As digital control of PWM converters is turning to be more relevant, the need for effective and convenient design procedures for digital compensators is becoming apparent. The conventional techniques of digital controller design for switching systems are mostly based on the frequency domain. On the other hand, digital compensators operate in the sampled-data domain. In as much that there is a theoretical relationship between the frequency domain and the sampled-data domain (via the various transformation algorithms), a digital compensator operates, in reality, in the time domain and the notions of phase margin, bandwidth and the like are alien to the finite difference equation algorithm that is implemented on the digital platform. Thus, it would be high beneficial to have design methods that are dedicated especially for digital control and do not go around various domains, transformations and approximations.

This seminar covers the basics of feedback loop design of PWM converters for analog and digital feedback. It discusses the basic theory and design methods that can be used to close the loop in switch mode systems. The seminar addresses the design of analog feedback control as well as digital control. The advantages and limitation of each approach will be delineated in relation to present day technology.

The aspects of digital controller design for PWM converter will be covered, including a newly developed time domain based design method and digital system identification. The seminar discusses the conceptual terminology of time-domain attributes, control strategy and practical aspects for realization of such techniques.

The issues to be discussed will be supported by design examples and the resulting responses will be demonstrated by simulation.

The seminar is of intermediate level intended for novices and experienced engineers.

Seminar Outline

1. Introduction (25 min)

·       Basics of feedback theory and graphical representation

·       Block diagram

·       Behavior at large and small LoopGains

·       Graphical representation of the LoopGain

• Bode plane - the  Aol, 1/B plots

·       Relationship between LoopGain and dynamic response

·       Overshoot and Q

·       Output impedance

2. PWM converters as feedback systems (10 min)

·       Block diagram

·       What is Aol, what is Beta

·       Response in closed-loop

3. Analog feedback networks (15 min)

·       Shaping Beta

·       The lag-lead network

·       The double zero network

4. Digital feedback (30 min)

·       Survey – Analog vs. Digital

·       Block diagram

·       Discrete control

·       S to z transformation

·       The delay issue

·       A/D and Modulator resolutions

·       Frequency response design

·       Design using the SISO tool

5. New time-domain digital controller design (50 min)

·       Objectives

·       The approach – ideal compensator

·       Local response vs. complete response

·       Closed-loop response in time-domain terms

·       Template-oriented controller

·       Design examples

6. System identification of PWM converters (50 min)

·       What is system identification

·       Parametric and non-parametric identification

·       Correlation-based method

·       Concept and motivation for time-domain identification

·       Generalized open-loop response of basic PWM topologies

·        Simulation-based ID

·       Identification of practical (switching) PWM system

·       Design examples

7. Q&A

Control Design of PWM Converters: The User Friendly Approach

Computer Aided Analysis and Design

of Single Phase APFC Stages

Feedback Design in Operational Amplifiers and  PWM Converters:

The User Friendly Approach

Fundamentals of PWM Converters

Introduction to CMOS Operational Amplifiers

Control Design of PWM Converters:

 The Intuitive Approach

Fundumentals of PWM Converters

Computer Aided design of Power Factor Correction Systems

Power Electronics of Piezoelectric Elements

Introduction to Power Management for Portables

Dynamics and Stability of Switch Mode Converters

Modern Soft Switched Converter Topologies

Control Design of PWM Converters: The User Friendly Approach

Switched Capacitors Converters

Essentials of Switch Mode Converters

מגברי שרת מודרניים

Power Electronics of Piezoelectric Elements

Digital Control Design of PWM Converters: The Time-Domain Approach