说明：  脉宽调制(PWM)是利用微处理器的数字输出来对模拟电路进行控制的一种非常有效的技术，广泛应用在从测量、通信到功率控制与变换及LED照明等许多领域中。
(Pulse width modulation (PWM) is to use digital microprocessor output to control a very effective technique for analog circuits, is widely used in many fields of measurement, communication and power control and conversion and LED lighting and other.)