with the development of PWM technology (eng. PWM) in our time receives a special place. A clear language is told about what is this process.
PWM (pulsed modulation) in the English-language literature is indicated as PWM (PULSE-WIDTH MODULATION). The main task of this process is to increase the efficiency of the power source to the maximum possible value and minimize energy loss.
In order to answer the question "What is PWM in the smartphone", you need to get a little familiar with the principle of displays and regulators.
A bit of theory
Imagine a small diagram of 3 elements: power supply, regulator (for example, any linear resistor) and load. The task of the first element is to supply power to the load. The regulator is necessary for a smooth change of this power and the transfer of its load only in the amount in which it is necessary (so as not to spend all resources).
To adjust the brightness of the display, we must supply the appropriate stress voltage from the power source. But the thing is that using conventional linear regulators, most of this supplied energy simply dissipates in the form of heat and does not reach the final item.
Engineers wondered how to reduce these losses and increase the efficiency of the entire scheme, so as not to lose a large amount of power on the regulator (resistor), for which the efficiency is only 20-30%.
Not linear, but pulse regulators began to use as a solution to this problem. When using them, the display voltage is not permanent (as we considered on the example above), and the pulse. Each ripple cycle has its own period and frequency that is measured in Hertz.
Consider the process on the chart. Simple words, "Gorki" is the ripples. These are the time intervals (highlighted in red), in which the regulator feeds the load voltage. Green lines denote places in which the voltage is not served and, in fact, at these points the display is turned off. Due to such an alternation, when the pulsed regulator, the efficiency is possible to reach the efficiency in the area of 90-95%.
If a simple linear regulator saves energy always, simply dissipating it as heat, then the impulse uses the cunning of the human eye in which we do not notice the flicker with frequency over 60 Hz. Due to this, it saves resources, constantly including / turning off the power of the display with frequencies of 150-400 + Hz.
What you need to know about this
We got acquainted with the principle of work of PWM. For completeness, the picture should be added that the working cycle on the graph corresponds to the display brightness level. For example, 100% brightness is 100% of the working cycle. It follows that the larger the duration of one pulsation, the less they have to have a certain period of time.
For example, you look at the screen for 10 seconds, without distracting. We calculate that the device has a display with a flicker level of 400 Hz (it means a period of 1 pulse is 0.0025 seconds.) And a brightness of 50% is installed. As we have already found out, the percentage of brightness = percentage of the working cycle, it means for all the time that you look at the display, exactly 5 seconds it will not be supplied at all.
But considering the features of our view and the frequency of 400 Hz, which is elusive for the human eye, to observe the picture for all 10 seconds we have enough 4000 pulses with a duration of 0.00125 seconds (since we set the brightness of 50%, which is 2 times less than the maximum, then "width", namely, the period also decreased by 2 times), which are evenly divided throughout Total time.
Such an interesting feature of work is observed in OLED Displays and its derivatives: AMOLED (including Dynamic, Super, etc.), Poled. So as not to satisfy, it is worth mentioning that in IPS-displays this technology is used, but in the case of such matrices on the effect of shima, it is not necessary to speak, since the frequency of the flicker there is extended high (about 4000 Hz) that unnoticed for us in any conditions.
The best smartphones without flicker
It's time to talk about the safest smartphones, the flickering of the screen on which the least noticeable human eye. As we know, our vision is not able to catch the shift of personnel at a speed of more than 60 Hz. That is, the pulsation at 70, 80, 90 and more hertz we no longer distinguish. But for the brain, the ceiling moves a little higher and is approximately 300 Hz.
And if the eyes, for example, already at 65 Hz will not be distinguished by impulses and shifts, the brain will still fix it. Therefore, if you want to protect yourself from the effect of PWM on smartphones with Amoled, OLED, POLED matrices, it is better to look for information about the level of flicker. It is undesirable if this indicator is at a mark below 300 Hz.
There are models with a flicker level in the area of 250 Hz, but due to the peculiarities of the PWM process, on low brightness, the use of the device can deliver you discomfort (ripple width It will decrease after the working cycle, but this will have to compensate for the large number of these most ripples and, as a result, greater flicker).
It is noteworthy that even on the devices of a strong middle class or at all on expensive flagships, manufacturers often save in this regard. For example, the level of flicker on Oneplus 9 Pro is only 192 Hz, whereas on the relatively budget OnePlus NORD this indicator is located in the area of 367-368 Hz. Be careful if you truly worry for your eyesight.
The most secure smartphones in this plan are currently:
- Xiaomi : Black Shark 3 Pro, Redmi Note 10 Pro, Mi 11, Mi 10 Ultra, Mi 10 Pro, Mi 10.
- Huawei : P40 Pro Plus, P40 Pro.
- OPPO : Find X2 Pro, Find X2 Neo, Find X3 Pro, Find X3 Neo, Find X3 Lite, Reno4 Pro, Reno3 Pro (+ version with 5G ).
- OnePlus: 8T, 8, NORD, 7T.
How to get rid of the flicker
There are several tips that you can use if you feel discomfort from the twinkling of the display in The use of your device.
The easiest and Banal Council - the replacement of the device. Check your smartphone with an IPS matrix or if you are important to have OLED / AMOLED / POLED, look at what we have allocated above. These are relatively safe gadgets, the level of flicker on which exceeds the level of 300, and even in 400 Hz, which is not caught even the human brain.
Also remember that the negative effect will increase in proportion to the decrease in the brightness of the screen. In addition, you can use multiple useful applications that are superimposed by a special filter and automatically manage this parameter.
OLED SAVER [NO ROOT]
is a very simple and easy application that practically does not occupy A place in memory (the installation file "weighs" less than 0.4 MB), but can help you minimize the unpleasant effect of OLED / AMOLED / POLED matrices.
Step 1. Go to the Official Google Play Store and download the OLED SAVER program to your device. Run it.
Step 2. On the main screen, press the button "Watch The Wizard". Next, a small instruction with illustrations will immediately appear, which will prompt you how to activate the applications you need in the settings.
Step 3. Turn on the service by clicking on "Enable Service" and set the brightness parameters and other features of the program, and then press the key " NEXT ".
Step 4. Give permission to change system settings (you need, for example, to change the brightness) and press "NEXT".
Step 5. We again turn on the desired option, selecting "USE Service" and continue by clicking on "Next" other stages.
LUX AUTO BRIGHTNESS [ROOT]
Another useful program - LUX AUTO BRIGHTNESS. For the whole functionality will have to pay, but the store has a free version of "Lux Lite". Unfortunately, it is necessary to have a superuser's right to work, so they will not all be able to try the capabilities of the utility.
As in the case of OLED SAVER, you download the program on the link, run and just follow the instructions on the screen, providing the necessary permissions. The only minus may be, except that, bad compatibility with the most relevant versions of Android (already with 9.0 PIE there may be problems).
What is DC Dimming
there is another way which will help to eliminate the Shimi effect. This is a DC DIMMING function, which is actively used by some manufacturers and is embedded in many mobile devices. It can mostly be found in the phones Samsung, Oneplus, Xiaomi, Huawei with an urgent version of Android.
Perhaps this is the most effective method of suppressing a flicker, which at times exceeds any applications. To enable the DC DIMMING option, there is no specific algorithm, you will have to finge yourself in the device settings.
On some systems, it may be called "suppressing flicker" or "flicker protection mode" (Xiaomi, OPPO ) and will be in the display settings. On other smartphones, you may have to search for other tabs. For example, DC dimming on some OnePlus firmware is in the section "OnePlus laboratory".
An example of using the technology (on the left turned off, the right is turned on):
