Overview of AMOLED flicker-free displays
Of course, the screen is one of the main components of a smartphone and the companies have always paid great attention to its improvement.
As known, the first light-emitting PPV polymer (polyphenylenevinylene) was synthesized at the Cavendish Laboratory of the Cambridge University in 1989. Three years later, Cambridge Display Technolodgy (CDT) was founded to produce polymer light emitting materials. The first Samsung X120 phone with an OLED screen was introduced in 2004.
After 4 years Nokia introduced the N85 with an AMOLED display.
Introduction
Since 2007, AMOLED technology has been widely used in phones, media players, digital cameras, etc. Today it’s the main and only competitor to traditional LCD screens, and the comparison AMOLED vs LCD often is present in many reviews.
As known, multilayer organic polymers in OLED-matrices emit their own light under the electric current action, without requiring backlight. Today companies only use matrices with an active matrix, which are called AMOLED (Active Matrix Organic LED). But OLED TVs makers continue to use the traditional OLED acronym without the addition of AM.
Several years ago, companies started using AMOLED screens even in mid-budget models. This technology delivers vivid colors, excellent viewing angles and infinite contrast with low power consumption. Unfortunately, it has a significant drawback. The developers adjust the brightness of the AMOLED matrix using PWM (pulse-width modulation). This technology provides high precision and wide range of adjustment, but its operation is accompanied by flicker.
Until a few years ago, companies did not attach importance to it. According to statistics, only about 20% of people visually perceive flicker with a frequency of more than 200 Hz. But according to many physiologists, the brain perceives it on a subconscious level, even without visualization. Therefore, some users experience headache and eye strain. As a result, fierce competition forced the developers to tackle this problem and they did an excellent job with this task, developing quite effective methods for reducing the flicker of AMOLED screens.
PWM (pulse-width modulation)
As known, screen brightness can be adjusted with increasing / decreasing the current (voltage) or using the pulses. As the name suggests, PWM uses the pulse width (duration) for this purpose. Simplified, this technology works as follows. For example, frequency is 4 pulses per second. In this case, the duration of each pulse is only 0.25 sec. Each pulse turns on the LED. Accordingly, a twofold reduction in the pulse width will reduce the brightness by 50% without changing the voltage and frequency. In this example, each new pulse will arrive in 0.25 seconds, but their duration will be reduced to 0.12 seconds. Accordingly, the LED will only be on for half the time, which will reduce its overall brightness. Reducing the pulse width to 0.01 seconds will reduce the brightness to a minimum because the LED will only turn on for 0.01 seconds and turn off for 0.24 seconds.
Compared to direct voltage regulation, PWM is very efficient, economical and provides much wide range of brightness control.
Additionally, the appeal of PWM is due to the features of organic LEDs. First, the constant glow with analog control causes them to heat up, shortening their service life. Secondly, the specs of organic LEDs are non-identical, which causes non-uniform brightness. This effect is especially pronounced at low brightness and significantly reduces the image quality.
PWM provides perfect uniformity. Unfortunately, its relatively low frequency (200-300Hz) causes human perceived flicker. Wherein, the flicker intensity increases at maximum brightness.
Similar to LCD, increasing the PWM frequency can also solve the flickering problem. For example, Microsoft Lumia 950 used PWM with 500Hz.
Unfortunately, this idea has not been continued.
Hybrid brightness control
Many IPS screens also use PWM. Popular smartphones with this technology include Sony Xperia 10 and 10 Plus, Xiaomi Redmi Note 7, Huawei P Smart Plus, Xiaomi Mi 8 Lite, etc. But their flickering is not a problem due to the very high frequency, which exceeds 2000 Hz. For comparison, the iPhone 11 Pro, Xiaomi Mi 9 and Samsung Galaxy S10 with AMOLED screens operate at 290 Hz (290 pulses per second), 245 Hz and 240 Hz, respectively. over, some AMOLED models use even lower PWM frequency:
– Samsung Galaxy A50 – 119 Hz;
Their intense flickering at maximum brightness quickly tires the eyes, even for people with excellent vision.
