采用PWM的强抗干扰模数转换(英文)

Reasearch on A/D Conversion with Strong Anti-jamming Ability Using PWM

在流量、压力和温度控制中,系统会受到一定的干扰,同时具有低频信号反馈的特点,采用 A/D 转换难以达到抗干扰的要求。为此采用一种新的脉宽调制( PWM) 电路实现转换,将被测模拟信号经过放大、整流以及滤波处理后,与三角波调制信号进行比较,得到 PWM 信号,该信号的占空比与被测量信号的大小成正比。微处理器只要采用定时器测量占空比,就可以计算出输入的模拟信号,其 A/D 转换精度为处理器时钟周期和三角波周期的比值,三角波周期越低,精度越高。这种模数转换电路简单,抗干扰能力强,特别适合低频信号反馈的模数转换。实验结果表明,可以较低成本达到较高转换位数的精度效果。

System that has somewhat the characteristics of interference and feedback from low frequency signal is always controlled of three factors： flow, pressure and temperature,so that A/D conversion is difficult to achieve the requirements of anti-interference. This paper adopts a new pulse-width modulation （PWM） circuit to realize the conversion, by which the measured analog signal is amplified, rectified and filtered, and then is compared with the triangle wave modulation signal. So the PWM signal’s duty cycle is proportional to the level of measured signal which is obtained. Just by using the timer to measure the duty cycle, the microprocessor can calculate the input analog signal. Ratio of processor clock cycle and triangular wave cycle is the accuracy of A/D conversion. The frequency of PWM is lower, the accuracy is higher. This analog-to-digital conversion circuit is simple, has a strong anti-jamming capability, and is suitable for the analog-to-digital especially conversion of low frequency feedback signal. According to the experiment result, it is verified that the accuracy effect of higher conversion-digital can be achieved with a low cost.