quasi-square-wave zvs converters
DESCRIPTION
Quasi-square-wave ZVS converters. A quasi-square-wave ZVS buck. Resonant transitions but transistor and diode conduction intervals are similar to PWM Tank capacitor is in parallel with all semiconductor devices, hence all semiconductors operate with ZVS - PowerPoint PPT PresentationTRANSCRIPT
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Quasi-square-wave ZVS converters
+– CrVg
D1
D2
Q1
+
v2(t)
–
i1(t) i2(t)
+
v1(t)
–
Lr
L
C R
+
V
–
I
0Ts
i2(t)
v2(t)V1
0t
0
Conductingdevices: D2X XQ1D1
A quasi-square-wave ZVS buck
Resonant transitions but transistor and diode conduction intervals are similar to PWM
Tank capacitor is in parallel with all semiconductor devices, hence all semiconductors operate with ZVS
Peak currents are increased, and are similar to DCM
Peak voltages applied to semiconductors are same as PWM
Magnetics are small, and are similar to DCM
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Quasi-square-wave versions of other converters
Boost Flyback
Single transistor version of switch is restricted to 0.5 < µ < 1
So for boost, M > 2
For flyback, M > n
Boost inductor and flyback transformer are very small, and are similar to DCM devices
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Interleaved quasi-square-wave buck converters as VRM
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Waveforms
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State plane
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Interval 1Q1 conduction
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Interval 2Resonant transition
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Interval 3Diode D2 conduction
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Interval 4Resonant Transition
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Interval 5D1 conduction
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Average switch input current
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Length of switching period
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Another approach: Find dc component of output current
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Average output current, p. 2
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Control input: transistor/diode conduction angle
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A way to solve and plot the characteristics
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Solving, p 2
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Results: Switch conversion ratio µ vs. F
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Switch conversion ratio µ vs.
Course website contains Excel spreadsheet (with function macros) that evaluates the above equations and can plot the above characteristics.