Average Current-Mode Control Scheme for a Quadratic Buck Converter With a Single Switch

A controller for a quadratic buck converter is given using average current-mode control. The converter has two filters; thus, it will exhibit fourth-order characteristic dynamics. The proposed scheme employs an inner loop that uses the current of the first inductor. This current can also be used for overload protection; therefore, the full benefits of current-mode control are maintained. For the outer loop, a conventional controller which provides good regulation characteristics is used. The design-oriented analytic results allow the designer to easily pinpoint the control circuit parameters that optimize the converter´s performance. Experimental results are given for a 28 W switching regulator where current-mode control and voltage-mode control are compared.