Dimming Mode Research Articles

84‐1: Studies on Optical Performance and Driving Method of HTN Mode Dye‐Doped Liquid Crystal Smart Window

Transmittance, haze and texture performance of new high twisted nematic(HTN)mode dichroic dye‐doped liquid crystal device under different voltages when power on and power off were studied. According to the elastic free energy theory of liquid crystal, two key phase transition voltages VPH and VHP of HTN mode liquid crystal were calculated. From a theoretical perspect, it was verified that the liquid crystal transition state under different voltages could correspond to the actual dimming performance, which could provide technical driving reference for other similar HTN device. Finally, based on the above analysis results, driving methods of three light dimming modes which included anti‐glare, privacy protect and high transparent mode were studied to meet the needs of different application scenarios.

Dimming Techniques Focusing on the Improvement in Luminous Efficiency for High-Brightness LEDs

The pulse width modulation (PWM) dimming mode features good dimming linearity and has been widely used for driving high-brightness light-emitting diodes (HBLEDs), in which the brightness change is reached by modulating the duty cycle of the dimming signal to regulate the average current flowing through LEDs. However, the current-illuminance characteristic curve of most LEDs is nonlinear in nature. Namely, under the same lighting power fed, the conventional PWM dimming cannot make the LED exert its best luminous efficiency (LE) specified in datasheets. This paper focuses on the study of further improving LED luminous efficacy via dimming manipulation. Thereby, two multilevel current dimming techniques with varied dimming signal voltage and varied current sensing resistance are presented. With limited dimming capability, the proposed dimming strategies can efficiently raise the luminous flux ratio without increasing the power consumption. A prototype constructed for a 115 W HBLED driver is developed and the devised dimming schemes are realized by a digital signal controller (DSC). Experimental results exhibited with illuminance-power curves and CIE1931 and CIE1976 chromaticity diagrams are given to validate the theoretical derivation and effectiveness. Compared with conventional PWM dimming, under the same illuminance, the driver average output power is respectively reduced by 17.08% and 13.17%; the improvement in average illuminance under the same output power is 13.66% and 11.17%, respectively. In addition, the entire average LE boost has respectively increased by 21.36% and 16.37%.

A high-power PCCM LED driver based on GaN eHEMT with hybrid dimming modes

PurposeThe purpose of this study is to design a more flexible and larger range of the dimming circuit that achieves the independence of multiple LED strings drive and can time-multiplex the power circuit.Design/methodology/approachThe state-space method is used to model the BUCK circuit working in Pseudo continuous conduction mode, analyze the frequency characteristics of the system transfer function and design the compensation network. Build a simulation platform on the Orcad PSPICE platform and verify the function of the designed circuit through the simulation results. Use Altium Designer 16 to draw the printed circuit board, complete the welding of various components and use the oscilloscope, direct current (DC) power supply and a signal generator to verify the circuit function.FindingsA prototype of the proposed LED driver is fabricated and tested. The measurement results show that the switching frequency can be increased to 1 MHz, Power inductance is 2.2 µH, which is smaller than current research. The dimming ratio can be set from 10% to 100%. The proposed LED driver can output more than 48 W and achieve a peak conversion efficiency of 91%.Originality/valueThe proposed LED driver adopts pulse width modulation (PWM) dimming at a lower dimming ratio and adopts DC dimming at a larger dimming ratio to realize switching PWM dimming to analog dimming. The control strategy can be more precise and have a wide range of dimming.

Microsoft Office for Android at last gets a dim mode

Microsoft Office for Android at last gets a dim mode

Multi-Objective Solar Power Conversion System With MGI Control for Grid Integration at Adverse Operating Conditions

This article presents a new control for the multi-functional operation of a grid-connected solar power conversion system (SPCS). It is a combination of several generalized integrals for grid synchronization as well as fundamental load current component extraction. This multiple generalized integral (MGI) control is designed to overcome the demerits of conventional integral controllers with inadequate operation at adverse grid conditions such as grid frequency variation, phase jumps, DC offsets, noise, harmonics and other waveform distortions. The control is designed to separate the load power accurately into two-parts, i.e. active fundamental part (AFP) and non-active fundamental part (NAFP). This control extracts the AFP of the load current even during the disturbed grid and unbalanced load conditions. According to the comparison with the load current AFP and the photovoltaic (PV) available power ( $P_{pv}$ ), three operating modes are used such as bright mode, dim mode and dark mode. During the bright mode, the total load power is being supported by the system and the remaining power is injected to the grid, the load power is shared by the system and the grid during the dim mode, and the load current AFP is supported by the grid during the dark mode. In every mode of operation, the SPCS mitigates the total load demanding NFAP and thereby keeping the grid currents as sinusoidal and in-phase with the fundamental grid phase voltages and maintaining the IEEE-519 grid power quality standard. This system is modelled and the performance is simulated in MATLAB/Simulink platform, and simulated results are presented. A prototype of the system, is developed in the laboratory and test results at various operating conditions are reported for validation of the system.

