Research of Dynamic Characteristics of LEDs by the Small Disturbance Method

The introduction of LED light sources, which has led to significant energy savings, requires energy-saving power sources. The main attention of LED driver developers is paid to the search for pulsed sources, the work of which is based on the results of studies of dynamic processes occurring in the LED structure itself. To study the influence of current pulses on the electrophysical parameters of LEDs, the small perturbation method was used in this work. The results of measurements of the differential resistance and capacitance of LEDs for various stationary states are presented. They are the main quantities that control transient processes in electrical circuits and play an important role in the development of pulsed power sources. It is shown that the increase and decrease of the injection current and the light flux are well described by an exponential dependence, and the time constant of the kinetics of the light flux is much greater than the current, which is associated with the lifetime of the donor-acceptor pairs. It was established that at a forward bias voltage of ≥ 2.65 V and a pulse frequency of 1 kHz, the reactive component associated with the capacitance of the LED disappears in the relaxation current, which makes it an active energy consumer. Based on the results of the study of the kinetics of the light flux, the maximum pulse frequency of the LED driver was determined to be 100 kHz.