Steady-state analysis of PWM DC/DC switching regulators using iterative cycle time-domain simulation

A new iterative technique for the steady-state analysis of pulsewidth modulated (PWM) DC/DC switching regulators is presented. The methodology is based on transforming the closed-loop regulator into an open-loop configuration. The steady-state solution is solved by two iteration loops. The first loop is to find the steady-state state variables when the power converter is at a fixed duty cycle. The circuit waveforms are obtained by a stepwise time-domain simulation method, which is based on using stepwise quadratic formulation of the circuit state variables with progressive analysis of the switches' states. The second iteration loop is to determine the steady-state duty cycle of the PWM modulator output, using an explicit "fictitious" ramp offset value as the error index. This two-loop iteration approach lessens the occurrence of the nonconvergence problem that is sometimes found in the single-loop iteration method. Furthermore, the advantages of this method include the following: (1) substantial improvement in speeding up the convergence to steady-state solution; (2) simplicity in requiring simple algebraic manipulations; (3) generality in determining valid topology without prior knowledge of the regulator operation; and (4) directness in determining the switching instants. Several examples illustrating the computational efficiency and the accuracy are presented and are verified with the available literature.