## 3 Results
As seen, an increase in the LED current (Figure 3) at a constant voltage value partially compensates for the drop in its luminous flux with an increase in temperature. The temperature dependence in relative units for a pulse voltage at \(D=\) 0.5 is shown in Figures 4 and 5. Figure 4 shows the LED characteristics at a current value \(I_{d\,imp25^{\circ}\text{C}}=\text{const}\). The graph shows that the LED voltage with a constant current decrease with an increase in temperature by no more than 2%, and the luminous flux decreases to 6% at 60 \({}^{\circ}\)C versus its value at 25 \({}^{\circ}\)C.  
Comparing the dependencies in Figures 2 and 4, we see that the LED voltage and luminous flux (Figure 4) decrease with an increase in temperature almost half as much as in Figure 2. Therefore, supplying LEDs with a pulsed voltage with a coefficient \(D=\) 0.5 is more efficient compared to supplying them with a pulsed voltage with a coefficient \(D=\) 0.33. When \(U_{d\,imp25^{\circ}\text{C}}=\text{const}\) (Figure 5), the current increases by only 4% at \(T_{c}=\) 60 \({}^{\circ}\)C with an increase in temperature, and the luminous flux decreases by only 4% in the temperature range studied. Figure 4: Temperature dependence in relative units of the LED voltage, current, and luminous flux for a pulse voltage at \(D=\) 0.5 with a constant current value. Figure 5: Temperature dependence in relative units of the LED voltage, current, and luminous flux for a pulse voltage at \(D=\) 0.5 with a constant voltage value. LEDs powered by a constant voltage, where the luminous flux decreases much more with an increase in temperature. Thus, even in this case, switching to a power supply with \(D=0.5\) is more optimal in terms of the higher efficiency of LED light sources. Oscillograms of an smd2835 LED with the voltage and current waveforms at a frequency of 20 kHz at \(D=0.33\), \(D=0.5\), and \(D=0.67\) are shown in \[I_{d\text{ }imp}=I_{m\text{ }imp}/k_{a}=2\times I_{d\text{ }nom}/1.41=1.41\times I_{d\text{ }nom},\]0 As is seen from the oscillograms, the LED current and voltage have the form of rectangular pulses, which is characteristic of an active load. Therefore, LEDs should be considered purely active loads in the frequency range studied. Let us analyze how the power of \(P_{d}\) LEDs and their luminous efficiency \(\eta=\Phi/P_{d}\) change with temperature, the values of which were obtained through calculation based on the results on the experimental temperature dependence for the LED luminous flux, voltage, and current under a pulsed power supply using different values for the \(D\) coefficient (Figures 2 and 7). Figure 9 shows the dependence of the relative values of the LED power \(P_{d\;imp}/P_{d\;imp25^{\circ}C}\) and light output \(\eta_{imp}/\eta_{imp25^{\circ}C}\) on temperature obtained at a constant current value for \(D=0.33\) from the graphs (Figure 4). As is seen, the power consumption drops by 4% in the entire temperature range, and the luminous efficacy drops by 8%. This accounts for decreased luminous flux with an increase in temperature (Figure 2). Figure 10 shows the same dependence obtained from the graphs at a constant LED voltage (Figure 3). In this case, the luminous flux decreases less with temperature (Figure 3),  
\[I_{d\text{ }imp}=I_{m\text{ }imp}/k_{a}=2\times I_{d\text{ }nom}/1.41=1.41\times I_{d\text{ }nom},\]1 Voltage (lower waveforms in each figure) and current (upper waveforms) waveforms of smd2835 LED at 20 kHz at (**a**) \(D=0.33\); (**b**) \(D=0.5\); (**c**) \(D=0.67\). \[I_{d\text{ }imp}=I_{m\text{ }imp}/k_{a}=2\times I_{d\text{ }nom}/1.41=1.41\times I_{d\text{ }nom},\]2 Dependence of the relative values of power and luminous efficiency of LEDs on temperature obtained at a constant current value for \(D=0.33\). but the power consumption increases significantly (by more than 10%), and the luminous efficiency decreases significantly (by up to 13%).