LOCAL AND GLOBAL STABILITY OF SWITCHING REGULATORS

A discrete-time model of closed-loop PWM regulators is derived to desc ribe their dynamic behavior. No small-ripple approximations are requir ed. The same model serves both local and global stability study: by di scarding the nonlinear terms and using the z-transform, stability for small-signal perturbations is checked; by keeping the nonlinear terms (products of disturbances) and using the state-plane portrait, in whic h equilibrium points are located, stability for large-signal perturbat ions is studied. The theory is applied to a multiple feedback boost re gulator operating in continuous conduction mode. Its local/global stab ility/instability for different values of the feedback gains is determ ined based on the new method.