A digital predictive critical conduction mode buck converter control method

Digital control of power converters has been recently recognized as a feasible solution due to its advantages over analog controllers; enhanced reliability, flexibility and modularity. Power electronic systems such as high intensity discharge (HID) lamp ballasts require relatively complex control methods and various stages of control schemes. By utilizing digital signal processors, advanced control algorithms can be easily implemented while using the left over computational capacity for basic pulse-width modulations for gate drives. This paper presents a fully digital control method for a buck converter operating in critical conduction mode (CRM). The switching frequency which assures CRM is calculated and predicted for the next period using the sensed voltage and current information generally needed for controlling the output of the converter. Simulation and experimental results of a 125 W buck converter prototype verify the feasibility of the proposed control method implemented by a digital signal processor (DSP).