Optimal Switching Control of a Step-Down DC-DC Converter

This paper applies a general computational technique for optimal control of switched-mode hybrid systems, recently developed by the authors, to voltage-regulation problems in a step-down DC-DC converter. Unlike existing techniques that are based on model-predictive control and a specific algebraic structure of the problem, the algorithms presented here are based on gradient descent with Armijo step size, and consequently can incorporate time-dependent state constraints in a natural way. The approach proposed in this paper is complementary to the extant MPC-based techniques, and it appears to compare favorably with some of the established works. Two problems are being addressed: one concerns pulse-width modulation and computes the optimal duty ratio, and the other computes an optimal switching schedule without a fixed cycle time.