For outdoor lighting products, important evaluation factors were luminous efficacy, luminance, correlated color temperature (CCT) and Scotopic/Photopic (S/P) ratio. The higher the S/P ratio, the better the energy savings and visual performance. Recently color rendering properties of outdoor lightings gain interest, and parameters such as color fidelity (Rf), color gamut (Rg), and color quality scale (Qa) were proposed to replace color rendering index (CRI) because saturated lightings such as LEDs score lower values. However, as the S/P ratio is in trade-off relation with CRI, it is difficult to improve both of them simultaneously. In this paper, the change in S/P ratio and color rendering characteristics was confirmed through combination of multi-chip LEDs composed of RGB or RGBY or phosphor-converted LEDs consisted with warm and cool white LEDs by simulation and measurement.

First, CCT-tunable RGB or RGBY multi-chip LED lighting was fabricated on the Planckian locusand its characteristics were evaluated after optimization through simulating spectral combinations. Compared to the existing multi-chip LED lighting, the S/P ratio and color rendering characteristics have been improved. The RGB multi-chip LED lightings gave Ra>78, Qa>84, R9-14>59, Rf>82, and Rg>100 with S/P ratio values of 1.55, 1.73, 1.84, 2.07, 2.26, 2.34, 2.38, and 2.58 accordin to CCTs. Compared to the typical S/P ratios of IESTM-12-12, it was improved by 0.45 to 0.2. The RGBY multi-chip LED lightings offered Ra>85, Qa>87, R9-14>75, Rf>82 and Rg>97 with S/P ratios of 1.46, 1.52, 1.79, 1.91, 20.3, 2.17, 2.29, 2.46 for CCTs. Compared to the typical S/P ratios of IESTM-12-12, it is improved by 0.4 to 0.11.

Second, color rendering properties ans S/P ratio around the Plankian locus were investigated with different Duv ranges from the locus for each CCT. With the optimized RGB multi-chip LED lighting S/P ratio increased from 0.05 to 0.09 on the Duv-0.015 and decreased from 0.03 to 0.09 on Duv+0.015. On the other hand, Ra and R9∼14 decreased by 1∼4 on Duv-0.015, increased by 2∼6 on Duv+0.015, and Qa decreased with the changes of Duv. Rf and Rg increased as moving from Duv-0.015 to Duv+0.015. With the optimized RGBY multi-chip LED lighting S/P ratioincreased by 0.04～0.06 on Duv-0.015 and decreased by 0.03～0.08 on Duv+0.015. To the contrary, Ra and R9∼14 decreased by 1∼4 on Duv-0.015, increased by 1∼6 on Duv+0.015, and Qa decreased with the changes of Duv. Rf and Rg increased as moving from Duv-0.015 to Duv+0.015.

Third, 5,000 K phosphor-converted LED lighting was optimized by simulation and fabricated to evaluted S/P ratio and color rendering characteristics. The manufactured 5,000 K LED module gave a luminous efficacy of 140 lm/W, Ra of 96, R9∼14 of 94, Qa of 95, Rf of 91, Rg of 97. and S/P ratio of 2.22, which is higher by 0.18 than 2.04 of the IES TM-12-12

Fourth, a combination of WW-LED, CW-LED and single wavelength LED was silmulated and fabricated to evaluate the characteristics tracing the Planckian locus. Optical properties were Ra>86, Qa>89, R9-14>76, Rf>89, and Rg>86 with S/P ratios of 1.56, 1.63, 1.79, 1.87, 1.99, 2.06, 2.17, and 2.22 according to CCTs. S/P ratio was improved by 0.35∼0.66 than the typical value 1.21 of WW-LED and by 0.02∼0.18 than the typical value 2.18 of CW-LED in IES TM-12-12.

Finally, through the results of this paper design guideline for LED lighting system with high S/P ratio and color rendering properties for RGB LED, RGBY LED, phosphor-converted WW-LED and CW-LED, and CCT-tunable LED lighting composed of WW and CW-LED. By locating the position of LED lighting around the Plankian locus in the color chromaticity, optical characteristics can be changed according to the changes of Duv.