Forbidden state space trajectories of PWM converters: implication to digital control

The possible trajectories of the state vector values (i/sub L/(t) and v/sub C/(t)) of buck and boost PWM converters under large transients are examined and evaluated. The forbidden trajectories, detected by examining the state space traces, impose sever limitation on the control design. These limitations are best demonstrated by investigation of large signal transient response of conventional linear controllers. Based on this investigation, a simple discrete control rule is proposed. Based on it, a preliminary simple discrete control function for a boost converter was tested and compared to a linear peak current mode (PCM) control.