Owners of modern Xiaomi, Redmi and Poco often come across the term “PWM” when it comes to display quality. It’s not just a technical acronym, but a physical phenomenon that directly affects the comfort of using a gadget. If you notice that when the brightness decreases, the screen begins to pulsate unpleasantly and the eyes quickly tire, you are dealing with this effect. Understanding the nature of this process will help you adjust the device correctly.
In this article, we will discuss in detail why manufacturers use this brightness control technology and what consequences it has for the health of the user. You will learn how to determine the pulse level without special equipment and what software crutches Xiaomi has implemented in the shell of MIUI and HyperOS to combat this phenomenon.
Physical nature of PWM and the principle of operation of OLED matrices
PWM stands for pulse-width modulation. In the context of smartphone screens, it's a method of controlling the brightness of the backlight, which is fundamentally different from how we used to adjust light with a light bulb. Instead of smoothly reducing the voltage applied to the LEDs, the system quickly turns on and off the backlights at a high frequency.
The human eye can't see these switches if they're fast enough and it can sense the average brightness, but the lower you put the brightness slider in the settings, the less time LEDs are on and longer they're off, and that's what's causing the flashing cycle to ripple.
The problem is particularly acute for OLED and AMOLED arrays, which are widely used in flagships and mid-budget models of Xiaomi. Unlike IPS screens, where brightness is often regulated by voltage change (which does not cause flickering), OLED diodes are difficult to accurately control current at low values, so manufacturers resort to PWM as the most effective way to get a deep black color and save battery power.
⚠️ Attention: In some people, low-frequency PWM can cause not only eye fatigue, but also headaches, decreased concentration and even migraines. If you are sensitive to light flickering, you should pay special attention to the frequency of PWM when choosing a new smartphone.
It is important to understand that the frequency of this blinking can range from 240 Hz to 480 Hz and higher. The higher the frequency, the less noticeable the pulsation for the nervous system. Older smartphone models often had a frequency of 240 Hz, which is considered low by modern standards. New flagships Xiaomi gradually move to higher frequencies or introduce hybrid control methods.
The effect of low-frequency PWM on vision and well-being
The long-term exposure to the flickering screen does not go unnoticed by the body. The main load is placed on the visual apparatus. The pupil of the eye constantly tries to adapt to changing brightness, even if the brain is not consciously aware of it, which leads to overstrain of the muscles of the eye and dryness of the mucosa.
A list of the main symptoms that may indicate a negative effect of PWM:
- 😫 Feeling of “sand” in the eyes and redness of proteins after 30 minutes of using a smartphone.
- 🤕 Pressing headache in the forehead and temples, occurring in the evening.
- 📉 Reduced concentration and fatigue when reading text from the screen.
- 🌑 Increased discomfort when using the device in the dark.
The most dangerous is the use of a smartphone with low brightness in complete darkness, in which the pupil dilates, allowing more light to pass through, and the pulsation becomes critically noticeable to the nervous system, which is why many users of the Redmi Note or Poco F series complain of discomfort when reading books at night.
It's worth noting that PWM susceptibility is personal, with users who can use 240Hz devices for years without feeling a problem, others starting to feel uncomfortable within 10 minutes, but doctors recommend minimizing contact with flickering light sources for everyone.
DC Dimming Technology in Xiaomi Smartphones
To solve the flicker problem, engineers have developed a technology called DC Dimming, which, unlike the classic PWM, regulates brightness by changing the current through the LEDs without turning them off. In theory, this should eliminate the pulsation completely.
In Xiaomi devices, this feature is often hidden in a special engineering menu or displayed in the screen settings called “Flicker Protection”, activating this mode puts the display in a mode close to IPS-matrixes, where brightness changes smoothly.
How to activate DC Dimming on most MIUI and HyperOS devices:
- 📱 Open the phone app and dial the code ##7777##.
- ⚙️ In the menu that appears, find the switch «DC Dimming or "Anti-flicker».
- ✅ Activate the function and restart the device to apply the changes.
Unfortunately, not all models support this feature natively. In some cases, activation is only possible through third-party applications or modified firmware, which can violate the warranty. In addition, at very low brightnesses, DC Dimming can lead to uneven screen lighting (the “dirty screen” effect), when colors are displayed incorrectly.
Why Xiaomi doesn’t include DC Dimming by default?
