说明：  本设计的题目是基于SG3525的双闭环直流电机调速系统的设计。SG3525是电流控制型PWM控制器，所谓电流控制型脉宽调制器是按照接反馈电流来调节脉宽的。在脉宽比较器的输入端直接用流过输出电感线圈的信号与误差放大器输出信号进行比较，从而调节占空比使输出的电感峰值电流跟随误差电压变化而变化。
(The topic of this design is the design of double closed loop DC motor speed control system based on SG3525. SG3525 is a current controlled PWM controller. The so-called current controlled pulse width modulator is based on the feedback current to regulate the pulse width. The input of the pulse width comparator is compared with the output signal of the error amplifier directly by the signal passing through the output inductor coil, so the duty ratio is adjusted to change the peak current of the output inductor with the variation of the error voltage.)