## 4 Parameters Design and Experimental Results
### Experimental Results  
Table 2 shows the component parameters of the prototype LED driver. In practice, it is not easy to produce a coupled inductor whose mutual inductance and leakage inductance meet the design values at the same time. Therefore, in this prototype circuit, first, a coupled inductor with a mutual inductance equal to 16.54 mH was implemented, and then two small inductors were, respectively, connected in series with the two windings of this coupled inductor. In addition, the sum of the leakage inductance of the coupled inductor and the inductance of each small inductor is equal to 1.84 mH. \begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Value** \\ \hline Low-pass filter \(L_{f}\), \(C_{f}\) & \(L_{f}=0.5\text{ mH}\), \(C_{f}=2\text{ }\mu\text{F}\) \\ Diodes \(D_{r1}\)–\(D_{r4}\) & MUR460 \\ Diodes \(D_{1}\)–\(D_{2}\) & C3D10060A \\ PFC inductance \(L_{p1}\), \(L_{p2}\) & 0.58 mH \\ DC-link capacitance \(C_{B1}\), \(C_{B2}\) & 100 \(\text{ }\mu\text{F}\) \\ Mutual inductance \(L_{m}\) & 16.54 mH \\ Leakage inductance \(L_{l1}\), \(L_{l2}\) & 1.84 mH \\ Output capacitance \(C_{o}\) & 100 \(\text{ }\mu\text{F}\) \\ Active switches \(S_{1}\), \(S_{2}\) & IPW65R080 CFD \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Component parameter. Figure 5 shows the control voltages of the two active switches. As shown in the figure, the duty cycles of \(v_{GS1}\) and \(v_{GS2}\) both exceed 0.5, so both \(S_{1}\) and \(S_{2}\) are in a conductive state for a certain period of time. Figure 6a shows the inductor current waveforms of two PFC converters for several input voltage cycles. It can be seen that the envelope of the inductor current follows the input voltage to be a sinusoidal waveform. The peak value of the inductor current is high at high input voltage, and vice versa. Therefore, the time required for the inductor current to decrease from a peak value to zero is not the same. When the input voltage is at a high point, it requires more time for the inductor current to decrease from a peak value to zero. It can be concluded that if PFC converters can operate in DCM when the input voltage is at its peak point, then they can operate in DCM throughout the input voltage cycle. Figure 6b shows the expanded waveforms when the input voltage is near the peak value. As shown, the inductor current does decrease to zero. Figure 7a shows the waveforms of input voltage and input current. It can be seen that the input current follows the input voltage and is in phase with the input voltage. A power analyzer was used to measure the power quality of the input line. At rated power operation, the values of the active power, reactive power, and apparent power were 196.7 W, 34.5 Var, and 199.7 VA, respectively. The measured power factor and THDi are 0.985 and 5.27%, respectively. The specifications of the proposed LED were measured. Figure 7b shows the harmonic spectrum of the input current. The current harmonics are compared with the IEC 61000-3-2 Class C standard [6]. It can be seen that all measured current harmonics are below the standard. It verifies that operating a boost converter in DCM can indeed achieve a high power factor and low THDi. Figure 8 shows the current waveforms in the two windings of the coupled inductor. As mentioned in the section on analysis of operation mode, Mode 3 is the time to discharge the parasitic capacitance from high voltage to zero volts, and Mode 4 is the time for the inductor current to rise from zero to greater than the absolute value of the inductor current. Generally, the parasitic capacitance is very small. The typical output parasitic capacitance of the active switch (IPW65R080 CFD, Infineon Technologies, Neubiberg, Germany) is 215 pF. Therefore, the time required for Mode 3 and Mode 4 is very short. The mutual inductance current is converted between the primary and secondary windings. When the current in one winding decreases, the current in the other winding increases. Additionally, the winding current will drop to a negative value.