Why Xiaomi is changing the brightness of the screen – all the reasons and how to fix it

Have you noticed that screen brightness on your Xiaomi (whether it’s a Redmi smartphone, POCO or a Mi TV) drops and suddenly increases without you? This is a common problem that annoys users, especially when watching videos, reading or working in the dark. 90% of the time, this behavior is not due to a breakdown, but to the work of built-in functions or software failures.

In this article, we will take a look at all the possible causes of automatic brightness changes on Xiaomi devices, from adaptive lighting and a faulty light sensor to hidden energy saving settings. You will learn how to turn off auto-adjustment, check sensors, reset to factory settings and even manually calibrate the screen. And for Mi TV owners, we have prepared a separate section with nuances of backlight settings.

Spoiler: Most of the time, you can fix the problem in 2-3 minutes without having to repair it, but if the brightness changes randomly, flashing or accompanied by artifacts on the screen, it can indicate a hardware malfunction (such as a plume detachment or a matrix failure), such symptoms require diagnosis at a service center.

1. Adaptive brightness: how it works and why it “glues”

The main reason for the spontaneous brightness change on Xiaomi is the Adaptive Brightness function, which uses a light sensor to automatically adjust the brightness of the screen depending on the ambient light. In theory, this is convenient, but in practice it often malfunctions:

• 🔦 Inflated sensor sensitivity – responds even to a shadow from the hand or a cloud outside the window.
• 📱 Incorrect calibration after the update MIUI The brightness “jumps” between extremes.
• 🌓 Night mode conflict – adaptive brightness and dark theme “argue” for backlight control.

To check if adaptive brightness is to blame, open Settings → Display → Brightness and turn off the Adaptive Brightness slider. If the problem has disappeared, the cause is found. If not, read on.

⚠️ Note: On some models POCO (for example, POCO F3) Adaptive brightness hidden in the Settings menu → Special facilities → Display enhancements. Don't confuse it with Automatic Contrast Adjustment -- these are different settings!

If you want to keep adaptive brightness but reduce its aggressiveness, try recalibrating the sensor:

1. Open the settings → Display → Brightness.
2. Turn on adaptive brightness and set the hand slider to a comfortable level.
3. Point your phone at a light source (such as a lamp) and hold for 5-10 seconds.
4. Repeat the same thing in a dark room.

2. Light sensor: how to check and clean

If the adaptive brightness is turned off, but the screen still changes the backlight, the problem may be the light sensor, which is located next to the front camera (usually at the top of the screen) and over time gets clogged with dust or covered with a protective film.

To check the sensor:

1. Open the Phone app and type ##6484## (some models run #4636##).
2. Choose Hardware Testing → Light Sensor.
3. Point a flashlight at the sensor, the value should change dramatically (e.g., from 10 to 10,000 lux), and if there is no reaction, the sensor is defective or contaminated.

If the sensor is responsive but weak:

• 🧹 Clean the sensor area with a soft wipe (do not use alcohol!).
• 📱 Remove the protective film or case if they close the sensor.
• 🔧 Update the firmware - in new versions MIUI Improved processing of data from the sensor.

⚠️ Attention: On Mi TVs TV The light sensor is only available in models with the prefix Pro (for example, Mi). TV Q2 If you have the usual version, look for the reason for the brightness jumps in the Picture settings. → Eco regimes.

3. Energy saving and smart MIUI modes

Xiaomi smartphones aggressively optimize power consumption, and sometimes it affects the brightness of the screen, for example, in the “Ultra-saving” mode (Settings → Battery → Battery Modes), the brightness is forced to decrease to 30-40%, even if you set it to a maximum.

Other “hidden” features that affect brightness:

• 📉 «Adaptive battery" - limits brightness for background applications (disabled in Settings → Battery → Battery settings).
• 🌙 «Scheduled Dark Mode – may conflict with adaptive brightness (check Settings) → Display. → Dark mode).
• 🔋 «Optimization of charging" - on some models (Xiaomi) 12T, Redmi Note 11 Pro+) When charging, the brightness automatically decreases.

To eliminate the impact of energy saving:

1. Open the Settings. → Battery.
2. Select Battery Modes → Performance (or No Limits).
3. Disable the Adaptive Battery and MIUI Optimization.

Disable the adaptive battery

Select the “Productivity” mode

Check the dark mode settings

Disable charging optimization (if any)

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4. firmware failures and application conflicts

If the brightness started to "jump" after the MIUI update or installing a new application, the software is to blame.

