Light & Engineering Vol. 23, No. 3, pp. 73-77, 2015 Svetotekhnika No. 4, 2015, pp. 14-17 PULSATION OF LUMINOUS FLUX OF LIGHT EMITTING DIODES AND FEATURES OF THEIR MEASUREMENT AND RATIONING Sergei A. Georgobiani, Mikhail E. Klykov, and Mikhail. <...> V. Lobanov VNISI Open Company, Moscow E-mail: klykov41@mail.ru ABSTRACT Some features of luminous fl ux pulsation of light emitting diodes caused by their characteristics and by their power supply devices are considered in this article. <...> It is shown that the pulsation of radiation of luminaires with light emitting diodes and with gas-discharge lamps can differ essentially from each other by its intensity, waveform and frequency. <...> Therefore, it is concluded that the luminous fl ux pulsation measurement methods accepted today and their standards developed in the middle of the twentieth century for gas-discharge illumination, in some cases cannot be used for light-emitting diode illumination and should be revised. <...> Keywords: light emitting diodes, luminous fl ux ripple, stroboscopic effect, power supply devices, current linear stabilizers, pulse-width control INTRODUCTION Luminous fl ux pulsation fi rst presented at the end of the nineteenth century, when incandescent lamps supplied with alternating current appeared. <...> However, due to an incandescent fi lament’s thermal inertia, the pulsation was insignifi cant and did not infl uence visual perception. <...> The issue of light source luminous fl ux pulsation became challenging from around the 1950s in connection with a mass introduction of gas-discharge light sources supplied with alternating current of 50 Hz frequency using electromagnetic ballasts. <...> Because of the small inertia of discharge and phosphor, 73 the curve of the discharge lamp’s luminous fl ux is close in waveform to the current straightened curve and therefore, has a considerable alternating component of 100 Hz frequency (Fig. 1). <...> This pulsation was noticed at once because of two harmful consequences: the fi rst one was discomfort, headache and increased fatigue; the second one was the possibility of an optical illusion because of a stroboscopic effect, which consisted in an apparent change of rotation speed of observable objects, down <...>