Of course, industry leaders have tried to find a compromise solution to this problem. For example, in 2015 LG first introduced flicker-free OLED panels in its experimental LG G Flex 2 with a curved P-OLED screen.
Its brightness control is implemented at the hardware level using current modulation that drives organic LEDs. Screen controller did not use a PWM (pulse width modulation) module. Accordingly, there was no flicker even at the maximum brightness. Unfortunately, the image quality was very low due to the poor quality of the P-OLED matrices.
As a result, the company abandoned these attempts.
But later the developers found an elegant solution to the problem by combining two control methods. For example, OLED iPhones use PWM only at low brightness with minimum flicker, and switch to analog control at 50% or higher brightness when the unevenness is minimal. Samsung and LG use this algorithm as well.
DC Dimming
Several years ago, Xiaomi introduced the innovative DC Dimming technology. The company does not disclose its key features, but it does significantly reduce PWM flicker by radically smoothing out the pulses amplitude.
Perhaps DC Dimming turns on the brightness to the maximum, while simultaneously reducing the filter transparency. Unfortunately, DC Dimming has cons, including the loss of midtones on a dark background at low brightness.
Some experts positione DC Dimming as the next generation of hybrid brightness control for AMOLED displays. Indeed, its efficiency significantly surpasses the algorithms of other companies.
Today this feature is supported by the following models:
– OnePlus 7 Pro and OnePlus 7;
Conclusion
Probably, eye safety when using gadgets can be positioned as a steady trend in recent years. The effective innovative ways to reduce blue, glare and flicker, the increase in image quality through resolution, color gamut and contrast, demonstrate the determination of companies to actively use the eye safety of their devices as an important element of the competition. Gradually, this factor is becoming a selection criterion for many consumers. But, of course, it requires at least basic information, which today can be easily obtained on the Internet.
This video offers Realme X2 Pro (Realme is OPPO sub-brand) with fixing DC Dimming mode errors.
DC-Like Dimming vs 1920Hz PWM Dimming
Xiaomi Pad 6 Series Comes with Upgrades to Compete with the OnePlus Pad
Xiaomi recently held an event to launch the flagship Xiaomi 13 Ultra and the Xiaomi Band 8 in China. The list of new products also includes the company’s next-gen tablets; the Xiaomi Pad 6 and the Pad 6 Pro. These come with a number of upgrades over their predecessors to compete with the likes of the latest OnePlus Pad. Have a look at the details below.
Xiaomi Pad 6 Series: Specs and Features
The Xiaomi Pad 6 series features an all-metal chassis and looks similar to the Xiaomi Pad 5. The first upgrade is in the form of the 11-inch 2.8K LCD display with support for a 144Hz variable refresh rate, much like the OnePlus Pad. The display supports 550 nits of brightness, HDR10, Dolby Vision, TÜV Rheinland low blue light certification, and DC dimming.
Faster performance is also ensured with the presence of an upgraded chipset. While the Xiaomi Pad 6 has the Snapdragon 870 SoC, the Xiaomi Pad 6 Pro is powered by the high-end Snapdragon 8 Gen 1 chipset. While this is a year-old chipset, we can expect some decent performance out of it. The tablets come equipped with up to 12GB of RAM and 512GB of storage.
You can get access to features like the Smart portrait center and the Conference toolbox for convenient video calls, screen mirroring, Smart translation, and several multitasking features too.
You get support for Wi-Fi 6, Bluetooth version 5.3, USB Type-C, and a quad-speaker setup. Both of them run MIUI 14 for Pad based on Android 13. And to make this a sweet deal, the tablets come with a Smart keyboard (with a larger trackpad and NFC support) and the second-gen stylus (with 4096 levels of pressure sensitivity and a battery life of about 150 hours).
Price and Availability
The Xiaomi Pad 6 series starts at CNY 1,999 (~ Rs 23,800) and are now available to buy in China. Given the leaked pricing of the OnePlus Pad, this appears like a tough contender. Let’s see how OnePlus decides on the pricing part! Here’s a look at the prices.
