# A New Circuit Design of AC/DC Converter for T8 LED Tube
## 4 Experimental Results  
A 10 W prototype of the LED converter was designed to perform the experiments, as shown in Figure 5. The input voltage is 100-240 VAC and the line frequency is 50 Hz and 60 Hz. The output current is 87 mA, and output voltage is 106 V with 35 LEDs in series to satisfy the luminous uniformity. Table 2 shows the specifications of the key components. Figure 6 shows the input voltage and current waveform of the proposed LED converter. The input current waveform follows the input voltage, which means it operates properly for power factor correction. Since the PFC operation is not affected by the output ripple eliminator, there is no difference in the power factor between the reference converter and the proposed converter. \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{1}{c}{Fuse} & 250 V, 1 A \\ \cline{2-3}  & Line Filter & TOROIDAL, 31 uH, 4 A \\ \cline{2-3}  & X-capacitor & 275 VAC, 100 nF \\ \cline{2-3}  & Bridge Diode & VRRM = 1000 V, IO = 1 A \\ \cline{2-3}  & Film Capacitor & 600 V, 100 nF \\ \cline{2-3}  & PCB & CEM-3, 1T, 0.5 oz, Single Layer \\ \hline  & Film Capacitor & 630 V, 100 nF \\ \cline{2-3}  & Inductor & EE1616, 1.38 mH \\ \cline{2-3}  & Electrolytic Capacitor & 400 V, 22 uF, 105 \({}^{\circ}\)C \\ \cline{2-3}  & \multirow{2}{*}{EC Driving Circuit} & \multirow{2}{*}{FET} & VDSS = 800 V, ID = 2.5A, \\  & & RDS(ON) \textless{} 4.5\(\Omega\) \\ \cline{2-3}  & Diode & VRRM = 1000 V, IO = 1 A \\ \cline{2-3}  & PCB & FR-4, 1T, 0.5 oz, Double Layer \\ \cline{2-3}  & Darlington Transistor & NPN, VCE 100 V, IC = 10 A \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Specifications of key components. Figure 5: (a) AC driving circuit, (b) DC driving circuit, (c) LED module with the output ripple eliminator. Figure 7 shows the measured waveform of the output voltage, output current, and light output at 240 VAC/50 Hz. The light output waveform measured with the photosensor amplifier contains a double line frequency ripple in the reference converter without an output ripple eliminator. However, with the proposed converter, the light flicker is completely removed and the result is almost a straight line. Using Equation (1), the percent flicker can be calculated in each input condition. Table 3 shows the calculated percent flicker of the reference and the proposed converter which are 13.5% and 1.9%, respectively. When using the output ripple eliminator, the light flicker almost disappeared, and the percent flicker of the proposed converter with the output ripple eliminator was improved by 11.6% on average. Figure 6: Input voltage waveform (red) and input current waveform (blue) (a) at 100 VAC/60 Hz, (b) 100 VAC/50 Hz, (c) 240 VAC/50 Hz, (d) 240 VAC/50 Hz. Figure 7: Waveform of the output voltage (dark yellow), output current (blue) and light output (green) of the (a) reference converter, (b) proposed converter. Figure 8 shows power efficiency and efficiency difference according to the input voltage measured at 50 Hz. There is no big variation according to the line frequency. The power efficiency of the proposed converter is 2.6-2.9% lower than that of the reference, which means the output ripple eliminator consumes less than 2.6-2.9% of power. Although the total power increases 2.7% on average, the power efficiency is still more than 87% in 100-240 VAC, and the light flicker can be completely removed. Figure 9 shows the measured output current of the reference and proposed LED converters, which was measured using an LED module with 35 LEDs in series. The measured data of the proposed LED converter is almost the same as that of reference, which shows that the output current regulation is hardly affected by the output ripple eliminator. The average output current and its standard deviation were 87.1 mA and 0.19 mA for the proposed LED converter at 60 Hz, respectively. The positive and negative maximum deviations from the average output current were measured as +0.3 mA (0.34%) and \(-0.2\) mA (0.23%) at 60 Hz.