Switching power supplies are widely used in nowadays equipments, ranging from a few tens of watts in consumer applications to several hundred of watts and above in industrial applications. Despite the various architectures found in this field, they all share the need for a control circuit that maintains one or several delivered variables within a defined range. The compensator is the place where the designer shapes the loop frequency response for a particular performance and ensures stability over the entire operating range. Depending on the selected controller, the active element used to perform compensation can be an operational amplifier, a TL431 or a digital architecture. Targeting engineers and graduating students, this seminar describes how to efficiently compensate a power converter using an active analogue amplifier. Compensator types such as 1, 2 and 3 are covered in great details, with design examples used as a support. More complex implementations including anti-windup structures as well as a quick introduction to digital filters are also covered in this seminar. Using mathematical analysis and different tools such as SPICE, Mathcad® and SIMPLIS®, the author maintains a permanent link between theory and practical reality. Balancing analytical aspects and real case examples, the seminar targets an audience with an intermediate background in the presented subject.