Digital Current-Limited Sliding-Mode Control For Synchronous Buck Converter With Curved Switching Surface

In this paper, a digital current-limited sliding-mode control (DCLSMC) for synchronous buck converter with curved switching surface is proposed. First, by discretizing the derivatives of a hybrid switching surface (SS) (consisting of second-order and first-order SS) and utilizing the reaching law method, a discrete-time sliding-mode control (SMC) is derived. Then, this SMC is integrated with a current-limited control to construct the DCLSMC. Simulation results show that it can provide a current-limited near-time-optimal dynamic response. The proposed SMC is implemented by pulse-width modulation (PWM) technique, so it can provide a fixed switching frequency and has a low sampling requirement. The reachability of the SS for the proposed SMC and the stability of the quasi-sliding mode motion is proven. Moreover, an additional PI control is introduced to eliminate the steady-state error, and some implementation issues are discussed. Experimental results are given to verify the high dynamic performance and practical value of the proposed method.