  Stability guarantees are critical for cycle-by-cycle controlled dc-dc
converters in consumer electronics and energy storage systems. Traditional
stability analysis on cycle-by-cycle dc-dc converters is incomplete because the
inductor current ramps are considered fixed; but instead, inductor ramps are
not fixed because they are dependent on the output voltage in large-signal
transients. We demonstrate a new large-signal stability theory that treats
cycle-by-cycle controlled dc-dc converters as a particular type of feedback
interconnection system. An analytical and practical stability criterion is
provided based on this system. The criterion indicates that the L/R and RC time
constants are the design parameters that determine the amount of coupling
between the current ramp and the output voltage.
