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DC-DC Switch-Mode Converters
Chapter 7 DC-DC Switch-Mode Converters dc-dc converters for switch-mode dc power supplies and dc-motor drives Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Block Diagram of DC-DC Converters
Functional block diagram Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Stepping Down a DC Voltage
A simple approach that shows the evolution Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Pulse-Width Modulation in DC-DC Converters
Role of PWM Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Chapter 7 DC-DC Switch-Mode
Step-Down DC-DC Converter Pulsating input to the low-pass filter Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down DC-DC Converter: Waveforms
Steady state; inductor current flows continuously Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Chapter 7 DC-DC Switch-Mode
Step-Down DC-DC Converter: Waveforms at the boundary of Cont./Discont. Conduction Critical current below which inductor current becomes discontinuous Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down DC-DC Converter: Discontinuous Conduction Mode
Steady state; inductor current discontinuous Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down DC-DC Converter: Limits of Cont./Discont. Conduction
The duty-ratio of 0.5 has the highest value of the critical current Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down DC-DC Converter: Limits of Cont./Discont. Conduction
Output voltage is kept constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down Conv.: Output Voltage Ripple
ESR is assumed to be zero Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter
Output voltage must be greater than the input Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter Waveforms
Continuous current conduction mode Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Limits of Cont./Discont. Conduction
The output voltage is held constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Discont. Conduction
Occurs at light loads Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Limits of Cont./Discont. Conduction
The output voltage is held constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Effect of Parasitics
The duty-ratio is generally limited before the parasitic effects become significant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter Output Ripple
ESR is assumed to be zero Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Down/Up DC-DC Converter
The output voltage can be higher or lower than the input voltage Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Waveforms
Continuation conduction mode Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Limits of Cont./Discont. Conduction
The output voltage is held constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Discontinuous Conduction Mode
This occurs at light loads Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Limits of Cont./Discont. Conduction
The output voltage is held constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Effect of Parasitics
The duty-ratio is limited to avoid these parasitic effects from becoming significant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Step-Up DC-DC Converter: Output Voltage Ripple
ESR is assumed to be zero Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Chapter 7 DC-DC Switch-Mode
Cuk DC-DC Converter The output voltage can be higher or lower than the input voltage Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Cuk DC-DC Converter: Waveforms
The capacitor voltage is assumed constant Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Converter for DC-Motor Drives
Four quadrant operation is possible Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Chapter 7 DC-DC Switch-Mode
Converter Waveforms Bi-polar voltage switching Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Chapter 7 DC-DC Switch-Mode
Converter Waveforms Uni-polar voltage switching Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Output Ripple in Converters for DC-Motor Drives
bi-polar and uni-polar voltage switching Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Switch Utilization in DC-DC Converters
It varies significantly in various converters Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Equivalent Circuits in DC-DC Converters
replacing inductors and capacitors by current and voltage sources, respectively Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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Reversing the Power Flow in DC-DC Conv.
For power flow from right to left, the input current direction should also reverse Copyright © 2003 by John Wiley & Sons, Inc. Chapter 7 DC-DC Switch-Mode Converters
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