Super-resonant converter with switched resonant inductor with PFM-PWM control

The efficiency of the series-resonant power converters is proved to increase with the improvement of the current form factor of the resonant current. The application of “soft-switching” reduces the switching losses. The maximum value for the pulse frequency in a super-resonant converter is limited by the introduction of a method of pulse width modulation. To improve the current form factor a second inductance is placed in the output side of the converter. This inductance is alternately included in the resonant circuit. The paper offers graphical presentation of the characteristics made to select the choice of the best suitable relationship between the resonant and output inductances and to support the design. The role of the parasitic elements of a transformer is specified