Simulation Studies of a Slope Compensated Current Mode Controlled Boost Converter

This paper discusses the design and simulation of Slope compensated Current mode Controlled Boost converter which is used in several applications like regulated switch mode dc-dc power supplies. There are several types of dc-dc converters. A boost converter simply steps up a source voltage to a higher, regulated voltage. This allows one power supply to provide different voltage levels at different sections in a circuit. The output voltage of boost converter is to be regulated within a specified tolerance band. The control strategy used may be direct duty ratio control, PWM control, voltage feed forward control or current mode control. The current mode control strategy is discussed in this paper wherein the peak inductor current is sensed and used to control the duty ratio of the switches such that the output voltage is regulated within the specified tolerance band. Simulation studies have been carried out on a 7.5 watt boost converter designed with its power circuit and IC UC 3844 is modelled to implement the current mode control of output voltage. The output voltage is maintained at 30V irrespective of the fluctuations in input voltage. An instability is observed at duty ratio’s nearing 0.5 resulting in sub harmonic oscillations. This issue is addressed by proper slope compensation. The entire circuit is designed and modelled using the power electronic software PSIM©.