说明：  智能充电器实例 功能：通过定时器定时从AD上读取数据，根据不同的电压选择不同的控制 充电方案，使用PWM控制输出脉宽来控制电流
(Examples of Intelligent Charger Features: Timer timer through to read data from the AD, in accordance with different voltage charging control to select a different program, the use of PWM control output pulse width to control the current)