Software controlled switched-mode power supply using DSP

This paper discusses the software control method for a switched-mode power supply with a current control system as a minor loop of the output voltage control. When a control system is configured on DSP software, one obtains a dead time control system due to the execution time of the software and can not obtain expected current controlled characteristics. For this problem, w e propose a current estimation method for compensating the dead time, a hig hspeed current control method for realization of a high-speed response of t he current control, and an input de voltage estimation method for control d eviation elimination of the current. For confirmation of the effectiveness of these proposed methods, a switched-mode power supply rated at 50 W, 24 V , 2.1 A, and a switching frequency of 140 kHz is controlled by a test contr ol system using a DSP (TMS320C25). A control system is constructed with a s ampling period of 35.6 mus that is five times the switching period. The out put voltage control error is less than 14.5 mV, the maximum output voltage control error is 60 mV at a sudden change of the load of 50/100%, and the o utput voltage recovery time is 0.8 ms in the experiment. These characterist ics are sufficiently practical. (C) 2000 Scripta Technica.