Common LED lighting dimming control methods and their advantages and disadvantages-PWM dimming

For lighting, dimming is very important. Not only is it to get a more comfortable environment in the home, but today, it is more important to reduce unnecessary electric light in order to further realize the purpose of energy saving and emission reduction. And for LED lighting, dimming is easier to achieve than other fluorescent lamps, energy-saving lamps, and high-pressure sodium lamps. Commonly LED lamp dimming control methods are: TRIAC dimming, 0-10V dimming, PWM dimming, DALI dimming.

PWM dimming:

The full name of PWM dimming is Pulse Width Modulation. LED is a diode, it can realize fast switching. Its switching speed can be as high as above meager profit which is unmatched by any light-emitting device. Therefore, as long as the power supply is changed to a pulse constant current source, the brightness can be changed by changing the pulse width. This method is called pulse width modulation (PWM) dimming method.

PWM dimming technology is currently considered to be the most promising LED dimming technology. And the LED PWM (Pulse Width Modulation) dimming method has the following advantages:

1) No LED chromatogram shift will occur, because the LED always works between the full amplitude current and 0.　　

2) It has a very high dimming accuracy, because the pulse waveform can be controlled to a very high precision, thus, it is easy to achieve a precision of one ten thousandth.　　3) Even if the light is dimmed in a wide range, there will be no flicker. Because the working conditions (boost ratio or buck ratio) of the constant current source will not be changed, problems such as overheating are less likely to occur.　　

4) It can be combined with digital (DALI/DSI/DMX 512) technology to control, because the digital control signal can easily be transformed into a PWM signal.

Although the LED PWM (Pulse Width Modulation) dimming method has many advantages, you should also need to pay attention to the following two issues:

1) The choice of pulse frequency, because the LED is in a fast switching state, if the operating frequency is very low, the human eye can feel the flickering . In order to make full use of the residual visual phenomenon of the human eye, its operating frequency should be higher than 100 Hz, preferably 200 Hz.　　

2) To avoid the howling caused by dimming. Although the human eye can't detect the pulse frequency above 200Hz, but it is within the range of human hearing until 20kHz, in this way, people will possible to hear the sound of sibilance. While, there are two methods to solve this problem. One is to increase the switching frequency above 20kHz, out of the range of human hearing. Another method is to find out the sound-producing device and deal with it.