Sample and hold effect in PWM DC-DC converters with peak current-mode control

Abstract

The sample and hold effect, or quasi-digital (discrete) behaviour, of constant-frequency peak current-mode control (PCM) is pulse-width modulated DC-DC converters is presented in a manner consistent with the physical behaviour of the circuit. This approach develops a transfer function using control theory that captures the quasi-digital behaviour encountered when the current control loop is closed in PCM. The new transfer function accurately captures the current loop behaviour, leading the way for a compete linear time-variant system circuit for PWM DC-DC converters. This work improves upon previous derivations by remaining true to the physical behaviour of the circuit while resulting in a rational transfer function that can be used in a multiple loop complete linear system circuit to accurately predict converter behaviour due to changes in input voltage, output current, and reference voltage.