Small-signal high-frequency analysis of the free-running current-mode-controlled converter

The small-signal high-frequency model of the free-running current-mode-controlled converter is determined using the analysis method of injected-absorbed currents and introducing high-frequency correction terms. The model is valid up to one-half of the switching frequency. The model parameters (the characteristic coefficients of the switching cell) can be obtained with a few lines of calculation while retaining the insight into the physical operation of the converter. The technique is applied for the buck, boost, and buck-boost cells, using hysteretic, constant off-time, or constant on-time control. A general procedure is recommended for determining the coefficients. The possible approximations for the high-frequency correction terms are discussed. Tables of characteristic coefficients are provided. Experimental data that are in excellent agreement with theoretical prediction are presented.<
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