Owners of Xiaomi, Redmi and POCO smartphones often face a situation where the display of the device suddenly decreases brightness, despite the set maximum values in the settings. This phenomenon can occur at the most inopportune time: while watching a video, during the game or during a normal conversation on speakerphone. Users often describe this as “the screen goes out” or “blackens”, which causes irritation and reduces the usability of the gadget.
The reasons for this behavior can range from software features of the MIUI shell to physical damage to sensors. Sometimes the problem lies in the banal overheating of the body, and in other cases, the security glass that covers the sensor is to blame. Understanding the nature of the darkening is the first step to successfully solving the problem without going to the service center.
In this article, we will discuss in detail the main scenarios in which automatic brightness control is not working correctly, and provide step-by-step instructions for troubleshooting, you will learn how to distinguish a software bug from a hardware malfunction, and what hidden settings can affect the operation of the backlight.
Influence of the proximity sensor and protective glasses
The most common reason Xiaomi gets its screen dark during a conversation is because of a false alarm of the proximity sensor, which is located at the top of the front panel and is designed to turn off the display when you hold the phone to your ear to avoid accidental cheek pressing.
If you get dust, greasy fingerprints, or the edge of a mispatched security glass, the system perceives it as being close to an object, and as a result, the screen instantly goes out, even if you're not holding the phone to your ear, especially in models with a cut-out droplet or a hole in the screen where the sensor is hidden under the display.
⚠️ Attention: The use of thick protective glasses with a black frame covering the sensor area, in 90% of cases leads to permanent darkening of the screen at the top of the screen.
To check the sensor's performance, you can use the engineering menu. Go to the call menu and enter the code ##6484##. From the list that opens, select Proximity Sensor and palm the top of the screen. If the value changes from 5.0 to 0.0, the sensor is good, and the problem is likely contamination or accessories.
☑️ Diagnostics of the proximity sensor
Autobrightness and calibration of light
The second most common cause is the malfunction of autobrightness algorithms. MIUI analyzes indoor lighting with a light sensor and tries to adjust the level of illumination to save energy or eye comfort. However, calibration often gets confused, and the phone begins to "think" that it is in complete darkness, even in bright sun.
Users often notice that the screen darkens when unlocked or when they leave applications, because the software does not have time to respond to a sudden change in light flux, in which case manual brightness control becomes the only way out until recalibration is performed.
- 🌞 Sharp drops: When leaving a dark room to the light, the sensor may not have time to raise the brightness, creating the illusion of dimming.
- 📉 Charge savings: Algorithms can artificially lower brightness if battery level drops below 20%.
- 📱 Application conflict: Some reading programs or video players can intercept the control of the light sensor.
To remedy this, try turning off the automatic adjustment in the notification curtain and manually place the slider. Then turn it on again and smoothly swipe your hand over the top of the screen, changing the lighting so that the system will re-remember the range of values.
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For quick calibration of the light sensor, use the Equipment Test application in the settings menu, sequentially closing and opening the sensor in different lighting.
Processor overheating and backlight trolling
Modern Xiaomi smartphones are equipped with powerful processors that, when loaded (games, navigation, shooting 4K video) emit a significant amount of heat. When the temperature of the case or internal components reaches a critical point, the trottling system comes into operation.
One way to lower the temperature is to reduce the power consumption of the display, which is one of the main energy consumers, so if you notice that the screen darkens during heavy periods of time. 3D-games or long-term video recording, this is a regular reaction of the system to overheating.
In this case, the software settings are powerless. The only solution is to reduce the load on the device. Remove the case, improve the ventilation or take a break from use. Trying to boost the brightness in this state can lead to accelerated wear of the battery.
| Symptoms. | Probable cause | User action |
|---|---|---|
| The screen goes out when you talk. | Approximation sensor | Screen cleaning, glass checking |
| Dim in games | Overheating (Trottling) | Cooling the device, pause |
| Changes brightness spontaneously | Autobrightness | Manual tuning, calibration |
| Darkening in the corners | Reading Mode / Sunlight | Disabling special modes in settings |
Special modes: Reading and sunlight
There are special features in the MIUI and HyperOS shell that can affect brightness and color reproduction. Reading Mode adds a warm yellow filter and can reduce the brightness to simulate a paper book. If this mode is on on a schedule or constantly, the screen will appear darker than usual.
There's also a Sunlight Mode feature that should, on the contrary, increase the brightness outside. However, sometimes there's a failure and the phone gets stuck in the intermediate state when the standard brightness is limited by software. → Screen.
Special attention should be paid to DC Dimming (or Anti-Flicker), which is available in advanced screen settings, which eliminates flickering at low brightness, but visually can make black less deep and minimal brightness slightly higher than without this feature, which some users perceive as strange backlight behavior.
How to find hidden screen settings?
Problems with energy saving and background processes
Aggressive battery optimization is a signature feature of Xiaomi smartphones, which can force the screen to darken if it believes that the running application does not require high brightness, or if the phone is inactive for a long time, it is part of a strategy to extend battery life.
In addition, some third-party “optimizers” and memory cleaners may conflict with the display’s system settings, and may force the brightness to a minimum to “save” charge while ignoring user preferences.
Check the battery settings for specific applications. If you have banned background activity or set strict restrictions, the system may not properly control the screen when switching between programs. It is also worth turning off Ultrasaving if it is activated, as it severely limits the functionality of the display.
⚠️ Warning: Turning on the "Ultrasaving" mode limits the brightness and frequency of the screen update, which can be perceived as a malfunction, although it is a standard saving function.
Hardware malfunctions and plumes
If the software methods didn't work, and the screen continues to behave unpredictably, there's a high probability of hardware failure, and the most common cause is a slipping of the display plume or oxidation of the contacts, which often happens after falls, bumps or moisture gets inside the housing.
In such cases, the dimming can be chaotic: the screen can blink, change brightness with jerks or go out completely with the preservation of sound and vibration, and the degradation of the matrix itself can be possible, when the backlight loses its maximum power over time and dims at the edges or in the center.
To diagnose, you can carefully (without strong pressure) press the upper and lower frames of the smartphone. If the brightness changes from mechanical action, then the problem lies in poor contact of the plume or the backlight power controller, in which case only qualified repair will help.
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If the screen darkens chaotically and reacts to pressure on the body, this is a sign of a hardware malfunction of the plume or matrix requiring repair.
Resetting and radical measures
Once all the software diagnostics are exhausted, you have to reset your settings, which will return the phone to factory status and remove any conflicts in system files that may have accumulated during use.
Go to Settings → About Phone → Reset. Select "Erase All Data." Once you reboot, the phone will look like new. If the dimming problem persists even on a clean system without installed applications, it confirms the hardware nature of the malfunction.
Sometimes it helps to update the firmware to the latest available version. Xiaomi developers regularly release patches that fix brightness control and sensors. Check for updates in the Settings menu → About the phone → MIUI version.