## 5 Conclusions  
Based on the results of this experimental research, we can draw the following conclusions.  
Powering LEDs in lighting devices with a rectangular pulsed voltage has advantages over powering them with a constant voltage. In the latter case, ambient temperature from 20 to 60 \({}^{\circ}\)C has little effect on their luminous flux and light output.  
When LEDs are powered by a constant voltage source, their luminous flux and efficiency decrease by more than 10% at 60 \({}^{\circ}\)C versus 25 \({}^{\circ}\)C. The main disadvantage of theses operating conditions is a significant (up to 10%) decrease in light output with an increase in temperature.  
Pulse voltage with coefficients \(D\) = 0.33 and \(D\) = 0.67 also has certain advantages. In this case, the temperature dependence of the LED's light output and power consumption is lower at a constant current than at a constant voltage. But it is still much higher than at a pulse voltage with a coefficient \(D\) = 0.5.  
Therefore, stabilizing the LED's current in LED lighting devices with an increase in ambient temperature appears to be the best operating conditions. In addition, LEDs should be powered by a pulsed voltage with a filling factor \(D\) = 0.5 and a frequency of 20-30 kHz.  
Supplying LEDs with pulse voltage of a rectangular shape makes it possible to simplify the driver of the lighting device. As a result, we obtain a more technologically advanced structure. Its scheme excludes the elements of the voltage rectifier (inductor, capacitor), through which the constant voltage is supplied to the LEDs.  
Special requirements may be required from time to time of the luminous flux stability of LED lighting devices, in particular, in conditions of variable ambient temperatures. In this case, LED lighting devices can be powered both by constant voltage sources with voltage stabilization and pulse power sources with a coefficient \(D\) = 0.5 and a constant voltage (Figure 5). However, with an increase in temperature, the power consumption of LED lighting devices increases significantly, and their light output decreases (Figure 12). That is, the efficiency of their use drops significantly.  
**Author Contributions:** Conceptualization, V.M. and V.P.; methodology, R.M. and O.S.; validation, P.M. and I.B.; formal analysis, I.B. and R.M.; investigation, I.B., V.P., P.M., O.S., V.M. and R.M.; data curation, V.P.; writing--original draft preparation, I.B., V.P., P.M., O.S., V.M., L.K. and R.M.; writing--review and editing I.B., V.P., P.M., O.S., L.K. and V.M.; visualization, I.B.; supervision, V.M. and V.P.; project administration, P.M. and R.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to the fact that the dataset production is part of the innovation point of this paper, the dataset will not be open-sourced at the first time, we will continue to explore new possibilities in the subsequent experimental research, and then the dataset will be made public along with the related code.  
The authors declare no conflicts of interest.