SAMPLED-DATA SIMULATION OF CIRCUITS WITH INTERNALLY CONTROLLED SWITCHES - Computer Methods for Analysis of Mixed-Mode Switching Circuits - page 176

controlled switch must be evaluated in each step of simulation in or-
der to determine the state of the switch. In Section 2, methods that
compute the time instant at which internally controlled switches change
their state are developed. Section 3 examines the generation of impulsive
network variables at switching instants and its complication in analysis
of circuits with internally controlled switches. We show that impulses
generated at switching instants not only give rise to inconsistent initial
conditions, they may also initiate a sequence of switching activities of
other internally controlled switches in the circuits. In Section 4, a lin-
ear voltage regulator is used as an example to illustrate the analysis
of circuits with internally controlled switches in detail. The chapter is
summarized in Section 5 with concluding remarks.
1. Internally Controlled Switches and Switching
Variables
Unlike circuits with externally clocked switches, the time instants at
which the topology of circuits with internally controlled switches changes
are determined by the state of the switching variable of the switches in
the circuits only. The switching variable of an internally controlled
switch controls the state (ON or OFF) of the switch in accordance with
the following criterion
In what follows we examine internally controlled switches typically
encountered in mixed-mode switching circuits and the switching variable
characterizing the state of these switches.
1.1 Diodes
Ideal diodes are the simplest internally controlled switches. The op-
eration of an ideal diode is controlled by the voltage across the diode, as
shown in Fig.8.1. The switching variable of an ideal diode is the forward
biasing voltage of the diode.