## 3 Results and Discussions  
### Validation with Experiment Results  
The proposed approach to the change of driver design for compensation of luminous flux alternation of LED light source at the environment temperature changes.  
For further analysis, let us use the characteristics of LEDs, which are freely available in the form of graphical or tabular data of most manufacturers of LED products.  
Let us review the dependence of direct voltage on \(U_{d}\) LED on temperature \(T_{c}\) at constant (nominal) current value \(I_{d\;nom}\) (Figure 34) and dependence of the relative luminous flux value \(F/F_{25}\) of LED on the temperature \(T_{c}\) (Figure 35) [12].  
Characteristics of SMD2835 LED with voltage 3 V were shown in Figures 34 and 35. LEDs with 6 V, 9 V, 12 V, 18 V and higher voltages, which were used mainly in LED lighting devices, are the design of LEDs gradually connected with voltage 3 V located in one SMD-case [22; 23; 24; 25; 26]. Therefore, we can consider the characteristics shown in Figures 34 and 35, given to relative values, as fair for other LEDs of this type Let's build the dependence \(U_{d}\) on temperature (Figure 34) in relative values, that is, as \(U_{d}/U_{d25}\) on \(T_{c}\), where \(U_{d25}\) is voltage on LED at \(T_{c}=+25\)\({}^{\circ}\)C (Figure 36).  
Figure 34: Dependence of direct voltage \(U_{d}\) (V) of the SMD2835 LED on the temperature \(T_{c}\) at nominal current value \(I_{d\;nom}\).  
Figure 35: Dependence of the relative luminous flux value \(F/F_{25}\) of SMD2835 LED on the temperature \(T_{c}\).  
In the same graph, we will show the dependence of the relative value of the luminous flux _F_/_F_\({}_{25}\) on temperature \(T_{c}\). The amount of current through LED is constant and equal to its nominal value \(I_{d\,nom}\). On the graphs \(I_{d25}\), \(F_{25}\) were relevantly the nominal current and luminous flux of the LED at +25 \({}^{\circ}\)C. It is evident from Figure 36 that current stabilization through the LED does not ensure the stabilization of its luminous flux with ambient temperature changes.  
But, if you maintain constant voltage on LED, the drop in luminous flux should not be so significant (Figure 37).  
That means, voltage drop on the LED can be used as temperature sensor during LED lighting device operation, without maintaining constant current through it.  
Let us give the quantitative estimate of LED current and its luminous flux changes depending on the environment temperature in case when voltage on the LEDs is constant.  
Dependencies given in Figure 37, are linear within temperature range +15... +60 \({}^{\circ}\)C, so we will use the linear approximation of the characteristics for the case when voltage on LEDs is \(U_{d}=const\).  
The expression for dependencies of the relative values of current \(I_{d}\)/\(I_{d25}\) on temperature \(T_{c}\) (Figure 37) is as follows:  
\[I_{d}\)/\(I_{d25}=0.97+0.0013\ T_{c}, \tag{3}\]  
or  
\[I_{d}=I_{d25}\ (0.97+0.0013\ T_{c}), \tag{4}\]  
where \(I_{d25}\) is nominal value of LED current at +25 \({}^{\circ}\)C.  
Figure 36: Dependencies of the relative values \(U_{d}\)/\(U_{d25}\), \(I_{d}\)/\(I_{d25}\) and _F_/\(F_{25}\) on temperature \(T_{c}\) for SMD2835 LED, \(I_{d}=const\).  
In order to approximate the dependence of the relative values of the luminous flux on the environment temperature (Figure 37), let us use the linear approximation (3).  
\[F/F_{25}=1.025-0.001\ T_{c}, \tag{5}\]  
or  
\[F=F_{25}(1.025-0.001\ T_{c}). \tag{6}\]  
Dependencies (3) and (5) make it possible to estimate the change in current through SMD2835 LEDs and their luminous flux as a part of LED light sources when the environment temperature changes within temperature range +15... +60 \({}^{\circ}\)C.