Comparison of display brightness control methods
To better understand the difference, it is worth comparing the main technologies used in the industry, each with its own advantages and disadvantages that affect the final perception of the image by the user.
| Parameter | Classic SHIM | DC Dimming | Hybrid method |
|---|---|---|---|
| Principle of work | Switching on/off | Change in current | Combination of methods |
| Effect on the eyes | High (at low frequency) | Minimum | Average. |
| Color rendering | Stable. | It can be distorted. | Stable. |
| Energy consumption | Low. | Average. | Optimized |
The hybrid method, which is now being implemented in many new Xiaomi 13, Xiaomi 14 and their Pro versions, tries to combine the advantages of both worlds. DC Dimming is used at high brightness, and when lowered below a certain threshold (usually 30-40%), the system switches to high-frequency PWM, which is less harmful.
And users should remember that software crutches don't always work perfectly, and sometimes once you turn on flicker protection, you can see gradients dissecting or you can see a change in the shade of white, and that's a cost for reducing the pressure on the optic nerve.
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If you are sensitive to PWM, try not to dip the brightness below 30-40%.It is better to use Black and White or Electronic Ink mode in the reading screen settings than to reduce the brightness to a minimum.
Practical ways to reduce harm from flickering
Even if your smartphone doesn't have DC Dimming built in, there are ways to minimize the impact. The first and easiest is to control the brightness level. Try to keep it above the 40-50% mark, where the pulsation amplitude is much smaller.
The second way is to use dark themes. On AMOLED screens, black means the pickle is off. The more black the screen has, the less the overall brightness of the glow, and the less visible the ripple of the active areas. Include dark theme in Settings → Screen → Dark Mode.
Also effective is the use of blue light filter applications that darken the screen programmatically without lowering the backlight of the matrix, but this method can lead to color distortion, which is unacceptable for designers or photographers.
Checklist for setting up safe use of the smartphone:
- 🌙 Turn on Night Mode or Read Mode in the evening.
- ☀️ Avoid using the gadget in bright sun with minimal brightness.
- 👓 Take breaks every time. 20 minutes (rule) 20-20-20).
- 📉 Set autobrightness so that the screen doesn’t go out too much in the dark.
☑️ Screen safety check
How to check the presence and frequency of PWM on your own
There's a simple folk-made method of checking for flickering that doesn't require expensive equipment, so you'll need a camera from another smartphone, point the camera at the screen of the device being tested, and minimize the brightness.
If you see dark bands running on the camera screen, PWM is present. The wider and slower the bands move, the lower the flicker frequency and the more harmful the screen is, if the bands are barely noticeable or absent, then the frequency is high or DC Dimming is used.
A more professional approach is to use specialized applications from Google Play, such as OLED Tester or Screen Test, which can infer special patterns and help assess the uniformity of glow and the presence of artifacts at different brightness levels.
⚠️ Warning: Don’t blindly rely on the camera tests of other smartphones, as they too have their own shutter speed and frame rate settings, which can distort the result.
Choosing a Xiaomi smartphone with eye safety in mind
When buying a new device, you should pay attention not only to the processor and camera, but also to the characteristics of the display. The specifications often indicate the frequency of PWM. Models with a frequency of 1920 Hz, 2160 Hz and above are considered safe (High-frequency PWM dimming).
The flagship Xiaomi 13 Ultra, Xiaomi 14 Pro lineups already feature screens with modulation rates up to 3840Hz, which almost completely eliminates eye damage. At the same time, entry-level low-end Redmi Note models can still use 240Hz.
If you plan to read a lot from your phone or work with text, it is more important to choose a model with an IPS matrix (where PWM is usually absent) or a modern OLED with a high frequency.
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The current security standard for OLED screens is PWM frequency above 1440 Hz or the presence of a full DC Dimming without image artifacts.
Conclusion and prospects for technology development
The PWM problem in Xiaomi and other brands is gradually fading into the past due to the development of matrix manufacturing technologies. However, while you are using the current device, it is important to be aware of the risks and be able to customize the gadget to minimize harm.
Use the available protection features, monitor brightness and take breaks. Eye health is more important than maximum contrast or a couple percent of battery power. In the future, a full transition to technology that excludes flickering, but until then, control remains in the hands of the user.
Remember that getting the display right is an investment in your long-term well-being, don’t ignore body signals like fatigue or headache, and adjust your electronics usage settings in a timely manner.