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