在调制频率足够小的前提下，不同的占空对应于不同的电压输出，而不同的电压对应不同的LED亮度，这样，我们可以通过改变占空比，就可以实现LED的渐亮渐灭控制了。-Small enough in frequency modulation, under the premise of representing different space corresponds to a different voltage output, the voltage difference between the different brightness of the LED, so that we can by changing the duty cycle can be achieved gradually LED light gradually out of control the.