Small-signal Laplace-domain model for digital predictive current mode controls

Predictive current mode control is one of the promising digital current mode control method featuring fast dynamic response and low cost implementation. To understand the benefit and the limitation of each implementation, choose the modulation scheme and design the control loop, this paper proposes small signal Laplace-domain models for a family of digital predictive current mode controls, including peak current control, valley current control and average current control with single edge modulation and symmetric/asymmetric double edge modulation. The model is extended to the multi-sampled implementation. The proposed model considers the dynamic nonlinearity caused by the feedback of sideband frequency components of virtual inductor current, so that it is more precise than conventional Z-domain model based on averaging modeling concept and discretization. Implementation selection and sampling number selection guideline are also discussed. The theoretical analysis of this paper is verified by both simulations and experimental results.