The Study On The Optoelectric And Colorimetric Properties Of1W White LEDds Under PWM Pulse Drive

As the fourth generation lighting source, white LED has been widely used in the different illumination fields due to its energy-saving, environmental protection, long lifetime and convenient regulation. However, the reliability and long lifetime of LED chips still depend on the adopted proper drive mode. This subject mainly studies the photoelectric properties of white LEDs under the pulse drive and constant current drive.Firstly, we introduce simply the development history, performance properties, and drive modes for white LED and the significance of the research subject.Then, a pulse drive power source with adjustable duty ratio is designed based on the principle of PWM (pulse width modulation), and a lot of simulations and measurements are conducted. We devise an experimental method that can measure accurately the peak current of pulse driver LED. And the actual power consumption of pulse driven white LED with different duty ratio is obtained based on this measurement method. Then, the same batch of white LED is driven under the pulse source and constant source, respectively, and20observers are selected to estimate the brightness under the same dark condition. In the case of keeping the pulse parameters constant, adjust the constant current drive parameters, and record the constant current drive power when the visual luminance are considered to be equal. Then, take the mean value to avoid the individual difference in the visual luminance. At last, when the visual luminance is considered to be equal, the optoelectric and colorimetric properties of white LEDs under the two drive modes are analyzed contrastively, including the luminous flux, luminous efficiency, color purity, etc. The phenomenon that pulse drive can enhance the visual luminance of human eyes can be well explained based on the discussion and analyzation of the experimental results. It proves that pulse drive not only can raise the current density saturation point of LED chip, but also enhance the stimulation response of human eyes to LED luminance.