Stability Analysis for Peak Current-Mode Controlled Buck LED Driver Based on Discrete-Time Modeling

Considering that the state equations of peak current-mode (PCM) controlled buck light-emitting diode (LED) driver with proportion-integration (PI) compensator are third-order singular matrices with maximum rank 2, it is not invertible and may lead to nonconvergent problem under certain circuit parameters. Therefore, an improved discrete-time modeling is performed by substituting state variables of power stage circuit for PI compensator equivalently in this paper. Based on this modeling, the stability of PCM-controlled buck LED driver is investigated by analyzing bifurcation diagram and the maximum Lyapunov exponent spectrum, while the conduction-mode boundary and stability boundary are deduced which indicate the operation regions of the system intuitively, providing design guidelines for LED driver. Experimental results are further presented to verify the theoretical analysis.