## 5 Discussion  
A comparative study (including wavelength, optical power, viewing angle, and operating current) of the utilized UV-C LED sterilization and germicidal module in ref. [26] in comparison with the one utilized in this paper is presented. Table 4 illustrates a comparison between the UV-C LED sterilization and germicidal module in [26] and the module utilized in this paper. As can be seen from Table 4, the UV-C LED sterilization and germicidal module utilized in this paper has similar wavelength, viewing angle, and operating current compared with the module in [26]. In addition, the UV-C LED sterilization and germicidal module used in [26] has higher optical power. In this investigation, the proposed driver circuit is studied in comparison with the driver circuit in the reference literature [26] (including circuit structure, DC-input voltage, output power (output voltage/current), measured circuit efficiency, and number of circuit components required). Table 5 compares the existing DC-DC LED driver from [26], a  
Figure 17: Experimental waveforms of output voltage \(V_{O}\) (5 V/div) and output current \(I_{O}\) (200 mA/div); time scale: 10 \(\upmu\)s/div. Figure 18: A photograph of supplying the experimental UV-C LED lamp for sterilization and germicidal applications with a prototype driver circuit applied to a DC-input voltage source of 18 V.  
Cuk converter that delivers 7.5 W of rated power (75 V/0.1 A) from a 48 V DC input, with the proposed design, a modified buck-flyback converter that provides 3.3 W of rated power (10 V/0.33 A) from an 18 V DC input. As can be seen from Table 5, the proposed DC-DC LED driver circuit has one more diode and saves one capacitor and one magnetic component compared to the driver circuit in [26]. In addition, the measured efficiency of the proposed DC-DC LED driver circuit is 91.22%, which is slightly lower than the measured efficiency of 91.69% of the existing driver circuit in [26]. The proposed DC-DC power supply can provide UV-C LED lamps on a DC-input voltage source for sterilization and disinfection applications. The novelty and advantages of the proposed DC-DC power supply are compared with those of the existing power supply in [27] (including the circuit structure, DC-input voltage, output power (output voltage/current), measured circuit efficiency, and number of circuit components required). A comparison between the existing DC-DC LED driver of [27], which is a modified buck converter utilizing coupled inductors to deliver 8 W of rated power (8 V/1 A) from a 12 V DC input, and the proposed DC-DC LED driver of [27], which is a modified buck-flyback converter that delivers 3.3 W of rated power (10 V/0.33 A) from an 18 V DC input, is shown in Table 6. From Table 6, it can be seen that the proposed DC-DC LED driver circuit saves one diode compared to the circuit in [27]. Additionally, the measured efficiency of the proposed DC-DC LED driver circuit is 91.22%, which is slightly higher than the measured efficiency of 91% of the existing driver circuit in [27]. In addition, ref. [29] developed a driver circuit which consists of a buck converter combined with a flyback converter to provide 72 W (36 V/2 A) of output power to an LED streetlight module at a DC-input voltage of 48 V. In this paper, we propose a driver circuit which consists of a modified buck converter and a flyback converter to provide a 3.3 W power rating (10 V/330 mA) to a UV-C LED sterilization and germicidal lamp at a DC-input voltage of 18 V. The design concept of this paper is similar to that of ref. [29] and the difference between the two manuscripts lies in the location of the two output capacitors. In ref. [29], the positive polarity of the upper output capacitor located on the