消去开关刀节点的开关电容电路分析法

本文介绍一种旨在减少电路变量的线性开关电容电路(简称SC电路)的分析方法。这种方法借消去所谓开关刀节点(Pivot nodes)而使电路变量数显著减少。与文1]中的方法相比,该法所减少的电路变量的个数为SC电路中单刀双掷开关的个数。为在计算机上自动形成消去开关刀节点后的电路的时域方程,在描述SC电路时,将采用以下4种电路元件模型:1.一般电容(它的两个极板永久地与某两节点相连);2.开关电容(它的一个或两个极板通过开关与电路中某些节点相连);3.独立电压源(表示电路的激励信号);4.电压控制电压源(表示运算放大器)。用本文所介绍的方法所导出的SC电路的时域方程与以节点电压为变量的时域方程具有完全相同的形式,但方程的变量数却显著地减少,从而使电路分析所需的计算时间明显减少。文中介绍的方法不仅适用于SC电路的时域分析、频域分析,而且结合文献2]的基本思想还能方便地实现灵敏度分析。

A METHOD OF ANALYSIS OF SC CIRCUITS WITH PIVOT NODES OF SWITCHES ELEMINATED

A method to reduce the number of variables for analysis of linear switchedcapacitor circuits is presented. This method reduces the number of variablessignificantly by eliminating pivot nodes of switches. Comparing with the me-lhod presented in the reference 1], the number of variables reduced is equalto the number of SPDT (Single Pole Double Throw) switches in a SC circuit.To formulate equations of a SC circuit with pivot nodes of switches eliminatedin time domain automatically. the SC circuit will be described with four typesof models: GC (capacitor of which two plates are connected to two specificnodes Permanently); SC (Capicitor of which one or two plates are connectedto specific nodes through switches); indeperdent voltage source (to representexcitation signal) and voltage controlled voltege source (to represent op-amp).For a SC circuit, equations in the time domain derived by this method are ofthe same form as those derived by the method presented in 1]. But the sizeof the set of equations is much smaller. It results in considerable saving ofcomputing time. The method presented in this paper can be used not only for analysis inthe time domain, but also for analysis in the frequency domain as well assensitivity analysis. The method has been implemented in a computer programSCF 85 running on ACS 68000 microcomputer for more than one year.