Что лучше Direct LED или QLED?
Основные различия между LED и QLED заключаются в уровне цветопередачи, остальные характеристики зависят от конкретного типа встроенной LCD-матрицы. Поэтому если у вас есть бюджетные ограничения, мониторы LED LCD — наилучшее решение по соотношению цены и качества, которое к тому же предлагает широкий диапазон размеров.
Чем отличается Direct LED от QLED?
LED и QLED телевизоры похожи друг на друга, так как каждый из них использует ЖК-панели со светодиодной подсветкой; единственное отличие заключается в том, что в QLED телевизорах используется квантовый слой точек, что позволяет им производить более широкую цветовую гамму.
Что лучше OLED или Direct LED?
Как мы уже разобрались, OLED -дисплеи благодаря своему принципу работы способны передать черный цвет значительно лучше LED . Матрица из органических светодиодов также обладает высокой контрастностью, но слегка проигрывает в яркости изображения.
Чем отличается LED от QLED OLED?
QLED : в данной модели используются VA-панели, но нет локальных функций затемнения, соответственно, возможности управления контрастностью меньше, чем у модели из категории LED LCD . OLED : хоть эта картинка не отображает в полной мере возможности затемнения, уровни чёрного абсолютны и контрастность бесконечна.
Какой экран лучше LED или QLED?
Главное отличие LED от QLED Samsung как раз и состоит лишь в том, что эти самые модели QLED используют новые специализированные металлические нанофильтры на квантовых точках, расположенные на плёночной матрице над светодиодной панелью подсветки. В общем и целом, это даёт нам более яркие, более насыщенные цвет
В чем отличие QLED от UHD?
Например, Samsung производит телевизоры 4K QLED , а также телевизоры 4K LED, телевизоры Micro LED и телевизоры Neo QLED с довольно запутанным названием ( QLED , но с подсветкой Mini LED). « Ultra HD » относится к стандарту цифрового кино 4K, тогда как «4K» обычно используется для бытовых телевизоров для дома.
Что выбрать OLED или QLED?
Что выбрать ? OLED -дисплеи представляются оптимальным выбором, но есть нюанс — такие экраны применяются только в телевизорах с диагональю 55, 65, 77 и 88 дюймов, тогда как выбор QLED -дисплеев с точки зрения размеров гораздо шире. Так что, если вы можете позволить дорогой большой телевизор, то ваш выбор — OLED
Что такое Кью лед?
Сегодня термин QLED использует компания Samsung в качестве коммерческого названия для своих новых мониторов. Взяв за основу традиционный LED LCD разработчики установили между ЖК-дисплеем и светодиодной панелью плёнку — металлический нанофильтр на основе квантовых точек.
Как выбрать телевизор LCD или LED?
LED от LCD принципиально отличается тем, что светодиоды намного меньше, чем лампы CCFL. Это означает, что LED телевизоры можно изготовить намного более тонкими. . Отличие LED от LCD и в том, что в случае со светодиодами можно равномерно распределить подсветку по всему периметру экрана. Контрастность становится лучше .
What is main difference between Digital and Analog LED strips?
Analog LED strips can be controlled by DMX. DMX is a signal used to control LED strips through the DMX unit. A DMX unit receives the DMX signal from a DMX console – where you can decide which color you want to pick and what luminous intensity you want for the whole LED strip. Therefore you have total control of every aspect of your installation!
Voltage
Usually, analog LED strips use 12V, 24V or 220V voltage. They are normally distributed in 5 meter rolls and use 60 LED diodes per meter (versions with less or more diodes per meter are of course available).
Usage
Typical usage of analog LED strips is for a home decorations, restaurants, bars, outdoor lightning, TV studios, shopping malls. Hence you can use the strip as a constant source of decoration light or as a background.
Digital LED Strips
Digital LED strips are also called video, dream, pixel or addressable LED strips. All of them belong to the same category.
Color change
The main benefit comparing to analog LED strips is that you can control every single LED diode (nice article) separately (hence addressable LED strip), creating various colours in different sections of one LED strip. This allows you to use digital LED strips to display even videos. It is achieved thanks to additional chips (IC) directly inside the LED diode or on the digital strip board.
