Chapter 5
Diode Rectifiers
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-1
Diode Rectifier Block Diagram
• Uncontrolled utility interface (ac to dc)
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-2
A Simple Circuit
• Resistive load
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-3
A Simple Circuit (R-L Load)
• Current continues to flows for a while even after the input
voltage has gone negative
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-4
A Simple Circuit (Load has a dc back-emf)
• Current begins to flow when the input voltage exceeds the dc back-emf
• Current continues to flows for a while even after the input voltage has
gone below the dc back-emf
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-5
Single-Phase Diode Rectifier Bridge
• Large capacitor at the dc output for filtering and energy
storage
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-6
Diode-Rectifier Bridge Analysis
• Two simple (idealized) cases to begin with
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-7
Redrawing Diode-Rectifier Bridge
• Two groups, each with two diodes
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-8
Waveforms with a
purely resistive load
and a purely dc current
at the output
• In both cases, the dc-side
voltage waveform is the same
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-9
Diode-Rectifier Bridge Input Current
• Idealized case with a purely dc output current
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-10
Diode-Rectifier Bridge Analysis with ACSide Inductance
• Output current is assumed to be purely dc
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-11
Understanding Current Commutation
• Assuming inductance in this circuit to be zero
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-12
Understanding Current Commutation (cont.)
• Inductance in this circuit is included
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-13
Current Commutation Waveforms
• Shows the volt-seconds needed to commutate current
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-14
Current Commutation in Full-Bridge Rectifier
• Shows the necessary volt-seconds
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-15
Understanding Current Commutation
• Note the current loops for analysis
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-16
Rectifier with a dcside voltage
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-17
DC-Side Voltage and Current Relationship
• Zero current corresponds to dc voltage equal to the peak of
the input ac voltage
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-18
Effect of DC-Side Current on
THD, PF and DPF
• Very high THD at low current values
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-19
Crest Factor versus the Current Loading
• The Crest Factor is very high at low values of current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-20
Diode-Rectifier with a Capacitor Filter
• Power electronics load is represented by an equivalent load
resistance
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-21
Diode Rectifier Bridge
• Equivalent circuit for analysis on one-half cycle basis
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-22
Diode-Bridge Rectifier: Waveforms
• Analysis using MATLAB
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-23
Diode-Bridge Rectifier: Waveforms
• Analysis using PSpice
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-24
Input Line-Current Distortion
• Analysis using PSpice
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-25
Line-Voltage Distortion
• PCC is the point of common coupling
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-26
Line-Voltage Distortion
• Distortion in voltage supplied to other loads
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-27
Voltage Doubler Rectifier
• In 115-V position, one capacitor at-a-time is charged from the
input.
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-28
A Three-Phase, Four-Wire System
• A common neutral wire is assumed
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-29
Current in A Three-Phase, Four-Wire
System
• The current in the neutral wire can be very high
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-30
Three-Phase, Full-Bridge Rectifier
• Commonly used
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-31
Three-Phase, Full-Bridge Rectifier: Redrawn
• Two groups with three diodes each
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-32
Three-Phase, Full-Bridge Rectifier Waveforms
• Output current is
assumed to be dc
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-33
Three-Phase, Full-Bridge Rectifier: Input
Line-Current
• Assuming output current to be purely dc and zero ac-side
inductance
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-34
Three-Phase, Full-Bridge Rectifier
• Including the ac-side inductance
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-35
3-Phase Rectifier: Current Commutation
• output
current is
assumed to be
purely dc
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-36
Rectifier with a Large Filter Capacitor
• Output voltage is assumed to be purely dc
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by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-37
Three-Phase, Full-Bridge Rectifier
• THD, PF and DPF as functions of load current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-38
Crest Factor versus the Current Loading
• The Crest Factor is very high at low values of current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-39
Three-Phase Rectifier Waveforms
• PSpice-based analysis
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 5 Line-Frequency Diode
Rectifiers
5-40