Three kinds of Common Dimming Methods for LED switching power supply

PWM dimming
PWM dimming is one of the commonly used LED switching power supply dimming technology, it is also known as Pulse Width Modulation technology(PWM), which is a traditional dimming method. The working principle of this method is turning on/off the LED driver repeatedly by using simple digital pulse, the system only needs to provide different width of digital pulse so as to change the output current, thus the brightness of the LED can be adjusted. PWM dimming technology has the advantage of providing high-quality white light, and the application is simple and high efficiency. For example, in a mobile phone system, a dedicated PWM interface can be used to simply generate any duty cycle pulse signal, which is connected to the EN interface of the drive through a resistor.
However, as a traditional method of LED switching power supply dimming, PWM dimming also has some disadvantages in the application process, for example, this method is easy to make white LED drive circuit to produce audible noise. If the PWM signal frequency falls between 200Hz to 20kHz when the driver is in PWM dimming,, the inductance and output capacitor around white LED driver will produce the human audible noise, so the design of this method should avoid using of 20kHz or lower frequency.

 

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Analog dimming
Analog dimming technology is another common LED switching power supply dimming technology, this method can also change the White LED current so as to change the brightness of the LED. The most important advantage of analog dimming technology is that it avoids the noise generated by dimming. LED forward voltage drop will be reduced with the LED current decreases when we use analog dimming technology, this will make the white LED energy consumption be reduced. But this method is different from traditional PWM dimming technology, the white LED driver is always in the working mode when we use analog dimming.Moreover, the power conversion efficiency of the drive decreases rapidly as the output current decreases. Therefore, analog dimming technology often increases the energy consumption of the whole system.
Digital dimming
Digital dimming technology is the third common LED switching power dimming technology, , white LED driver with digital dimming technology will have a corresponding digital interface, this digital interface can be SMB, 12C or single-line digital interface. The system designer can change the brightness of the white light LED as long as a series of digital signals are sent to the driver according to the specific communication protocol.