Quasi-square-wave ZVS converters

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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 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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Interleaved quasi-square-wave buck converters as
VRM
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Quasi-square-wave versions of other converters
Flyback
Boost
Single transistor version of switch is restricted
to 0.5 lt µ lt 1 So for boost M gt 2 For flyback M
gt n
Boost inductor and flyback transformer are very
small and are similar to DCM devices
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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 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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Goal Find steady-state solution for this
resonant switch cellApproach State plane
analysis followed by averaging of terminal
waveforms
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Interval 1Q1 conduction
Begins when Q1 starts to conduct For ZVS
operation this occurs when D1 had been
previously conducting
Circuit Initial conditions Dynamics What ends
interval Endpoints Length of interval
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State plane
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Interval 2Dead time
Circuit Initial conditions Dynamics What ends
interval Endpoints Length of interval
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Interval 3D2 conduction
Circuit Initial conditions Dynamics What ends
interval Endpoints Length of interval
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Interval 4Dead time
Circuit Initial conditions Dynamics What ends
interval Endpoints Length of interval
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Interval 5 (1)D1 conduction
Circuit Initial conditions Dynamics What ends
interval Endpoints Length of interval
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Waveforms
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Average switch input current
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Average 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.
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