1 Quasi-square-wave ZVS converters + – C r V g D 1 D 2 Q 1 + v 2 ( t ) – i 1 ( t ) i 2 ( t ) + v 1 ( t ) – L r L C R + V – I 0 T s i 2 ( t ) v 2 ( t ) V 1 0 t 0 C onducting devi ces: D 2 X X Q 1 D 1 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 voltages applied to semiconductors are same as PWM Magnetics are small, and are similar to DCM
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1 Quasi-square-wave ZVS converters A quasi-square-wave ZVS buck Resonant transitions but transistor and diode conduction intervals are similar to PWM Tank.
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1
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
2
Interleaved quasi-square-wave buck converters as VRM
3
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
4
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
5
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 conductFor ZVS operation, this occurs when D1 had been previously conducting
CircuitInitial conditions
DynamicsWhat ends interval
EndpointsLength of interval
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State plane
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Interval 2Dead time
CircuitInitial conditions
DynamicsWhat ends interval
EndpointsLength of interval
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Interval 3D2 conduction
CircuitInitial conditions
DynamicsWhat ends interval
EndpointsLength of interval
10
Interval 4Dead time
CircuitInitial conditions
DynamicsWhat ends interval
EndpointsLength of interval
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Interval 5 (1)D1 conduction
CircuitInitial conditions
DynamicsWhat ends interval
EndpointsLength 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.