Unified Control Strategy Covering CCM and DCM for a Synchronous Buck Converter

In general, transfer functions of switch-mode converters are treated differently when operating in continuous-conduction mode (CCM) or discontinuous-conduction mode (DCM). This complicates the development of a control algorithm for a converter operating in both operating modes. To solve this problem, a control algorithm is developed, which is applicable for CCM and DCM. Since the developed control algorithm is based on linear equations instead of differential equations, it is easy to implement and its calculation effort is minor. It is based on equating the volt-seconds across the inductor for both operating modes and adjusting the duty cycle d. All necessary equations are derived and the functionality of the developed algorithm is shown by means of simulation and measurements.