摘要
本文提出了一种新的应用电压频率变换技术的模数变换方案。常规的A/D方案是先加一个采样保持器将信号离散化,然后进行模数变换,因而变换时间必须小于采样间隔,这就限制了积分型A/D在要求采样频率较高的场合的应用。本文提出的方案的特点是不需要采样保持器。分析指出,该方案具有精度高、同CPU的接口简单、抗电磁干扰能力强等优点,因而特别适用于微机型继电保护装置。
A new approach of A/D using voltage to frequency convertion technique is Proposed. In coventional A/D schemes, a S/H unit is used prior to A/D, therefore the converting time must be less than the sampling period. This limits the application of integral type A/D in areas where high sampling frequency is required. This paper proposes a new technique where no S/H is necessary. It is found that the method has a number of advantages, such as high accuracy, minimal interfacing with CPU, high EMI immunity. Hence it is particularly suitable to microprocessor based protection systems.
