Current-mode control: a unified model for open-loop instability

A model describing the open-loop instability of constant-frequency current-mode-controlled switching power cells operating in a heavy mode is presented. The instability is a common feature of many different cells, and is independent of their topology. The oscillations occur at one-half of the switching frequency and can be suppressed applying compensating waveforms. These unifying features are at the base of a synthesis of a general, topology-independent model. The model retains the simplicity of the analysis using characteristic coefficients. Comparison to the results obtained by sampled-data approach and measurements show that the model is a powerful, user-friendly design tool