Modelling, Simulation and Validation of Average Current and Constant Voltage Operations In Non-Ideal Buck and Boost Converters

Abstract

DC-DC converters play a major role in a various applications in automobile engineering, portable electronics and LED drivers. In this work, basic converters like Buck and Boost converters operating in continuous conduction mode (CCM) considering the non-ideal parameters are modelled using volt-sec and amp-sec balance equations. The equations were simulated using MATLAB®/Simulink® software using appropriate step time, solver and the transients in inductor current and capacitor voltage were observed. Later, using the state space averaging (SSA) technique the transfer function of inductor current to duty ratio (G id) and output voltage to duty ratio (G vd) were derived. The parameters like low-frequency gain, gain margin (GM), phase margin (PM), crossover frequency, and stability were analysed using MATLAB software. It was found the non-ideal boost converter showed instability under constant voltage operation due to the presence of right half plane (RHP) zero. In order to validate the obtained transfer function using SSA, a new control technique called circuit averaging technique was used. The validation was performed using LTspice software tool. The frequency response of G id and G vd obtained using MATLAB and LTspice software tools showed a perfect match.