What Is DC Dimming and PWM? A Complete Guide to Display Brightness Control

Smartphone displayed with camera interface on

Understanding Display Brightness: Why Dimming Matters

When you adjust the brightness on your phone or monitor, what’s really happening behind the scenes? The answer lies in dimming technologies that control how much light your screen emits. Two key methods are DC dimming and PWM dimming—each with unique ways to adjust brightness and distinct effects on your viewing experience.

If you’ve ever wondered why some screens flicker or cause eye strain at low brightness, understanding these dimming methods is essential. This article breaks down what DC dimming and PWM dimming are, their pros and cons, and why they matter for your eyes and display quality.

What Is DC Dimming? The Analog Approach to Brightness Control

DC dimming, also called analog dimming, controls brightness by directly adjusting the amount of electrical current or voltage sent to the screen’s LEDs (light-emitting diodes). When you lower the brightness, DC dimming reduces the power flowing through these LEDs, making the display dimmer in a smooth, flicker-free way.

How DC Dimming Works

It lowers the current supplied to the LED pixels.
The LEDs shine less brightly because they get less power.
The brightness change is continuous and steady, without turning the LEDs on and off rapidly.

Advantages of DC Dimming

No flicker: Because power is steadily reduced, your screen doesn’t rapidly blink on and off.
Eye comfort: Reduced flicker minimizes eye strain and headaches, especially for sensitive users.
Simpler technology: DC dimming circuits tend to be less complex, which can reduce manufacturing costs.

Disadvantages of DC Dimming

Color shifts: As the current lowers, the color temperature of the display can change, often appearing warmer or reddish at low brightness.
Uneven color reproduction: Dark tones may lose accuracy, affecting overall image quality.
Less precise brightness control: Compared to PWM, DC dimming may not be as fine-tuned, especially on AMOLED panels.

DC dimming is often preferred in devices where flicker-free viewing is critical, such as for people who suffer from flicker sensitivity or want a more comfortable experience at night. However, it can compromise color fidelity, especially at lower brightness levels.

What Is PWM Dimming? The Digital Flicker Control

PWM dimming stands for Pulse Width Modulation. Instead of reducing power steadily, PWM controls brightness by rapidly switching the display’s LEDs on and off at a high frequency—often hundreds of times per second. The perceived brightness depends on the proportion of time the LED is “on” versus “off” during each cycle, called the duty cycle.

How PWM Dimming Works

The LED is switched fully on and off repeatedly.
The brightness level depends on how long the LED stays on during each cycle.
At 50% brightness, the LED is on half the time, off half the time; at 10%, it’s on only 10% of the time.

Advantages of PWM Dimming

Color accuracy: Since the LED current remains constant when on, colors stay consistent across brightness levels.
Energy-efficient: PWM can reduce power consumption and heat generation.
Precise control: Fine-tuned brightness steps enable smoother transitions.

Disadvantages of PWM Dimming

Flicker: Although usually at high frequencies (200–250 Hz or more), some users notice screen flicker, which can cause eye strain, headaches, or discomfort.
Not ideal for sensitive users: People sensitive to flicker may struggle with prolonged use of PWM-controlled screens at low brightness.

PWM dimming remains the standard for many OLED and AMOLED displays because it preserves color fidelity and energy efficiency. However, the flicker it introduces can be bothersome, especially on devices with lower PWM frequencies.

DC Dimming vs. PWM: How They Compare for AMOLED and LCD Screens

Feature	DC Dimming	PWM Dimming
Brightness control	Adjusts current/voltage directly	Adjusts duty cycle (on/off timing)
Flicker presence	No flicker (steady light)	Flicker present at low brightness levels
Color accuracy	Color shifts possible at low brightness	Maintains consistent color
Eye comfort	Better for flicker-sensitive users	May cause eye strain in sensitive users
Power efficiency	Slightly less efficient	More efficient due to constant current
Complexity	Simpler circuit design	Requires precise timing control
Common usage	Often in LCDs and some AMOLEDs	Widely used in AMOLEDs and modern displays

In practical terms, AMOLED displays—known for their vibrant colors and deep blacks—often use PWM dimming because it preserves color accuracy. However, some manufacturers now include DC dimming options to reduce flicker for users sensitive to it. LCD screens, which backlight pixels differently, generally work well with DC dimming.

Why Does Flicker Matter? The Impact on Your Eyes and Experience

Though PWM flicker is usually too fast to consciously notice, it can still affect your eyes subconsciously. Some common issues linked to PWM flicker include:

Eye strain and fatigue during prolonged screen use
Headaches and migraines, especially for flicker-sensitive individuals
Discomfort when using the device in low-light conditions or at low brightness

DC dimming eliminates this flicker by providing a steady light output, offering relief for users affected by PWM flicker. That said, DC dimming’s color shifts at low brightness might not be acceptable for users who prioritize perfect color accuracy.

Manufacturers’ Responses

Many smartphone brands now offer higher PWM frequencies (above 1,000 Hz) to reduce flicker perception or include DC dimming modes as an option in display settings. For example, brands like OnePlus have integrated DC dimming to help users reduce eye strain without compromising too much on color quality.

How to Choose Between DC Dimming and PWM on Your Device

If you’re wondering which dimming method is better for you, consider these factors:

Are you sensitive to flicker or prone to eye strain? DC dimming may provide a more comfortable viewing experience.
Do you prioritize color accuracy, especially in media or gaming? PWM dimming generally maintains better color consistency.
Does your device support adjustable dimming modes? Some phones let you toggle between DC dimming and PWM or offer high-frequency PWM to minimize flicker.
What kind of display does your device have? AMOLED displays often use PWM, while LCDs lean toward DC dimming.

Ultimately, the best choice depends on your personal comfort and how you use your device.

Future of Display Dimming: Combining the Best of Both Worlds

Display technology continues to evolve, with manufacturers seeking to balance eye comfort, color accuracy, and power efficiency. Some innovations include:

Hybrid dimming techniques that combine DC dimming at very low brightness levels and PWM at higher levels to reduce flicker without color compromise.
Increasing PWM frequencies into the tens of thousands of Hz, effectively eliminating flicker perception.
Software optimization to smooth brightness transitions.
More extensive user control over dimming modes within device settings.

These advances aim to make displays more comfortable for all users while maintaining vibrant, accurate visuals.

Conclusion: Understanding DC Dimming and PWM Enhances Your Display Experience

DC dimming and PWM dimming are two fundamental methods to control screen brightness, each with unique benefits and trade-offs. While DC dimming offers flicker-free viewing, it may cause color shifts at low brightness. Conversely, PWM dimming preserves color fidelity but can introduce flicker that affects some users’ eye comfort.

By understanding these differences, you can make informed choices about your device settings and find a display experience that suits your needs—whether for gaming, reading, or everyday use.

Curious to explore devices with DC dimming or high-frequency PWM? Many flagship smartphones now provide these options, so keep an eye out when shopping for your next phone or monitor!