A PWM-Based Discrete Double Integral Sliding Mode Current Controller Design for a Class-D Amplifier

This article presents the design and analysis of a discrete-time, fixed-frequency, pulsewidth modulation (PWM)-based double integral sliding mode controller (DISMC) for class-D amplifiers (CDAs), a concept rarely explored in the literature. The proposed controller addresses the unique challenges posed by the time-varying reference signals inherent to CDAs, which complicate stability analysis and gain determination. To overcome these challenges, an alternative approach for stability analysis and gain tuning is introduced, tailored specifically to the dynamic behavior of the ac tracking system. The feasibility of the proposed DISMC is demonstrated through rigorous simulations and experimental evaluations. The controller adopts a double-loop configuration, utilizing both voltage and current errors as state variables, which significantly improves output voltage regulation, transient response, and robustness to line and load variations. Experimental results validate the superior performance of the DISMC under step load changes. For a transition from 200 to 20 Ω, the DISMC exhibits a voltage deviation of 12  V with a regulation time of 40 μs, outperforming the proportional–integral (PI) controller, which shows a deviation of 14  V and regulation time of 60 μs. Similarly, for a transition from 20 to 200 Ω, the DISMC achieves a regulation time of 120 μs compared to 320 μs for the PI controller.