## 2 Investigation of Temperature Dependence of Current and Luminous Flux
The change of luminous flux with temperature is significant (Figure 8) and within +15\(-\)60 \({}^{\circ}\)C temperature range is up to 10% at 198 V voltage of, up to 8% at 220 V voltage, and up to 17% at 242 V  
Figure 2.8 Dependencies of the relative luminous flux values \(F/F_{25}\) on \(T_{c}\) temperature at 198 V, 220 V and 242 V supply voltages for \(p=6\) W lamp. Figure 2.9 Dependencies of the relative voltage values \(U_{d}/U_{d25}\) of LEDs lamp with power 6 W on \(T_{c}\) environment temperature at 198 V, 220 V and 242 V supply voltages for \(p=6\) W lamp. voltage. Voltage on LEDs for both 3 W lamp (Figure 6) and 6 W lamp (Figure 9) practically did not change with temperature changes and slightly depends on \(U_{AC}\) voltage. The Investigation of Temperature Dependencies of the Current and Luminous Flux of the LED Lamp Built on IC Driver with Voltage Pulse-Width Modulation of the Voltage on LEDs  
Premier-10 E27 LED lamp with power 10 W produced by HOROZ ELECTRIC trade-mark was investigated (Figure 10, general view without light diffuser). The lamp contains nine SMD 2835 LEDs (nominal voltage 12 V, nominal current 75 mA, power 1 W, color temperature 4000 K) [17]. LEDs were connected gradually. Praciple electric scheme of Premier-10 lamp is shown in Figure 1.0  
The lamp driver is made on BP2863 chip, the structure of which is shown in Figure 12[18]. Chip \(D1\) is high-frequency converter with pulse width regulation of the output voltage (DRAIN output), switched on LEDs were connected to it gradually through \(L2C2\) filter elements (Figure 11). The current through on the LEDs is constant. The microcircuit, in fact, is _current stabilizer_, where the regulating element was the field-effect transistor (Figure 12), and current sensor was the resistor \(R2\) (Figure 11). The current through LEDs was regulated by pulse density at DRAIN output. The oscillogram of the voltage at DRAIN output circuit (Figure 11) at \(U_{AC}=220\) V supply voltage was shown in Figure 1.1 Dependencies of relative current values \(I_{in}/I_{in25}\) of  
Figure 1.2 Principle electric scheme of Premier-10 lamp with 10 W power. Figure 1.3 Premier-10, 10 W LED lamp. of the pulses increases. In the first case, the duration of the pulses at DRAIN output of the microcircuit increases, in the second--it decreases, ensuring current stabilization through the LEDs. The dependencies of current relative values \(I_{d}\)/\(I_{d25}\) of LEDs on the environment temperature \(T_{c}\), where \(I_{d}\) is current value of the current, \(I_{d25}\) is the current value at +25 \({}^{\circ}\)C and \(U_{AC}\) = 198 V, 220 V and 242 V were shown in Figure 1.4  
The value of the current through LEDs practically did not changed with the change of supply voltage \(U_{AC}\). Dependencies of the voltage relative values \(U_{d}\)/\(U_{d25}\) of the lamp LEDs on temperature \(T_{c}\) were shown in Figure 1.5 Both current and voltage on LEDs practically does not depend on the change in voltage \(U_{AC}\). The luminous flux of the lamp decreases by 5% with increasing temperature (Figure 17), but not so significantly as it happens in the lamps with linear driver without current stabilization. Figure 1.6 Dependencies of the relative voltage values \(U_{d}\)/\(U_{d25}\) on \(T_{c}\) temperature at 198 V, 220 V and 242 V supply voltage for Premier-10 lamp. Figure 1.7 Dependencies of the relative values luminous flux \(F\)/\(F_{25}\) on \(T_{c}\) temperature at 198 V, 220 V and 242 V supply voltage for Premier-10 lamp. Figure 1.8 Dependencies of current relative values \(I_{d}\)/\(I_{d25}\) on the environment temperature \(T_{c}\) at 198 V, 220 V and 242 V supply voltage for Premier-10 lamp. This was explained by the fact that despite the ability of BP2863 chip to stabilize the output current also when the environment temperature changes, as it follows from its technical characteristics, the luminous flux of LEDs at current constant value still decreases with increasing temperature [11].