Control System
Digital LED strips are usually more complicated to control since you have to provide video content for the LED strips. Users often use computer software , Art-Net (a short overview what is ArtNet, recommended!), live video stream or SD card as a video source. On the hardware level, the digital strips receive the video information over SPI (Serial Protocol Interface). Every single diode of the digital strip uses one chunk of RGB data in SPI data packet. Now, pay attention, as it gets a bit tricky with digital LED strips SPI communication – there is not only one standard! There are many control IC chips and every one of them uses a different kind of SPI signal. The most common types are WS2811, WS2812, TM1803, TM1809, SK6812, UCS, APA102 or APA104. LED Strip Studio system supports all common types of IC .
Control options
Typically, the SPI controllers receive video information over Ethernet cables from computer software or Art-Net. Some controllers can play video content from SD-card or stream live video (e.g. grabbing display through HDMI).
Why start using LED Strip Studio Controllers?
We are offering you great LED Controllers with long tradition, made in Europe and tested on hundreds of installations. LSS controllers are easy to use, have detailed documentation, strong customer support and own software solution. The technical details of LED controllers – LEC 3 , SPI LED Controller , SPI Matrix , Powered LEC .
Voltage
Digital LED strips usually works at a 5V voltage, although there are also some 12V or 24V versions (these allow control of only 3 LED diodes as one pixel). We often use 42 LEDs/m version, but you can find many kinds of digital LED strips, anyway.
Usage
Digital LED strips can be used to achieve amazing animated light effects in club interiors, TV studios, TV shows and even on buildings. They can be used as decorations, but also for displaying video content for advertisement purposes. This larger spectrum of options allows you to be more flexible and innovative with your LED projects. This is an example of what you can achieve with digital LED strips. A simple wall decoration pattern and a huge LED ceiling with video content “grabbed” from computer through our LED Strip Studio software.
Recap of main differences between analog and digital LED strips
| Analog | Digital | |
| Colors | only one | different for each LED |
| Controls on hardware level | DMX | SPI |
| Typical user control | DMX console or software | video software, live video stream, Art-Net, SD-card |
| Voltage | 12V, 24V, 220V | 5V |
| Typical number of LEDs per meter | 32, 60, 80 | 30, 32, 42, 60, up to 144 |
| Cut segment | 3 or 6 LEDs | 1 LED |
| Typical usage | decorative lightning | decorative lightning with video projection |
| Installation | easy | complicated |
| Typical current per meter of strip | 1A at 12V, 0.5A at 24V | 1.2A at 5V |
| Can be controlled using LED Strip Studio | yes (additional LED DMX dimmers are required) | yes |
чем лед подсветка Direct LED отличается от RGB LED и какая лучше.
Следует уточнить, что существует целых три варианта реализации LED-подсветки.
Первый вариант предусматривает использование множества одноцветных светодиодов, равномерно распределенных за экраном по всей его площади (так называемая direct-LED подсветка) .
рис 1 direct-LED
Рис 1. Подсветка direct-LED: диоды подсветки равномерно распределены по всей площади экрана.
Светодиоды испускают свет довольно узкого спектра, которого совершенно недостаточно для получения богатой цветовой гаммы жидкокристаллической панели телевизора. Расширенный цветового охват дисплея обеспечивается уже свечением люминофора, который под воздействием света светодиодов испускает яркий белый свет с широким спектральным составом.
Еще один вариант LED технологии предусматривает использование RGB-подсветки. В этом случае вместо одноцветных (обычно синих) используются светодиоды трех разных цветов: в типичном варианте на каждый красный ® и синий (B) диод приходится два зеленых (G). Цветовая палитра у такого типа подсветки шире, она дает более плавные переходы между оттенками. Однако если в этом случае количество цветов на экране действительно больше, это вовсе не значит, что цвета автоматически воспроизводятся естественно и точно. Скорее наоборот – аппаратное управление RGB подсветкой сложнее и требует точных выверенных решений, что не всегда удается производителям.
