age and intelligence (8–12 years, n = 54 per group). As expected, the higher modulation resulted in higher flicker fusion thresholds in both groups. Compared to neurotypicals, the dyslexic group displayed significantly lower ability to detect flicker at high temporal frequencies, both at low and high temporal contrast. Yet, discriminant analysis did not adequately distinguish the dyslexics from neurotypicals, on the basis of flicker thresholds alone. Rather, two distinct dyslexic subgroups were identified by cluster analysis – one characterised by significantly lower temporal frequency thresholds than neurotypicals (referred to as ‘Magnocellular-Deficit’ dyslexics; 53.7%), while the other group (‘Magnocellular-Typical’ dyslexics; 46.3%) had comparable thresholds to neurotypicals. The two dyslexic subgroups were not differentially associated with phonological or naming speed subtypes and showed comparable mean reading rate impairments. However, correlations between low modulation flicker fusion threshold and reading rate for the two subgroups were significantly different (p = .0009). Flicker fusion threshold performances also showed strong classification accuracy (79.3%) in dissociating the Magnocellular-Deficit dyslexics and neurotypicals. We propose that temporal visual processing impairments characterize a previously unidentified subgroup of dyslexia and suggest that measurement of flicker fusion thresholds could be used clinically to assist early diagnosis and appropriate treatment recommendations for dyslexia.