Discrete-Time Modeling and Stability Analysis of Peak-Current-Mode Controlled Buck Converter with Constant Current Load

With the extensive use of light-emitting diode (LED), switching DC-DC converter with constant current load (CCL) is popularity as LED driver. However, unstable phenomenon, which exists in peak-current-mode (PCM) controlled switching DC-DC converter with CCL, is a key factor limiting the performance of the system. Taking PCM controlled buck converter with CCL as a research object, a novel and simple discrete-time modeling is performed in this paper to analyze the stability of the converter. Based on which, the stability boundary equation of the converter is thus derived by Jacobian matrix. It is found from this boundary equation that the duty cycle should be less than 0.5 for the converter without slope compensation to operate in stable. Besides, the stability regions in the parameter space between the proportional coefficient of error amplifier and output capacitance are enlarged by decreasing the duty cycle. However, the equivalent series resistance of output capacitor and the inductance almost have no effect on the stable state. Finally, the experimental waveforms verified the theoretical analysis results.