electrónica de potência © 2008 josé bastos chapter 2 power semiconductor switches: an overview...
TRANSCRIPT
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Chapter 2 Overview of Power Semiconductor Devices
• Introduction• Diodes• Thyristors• Ideal switches• Bipolar transistors• MOSFETs• MOS-Controlled Thyristors• Comparison of controllable switches
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Electrónica de Potência© 2008 José Bastos
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Electrónica de Potência© 2008 José Bastos
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Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Thyristors
• Semi-controlled device• Latches ON by a gate-current pulse if forward biased• Turns-off if current tries to reverse
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Thyristor in a Simple Circuit
• For successful turn-off, reverse voltage required for an interval greater than the turn-off interval
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Generic Switch Symbol
• Idealized switch symbol• When on, current can flow only in the direction of the arrow• Instantaneous switching from one state to the other• Zero voltage drop in on-state• Infinite voltage and current handling capabilities
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Switching Characteristics (linearized)
Switching Power Loss is proportional to:• switching frequency• turn-on and turn-off times
cod tIVW
dtivW
ivtpdt
tdW
2
1
)()(
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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• Small leakage current in off state• Small on state voltage• Short turn-on and turn-off• Large forward and reverse voltage• High on state current rating• Positive temperature coefficient• Small control power required to switch• Capability to survive rated voltage and rated current simultaneously
Switch: ideal characteristics
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Bipolar Junction Transistors (BJT) #1
• Used commonly in the past• Now used in specific applications• Replaced by MOSFETs and IGBTs
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Bipolar Junction Transistors (BJT) #2
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Bipolar Junction Transistors (BJT) #3
Electrónica de Potência© 2008 José Bastos
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Various Configurations of BJTs
Electrónica de Potência© 2008 José Bastos
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Conclusions BJTs
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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MOSFETs #1
• Easy to control by the gate• Optimal for low-voltage operation at high switching frequencies• On-state resistance a concern at higher voltage ratings
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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MOSFETs #2
Electrónica de Potência© 2008 José Bastos
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Electrónica de Potência© 2008 José Bastos
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IGBT
Electrónica de Potência© 2008 José Bastos
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Conclusions IGBT
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Gate-Turn-Off Thyristors (GTO)
• Slow switching speeds
• Used at very high power levels
• Require elaborate gate control circuitry
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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MOS CONTROLLED THYRISTORS (MCT)
Electrónica de Potência© 2008 José Bastos
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Electrónica de Potência© 2008 José Bastos
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Comparison of Controllable Switches
Electrónica de Potência© 2008 José Bastos
Chapter 2 Power Semiconductor Switches: An Overview
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Summary of Device Capabilities