## 4 Experimental Results  
A prototype driver has been successfully implemented and tested for powering a 165 W-rated LED streetlight module (LMD003 from AcBel Polytech Inc., New Taipei City, Taiwan) with input utility-line voltages of 220 V \(\pm\) 5% (from 210 to 230 V). Tables 1 and 2 show the specifications and key components utilized in the presented single-stage LED driver for streetlight applications, respectively. Figure 7: Resonant capacitor \(C_{r}\) versus the switching frequency \(f_{s}\) under different levels of quality factor \(Q_{r}\). The measured waveforms of coupled inductor currents \(i_{LB11}\) and \(i_{LB22}\) are shown in Figure 8; both of which have interleaved features and operate in DCM. Figure 9 shows the measured switch voltage \(v_{DS1}\) and current \(i_{DS1}\); Figure 10 presents the measured switch voltage \(v_{DS2}\) and current \(i_{DS2}\); thus, ZVS occurred on both switches for lowering the switching losses. Figure 11 presents the measured switch voltage \(v_{DS2}\) and resonant inductor current \(i_{L}\). The current \(i_{L}\) lags with respect to voltage \(v_{DS2}\) so that the series resonant tank resembles an inductive load. Figure 12 depicts the measured output voltage \(V_{O}\) and current \(I_{O}\); their average values are approximately 235 V and 0.7 A, respectively. Figure 13 shows measured voltages on the diodes \(D_{B11}\) and \(D_{B22}\). The voltage spikes on \(D_{B11}\) and \(D_{B22}\) are approximately 360 V. In addition, the voltage rating of the diode (C3D10060) is 600 V. Therefore, the utilized diodes are capable of sustaining these voltage spikes. The measured waveforms of input utility-line voltage \(v_{AC}\) and current \(i_{AC}\) are shown in Figure 14, and the input current is in phase with utility-line voltage, which results in high power factor. In addition, experimental waveforms from Figure  
Figure 11: Measured switch voltage \(v_{DS2}\) (200 V/div) and resonant inductor current \(i_{Lr}\) (2 A/div); time scale: 5 \(\upmu\)s/div. Figure 10: Measured switch voltage \(v_{DS2}\) (200 V/div) and current \(i_{DS2}\) (2 A/div); time scale: 5 \(\upmu\)s/div. Figure 14: Measured input utility-line voltage \(v_{AC}\) (200 V/div) and current \(i_{AC}\) (2 A/div); time scale: 5 ms/div. Figure 12: Measured output current \(I_{O}\) (0.5 A/div) and voltage \(V_{O}\) (100 V/div); time scale: 2 ms/div. Figure 13: Measured voltages on the diodes \(D_{B11}\) and \(D_{B22}\). Voltage scale: 200 V/div; time scale: 5 μs/div. Figure 15 shows the measured input utility-line current harmonics comparing with the International Electrotechnical Commission (IEC) 61000-3-2 Class C standards at input utility-line voltages ranging from 210 to 230 V, and all current harmonics meet the requirements. Table 3 shows the measured output voltage ripple and current ripple of the presented LED streetlight driver among input voltages ranging from 210 to 230 V; additionally, the output voltage (current) ripple is obtained by the peak-to-peak level divided by the average value of output voltage (current). According to this table, the measured output voltage ripples and current ripples are smaller than 1% and 10%, respectively, during the tested input voltages. Figure 16 presents the measured power factor and current total-harmonics distortion (THD) of the presented LED driver under utility-line voltages ranging from 210 to 230 V. At a utility-line rms voltage of 220 V, the measured power factor and current THD are 0.992 and 6.55%, respectively. In addition, the measured highest power factor and lowest current THD are 0.993 and 6.5%; these occurred at a utility-line rms voltage of 230 and 210 V, respectively. Figure 17 shows the measured circuit efficiency of the presented LED driver under utility-line voltages ranging from 210 to 230 V; additionally, the measured maximum circuit efficiency is 91.23%, at a utility-line rms voltage of 210 V. In addition, the efficiency which drops with the increase utility-line voltages is related to the voltage gain of the LC series resonant tank.