Digital control of power supplies - opportunities and constraints

In this paper, we present a study of the opportunities and constraints of digital control in power supplies. The advantages and disadvantages between analog and digital controllers in switched-mode power supplies are discussed in detail. The effects of a digital controller on device's reliability and integration level are also discussed. A 48 V, 500 W rectifier having a switching frequency of 100 kHz was used as a practical case example. This switched-mode rectifier consists of two converter stages, i.e., AC/DC and DC/DC converters. Dynamic characteristics for digital controllers in both converters were studied by extensive simulations. Based on the simulation results, the values of the required sampling frequencies were determined. According to the obtained results and careful analyses made in our study, it can be stated that digital control is certainly a viable alternative also in power supplies. However, before digital controllers will become dominant in high-volume power supply products, low cost microcontrollers or signal processors, which are tailored for the specific application, are needed to reduce the existing cost barrier.