Transcript Slide 1
Chapter 1 Power Electronic Systems • Introduction • Power Electronics versus Linear Electronics • Applications Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-1 Power Electronic Systems • Block diagram • Role of Power Electronics • Reasons for growth Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-2 Linear Power Supply • Series transistor as an adjustable resistor • Low Efficiency • Heavy and bulky Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-3 Introduction: Switching Power Electronics Linear regulator Goal: control VX such that Vo=Vo,REF Plus: simple accurate, high-bandwidth Minus: low efficiency Pout Pin ( example Vo I o V in I o Vo V in : Vin 15V, Vo 5V, 33%) and power is dissipated in transis tor Pdiss V X I o 0 Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-4 Switching power converters Vo(t) VIN Add filtering <Vo> Vo(t) VIN <Vo> Add real devices Note: -only lossless elements -L, C energy storage Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-5 Switch-Mode Power Supply • Transistor as a switch • High Efficiency • High-Frequency Transformer Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-6 Basic Principle of Switch-Mode Synthesis V oi 1 TS TS v oi 0 dt t on TS vd • Constant switching frequency • pulse width controls the average • L-C filters the ripple Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-7 Application in Adjustable Speed Drives • • Conventional drive wastes energy across the throttling valve to adjust flow rate Using power electronics, motor-pump speed is adjusted efficiently to deliver the required flow rate Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-8 Power Processor as a Combination of Converters • Most practical topologies require an energy storage element, which also decouples the input and the output side converters Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-9 Uninterruptable power supply - UPS 220 V 220 V Batt 24V ~ load • Converter 1 rectifies line-frequency ac into dc • Capacitor acts as a filter; stores energy; decouples • Converter 2 synthesizes line-frequency ac to load Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-10 Power Flow through Converters • Converter is a general term • An ac/dc converter is shown here • Rectifier Mode of operation when power from ac to dc • Inverter Mode of operation when power from ac to dc Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-11 Scope and Applications Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-12 Interdisciplinary Nature of Power Electronics Electrónica de Potência © 2008 Jose Bastos Chapter 1 Introduction 1-13