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Computation of periodic steady state in nonlinear circuits is a key issue. Power electronics converters represent an interesting class of switched nonlinear circuits. The behavior of the converter is obtained by the commutations of the electronic devices which determine the switchings among the different converter modes. Switchings can be classified as external, if forced by directly manipulable control variables, and internal if determined by state dependent conditions. The presence of internal switchings makes it difficult to know a priori the sequence of modes and also open loop steady-state behaviors are difficult to be obtained. In this paper the complementarity modeling framework is proposed as a possible approach for computing periodic steady-state oscillations in power converters with internal switchings. It is shown how linear complementarity systems can be used to model the behavior of a wide class of power converters. The discretization of such model allows to formulate a static complementarity problem whose solution provides the steady-state oscillation of the converter. It is proved that the backward zero-order-hold technique preserves passivity through the discretization and allows to determine the unique solution of the complementarity problem. A resonant converter and a dc/dc voltage-mode controlled buck converter are used as examples. [ABSTRACT FROM PUBLISHER]

This paper proposes a small-signal model for variable-switching-frequency hysteretic converters operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The model is capable of predicting flip-bifurcation phenomena when the hysteretic converter operates below the CCM/DCM boundary. By developing a discrete-time state-space model of the converter, the z-domain model is derived using the advanced z-transform. Such a tool is suitable to transform in the z-domain signals varying within a switching cycle. A comparison with exact simulations is provided to validate the proposed model. The propagation delay of the feedback control circuit is included due to its significant influence on the low-frequency open-loop gain. Experimental results run on a test chip including a 10-MHz TSMC 0.18\ \mu\m-process hysteretic-mode buck converter are also reported along with the model results. [ABSTRACT FROM PUBLISHER]

A dual modulation technique to improve power conversion efficiency with minimal increase in output voltage ripple is presented. The worsening switching noise caused by parasitic resistance and inductance due to high-switching operation can also be alleviated by the proposed ac ripple detector. Furthermore, the dual modulation method can speed up the load transient response since the switching frequency can increase to 5 MHz during the transient period. At very light loads, the switching frequency is always kept higher than the acoustic frequency to avoid noisy sound. Experiment results show that the converter operates at 5 MHz using a small inductor of 1 \mu \H. The load transient response time is shorter than 3 \mu \s when load current changes from 150 to 450 mA or vice versa. Power efficiency is kept higher than 85% over a wide load current range. Specifically, light efficiency can be raised to about 45% above that of the conventional design. [ABSTRACT FROM PUBLISHER]