Fixed-frequency second-order sliding-mode control of buck DC-DC converter

A fixed-frequency second-order sliding-mode control for buck DC-DC converter is presented in this paper. The proposed method combines a concept of variable hysteresis and sliding-mode control technique. The switching frequency is maintained constant over a range of supply voltages and output voltages. The second-order sliding-mode controller is implemented digitally, using a simple state-machine structure, which does not need current sensing or an integral term. The proposed approach is verified by simulation results on a 1.25-V 10-A converter.