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Classification of Resonant‐Switch Converters
Cuk
Buck‐Boost
Boost
Buck
ZVS‐QR 1
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20.3.1 The zero‐voltage‐switching
quasi‐resonant switch cell
Cr
When the previously‐described operations are followed, then the converter reduces to
SW
Lr
D2
A full‐wave version based on the PWM buck converter:
+
+
–
–
Cr
i1(t)
Vg
vCr(t)
+
D1
v1(t)
Q1
–
iLr(t) i2(t)
L
I
+
+
Lr
D2
v2(t)
–
C
R
V
–
ZVS‐QR
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ZVS‐QR State Plane Trajectory
The average output voltage
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Results:
Quasi‐resonant switches
Output characteristics: Full‐wave ZVS buck
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20.3.2 The ZVS multiresonant switch
Cs
When the previously‐described operations are followed, then the converter reduces to
SW
Lr
D2
Cd
A half‐wave version based on the PWM buck converter:
i1(t)
+
Vg
+
–
v1(t)
–
Cs
i2(t)
D1
Lr
Q1
D2
L
I
+
+
Cd
v2(t)
–
C
R
V
–
ZVS‐MR Operating Modes
D Maksimovic, "Synthesis of PWM and Quasi‐Resonant DC‐to‐DC Power Converters," Ph.D. thesis, California Institute of Technology, 1989.
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ZVS QSW Converters: Already Studied
Lecture 21
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20.2.3 Quasi‐square‐wave resonant switches
ZCS
When the previously‐
described operations are followed, then the converter reduces to
SW
Lr
Cr
D2
ZVS
SW
Lr
Cr
D2
A quasi‐square‐wave ZCS buck with input filter
Lf
D1
Q1
L
I
+
Lr
Vg
+
–
Cr
D2
C
Cf
R
V
–
• The basic ZCS QSW switch cell is restricted to 0 ≤ µ ≤ 0.5
• Peak transistor current is equal to peak transistor current of PWM
cell
• Peak transistor voltage is increased
• Zero-current switching in all semiconductor devices
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Ac modeling of quasi‐resonant converters
Use averaged switch modeling technique: apply averaged PWM model, with d replaced by µ
Buck example with full‐wave ZCS quasi‐resonant cell:
Full-wave ZCS quasi-resonant switch cell
i1(t)
+
vg(t)
+
–
µ=F
D1
Lr
i2r(t)
+
i2(t)
+
L
i(t)
+
Q1
v1(t)
v1r(t)
–
–
D2
Cr
v2(t)
–
C
R
v(t)
–
Gate
driver
Frequency
modulator
vc(t)
Ac modeling of QR converters
Quasi‐resonant converters inherit properties of PWM parents, with
switch conversion ratio μ playing the role of the PWM switch duty cycle d
AC modeling approach:
• Start from μ(v,i,fs) found for the resonant switch
• Perturb and linearize
•
Replace d with in the small‐signal AC dynamic model of the PWM
parent converter
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Example 1: Half‐wave ZCS quasi‐resonant buck
Buck Converter Small Signal Model
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ZVS‐QR buck AC model
Example 2: Half‐wave ZCS‐QR buck
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Perturb and Linearize
AC SSM of half‐wave ZCS‐QR buck
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Summary of results
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