A state-space modeling of nonideal DC-DC converters

A model based on practical switches with finite turn-on, turn-off, delay, storage, and reverse recovery times is proposed. The effects of switching on the state equation, system stability, DC gain and efficiency are shown for the boost, buck, and buck-boost converters. The effect of current-based switching-time variation on system stability effect, and the effect of average duty cycle variation on system stability is considered. DC gains of the boost and buck-boost converters are shown to be greatly degraded by switching loss. It is also shown that no additional resistance is generated by switching, in contradiction to previous work. It is found that the buck converter is superior to the others from the viewpoints of systems stability and DC gain, and the efficiencies of all the converters are maximized when the DC gain is close the unity. Previous results are improved and unified using state-space modeling. Analysis results are very simple in spite of the complex switching waveforms. This modeling approach is believed to be very useful for the high-frequency or high-power applications where switching effects become dominant.<>