Switching Frequency Bifurcations in an LED Boost Driver

Under specific conditions LED driver circuits can be as susceptible to chaotic bifurcations, as conventional boost converters have proven to be. A significant relationship between the switching frequency of the boost converter’s transistor and the circuit’s nonlinear behaviour is shown. In order to examine such transistor switching frequency effects, an open-loop configuration is employed, since a feedback control system would obscure these particular nonlinearities. A theoretical method has been devised to predict the unstable frequency regions based on certain dependence equations. There are particular nonlinear parameters which influence the circuit’s behaviour, such as the reverse-recovery time of the boost diode, as well as the collective effect of the inductance and the diode’s junction capacitance. The dependence equations prove a correlation between these inherent nonlinearities and the switching frequency of the boost transistor. Period doublings and transitions to chaos occur for several regions of the examined switching frequency range. The theoretical method used for the numerical analysis is based on the periodicity of certain voltage waveform peaks, probed at key points on the converter. The LED boost driver displays a wealth of nonlinear phenomena and detrimental effects on its brightness levels throughout the nonlinear frequency regions.