Research Of Photo Biological Safety Of LED Lighting

With the rapid development of LED lighting,LED lamps is gradually replacing the traditional incandescent lamps and fluorescent lamps and the market penetration of LED is high.But there have some research showed that most of white LEDs are made from blue light LEDs inspired yellow phosphor,so it may be lead to blue light hazard to eyes.Due to the electrical characteristics of the LED and it’s driver circuit,it’s likely to cause flicker effect.So according to the standard files(IEC/EN 62471:2008 ‘Photo biological safety of lamps and lamp systems’ and ’Energy Star Lamps V1.0 draft 4’)which were set by the International Electrotechnical Commission(IEC)and American Energy Star.We mainly describe the photo biological safety of LED lighting in this master’s thesis.On one hand,we tested the Photo biological safety and flicker effect of automotive head lamp including halogen lamp(Philips H7)and LED(LED Headlight 2S from German company named KEM).Then,we compared and analyzed the result of the experiments.Through the experiment,we found that the blue light hazard of LED headlight is 2.2 times of the traditional halogen headlight,and the near ultraviolet hazard and retinal heat hazard of the LED headlight is worse than traditional halogen headlight.The LED headlight is belonging to the one level of hazard.On the other hand,many school replaced the traditional fluorescent lamp with LED panel light,so we tested the photo biological safety and flicker effect of LED panel light.Through test,we found that the blue light hazard,the near ultraviolet hazard and retinal heat hazard of this type of LED panel light is conform to the standard,so it belong to no hazard type lamps.However,when we test it’s flicker features,we found that it’s flicker depth was equal to 1.13%,the frequency of flicker was equal to 100 Hz which were less than 120 Hz that set by American Energy Star.So,the LED panel light will produce flicker effect.Aimed at the experimental results of photo biological safety of LED light which are used in indoor and outdoor in early stage,we proposed a method to improve the photo biological safety of LED light.The specific approach is to mix the low color temperature and high color index white LEDs with different color temperatures.Through the experiment and theoretical calculation,we researched the change conditions of the color temperature,color rendering index and blue light hazard.We adopt the method of mixing three different low color temperature(2200 k,2700 k,4000 k)white LEDs,the experimental results show that this method can improve the color rendering index and decrease the blue light hazard.Based on the experimental result of mixing white LEDs,we made a reading lamp which meet standard requirements.we designed the light source of reading light with eight LEDs of 4000 k and eight LEDs of 2700 k.We adapt the form of lithium batteries at power part.It can implement three-step dimmer through the way of PWM.The reading light we designed was meet the human comfort and meet the IEC/EN 62471:2008 ‘Photobiological safety of lamps and lamp systems’ and ’Energy Star Lamps V1.0 draft 4’.