Comparative study of digital PI control algorithm for Dc-to-dc converters

In this paper, comparative study of three algorithms of digital PI control, that is, conventional PI control, offset control and modified PI control, is presented. Conventional PI control is subjected to numerical error because the gain must be small in order to move zero of the control to output transfer function to low frequency. To prevent this undesired issue, authors have already proposed novel algorithm called “offset control” in the previous work. Another method (named modified PI control) that improves integral characteristics is proposed in this paper. Three algorithms are described in detail and are implemented for a buck converter. Frequency characteristics of transfer function of control system are measured. To move zero of the transfer function to lower frequency, both modified PI control and offset control are effective. Output voltage load regulation characteristics are also measured and it is found that offset control have the best regulation among three algorithms.