A New Model for Sigma-Delta Modulator Oriented to Digitally Controlled DC/DC Converter

Abstract

Recent research activities have shown the feasibility and advantages of using digital controller ICs specifically developed for high-frequency switching converters, highlighting a challenging future trend in Switched-mode power supplies (SMPS) applications. Up to a few years ago, the application of digital control for SMPS was impractical due to the high cost and low performance of DSP and microcontroller systems, even if the advantages that digital controllers offer were well known, such as immunity to analog component variations and ability to implement sophisticated control schemes and system diagnostics. Digital controller ICs potentially offer other advantages from the integrated design point of view, such as faster design process, ease of integration with other digital systems, and lower silicon area and power consumption than standard analog ICs. Digital control is also used for implementation of sophisticated control techniques and adaptive control. This paper presents a new modelling methodology of sigma-delta modulator, based on representing the nonlinear quantizer with a linear factor. Its use in DC/DC power converter systems permits implementation of a complete digital control. The digital control is implemented in a field-programmable gate array (FPGA) using a hardware description language (VHDL), providing flexibility and technology independence. Results of an investigation from a buck converter prototype, in terms of simulated and experimental performances, confirm the properties of the proposed approach.