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

Interleaved quasi-square-wave buck converters as VRM

Quasi-square-wave versions of other converters Flyback Boost 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

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

Goal: Find steady-state solution for this resonant switch cell Approach: State plane analysis followed by averaging of terminal waveforms

Interval 1 Q1 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

State plane

Interval 2 Dead time Circuit Initial conditions Dynamics What ends interval Endpoints Length of interval

Interval 3 D2 conduction Circuit Initial conditions Dynamics What ends interval Endpoints Length of interval

Interval 4 Dead time Circuit Initial conditions Dynamics What ends interval Endpoints Length of interval

Interval 5 (1) D1 conduction Circuit Initial conditions Dynamics What ends interval Endpoints Length of interval

Waveforms

Average switch input current

Average output current

Average output current, p. 2

Control input: transistor/diode conduction angle 

A way to solve and plot the characteristics

Solving, p 2

Results: Switch conversion ratio µ vs. F

Switch conversion ratio µ vs.  Course website contains Excel spreadsheet (with function macros) that evaluates the above equations and can plot the above characteristics.