DSP BasedSecond Order Sliding Mode Controller for Buck Converter

DC-DC Converters are used in effective conversion of the unregulated input voltages to regulated output voltages. Sliding mode control technique is one of the methods used to achieve smooth and robust voltage control. The first order sliding mode control method regulates the output voltage to the desired value but suffers from the phenomena called chattering. Chattering reduces the life of the converter switch. Various methods such as boundary layer control, higher order sliding mode control etc. can be used to reduce this chattering effect. Boundary layer control uses continuous approximation of the discontinuous control signal to reduce chattering. However it reduces the speed of response and introduces steady state error. Chattering can be effectively reduced by using higher order sliding mode control. In this paper, Second order Sliding mode controller is implemented by using the Super-Twisting Algorithm. Results for the second order control are compared with the first order control with and without boundary layer control and effectiveness is verified. Hardware prototype is developed using Microcontroller Piccolo C2000 TMS320F28069 Launchpad and the results are analyzed for robustness by varying the input voltage.