Topics in multiple-loop regulators and current-mode programming

Abstract

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A unified model for current-programmed converters

“…2. This is essentially the same as in Figs. (1 I)-( 13) of [5] is not due to the modulator; it will be shown later that its physical origin is the sampling effect.…”

“…Use of inductor current to determine duty ratio introduces feedback into the converter. Thus, small-signal dynamics is expected to change from a typical double pole high Q-factor low-pass filter to an effective single dominant pole [5].…”

“…The unified modulator model of (6) is a modification of that proposed in [5], and the modulator gain factor F, is equivalent to that of [12]. In terms of Fm and k , (6) becomes…”

“…The modulator model in [ 5 ] was derived by perturbation of an expression for inductor average current in steady state. This procedure was disputed in [6], where it is argued that the smallsignal modulator model needs to be derived by perturbing an expression for inductor average current in perturbed state.…”

Small-signal modeling of pulse-width modulated switched-mode power converters

“…In accordance with the procedure for linearizing a nonlinear element described in Section Ill, the transformer is characterized by a conversion ratio fixed at the value M(D) corresponding to agiven operating-point duty ratio D, and the d variation component is separated out into two "modulation'' generators proportional to d, where the proportionality factors are functions of large-signal operating point.This process, introduced in [4] and described in detail in [5] and [6], involves the usual small-signal restriction in order to eliminate the nonlinearity. Both a current and a voltage modulation generator are necessary, because a variation of the conversion ratio affects both current and voltage.…”