DC dimming is a brightness-control technique used in some modern OLEDsmartphones to reduce or eliminate visible screen flicker caused by PWM (pulse-width modulation). Instead of rapidly switching pixels on and off, DC dimming adjusts the voltage supplied to the OLED pixels, making the display dimmer or brighter without relying on high-frequency pulses. The feature is designed to improve visual comfort for users sensitive to flicker, particularly at low brightness levels.[1]
Most OLED smartphone displays control brightness using PWM, a method in which pixels flicker at high frequencies to simulate lower brightness levels. While effective and colour-accurate, PWM can cause eye strain, headaches, or discomfort in sensitive users — especially when manufacturers use low PWM frequencies (for example 240Hz or 360Hz). Higher PWM frequencies (1,920Hz, 2,160Hz, even 3,840Hz) reduce visible flicker but do not eliminate it entirely.[2]
DC dimming, by contrast, lowers brightness by reducing the pixel's electrical power directly. The LED or OLED subpixels emit less light because they physically receive less voltage, not because they switch on and off more slowly.[3]
How DC dimming works
PWM-driven OLED panels: the display keeps the same pixel brightness but adjusts how long each pixel remains lit within each cycle. Lower brightness means shorter “on” time.
DC dimming: instead of cycling pixels, the display decreases current or voltage to reduce the actual brightness output.[4]
When DC dimming is enabled:
flicker decreases or disappears entirely;
colour accuracy can degrade because OLED pixels do not behave linearly at very low voltages;
the display may shift toward cooler or greener tones at low brightness levels.[5]
Limitations and considerations
Colour accuracy trade-offs: OLED subpixels can become unstable at low voltages. This may cause inaccurate colours, reduced uniformity, subtle tinting, and banding artefacts.
Not always available: many manufacturers disable DC dimming by default to preserve colour fidelity.
Not ideal for HDR: high dynamic range modes often require precise brightness control and colour calibration, making DC dimming unsuitable.
Varies by device: the stability of OLED panels differs across suppliers, so the resulting quality depends heavily on panel hardware.[6]
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