• 🔄 Failed updates in new versions MIUI often with brightness control (especially in the MIUI 14 and HyperOS).
• 📱 Launcher conflict – third-party shells (like Nova Launcher) can intercept brightness control.
• 🎮 Game Turbo Forcedly Changes the Brightness in Games.

How to diagnose and correct:

If the problem appears after the update, try resetting the display settings:

1. Go to Settings → System → Resetting settings.
2. Select Reset Display Settings (not to be confused with a full reset!).
3. After rebooting, adjust the brightness manually.

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If brightness starts to change after installing custom firmware (like Pixel Experience or LineageOS), check the kernel compatibility with your model. Some firmware does not work properly with Xiaomi sensors due to the lack of proprietary drivers.

5. Features of Mi TVs: why brightness "breathes"

On Mi TVs (especially Mi TV 4S, Mi TV Q1, Mi TV A2), brightness may change for other reasons than on smartphones.

• 📺 Eco-Vision mode – automatically reduces brightness to save energy (disables in Settings) → Picture → Eco regimes).
• 🌈 Dynamic contrast is a function of Dolby Vision or HDR10+ It can change the lighting depending on the scene.
• 🔌 Unstable power supply – if the TV is connected through an extension cord or a weak power supply, the brightness may “sink».
• 📶 Update by air (OTA) — after the update, the lighting settings are lost.

To turn off automatic adjustment on the Mi TV:

1. Click on the Settings remote.
2. Go to Picture → Eco modes and turn off all options.
3. In the Picture menu → Additionally, turn off Dynamic contrast and Autobrightness.
4. For models with Dolby Vision, select Dolby Dark or Movie mode instead of Vivid.

If the brightness changes only in specific applications (such as Netflix or YouTube), check the HDR settings in the app itself. Some services force automatic backlighting for HDR10-enabled content.

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On OLED-screen Mi TVs (e.g. Mi TV OLED), automatic brightness control can cause pixel burnout. If you often watch content with static elements (channel logos, control panels), it is recommended to turn off adaptive lighting and use a fixed brightness of no more than 70%.

6. Hardware malfunctions: when to carry in the service

If all software methods have been tried, but the brightness still changes randomly, the problem may be hardware.

• 🔌 Poor contact of the display plume - after falling or hitting, the plume connecting the screen to the motherboard may move away.Symptoms: brightness "jumps" when pressing certain areas of the screen.
• 💡 Failure of LEDs backlighting - on smartphones with AMOLED (For example, Xiaomi 13, Black Shark, individual diodes can degrade, causing uneven brightness.
• 🔋 Power controller malfunction – if brightness drops when battery charge is low (even if percentage is high), the controller is to blame.
• 📱 Separation of the matrix - on old models (Redmi) 4X, Mi A1) Over time, the glue under the screen dries, which leads to flickering.

How to diagnose a hardware problem:

1. Check the reaction to press: gently press the top and bottom of the screen. If the brightness changes, the plume is to blame.
2. Look at the screen from an angle: if the backlight is uneven (one side is darker), the matrix may degrade.
3. Connect to charging: If brightness stabilizes, the battery or power controller is a problem.

⚠️ Warning: If colored bars, flickering dots or artifacts (such as "broken pixels") appear on the screen, immediately stop using the device! this may indicate damage to the graphics chip or matrix, and further exploitation will exacerbate the problem. In such cases, a replacement of the screen or motherboard is required.

7. Manual brightness calibration (for advanced users)

If standard settings do not help, you can manually calibrate the brightness using an engineering menu or ADB-This method is suitable for experienced users, as incorrect actions can lead to system failure.

Method 1: Through the Engineering Menu

1. Open the Phone app and type ##36446337## (or #4636## on new models).
2. Go to Hardware Testing → Lights Sensor.
3. Write down the current Min and Max values (e.g. 10 and 10,000 lux).
4. Enter new values (e.g. 50 and 8000) and save.

Method 2: ADB (computer required)

adb shell settings put system screen_brightness_mode 0 # Disables adaptive brightness


adb shell settings put system screen_brightness 150 # Sets fixed brightness (0–255)

For Mi TVs, calibration is done via the service menu:

1. Turn off the TV.
2. On the remote, press sequentially: Menu → 1 → 3 → 9 → Menu.
3. From the service menu, select Picture → Backlight Adjust and set a fixed value.

⚠️ Attention: Changing the parameters in the engineering menu can lead to sensors malfunctioning or system failure.Before experimenting, back up the data via Settings → System system → Backup.

FAQ: Frequent questions about brightness on Xiaomi