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ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date ____________TABLE OF CONTENTS

ACKNOWLEDGEMENTII

DECLARATIONIII

CHAPTER 1: INTRODUCTION3

CHAPTER 2: POWER LOSS MOFSET7

CHAPTER 3: SWITCHING APPLICATIONS12

Turn-On procedure13

Turn-Off procedure15

Power losses17

Effects of Parasitic Components21

CHAPTER 4: MOSFET SCALING25

Reasons for MOSFET scaling25

Trend of Intel CPU transistor gate length26

Difficulties arising due to MOSFET size reduction26

MOSFET construction27

Gate material27

Insulator29

Junction design30

Single-type MOSFET switch31

Dual-type (CMOS) MOSFET switch31

CHAPTER 5: CONCLUSION33

REFERENCES35

ABSTRACT

The main purpose of this paper is to demonstrate a systematic approach to design high performance gate drive circuits for high speed switching applications. It is an informative collection of topics offering a “one-stop-shopping” to solve the most common design challenges. Thus it should be of interest to power electronics engineers at all levels of experience. The most popular circuit solutions and their performance are analyzed, including the effect of parasitic components, transient and extreme operating conditions. The discussion builds from simple to more complex problems starting with an overview of MOSFET technology and switching operation. Design procedure for ground referenced and high side gate drive circuits, AC coupled and transformer isolated solutions are described in great details. A special chapter deals with the gate drive requirements of the MOSFETs in synchronous rectifier applications. Several, step-by-step numerical design examples complement the paper.

CHAPTER 1: INTRODUCTION

As high-brightness LEDs (HBLEDs) penetrate all avenues of the lighting market, various semiconductor manufacturers are offering constant-current drivers. Only by choosing a driver IC capable of meeting the flexibility and control required by today's applications can the true potential of HBLEDs be unleashed. Theatrical lighting, for example, often requires high dimming resolution while dynamically adjusting the current to account for fluctuating power sources and operating temperature. Since the quality of light output is intrinsically tied to the capability of the LED driver, it is important to choose a system that has the right specifications.

Today's HBLEDs typically have a nominal current rating of 300 to 700 mA. As the envelope of light output is pushed, devices requiring more than an ampere are appearing in the market. In all LEDs, due to the voltage-current relationship and the binning approach used by manufacturers, a constant-current source is used for accurate control of the light output. Choosing the right constant-current regulator depends on the operating voltage of load and source, the desired efficiency, and the cost and size of the system.

A high-power resistor in series with LEDs would be the simplest form of current regulator. However, since it alone cannot adapt to changing source voltages or the non-linear VI characteristics of an LED, a closed-loop system that changes the resistance based on output current may be used. In either case, the energy not used by the LED ...