Подсветка группами светодиодов разных участков жидкокристаллической матрицы позволяет максимально осветить яркие участки кадра и в то же время полностью отключить подсветку в той части экрана, где необходим абсолютно черный цвет (технология local dimming).
рис 2 local-dimming
Рис 2. Local dimming: технология локального затемнения экрана выключением части светодиодов.
Этим достигается очень высокий контраст изображения. Подобное просто невозможно реализовать, используя подсветку на базе CCFL: ведь люминесцентная лампа освещает огромный участок матрицы по всей длине экрана, поэтому локальное снижении яркости отдельного фрагмента изображения технически неосуществимо.
Однако телевизор, использующий технологию расположения светодиодов за матрицей, получается даже более толстым, более тяжелым и громоздким, чем телевизор с CCFL подсветкой! А ведь нам, потребителям, необходимо что-то красивое, тонкое и изящное…
Остальные ответы
Для информации — Типы светодиодной подсветки
1)Линейкой светодиодов по торцам экрана (для экранов небольшой диагонали)
2)Светодиодной матрицей по всей площади экрана
3)Светодиодной RGB-матрицей по всей площади экрана
Direct LED — это разновидность прямой, то есть подсветки по всей площади экрана, но только белым цветом, а RGB LED цветной, в зависимости от цветовой картины в данном участке, что позволяет резко увеличить его цветопередачу.
Basics of digital LED control
LED dimming isn’t just for mood lighting. Here’s how digital controllers can handle dimming chores necessary for creating multicolor displays.
Most engineers are quite familiar with typical low-power-indicator LEDs, whether they be surface-mount or the classical through-hole packages. All that’s needed to use them is a voltage source and a series resistor of the right value. The resistor, of course, keeps the current of the LED within spec — typically less than 5 mA. Tie this to a GPIO pin on a microcontroller and you get one of the world’s most common demonstrations — a blinking LED.
However, all of the simplicity goes out the window when you move to a high-brightness, high-current LED with a forward current of well over 350 mA. This is particularly true when you put 10 of them together in a string.
The first issue with a high-brightness LED is the complicated process of efficiently maintaining a high constant current. LED brightness and color both change as a function of current. The accompanying figure shows the luminous flux of the LED — effectively the measurement of the amount of visible light it emits — is a function of the forward current through the LED. This shows the need to maintain a constant forward current, IF, through the LED to get a consistent color and light output.
Consider the case of a simple resistor, R, in series with the LED. The diode forward current is determined by IF = (VSource—VF)/R where VF is the LED forward voltage. As the source voltage, VSource, varies, the forward current IF will also fluctuate, varying the amount of light the LED emits. This clearly shows that the LED must be driven by a power supply that actively regulates IF.
In general, one important characteristic of LEDs and diodes is that their VF rises with temperature — even with a constant and regulated forward current. This is another example of the need to properly regulate IF rather than VF.
The next major challenge is heat. High-power LEDs get extremely hot. Excessive heat will significantly reduce LED lifespan and possibly cause premature failure. Active control of the LED forward current gives designers the ability to determine the necessary heat-sinking based upon the target forward current and estimated forward voltage. The use of temperature sensors also provides the option of monitoring for possible over-temperature situations. Additionally, there are other issues with high-brightness LEDs that must be addressed. But the intelligence of a DSC (digital signal controller) lets designers handle these issues through the power of software-based control.
LEDs have the amazing ability to change their light outputs almost instantly. This makes them candidates for use in color light-fixtures that provide rapid color change. It’s possible to make any color of the rainbow by simply stringing together red, green and blue LEDs and then adjusting the brightness of the appropriate devices.
But dimming each LED becomes a design challenge in this scheme. Because the forward current of the LED dictates the brightness, the obvious approach is to simply raise or lower each LED’s forward current. However, this creates a problem, as the color of the LED will also change slightly when its forward current changes. A varying LED color is usually undesirable.
