# Designing Safe General LED Lighting that Provides the UVB Benefits of Sunlight
## 3 Methods: UVB LED General Lighting Design
### Overall Lighting Design Using the UVB LED Light Source  
IEC 62471 states that the stability evaluation of general lighting must be measured at an illuminance of 500 lux [27]. Further, considering that the average ceiling height of houses, apartments, and offices are 2.4-2.8 m, general lighting should be able to provide a brightness of 500 lux at a distance of 1.5 m. To this end, white multi-channel LEDs are used for such purposes. UVB LED light sources were utilized to provide UVB doses that are beneficial to the human body. LEDs can control the optical characteristics by adjusting the applied current output. LED light sources may be combined to form various types of lighting. Based on these characteristics, to control all LED light sources, a controller was developed so that the desired brightness and the UVB dose could be achieved. Figure 2 outlines the proposed lighting. Figure 2: Outline of indoor lighting with UVB LEDs. Two types of UVB LED light sources (LG InnoTek, Seoul, Korea) released in Korea were selected to provide safe UVB doses; their optical characteristics based on distances and applied currents were measured and analyzed. The two types of UVB LED light sources used in the experiment are shown in Table 3. The UVB LED light sources had an output power of 20 and 100 mW, respectively, and a current up to 350 mA could be applied. For the experiment, two test lighting modules combining 10 light source modules (each 20 mW UVB led or 100 mW UVB led) were developed. The light characteristics of the two UVB LED light source modules were measured from distances of 30, 60, 50, 90, and 150 cm, and the results are shown in Figure 3.  
Figure 3a,b show the results of the 20 mA UVB LED and the 100 mA UVB LED modules measured. Their irradiance decreased as the distance from the lamp increased. As expected for any light source, the irradiance of the 20 mW UVB LED module was 0.075 W/m\({}^{2}\) and 0.004 W/m\({}^{2}\) at 30 and 150 cm distances, respectively. The irradiance of the 100 mW UVB LED module was 0.326 W/m\({}^{2}\) and 0.017 W/m\({}^{2}\) at 30 cm and 150 cm distances, respectively. Further, considering the general lighting environment, the distance between the measurement equipment and the lighting was set to 150 cm; irradiance was then measured according to the adjustment of the applied current. Through increasing the applied current from 50 to 350 mA by 50 mA over seven phases, their UV characteristics were measured and analyzed. The results are shown in Table 4. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Model Name**} & **Size (L*W*H)** & **Peak** & **Optical Power** & **Maximum Current** \\  & **(mm)** & **Wavelength** & **(mW)** & **[mA]** \\ \hline LEUVA66G00 KV00 & 6.0 \(\times\) 6.0 \(\times\) 1.35 & 295–315 nm & 20 & 350 \\ LEUVA66H00 KU00 & 6.0 \(\times\) 6.0 \(\times\) 1.35 & 300–310 nm & 100 & 350 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specifications of UVB LEDs (LG InnoTek). Figure 3: Irradiance and spectral irradiance by distance step. (**a**) Measured results per wavelength increments: 100 mW UVB LED module; (**b**) measured results per wavelength increments: 20 mW UVB LED module; (**c**) irradiance calculation result by distance step. Although both modules used UVB LEDs, some of the optical characteristics of UVA were measured. However, the EUVA was close to 0 when the influence on the human body was weighted. Overall, it is expected that there will not be any harmful effects on the human body by UVA. In addition, the output of the applied current was proportional to the irradiance of UVB and EUVB, and it was confirmed that controlling the applied current can provide the required irradiance. The types and number of UVB light sources needed to support the synthesis of vitamin D were then selected. A previous study suggested that a EUV dose of 105 J/m\({}^{2}\) is required to meet 200 IU of vitamin D when 6-10% of the body (of Korean individuals) is exposed [26].