## 3 Results
### Proposed Design Solution  
Previously, we studied the temperature dependence of the current, voltage, and luminous flux of a 10 W Premier-10 LED lamp manufactured by HOROZ ELECTRIC with a pulse driver and with pulse width control of the LED voltage [11]. The electrical circuit of this lamp is shown in Figure 19, and a functional diagram of it is shown in Figure 20.  
Figure 19: Electrical circuit of a 10 W Premier-10 LED lamp. Figure 18: Dependence of relative values of LED power and luminous efficiency on temperature obtained at a constant voltage. \(U_{d}=U_{d0\,25\text{\textminus}}\text{C}=\text{const}\). The lamp driver is based on the BP2863 (\(D1\)) chip [26; 27; 28], which is a high-frequency pulse converter with pulse width control of the voltage at the \(DRAIN\) pin. The sequentially switched on LEDs \(VD1\ldots VD9\) are connected to the \(DRAIN\) output of the chip through the inductor \(L1\), and the anode of the first LED \(VD1\) is connected to the \(HV\) output of the diode bridge of the chip. The capacitor \(C2\) is connected in parallel to the LEDs (Figure 17). Therefore, the LEDs are supplied with a constant voltage. The lamp driver stabilizes the LED current, the value of which is regulated by changing the pulse fill factor \(D\) at the \(DRAIN\) pin. Figure 21a shows the voltage waveforms at the \(DRAIN\) pin of the driver when the lamp is  
As seen in Figure 22, with an increase in temperature \(T_{c}\), the current decreases by 3%, the LED voltage decreases by 2%, and the luminous flux decreases by 4%. The obtained dependencies remain practically unchanged when the supply voltage \(\sim\)\(U_{AC}\) changes by \(\pm\)10% [11]. The LED's current sensor is shown in Figure 19. The resistor \(R2\) is connected in series to the output transistor of the driver, which works in pulse mode (Figure 20). To increase the stability and luminous flux of the LED lamp in the temperature range from 20 to 60 \({}^{\circ}\)C, it would be advisable to supply LEDs with pulsed voltage directly from the \(DRAIN\) output of the driver chip rather than with a constant voltage (filter \(L1\), \(C1\), Figure 21a). In this case, the driver that stabilizes the LED's current needs to be investigated because the LED's current will also be pulsed (pulse voltage on the resistor \(R2\)) but not constant. At the same time, the driver circuit will become simpler (Figure 23) and more convenient since we have removed the technologically complex element \(L1\), as well as the high-voltage, high-frequency capacitor \(C1\)[29]. Figure 23: Electrical circuit of a lamp (Figure 17) with a rectangular pulse voltage on LEDs. To select the number of LEDs and their electrical parameters for the circuit (Figure 23), we make the following calculations. The current and total power of the LEDs, and thus the LED lamp, can be controlled. To this end, we select a certain number of LEDs with the required rated voltage, which are connected in parallel if necessary. The value of the pulse filling factor \(D\) should be close to \(D=0.5\). At the \(DRAIN\) output of the \(D1\) chip, the amplitude value Um will be equal to  
\[U_{m}=\sqrt{2}\ \times\ U_{AC} \tag{8}\]  
The same voltage will be supplied to the LEDs and its value can be written as  
\[U_{m}\geq n\ \times\ U_{d\ non}, \tag{9}\]  
where \(U_{d}\) nom is the nominal voltage across the LED at a temperature of 25 \({}^{\circ}\)C, and n is the number of LEDs connected in series. Taking into account expression (2), given that \(D=0.5\), the effective value of the LED voltage \(U_{de}\) will be approximately equal to  
\[U_{de}=U_{m}/k_{a}=n\ \times\ U_{d\ non}/1.41=0.71\ \times\ n\ \times\  
The temperature dependence of the relative values of power and luminous efficiency using a constant value for the LED current (Figure 11) is optimal. Their decrease with an increase in ambient temperature up to 60 \({}^{\circ}\)C does not exceed 3%. With an increase in the pulse filling factor (\(D\) = 0.67), the LED operating conditions approach those characteristic of a constant voltage [12].