Back to Basics: LEDs: Part 5: Dimming

LED Dimming

LED dimming is a fundamental aspect of modern lighting systems. Rarely do you see LED systems just doing ON and OFF these days. Mood lighting, custom fades and ambiance is all a rage now. It’s all about achieving the desired brightness for a particular application. The key reason why dimming is essential is that it increases energy efficiency and also keeps extending its lifespan by not driving it at its full brightness.

There are different kinds of dimming drives possible for LEDs. Before we get into that, it’s important to understand what dimming ratio is. This is a ratio number you see in most LED driver datasheets. The dimming ratio in LEDs refers to the ratio between the maximum brightness (luminance) of the LED at full power and its minimum brightness when dimmed. It essentially measures how effectively an LED can be dimmed. A higher dimming ratio indicates a better performance in terms of achieving lower brightness levels when dimmed. For instance, a dimming ratio of 1000:1 means the LED can dim down to 1/1000th of its full brightness.

It also corresponds to the dimming resolution of an LED driver which refers to the number of distinguishable steps or levels at which an LED light can be dimmed. It represents the granularity of control over the brightness levels. Meaning, that even if you have a high dimming ratio and low dimming resolution, you may be able to get to the lowest dimming ratio but the gradation from low to high may not be smooth and your eye might be able to pick it up when you go from high to low. The higher dimming resolution allows for finer adjustments to the light output. Some LED types of drives can achieve only some range of dimming ratios. We will look into those in detail next time.

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