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Chapter 9
Zero-Voltage or Zero-Current Switchings
• converters for soft switching
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-1
One Inverter Leg
• The output current can be positive or negative
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-2
Hard Switching Waveforms
• The output current can be positive or negative
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-3
Turn-on and Turn-off Snubbers
• Turn-off snubbers are used
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-4
Switching Trajectories
• Comparison of Hard versus soft switching
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-5
Undamped Series-Resonant Circuit
• The waveforms shown include initial conditions
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-6
Series-Resonant Circuit with
Capacitor-Parallel Load
• The waveforms shown include initial conditions
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-7
Impedance of a Series-Resonant Circuit
• The impedance is capacitive below the
resonance frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-8
Undamped Parallel-Resonant Circuit
• Excited by a current source
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-9
Impedance of a Parallel-Resonant Circuit
• The impedance is inductive at below the
resonant frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-10
Series Load Resonant (SLR) Converter
• The transformer is ignored in this equivalent
circuit
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-11
SLR Converter Waveforms
• The operating frequency is below one-half the
resonance frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-12
SLR Converter Waveforms
• The operating frequency is in between one-half the
resonance frequency and the resonance frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-13
SLR Converter Waveforms
• The operating frequency is above the resonance
frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-14
Lossless Snubbers in SLR Converters
• The operating frequency is above the resonance
frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-15
SLR Converter Characteristics
• Output Current as a function of operating
frequency for various values of the output voltage
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-16
SLR Converter Control
• The operating frequency is varied to regulate the
output voltage
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-17
Parallel Load Resonant (PLR) Converter
• The transformer is ignored in this equivalent
circuit
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-18
PLR Converter Waveforms
• The current is in a discontinuous conduction
mode
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-19
PLR Converter Waveforms
• The operating frequency is below the resonance
frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-20
PLR Converter Waveforms
• The operating frequency is above the resonance
frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-21
PLR Converter Characteristics
• Output voltage as a function of operating
frequency for various values of the output current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-22
Hybrid-Resonant DC-DC Converter
• Combination of series and parallel resonance
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-23
Parallel-Resonant Current-Source Converter
• Basic circuit to illustrate the operating principle
at the fundamental frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-24
Parallel-Resonant Current-Source Converter
• Using thyristors; for induction heating
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-25
Class-E Converters
Optimum mode
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-26
Class-E Converters
Non-Optimum
mode
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-27
Resonant Switch Converters
Classifications
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-28
ZCS Resonant-Switch Converter
• One possible implementation
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-29
ZCS Resonant-Switch Converter
• Waveforms; voltage is regulated by varying the
switching frequency
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-30
ZCS Resonant-Switch Converter
• A practical circuit
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-31
ZVS Resonant-Switch Converter
• Serious limitations
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-32
ZVS Resonant-Switch Converter
• Waveforms
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-33
MOSFET Internal Capacitances
• These capacitances affect the MOSFET switching
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-34
ZVS-CV DC-DC Converter
• The inductor current must reverse direction
during each switching cycle
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-35
ZVS-CV DC-DC Converter
• One transition is shown
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-36
ZVS-CV Principle Applied to DC-AC Inverters
• Very large ripple in the output current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-37
Three-Phase ZVS-CV DC-AC Inverter
• Very large ripple in the output current
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-38
Output Regulation by Voltage Control
• Each pole operates at nearly 50% duty-ratio
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-39
ZVS-CV with Voltage Cancellation
• Commonly used
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-40
Resonant DC-Link Inverter
• The dc-link voltage
is made to oscillate
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-41
Three-Phase Resonant DC-Link Inverter
• Modifications have been proposed
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-42
High-Frequency-Link Inverter
• Basic principle for selecting integral half-cycles of the
high-frequency ac input
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-43
High-Frequency-Link Inverter
• Low-frequency ac output is synthesized by selecting
integral half-cycles of the high-frequency ac input
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-44
High-Frequency-Link Inverter
• Shows how to implement such an inverter
Copyright © 2003
by John Wiley & Sons, Inc.
Chapter 9 Resonant Converters
9-45
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