How to effectively test the LED stroboscopic effect

- Nov 07, 2018 -

How to effectively test the LED stroboscopic effect

LED solid-state lighting products are increasingly favored by the market and consumers because of their unique luminous efficiency, long life and high reliability. But at the same time, because LED response speed is fast, and it does not have the thermal inertia and afterglow effect of traditional lamps, it is deeply affected by current fluctuations. The fluctuation of current directly affects the output of luminous flux. The flashing of light source is the external manifestation of the change of luminous flux, so The flashing problem of LED lighting products has also attracted everyone's attention.


On December 14, 2012, the European Union officially issued the (EU) NO 1194/2012 Regulations in the Official Gazette of the European Parliament and Council Directive No. 2009/125/EC on Directional Lights, LED Lights Implementation Rules for Ecological Design Requirements for and Related Equipment. Corresponding to the European Commission Regulation (EC) NO 244/2009, issued on March 18, 2009, the European Parliament and Council Directive 2005/32/EC on the implementation of the ecological design requirements for non-directional household lamps, At this point, the EU has formed a complete mandatory ecological design requirement for LED lights. Start-up time and rise time are two indicators of functional requirements, which are increasingly valued by manufacturers in the industry.

The flicker effect of LED lighting products, the essence of the light source flicker is the fluctuation of luminous flux. The substantial light source is driven by AC or pulsed DC, and the luminous flux, illuminance or brightness change correspondingly with the periodic variation of the current amplitude. The subjective response of the brain to this change. Usually flicker is divided into Visible Flicker and Invisible Flicker according to human feelings. When the frequency is greater than 100 Hz, the human eye does not feel the flicker phenomenon, but it still causes eye fatigue, headache, etc. This is the color flash effect, which is generally considered to exist within 500 Hz. For this ENERGY STAR lamps V1.0 draft 4, the requirements for flicker are specified in the requirements of dimming performance, and are used in all lamps. As shown in the following figure:


light source of the world

The range allowed for the light source to flash is:


1. The frequency is not less than 120Hz;


2. In the frequency range of 120Hz-800Hz, F1<0.001 X frequency


3. When the frequency is greater than 800 Hz, there is no requirement for F1;


4. When the frequency is uncertain, PF<30%;


In addition, the compact fluorescent light output frequency needs to be 20-30KHz, or greater than 40KHz.


The essence of the flashing of the light source is the instability of the luminous flux. When detecting the fluctuation of the light source with time, you can test the curve of the brightness and the curve of the luminous flux or illuminance under the same conditions. ENERGY STAR (V1.0) specifies the measurement requirements for flicker flicker:


1. Power supply and measuring instruments must meet the requirements of LM-79-08;


2. Multi-channel oscilloscope with storage function, if necessary, add attenuation probe. The sampling rate is greater than 2 kHz, and the sampling time is greater than 100 ms;


3, photometric probe, V (in) calibration, and the corresponding time needs to meet the requirements;


4. For absolute photometry: measuring the absolute value requires an integrating sphere; for relative photometry: ensuring that the detector can measure the relative light output and only accept light from the source to be measured.


Before the measurement, the compact fluorescent lamp needs to be aging for 100 hours, and it needs to be preheated before measurement. LED lights do not need to be aging, the ambient temperature is 25 +/- 5 degrees.