Digital PWM Generator Research Articles

Digital sinusoidal PWMs for a micro-controller based single-phase inverter, Part 1: Principles of digital sinusoidal PWM generation

Nowadays, Digital Sinusoidal Pulse Width Modulation (DSPWM) is playing a major role in the generation of pure sinusoidal waveforms using micro-controller based inverters (Kawabata, Miyashita and Yamamoto 1991; Herrmann, Langer and Broeck 1993; Ying-Yu 1995; PICREF-1 1997; Shih-Liang, Meng-Yueh, Jin-Yi, Li-Chia and Ying-Y 1999; The Electrical Engineering Handbook 2000; Koutroulis, Chatzakis, Kalaitzakis and Voulgaris 2001; Skvarenina 2002; Pop, Chindris and Dulf 2004; Zhongyi, Mingzhu and Yan 2005). The types of DSPWM that can be generated depend on the micro-controller hardware resources and are therefore limited, but provide performance benefits not possible with an analogue controller. For instance, digital controllers offer a programmable solution and therefore more flexibility, as advanced algorithms and additional features can be added to the system in software instead of hardware (Monti, Santi, Dougal, and Riva 2003; Brush 2005). Digital controllers are also less sensitive to environmental conditions and show precise behaviour compared with their analogue counterparts (Skvarenina 2002). This two-part article looks at the benefits and limitations of three major DSPWMs for a single-phase full-bridge inverter and investigates their performance. In Part 1, the theory of the three major DSPWMs are presented, including mathematical models and simulation results. It looks at the PWM patterns required to generate these DSPWMs and the benefits and limitations of each. To evaluate the proposed mathematical models and simulation results, a 2kVA single-phase full-bridge inverter was developed and the DSPWMs implemented. In Part 2, experimental results from the implementation of the DSPWMs on the prototype 2kVA inverter are presented, which confirms the validity of the proposed analysis in Part 1. Moreover, the performance, including efficiency and losses (switching, conduction, and transformer) of the different DSPWMs implemented on the 2kVA inverter under different loads were examined and recommendations presented.

Architecture and IC implementation of a digital VRM controller

This paper develops the architecture of a digital PWM controller for application in multiphase voltage regulation modules (VRMs). In this context, passive current sharing and VRM transient response with nonzero controller delay are analyzed. A scheme for sensing a combination of the VRM output voltage and output current with a single low-resolution window analog-to-digital converter (ADC) is proposed. The architecture and IC implementation of a digital PWM (DPWM) generation module, using a ring-oscillator-multiplexer scheme, is discussed. Experimental results from a prototype VRM and a partial controller IC implementation are presented.