A State-space Modeling of Non-ideal Dc-dc Converters

A modeling based on the practical switches with finite turn-on, turn-off, delay, storage and reverse recovery times is proposed. The switching effects on the state equation, system stability, dc gain and efficiency are shown for the boost, buck and buck-boost converters. The effect of switching time variation by current on system stability is given as an extension of the storage time modulation effect. And the effect of average duty cycle variation on system stability is newly introduced. DC gains of the boost and buck-boost converters are shown to be much deteriorated by switching loss. It is also shown that no additional resistance is generated by switching in contradiction to previous work. Besides, it is found that buck converter is superior to others from the viewpoints of the system stability and dc gain, and the efficiencies of all the converters are maximized when the dc gain is close to unity. Previous related papers are improved and unified using a new state-space modeling. Analysis results are very simple in spite of the complex switching waveforms. This new modeling is believed to be very useful for the high frequency or high power applications where switching effects become dominant.