1. Chapter 5 Line-Frequency Diode Rectifiers
Basic rectifier concepts
Single-Phase diode bridge rectifiers
Voltage-Doubler rectifiers
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

2. Diode Rectifier Block Diagram
Uncontrolled utility interface (ac to dc)
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

3. A Simple Circuit (R Load)
Resistive load
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

4. A Simple Circuit (R-L Load)
Current continues to flows for a while even after the input voltage has gone negative
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

5. A Simple Circuit (R-L Load)
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

6. 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
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

7. Single-Phase Diode Rectifier Bridge
Large capacitor at the dc output for filtering and energy storage
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

8. Diode-Rectifier Bridge Analysis
R load I load
Two simple (idealized) cases to begin with: (a) R load (b) current load
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

9. Waveforms with a purely resistive load at the output
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

10. Diode-Rectifier Bridge Input Current
THD=48.43%
DPF= PF=DPF x Is1/Is=0.9
Idealized case with a purely dc output current
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

11. Diode-Rectifier Analysis with AC-Side Inductance
Output current is assumed to be purely dc
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

12. Understanding Current Commutation
Assuming inductance to be zero
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

13. Understanding Current Commutation #2
Assuming inductance to be zero
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

14. Understanding Current Commutation #3
Assuming inductance to be zero
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

15. Understanding Current Commutation #4
Inductance is included
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

16. Current Commutation Waveformsvd u vL Id is
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

17. Current Commutation Waveforms
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

18. Average voltage <Vd>
When L=0
With finite L
Reduction in average output voltage
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

19. Current Commutation in Full-Bridge Rectifier
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

20. Current Commutation in Full-Bridge Rectifier
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

21. Current Commutation Waveforms
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

22. Reduction in average output voltage
Average voltage <Vd>
When L=0
With finite L
Reduction in average output voltage
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

23. Chapter 5 Line-Frequency Diode Rectifiers
Conclusions
Average output voltage drops with
increased current
increased frequency
Increased L
Load Regulation is a major consideration in most rectifier systems because
voltage changes with load (IL)
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

24. Diode-Rectifier with a Capacitor Filter
Power electronics load is represented by an equivalent load resistance
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

25. Diode-Bridge Rectifier: Waveforms
Analysis using PSpice
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by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers

26. Voltage Doubler Rectifier
input
input
In 115-V position, one capacitor at-a-time is charged from the input.
Copyright © 2008
by Jose Bastos
Chapter 5 Line-Frequency Diode Rectifiers