PWM控制就是脉冲宽度调制。

通过控制电机的电压脉冲宽度，可以改变其电压有效值.从而可以改变它的转速.

　　图中前部分波形与后部分波形周期是一样的，我们通过调节其占空比（图中tH1不等于tH2）。很明显图中前部分波形的电压有效值大于后部分波形的电压有效值，即前者驱动的电机速度比后者的大。

-PWM is pulse width modulation control. By controlling the electrical voltage pulse width, you can change its RMS voltage. So that we can change the speed. Fig waveform before and after the part of some form is the same cycle, we adjust its duty cycle (figure tH1 does not mean tH2 ). Obviously the first part of the figure of the voltage waveform is greater than the latter part of RMS voltage waveform RMS, that is, the former driver of the motor faster than the latter' s great.