300W DC to DC Converter for Use

in AC Inverters

A Major Qualifying Project Report:

Submitted to

WORCESTER POLYTECHNIC INSTITUTE

As a requirement for the

Degree of Bachelor of Science by:

_________________________

Seth Crocker

_________________________

Nathan Roux

Submitted on 08/01/2011

Approved By:

_________________________

Prof. Stephen J. Bitar

i

Abstract

The purpose of this project was to create a high voltage DC-DC converter for use in inverter

applications. Extensive background research was conducted to evaluate existing inverter device

functionality. Multiple prototypes were constructed to characterize losses and investigate ways to

maximize efficiency. Testing of the final prototype included load testing, thermal characterization,

efficiency evaluation, and noise level capture, with mixed results. Further work is required to provide

closed loop control, safety shut off and low battery warnings.

ii

Acknowledgements

We would like to thank the following people and parties for helping us with our project.

Our thanks first go out to the company Waste to Watts who came up with the problem of which

hopefully our project will be the solution. We wish the best of luck to them in their business, and hope

that it takes root and they make a great difference in the lives of the people in countries who are not

fortunate to have such a stable power infrastructure as we do here in the states.

Secondly we would like to thank our project advisor Professor Stephen Bitar, for overseeing our

project from the initial research to this paper. His time and effort as well as his advice and guidance

undoubtedly were the driving force behind our project.

Lastly we would like to thank the ECE department and WPI as a whole for our education and

help with understanding our material without which we would not possess the tools required for the

completion of this project.

iii

Table of Contents Abstract ...................................................................................................................................................... i

Acknowledgements ................................................................................................................................... ii

Table of Figures ......................................................................................................................................... v

Table of Tables ......................................................................................................................................... vi

Table of Equations ................................................................................................................................... vi

1 Introduction to Waste to Watts ........................................................................................................ 1

1.1 Our interaction with Waste to Watts........................................................................................ 1

2 Introduction ...................................................................................................................................... 2

2.1 Introduction to DC-DC Converters ............................................................................................ 2

2.2 Types of DC-DC Converters ....................................................................................................... 2

2.3 Research Space/ Goals .............................................................................................................. 8

2.4 Purpose of Circuit ...................................................................................................................... 8

2.5 Prior Art ..................................................................................................................................... 8

2.6 Real World Parts ..................................................................................................................... 13

2.7 Safety Standards ..................................................................................................................... 13

3 The DC-DC Converter Type We Chose ............................................................................................ 17

3.1 Advantages and Disadvantages with Our Possible Choices .................................................... 17

3.2 Our final decision .................................................................................................................... 18

4 System Level Design ........................................................................................................................ 19

4.1 How it works (Block Diagram Level/ qualitative explanation) ................................................ 19

4.2 Control Chips compatible with our design .............................................................................. 21

4.3 Detailed Front End and Transformer Bias Design ................................................................... 23

4.4 Detailed Switch Control Design ............................................................................................... 24

4.5 Transformer and Output Filtering Design ............................................................................... 25

5 Simulations ...................................................................................................................................... 26

5.1 Spice Models ........................................................................................................................... 26

5.2 Basic Realistic Transformer Model.......................................................................................... 26

5.3 DC-DC Boost Converter Model ............................................................................................... 27

5.4 Two-Stage DC-DC Converter ................................................................................................... 29

iv

5.5 V2.2 Prototype primary side ................................................................................................... 30

6 Testing/results ................................................................................................................................ 33

6.1 Potential Components ............................................................................................................ 33

6.2 V0 ............................................................................................................................................ 34

6.3 V2 ............................................................................................................................................ 38

6.4 V2.1 ......................................................................................................................................... 42

6.5 V2.2 ......................................................................................................................................... 45

6.6 Coil testing .............................................................................................................................. 48

7 Future Work/Improvements ........................................................................................................... 51

7.1 Safety ...................................................................................................................................... 51

7.2 Efficiency ................................................................................................................................. 51

7.3 Additional Functionality .......................................................................................................... 52

7.4 Conclusion ............................................................................................................................... 53

8 Conclusion ....................................................................................................................................... 54

9 Appendix A ...................................................................................................................................... 55

10 Appendix B: Waste to Watts ....................................................................................................... 57

10.1 Company Overview* ............................................................................................................... 57

10.2 Business Description and Vision ............................................................................................. 58

10.3 Product Description- Enzi ........................................................................................................ 59

11 References .................................................................................................................................. 61

v

Table of Figures

Figure 1: Basic boost converter schematic diagram ..................................................................................... 2

Figure 2: Buck boost converter schematic diagram...................................................................................... 4

Figure 3: uk converter schematic diagram ................................................................................................. 5

Figure 4: SEPIC