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The Dimming Method

Generally speaking, there are three method of LED luminance adjustment that most useful, and all these three technical skill are based on the change of LED input drive current.

The first one is to change the luminance by modulate LED drive current. Because the brightness of LED chip is in positive porsition with LED drive current, so we can control the brightness of LED luminaire by adjusting the LED drive current.

The second way is called mimic dimming method or linear dimming method.The advantage of this dimming method is that when the driving current linear increase or decreases, reducing the effect on LED chip life in the process of the drive current overshoot. However, its defect is that it must have certain effects on the LED chip temperature when the size of driving current is changing.

The third way is pulse width modulation (PWM). This kind of method is adjusted to make the drive current become a square wave, and the width of the pulse is variable. Through the modulation of pulse width to change the light time of LED lamps, in the same time, changing the input power, and so as to achieve the target of energy saving and adjusting light. As usual, the frequency is around 200Hz~10KHz, and because of the visual lag of human eye, we will not feel the flare of light source in the adjustment. On one way, this dimming method can improve LED heat dissipation performance; on another way, the defect is driving current overshoot must have certain influence on the LED chip’s life.

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