The usual solution is to pulse the forward current rather than directly lowering or raising it. The effect on dimming is the same as a reduced forward current.
Use of digital control greatly simplifies the process of pulsed current dimming. Many DSCs have advanced PWM (pulse-width modulation) modules able to control the power stage of the LED. These PWM modules have override inputs that can quickly and precisely shut off the PWM outputs, thereby sending a precisely pulsed current to the LED.
The amount of dimming is quantified by a number between zero and some value that represents full brightness. To, say, power the LED to 50% brightness, a designer would have the system monitor a counter which might count from zero to 255. It would trigger the PWM override when it noticed a count of 128. The PWM output then would shut off, effectively removing the current from the LED. When the counter reaches its maximum value of 255, it resets to 0, the PWM is again enabled, and the process repeats. The dimming frequency must be high enough so that the human eye cannot perceive the flicker in the LED. Typically, a frequency greater than 400 Hz will suffice.
Active control of LED forward current requires an active power supply. The topologies normally used for powering LEDs are the buck and the boost Switch Mode Power Supply (SMPS). Both actively control the current to the LED, and both benefit from the intelligence of a DSC.
A buck topology is best in cases where the forward voltage of the LED, or string of LEDs, is below the source voltage. A typical buck topology used to control an LED employs a PWM signal to control a switch, Q, in series with a sense resistor, Rsns, and the LED. Voltage across the sense resistor corresponds to the forward current of the LED when the switch Q is closed.
The voltage across Rsns is fed to the DSC comparator, which then compares this voltage against a configurable internal reference that is proportional to the desired forward current of the LED. If the sensed voltage exceeds the internal reference, the analog comparator disables Q, which causes an inductor, L, which is also in series with the LED, to discharge its stored current through the LED and a diode, D, across it. On the start of the next PWM period, switch Q closes, and the process repeats. The DSC’s advanced features let this method actively regulate the forward current through the LED while using no CPU overhead.
As the name implies, a boost topology is best in cases where the forward voltage of the LED or string of LEDs exceeds the source voltage. Like the buck topology, the PWM controls a switch, Q, and the forward current is monitored across a sense resistor, Rsns, in series with the LEDs. The A/D converter module on the DSC samples the voltage across the sense resistor, which corresponds to the forward current of the LED. This value is then fed into a proportional integral (PI) control loop software routine on the DSC. The integral term in the loop reduces oscillations in the LED current in response to changes in the dimming frequency.
Based upon the ADC reading and a software reference value corresponding to the amount of needed current, the PI loop adjusts the duty cycle to switch Q. The advantage of using a DSC here is that the PI control loop is implemented in software so a wide variety of more sophisticated control-loop methods can be used. Furthermore, the PI control loop uses little CPU overhead, so the DSC can handle multiple LED strings with headroom left over for other features.
One of those other features is often the ability to add communications to the system. A DSC has enough processing capability to intelligently control the LED fixture, while simultaneously exchanging data with the outside world. This eliminates the need for a separate communication-and-control device.
One common lighting-control protocol is DMX512. This standard uses one-way communication with one master and multiple slaves to send commands to individual light fixtures. DMX512 transmits 512 bytes of data per packet and lets each device or node be individually addressed. DSC high-speed processing lets it run a fast control loop, such as the PI controller for the boost converter, as its top priority. It can run the communication protocol, such as DMX512, in the background. Because software implements the communication scheme, the fixture isn’t limited to just one protocol. It can run as many as the designer needs.
Like any new technology, digital LED control has a learning curve. To simplify learning digital control, many silicon suppliers now offer digitally controlled LED lighting kits and reference designs. Many of these include free source code and hardware documentation.
Because there is such a wide variety of LED topologies, some reference designs even offer interchangeable power stages. For example, the LED Lighting Development Kit (part no. DM330014) from Microchip has the LED driver stage on a daughter card, permitting experiments with multiple driver stages using the same board.
All in all, digital control using a DSC can take designers and their lighting fixtures to the next level.
Resources
Microchip Technology Inc., Chandler, Az., (480) 792-7200, www.microchip.com
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