signal which controls a warm white light of a low color temperature to be outputted so as to maintain a low color temperature from a sunset to a sunrise and output a control signal which controls the color temperature to gradually change from a low color temperature to a high color temperature in the morning and output a control signal which controls a cool white light of a high color temperature to be outputted so as to maintain a high color temperature at noon and output a control signal which controls the color temperature to gradually change from a high color temperature to a low color temperature from a noon and to a sunset more specifically the light source unit 130 may output a color temperature control signal to maintain a color temperature at about 2500k 3000k by turning on only the warm white light from a sunset to a sunrise increase the color temperature up to about 4500k 5000k by adjusting the warm white light and the cool white light of the light source unit 130 from a sunrise to the morning time maintain the color temperature at about 7000k 8000k at a noon by turning on only the cool white light and decrease the.