Anti-flicker mode on Xiaomi Android 11 Mi 11 5G| The spect smartphone tricks #12
Xiaomi Pad 6 Pro
- 8GB128GB: CNY 2,399 (~ Rs 28,600)
- 8GB256GB: CNY 2,699 (~ Rs 32,100)
- 12GB256GB: CNY 2,999 (~ Rs 35,700)
- 12GB512GB: CNY 3,299 (~ Rs 39,300)
Xiaomi Pad 6
- 6GB128GB: CNY 1,999 (~ Rs 23,800)
- 8GB128GB: CNY 2,099 (~ Rs 25,000)
- 8GB256GB: CNY 2,399 (~ Rs 28,600)
The keyboard retails at CNY 599 (~ Rs 7,000) while the stylus is priced at CNY 449 (~ Rs 5,300). The Xiaomi Pad 6 series comes in Gold, Black, and Far Mountain Blue colors.
Xiaomi Pad 6 Series Comes with Upgrades to Compete with the OnePlus Pad
Xiaomi recently held an event to launch the flagship Xiaomi 13 Ultra and the Xiaomi Band 8 in China. The list of new products also includes the company’s next-gen tablets; the Xiaomi Pad 6 and the Pad 6 Pro. These come with a number of upgrades over their predecessors to compete with the likes of the latest OnePlus Pad. Have a look at the details below.
Xiaomi Pad 6 Series: Specs and Features
The Xiaomi Pad 6 series features an all-metal chassis and looks similar to the Xiaomi Pad 5. The first upgrade is in the form of the 11-inch 2.8K LCD display with support for a 144Hz variable refresh rate, much like the OnePlus Pad. The display supports 550 nits of brightness, HDR10, Dolby Vision, TÜV Rheinland low blue light certification, and DC dimming.
Faster performance is also ensured with the presence of an upgraded chipset. While the Xiaomi Pad 6 has the Snapdragon 870 SoC, the Xiaomi Pad 6 Pro is powered by the high-end Snapdragon 8 Gen 1 chipset. While this is a year-old chipset, we can expect some decent performance out of it. The tablets come equipped with up to 12GB of RAM and 512GB of storage.
The Pad 6 Pro is backed by an 8,600mAh battery with 67W fast charging. The Pad 6 settles for 33W but has a bigger 8,860mAh battery. Another change is the camera system. The Xiaomi Pad 6 Pro sports a dual-camera setup (50MP main camera and a 2MP depth sensor) and a 2MP selfie shooter. The Pad 6, on the other hand, has a 13MP single rear camera and an 8MP front snapper.
You can get access to features like the Smart portrait center and the Conference toolbox for convenient video calls, screen mirroring, Smart translation, and several multitasking features too.
You get support for Wi-Fi 6, Bluetooth version 5.3, USB Type-C, and a quad-speaker setup. Both of them run MIUI 14 for Pad based on Android 13. And to make this a sweet deal, the tablets come with a Smart keyboard (with a larger trackpad and NFC support) and the second-gen stylus (with 4096 levels of pressure sensitivity and a battery life of about 150 hours).
Price and Availability
The Xiaomi Pad 6 series starts at CNY 1,999 (~ Rs 23,800) and are now available to buy in China. Given the leaked pricing of the OnePlus Pad, this appears like a tough contender. Let’s see how OnePlus decides on the pricing part! Here’s a look at the prices.
Xiaomi Pad 6 Pro
- 8GB128GB: CNY 2,399 (~ Rs 28,600)
- 8GB256GB: CNY 2,699 (~ Rs 32,100)
- 12GB256GB: CNY 2,999 (~ Rs 35,700)
- 12GB512GB: CNY 3,299 (~ Rs 39,300)
Xiaomi Pad 6
- 6GB128GB: CNY 1,999 (~ Rs 23,800)
- 8GB128GB: CNY 2,099 (~ Rs 25,000)
- 8GB256GB: CNY 2,399 (~ Rs 28,600)
The keyboard retails at CNY 599 (~ Rs 7,000) while the stylus is priced at CNY 449 (~ Rs 5,300). The Xiaomi Pad 6 series comes in Gold, Black, and Far Mountain Blue colors.
Что такое DC Dimming и ШИМ в смартфонах Xiaomi?
