## 5 Results
### Supraharmonics Emission
#### 5.2.2 Case Study 2--LED 7 W Lamp  
Figure 7 shows the conducted emission in the frequency spectrum within 9-150 kHz generated by the LED 7 W lamp equipped with passive-PFC topology (PF = 0.85). This kind of lamp is constructed with a basic energy supply, accompanied by series capacitors or inductors, which are positioned either before or after the bridge diode rectifier, in order to increase the power factor PF (usually falling between 0.6 \(\leq\) PF \(\leq\) 0.9) [56]. Table 4 presents the measurement results that indicate that the LED 7 W lamp is characterized by relatively high resistance to blurring (shifting) of the emission characteristics in the frequency domain due to the change in the supply voltage level. Similar to case study 1, a level of emissions in the range of frequency 9-14 kHz cannot be attributed to the source of disturbances (EUT) and the real source of these disturbances is the programmable power supply device used in the research. The maximum observed shift, concerning the frequency for the reference value of nominal voltage level, i.e., 230 V, occurs for the frequency range of 74-84 kHz for the 210 V and is equal to 1.2 kHz. Figure 8 zooms in on the dominant bands of the tested LED 7 W lamp. For the EUT, a decrease in the value of the supply voltage causes a shift of the frequency domain band towards lower values. In comparison, an increase in supply voltage causes a shift of the frequency domain band towards higher values (Figure 8b). The highest observed disturbance produced by EUT supplied with 230V equals 52.56 dB\(\upmu\)V at 78 kHz bandwidth. The obtained results do not exceed the permissible limits specified in EN55015 standard [21]. The change in the supply voltage level does not significantly affect the emission amplitude change at higher frequencies, i.e., from 84 kHz to 150 kHz. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Supply** & **210** & **220** & \
\begin{tabular}{c} **230** \\ **Reference** \\ \end{tabular} & **240** & **250** &
\begin{tabular}{c} **Dominant** \\ **Frequency Band** \\ \end{tabular} \\ \hline Emission level U [dB\(\upmu\)V] & 32.73 & 32.10 & 31.16 & 31.13 & 30.85 & \\ Difference in emission level \(\Delta\)U [dB\(\upmu\)V] & +1.57 & +0.94 & 0 & \(-\)0.03 & \(-\)0.31 & \\ Dominant center frequency f [kHz] & 11.80 & 11.80 & 12.00 & 12.00 & 12.00 & 9–14 kHz \\ Frequency shift level \(\Delta\)f [kHz] & \(-\)0.2 & & & & & \\  & & \(-\)0.20 & 0 & 0 & 0 & \\ \hline Emission level U [dB\(\upmu\)V] & 52.83 & 52.97 & 52.56 & 51.83 & 51.77 & \\ Difference in emission level \(\Delta\)U [dB\(\upmu\)V] & +0.28 & +0.42 & 0 & \(-\)0.73 & \(-\)0.79 & 74–84 kHz \\ Dominant center frequency f [kHz] & 76.80 & 77.20 & 78.00 & 78.00 & 78.20 & \\ Frequency shift level \(\Delta\)f [kHz] & \(-\)1.2 & \(-\)0.8 & 0 & 0 & +0.20 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Selected dominant emission bands for the LED 7 W lamp. Figure 7: Supraharmonics spectrum of the LED 7 W lamp for various supply voltage values [21]. For all tested individual lighting devices, the generated emission does not exceed the permissible limits specified in the European standards. The emission spectrum shift in the frequency domain occurs when the supply voltage level is changed within permissible limits. This shift is not linear and depends on the type of load. In most cases, it can be observed that the components of the spectrum, for the selected dominant emission bands, shift towards higher frequencies with the increase in the supply voltage level. It is important to note that the direction of change can change at times, such as for high supply voltage levels compared to the nominal value in CFL lamps (Case 1) or when there is no specific relationship between the change in supply voltage level and the shift in emission characteristics (Case 3).