Significance of Gender-Specific Aging Profiles at the Highest Similarity of Paired Tests between Two Data Components on Medical Checkup Examinees: DIM Mode Analysis of Spherical Surface SOM

自己組織化を基礎とする研究は、近年、世界中で急速な発展が見られる。この応用である自己組織化マップ（Self-Organizing Map: SOM）解析法については複雑系の事象データの分析に対して、非線形回帰法として分布型の如何に影響されないというメリットを有している。さらにSOMでは相互の類似関係を保持したまま全体を要約することができるという特長がある。

UHD 3D medical system of small‐ and medium‐sized monitor

AbstractWith the development of ultra‐high definition (UHD) display technology and stereoscopic 3D display technology, 3D ultra‐high monitor will help surgeons obtain the spatial hierarchy of internal tissues, identify tissue surfaces and blood vessels clearly, locate the focus precisely and reduce surgery time. Compared with normal 2D medical monitors, 3D medical monitors will lose more brightness because of the 3D application, so it is necessary to design a high‐brightness backlight system to guarantee the display stability and the accuracy of the diagnosis. This paper presents a novel processing system for 4K UHD 3D medical monitor with the architecture combined with universal SOC (system on a chip) and specialized FPGA (field programmable gate array). A hardware system is designed with high efficiency and reliable brightness stability control for small‐ and medium‐sized monitors. Furthermore, we analyze the two dimming modes of linear dimming and PWM dimming for a better application in medical monitor.

DimRouter: A Multi-Mode Router Architecture for Higher Energy-Proportionality of On-Chip Networks

In the dark silicon era, many independent components of many-core processors are becoming voluntarily inactive due to the constraint of power consumption on a chip. However, to keep network connectivity, the on-chip interconnection must still be kept activated and wastes considerable energy to avoid the isolation of these inactive components, harming the energy-proportionality of the whole processor chip. In this paper, we propose a novel design to provide more energy-proportional on-chip connection without damaging the network connectivity. To achieve this goal, we redesign the router architecture. The new architecture, DimRouter, supports three modes: normal, dark and dim. In the dim mode, only part of the router is active and provides flexible connection while the dark mode puts all router elements in the asleep state. Moreover, to maximize the number of dark routers, we also propose a reconfiguration algorithm based on degree-constrained Steiner Tree. The evaluation result under synthetic traffic shows that the new design can reduce the energy consumption up to 85% compared with the common design. For real application traffic, the new design can also save average 46% energy consumption with 4% performance improvement.

Design of LED Street Lamp Intelligent Control System Based on Zigbee Technology

For the realization of the street lamp lighting as required and the use of real-time monitoring management requirements, this paper has designed a kind of street lamp management system, which has the function of monitoring and intelligent control. The system based on ZigBee wireless communication technology. Labview is taken as the control interface of the Upper computer and CC2530 chip is used as the microcontroller. The dimming circuit in this scheme uses the PWM dimming mode, CC2530 produce the PWM signal to realize the dimming control. The voltage acquisition circuit is responsible for detecting the output voltage of the street lamps. The actual device debugging and testing results show that the designed system can realize single lamp switch control and street lamp brightness can be adjusted. It can not only realize real-time monitoring of the working state of city street lamp, but also complete the remote control. The system has the characteristics of high efficiency and energy saving, which meets the requirements of the development of smart city energy.

Increasing luminous efficiency of led by joint dimming mode with adjustable peak current

Luminous efficiency and color temperature of LED chip are affected by current and temperature. PWM dimming mode only works at two kinds of current levels-rated current and zero current. It has smaller effect on color temperature compared with linear dimming mode, but it will reduce the luminous efficiency of lamps. Linear dimming mode has higher luminous efficiency by comparison. The two dimming modes above cannot keep color temperature stable and Luminous efficiency high. Therefore, the paper designed a joint dimming mode by integrating advantages of the two modes. The dimming method not only adjusts peak current, but also changes the duty cycle of dimming signals. The injected average current is kept stable by reducing peak current and increasing the duty cycle. The decreased luminous efficiency by the raise of temperature was made up for. Then according to the mathematical model of total flux and current, the author calculates the mathematical mode of flux affected by temperature. It proves the fact that adjusting peak current slightly can compensates for the reduced luminous efficiency affected by temperature through theoretical calculation. In addition, the final peak current after calculation can contribute to the adjustment parameter of joint dimming modes.

