1. Switching DC Power Supplies
Chapter 10
Switching DC Power Supplies
One of the most important applications of power electronics
overview of switching power supplies
dc-dc converters with electrical isolation
control circuits
electrical isolation in the feedback loop
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

2. Linear Power Supplies Very poor efficiency and large weight and size
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

3. Switching DC Power Supply: Block Diagram
High efficiency and small weight and size
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

4. Switching DC Power Supply: Multiple Outputs
In most applications, several dc voltages are required, possibly electrically isolated from each other
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

5. PWM to Regulate Output Copyright © 2008 Chapter 10 Switching
by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

6. Flyback Converter
Derived from buck-boost; very power at small power (> 50 W ) power levels
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

7. Forward Converter
Derived from Buck; idealized to assume that the transformer is ideal (not possible in practice)
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

8. Push-Pull Inverter Derived from step-down converter Copyright © 2008
by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

9. Half-Bridge Converter
Derived from step-down converter
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

10. Full-Bridge Converter
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

11. Control to Regulate Voltage Output
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Chapter 10 Switching
DC Power Supplies

12. Control to Regulate Voltage Output
Linearized representation of the feedback control system
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

13. Forward Converter: An Example
The switch and the diode are assumed to be ideal
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

14. Forward Converter:Transfer Function Plots
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Chapter 10 Switching
DC Power Supplies

15. Linearizing the PWM Block
The transfer function is essentially a constant with zero phase shift
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Chapter 10 Switching
DC Power Supplies

16. Gain of the PWM IC It is slope of the characteristic Copyright © 2008
by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

17. A General Amplifier for Error Compensation
Can be implemented using a single op-amp
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

18. Type-2 Error Amplifier Shows phase boost at the crossover frequency
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

19. Voltage versus Current Mode Control
current mode control has several advantages
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

20. A Typical PWM Control IC
Many safety control functions are built in
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

21. Current Limiting Two options are shown Copyright © 2008
by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

22. Implementing Electrical Isolation in the Feedback Loop
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by Jose Bastos.
Chapter 10 Switching
DC Power Supplies

23. Implementing Electrical Isolation in the Feedback Loop
A dedicated IC for this application is available
Copyright © 2008
by Jose Bastos.
Chapter 10 Switching
DC Power Supplies