With the continuous and rapid development of the LED application market, the continuous expansion of the application range has led to the continuous improvement of product requirements. Adjusting the LED brightness becomes very necessary to the LED terminal products. Dimming is a very common function of lighting systems. For incandescent lamps, it can be easily implemented at low cost.
The most important and common dimming methods for LED luminaires are three. These three dimming skills are based on changes in the LED drive current input. According to different circuit systems, it can also be divided into analog dimming and PWM dimming.
The first type: This dimming method is to dim the LED lamp by modulating the LED driving current. Since the brightness of the LED chip is proportional to the LED driving current, we can control the LED driving current to control the LED lamp.
Second: This dimming method is called a simulated dimming method or a linear dimming method. The advantage of the dimming method is that when the driving current linearly increases or decreases, the influence of the driving current overshoot on the lifetime of the LED chip is reduced, and the anti-noise of the dimming circuit is strong. The defect is that the process of changing the magnitude of the driving current definitely has a certain influence on the color temperature of the LED chip.
Third: This dimming method is called pulse width modulation (PWM). The method is characterized in that the driving current is square wave-shaped, and the pulse width is variable. After the modulation of the pulse width is converted into a time for modulating the continuous illumination of the LED lamp, the input power is also converted, thereby achieving energy saving and dimming. aims. The frequency is about 200Hz~10KHz as usual; because of the hysteresis of human eye vision, it will not feel the sparkle caused by the light source during the dimming process. The advantage of this dimming method is that it can improve the heat dissipation performance of the LED. The defect is that the overshoot of the driving current definitely has a certain influence on the life of the LED chip.
In general, analog dimming can usually be accomplished very simply. However, since the characteristics of the LED light are shifted with the average drive current. For a monochrome LED, its dominant wavelength will change. For white LEDs, the associated color temperature (CCT) will change. Dimming with PWM ensures that the LEDs emit the colors that the designer needs. PWM dimming also improves output current accuracy. Analog dimming with linear adjustment reduces the accuracy of the output current. In general, PWM dimming can be more accurate than linearly controlled light output relative to analog dimming.