Practical considerations for the design and implementation of digital-controlled power converters

The main theme of this paper is to present practical considerations for the design and implementation of digital-controlled power converters and thereby providing archival reference for the development of digital power converter. First, the effects of A/D converter, software-based compensator and digital pulse-width modulator on digital power converter are introduced. Second, the selection of modulation methods considering the delay contributed by compensator calculation and DPWM is explored. Then modeling of digital controlled DC-DC converter taking the above-mentioned delay effects into account are analyzed and developed. Finally, compensator design based upon analogue-controlled converter model and fully digital-controlled system are presented. Illustration using a digital-controlled buck converter as an example is designed and implemented. Several compensators which are popular for analog-controlled converter are discussed. It will be shown that for the same design specifications, two-pole two-zero compensator has the least phase lag and the highest phase margin. Experimental results derived from an FPGA-based system are presented for confirmation.