Adaptive Digital Current Mode Controller for DC-DC Converters

An adaptive control technique for a digital current mode control of dc-dc converters is proposed in this paper. The adaptive digital controller is designed to maintain the optimum gain-phase of the outer control loop regardless of the changes in the load value. In the control algorithm, the load resistance is calculated using the average current and output voltage values inside the digital processor. Next the calculated value of the load resistance is used to tune the Proportional-Integral ( PI) controller such that the requirements for crossover frequency and phase margin values are fulfilled. In order to avoid the calculation burden to slow down the program execution speed, the parameter values of PI controller for each value of the load resistance are inserted into a look-up table inside the digital processor. To verify the proposed technique, the controller is implemented in an FPGA to control a buck converter. The experimental results show the excellent performance of the controller in presence of a load change.