Lecture 7.2: More DC Modeling

In this video we model a switch mode power supply using the "reinterpretation" technique from the previous video, except this time we include conduction losses in the model. It turns out that the inclusion of losses tends to DECREASE the gain (conversion ratio), which means that to get the desired output voltage in a real converter we actually need a larger duty ratio than what is predicted from the ideal model. The boost converter specifically shows some interesting properties when we try to increase the duty ratio towards 1. Despite the ideal ratio indicating the boost can give us as large an output voltage as we want, conduction loss alone will prevent this from happening. Understanding DC modeling allows these aspects of real converters to become apparent and also allows to find DC solve solution using circuit theory techniques. 0:00 Introduction 0:30 Boost Converter with conduction losses 4:20 IVSB, CCB and input current equations 7:30 Circuit interpretations of the equations 12:05 Gluing the loops together 17:11 Solving the DC circuit model 22:25 Drawing Nonideal Conversion ratio 26:30 Outro Reference Textbook: Fundamentals of Power Electronics - Erickson and Maksimovic