В последнее время в спецификациях смартфонов Xiaomi, Redmi и Poco, вернее в параметрах их AMOLED-экранов, всё чаще указывается характеристика DC Dimming. Её наличие всячески нахваливают продавцы устройств, но многие пользователи попросту не знают что такое DC Dimming и для чего это нужно.
На самом деле, DC Dimming является очень полезной штукой, которая призвана повысить комфорт при использовании смартфона и, что важно, сберечь ваше зрение. То есть, если при достаточно продолжительном чтении или сеинге на смартфоне, оснащенном AMOLED-дисплеем у вас устают глаза — DC Dimming исправит ситуацию.
Что такое DC Dimming в смартфонах Xiaomi?
DC Dimming — это технология, применяемая для уменьшения яркости экрана на основе AMOLED матрицы в смартфонах Xiaomi, Redmi, Poco и других производителей. При этом используется она не только в мобильных устройствах.
Термин DC Dimming состоит из двух частей: DC обозначает постоянный ток, а Dimming — «затемнение» или уменьшение яркости.
Как известно, интенсивность свечения светодиодов AMOLED экрана определяется мощностью подаваемого на него тока. То есть, чем выше мощность, тем ярче светится экран, чем меньше мощность, тем меньше яркость дисплея.
В свою очередь, мощность равна произведению силы тока на напряжение. Что бы понизить мощность и, соответственно, яркость экрана, нужно снизить силу тока или напряжение, но на практике используется второй вариант — на светодиоды подается меньший вольтаж, за счет чего уменьшается интенсивность свечения экрана.
DC Dimming как альтернатива ШИМ
В смартфонах, оснащенных AMOLED-дисплеями для уменьшения яркости обычно используется другая технология — широтно-импульсная модуляция, или просто ШИМ. Причем до 2019 года она применялась практически во всех моделях смартфонов, но многочисленные жалобы пользователей на то, что после чтения на смартфоне с OLED-матрицами сильно устают глаза, вынудила производителей мобильных устройств искать альтернативные варианты.
При широтно-импульсной модуляции регулировка яркости осуществляется за счет изменения ширины импульса, который включает и выключает дисплей.
Суть в том, что светодиоды не святятся в экране постоянно, а включаются импульсом, после чего выключаются. Если импульс широкий (долгий), дисплей горит с максимальной яркостью. Чтобы уменьшить яркость, достаточно импульс сделать короче, а период бездействия светодиодов — длиннее.
На 50% яркости экрана периоды с включенными и выключенными диодами равны. На 25% яркости период бездействия светодиода в три раза дольше, чем время их включения. И так далее.
Проблема в том, что чередование фаз включения/выключения является ничем иным, как мерцанием. Мерцание воспринимается зрительным анализатором, даже если субъективно вы этого не замечаете, и от всей этой «светомузыки» быстро устают глаза.
ШИМ — основная причина утомления глаз при чтении с AMOLED экрана при пониженной яркости.
DC Dimming — альтернатива широтно-импульсной модуляции. Регулировка яркости за счет модулирования напряжения тока, а не ширины импульса, позволяет полностью исключить эффект мерцания.
При использовании DC Dimming незначительное мерцание на минимальной яркости все-таки присутствует (поскольку импульсы остаются), но благодаря большой длительности импульса оно уже не влияет на зрение. Работать с экраном, в котором для регулировки яркости применяется технология DC Dimming, намного комфортнее и безопаснее.
Недостатки DC Dimming
Технология DC Dimming — достаточно простое и элегантное решение серьезной проблемы негативного влияния смартфона, вернее его AMOLED-экрана, на зрение человека. Вопрос в том, почему производители телефонов вспомнили о DC Dimming только сейчас, хотя технология существует с незапамятных времен?
Причина кроется в единственном недостатке технологии DC Dimming — при уменьшении напряжения светодиоды AMOLED дисплея начинают искажать цвета, и искажать довольно-таки сильно. До полной инверсии цвета дело, конечно, не доходит, но степень искажения высока.
ШИМ лишен этого недостатка, и ради точности цветопередачи при любых значениях яркости производители выбирали эту технологию. Но когда пользователи начали массово отказываться от покупки смартфонов с AMOLED, разработчики изменили приоритеты и вспомнили о DC Dimming.
