Loop gain and margins of stability of inner-current loop of peak current-mode-controlled PWM dc–dc converters in continuous conduction mode

A general expression for the loop gain of the inner-current loop of peak current-mode-controlled PWM dc–dc converters operating in continuous conduction mode (CCM) is derived as a function of perturbation ratio and switching frequency. It is shown that this expression is identical for all conventional PWM dc–dc converters in CCM, such as buck, boost and buck–boost converters. However, the value of perturbation ratio is dependent on the converter topology. Also, an expression for required slope compensation at a specified phase margin and a maximum duty cycle is presented. The general expression of the loop gain enables the investigation of the margins of stability of the inner loop of peak current-mode-controlled PWM dc–dc converters irrespective of the converter topology.