LED lighting dimming method

LED lighting dimming

The dimmer that adjusts the brightness of LED lighting fixtures is currently very important in LED lighting. LED lamps and displays must be paid attention, LED lighting has become a new mainstream technology in the 21st century. One of the signs is the successive introduction of a large number of LED lighting standards and specifications. At present, lighting uses dimmers for incandescent lamps to realize dimming control function and high power factor performance. For the adjustment of LED brightness, it is mainly divided into analog dimming and PWM dimming. Introduce the related situation of LED dimming.

The dimming function can reduce costs for incandescent lamps. With the development of LED lighting products, it is unwilling to lose the advantages of dimming control applications when switching to LED lighting. The most important and common dimming methods of LED lamps are three. These three dimming techniques are all dimming according to the change of LED driver current input. According to different circuit systems, it can also be divided into imitation dimming and PWM dimming.

The first: This dimming method is to complete the dimming of the LED lamp by modulating the LED driver current. Since the brightness of the LED chip is proportional to the LED driver current, we can control the LED lamp by adjusting the LED driver current. Light and dark, such as dimming ceiling lights.

Second: This dimming method is called imitation dimming method or linear dimming method. The advantages of this dimming method are: when the driving current increases or decreases linearly, the influence on the life of the LED chip during the overshoot of the driving current is reduced, and the dimming circuit has strong anti-interference performance. The disadvantage is that the change process of the driving current must have a certain influence on the color temperature of the LED chip, such as linear track lights.

Third: This dimming method is called Pulse Width Modulation (PWM). In this method, the driving current is adjusted to be in the shape of a square wave, and its pulse width is variable. After the modulation of the pulse width is converted to modulate the continuous lighting time of the LED lamp, the input power is also changed at the same time, so as to achieve energy saving and dimming. Target. The frequency is about 200Hz~10KHz as usual; because of the hysteresis of human eyes vision, the flashing phenomenon of the light source during the dimming process will not be felt. The advantage of this dimming method is that it can improve the heat dissipation performance of the LED. The disadvantage is that the overshoot of the driving current will definitely have a certain impact on the life of the LED chip.

In general, analog dimming can usually be implemented very simply. However, due to the characteristics of LED light, it will be shifted with the average drive current. For monochromatic LEDs, the dominant wavelength changes. For white LEDs, the correlated color temperature (CCT) changes. Dimming with PWM ensures that the LED emits the color the designer wants. PWM dimming can also improve output current accuracy. Analog dimming with linear adjustment reduces the accuracy of the output current. Generally speaking, compared to analog dimming, PWM dimming can control light output with greater precision than linearity. In terms of energy saving, there is no comparison. Because PWM is to measure the current (light intensity) under the condition of CCT and color, analog dimming does not exist. If you want to sacrifice this premise to consider energy saving, you need measured data. But it is estimated that in the case of achieving the same illuminance, PWM will have an advantage. In terms of dimming response time, PWM dimming can be more precise due to its fast response speed. It is most widely used in practical use.

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