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.