Current crowding impact at spatially and temporarily resolved thermal characters of large-area AlGaInP light emitting diodes operating in dimming/flashing modes

By exploring spatially (μm-scale) and temporarily (ms-scale) resolved light and 8–12 μm thermal imaging analyses, we demonstrate how current crowding alternates the thermal parameters of light emitting diodes (LEDs) operating in dimming/flashing mode. For example, in AlGaInP/GaAs high-current (I ≥ 1 A) large-area (≥1 mm2) LEDs, we measured the thermal time constant (2.5 ms), heat diffusion length (110 μm), current crowding length (≤75 μm), thermal diffusivity (0.08 cm2/s) of GaAs substrate, and current-dependent thermal patterns taken from the front and sidewall facet of chips. We discovered that even at I = 100 mA emitting ships are already divided by two regions with different temperatures, small area high-temperature central regions (effective volumes) with high current density and larger area lower-temperature peripheral regions with much lower current density. The experiments evidence that the simplified computer simulations of dimming mode based on mean chip temperature, mean thermal resistance, and average current density, as well as temperature-independent ABC-modeling must be regarded with skepticism.

Kafka’s Letters to Milena and the Question of the Body

This article describes how Franz Kafka's correspondence with the Czech journalist and translator Milena Jesenska, from 1920 to 1923, documents the development of his illness, his fear of physical intercourse, and his consequent reliance on writing. Writing is exploited in this epistolary affair to replace both physical presence and physical love. Simply stated, writing negates the body in this correspondence. The ensuing erasure of the body leads to a dim mode of bodily presence, a ghostly one. Kafka’s Letters to Milena are read as a rich hunting ground for psychoanalytical and feminist interpretations of the (female) body and female sexuality. It is the mystery of femininity that Kafka tries to solve in the course of this correspondence. Sexuality and the female body are rendered in this epistolary love as a reviled “dark continent” that should be sublimated in favor of the symbolic realm of writing. Of special importance at this stage of Kafka’s life as a tubercular is his conception of the diabolical nature of his writing, an issue that has received very little critical attention. A man living close to death chooses for himself a life of seclusion and introversion from human relations and withdraws into a ghostly existence. The body that deteriorates into a ghostly presence finds its counterpart in "demonic" letter writing that conjures up physical presence in Kafka's relationship with Milena. The first section of this article introduces Letters to Milena in context. Section two presents a reading of the letters informed by psychoanalysis and feminism, and section three focuses on the final letters and presents Kafka as a “ghostly lover.

A novel on-chip step-dimmer for low cost AC-powered HV-LED driver

This letter proposes a novel on-chip step-dimmer using an analog dimming method for a high PF AC-powered LED driver. The full AC LED driver can achieve a very high PF and a low THD by using a self-adaptive power processing circuit while delivering a best-in-class dimming performance with the proposed step-dimmer. Under the control of the dimming signal, the dimming voltage is step-adjusted from 1.0V to 2.5V, the average LED current can be changed from 40% to 100% of the nominal LED current value. To verify the feasibility of the proposed scheme, an 8-string 4.4WAC-powered LED driver with the proposed step-dimmer was designed and simulated using a 0.35 um-700V BCD Magnachip process. The gained results verify that the proposed step-dimmer can maintain a high performance of the AC LED driver under different dimming modes with a PF and a THD around 0.998 and 6%, respectively.

A novel monolithic white LED driver with dual dimming mode

This paper presents a hysteretic-current-control LED driver with the dual dimming mode. This novel monolithic driver includes an output switch and a high-side output current sensing circuit using an external resistor to set the nominal average output current (IOUTnom). By applying an external control signal to the DIM pin, it can alter flexibly the control mode between the analog (DC) and switching (PWM) dimming. In the DC dimming mode, when the input DC control voltage is adjusted from 0.5 to 2.5 V, the average output current can be changed from 20 to 100 % of the current IOUTnom. While in the switching dimming mode, the output current is proportional to the duty cycle of the input switching signal and changed from about 0 to 100 % of the current IOUTnom. The driver circuit has been verified in a 0.5 μm HVCMOS process and the die size is about 1.2 × 1.5 mm2. This proposed driver can work in 8---40 V power supply, the maximum average output current is up to 1.0 A.

Analysis and Suppression of Overcurrent in Boost LED Drivers

Light-emitting diodes (LEDs) are the major backlighting source used in liquid crystal displays and dimming the LEDs is a common approach to increase the contrast ratio or save power. Pulse-width modulation (PWM) is more popular than analog methods of dimming, because it produces a less pronounced shift in chromaticity. However, in PWM dimming mode, overcurrent can shorten the lifespan of the LEDs. This paper proposes a technique to overcome the drawbacks inherent in conventional approaches to the suppression of overcurrent in LED devices. The design was implemented using the TSMC 0.25- $\mu{\hbox{m}}$ 60-V bipolar-CMOS-DMOS process, resulting in a chip area of 2.2 ${\hbox{mm}}^{2}$ . A comparison with two commercial chips demonstrates the effectiveness of the proposed design in the suppression of LED overcurrent and the subsequent extension of the lifespan.

Design and implementation of a smart networking control system for LED lighting based on CAN

The paper describes a smart networking control system for remote monitoring and controlling of lighting networks based on CAN bus. The nodes of network are LED lamps and environment sensors. The system provides LED lighting dimming control of a single lamp or a group of lamps. The master node will remote monitor the lighting condition of LED lamps and control the status of lighting system. The system was implemented in a simple lighting network based on CAN 2.0B, with the MCU using C8051F340. The driver for LED lamps uses PT4107 as the switching power supply chip and the dimming mode is based on PWM signal. The B&R PLC master the whole network as the host computer. Applications for this system include indoor lighting condition where it is desired to control LED lamps for saving energy consumption and creating various lighting effects.

A Universal-Input Single-Stag2e High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck–Flyback Converter

Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck-flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed.

Determination of absolute Ba densities during dimming operation of fluorescent lamps by laser-induced fluorescence measurements

Investigations of fluorescent lamps (FL) are often focused on the electrodes, since the lifetime of the lamps is typically limited by the electrode lifetime and durability. During steady state operation, the work function lowering emitter material, in particular, barium, is lost. Greater barium losses occur under dimming conditions, in which reduced discharge currents lead to increased cathode falls, the result of the otherwise diminished heating of the electrode by the bombarding plasma ions. In this work the barium density near the electrodes of (FL), operating in high frequency dimming mode is investigated using the high-sensitivity method of laser-induced fluorescence. From these measurements we infer barium loss for a range of discharge currents and auxiliary coil heating currents. We show that the Ba loss can very easily be reduced by moderate auxiliary coil heating.

Dynamic mode changes of cathodic arc attachment in vertical mercury discharges

Cathodic arc attachment after a steady state anodic phase is investigated in a vertically operated 0.7 MPa mercury high intensity discharge lamp with pure tungsten electrodes. Experimental evidence of a dynamic cathodic mode change of arc attachment influenced by convective effects is documented. Finite element simulation of the temperature field in the cathode body in two and three dimensions is performed. Nonlinear surface heating using Neumann's and Benilov's models is employed. The presheath voltage drop as a function of electron temperature is proposed as a compact input parameter. For Benilov's model two alternatives are compared. All models have the ability to show transient mode changes. The models show no sharp distinction. There are strong indications that the transient spot possesses a nonzero minimum life time when it abruptly emerges at a distinct threshold. The model fairly predicts the thresholds observed in experiments for the upper and lower electrodes depending on the convection heating. The evidence is more in favour of a lower presheath voltage drop, i.e. lower electron temperatures during the spot mode. The results are applicable for the design of dimming modes of HID lamps.

Radio-Frequency Oxygen Plasma as a Sterilization Source

An oxygen plasma sustained at 13.56 MHz in a standardized reactor with a planar induction coil was used for biological decontamination experiments. Optical emission, mass spectrometry, Langmuir probe, and electrical measurements were applied to detection of chemical species and ion-energy and e ux analysis. These diagnostics identie ed a plasma-mode transition in the range of 13 ‐67-Pa pressure and 100 ‐330-W power to the induction coil. At higher pressure and lower power, the plasma was sustained in a dim mode (primarily by stray capacitive coupling). A primarily inductive bright mode was attained at lower pressure and higher power. The coupling mode of plasma operation was then monitored by emission spectroscopy on an analogous, scaled-down reactor for biological degradation tests. Plasmid DNA degradation efe cacies were compared in both plasma modes. DNA removal was »25% more efe cient in the inductively coupled mode than in the capacitively coupled mode at the same power. The fast degradation was attributed to synergetic mechanisms (photo- and ion-assisted etching by