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LED strobe test method

Update:10 Nov 2018
Summary:

Check and discriminate whether the LED light source and […]

Check and discriminate whether the LED light source and the luminaire have strobe? The simple method is to turn on the camera's camera function to observe the LED light source at a close distance. If the light source has obvious black stripe scrolling or light and dark changes on the screen, you can conclude that there is stroboscopic.

For the characteristics of LED strobe, the following conditions must be met when performing stroboscopic measurement:

1) The photoelectric conversion detector used must have a fast response speed and can be quickly sampled;

2) The detector must be able to simulate the curve of the human eye's light, that is, the curve of the visual function, which can simultaneously measure the illuminance or brightness;

3) With software calculation function.

According to the above requirements, the current instrument for measuring stroboscopic light is a photometer. The ambient temperature during the test should be controlled between 20 and 30 °C. The photometer price is cheaper than the spectrometer, but it can only measure one wavelength at a time, but it is enough in the strobe. Because in the visible light band, for the same luminaire, the change in light intensity is synchronous and proportional. In a switching cycle, we only need to measure the luminous flux curve of a specific wavelength, calculate the fluctuation depth according to the peak and valley values, and calculate the average luminous flux (using the integral method to obtain the area S of one cycle in Figure 1) The average luminous flux is obtained by dividing the period length T, and then integrating the Q1 region, Q2 = S - Q1, and the stroboscopic index can be calculated from Q1 and Q2.

In addition, there are currently a variety of stroboscopes dedicated to testing the strobe of the light source. The specific data of the stroboscopic parameters can be read directly from the instrument, which can be roughly divided into three types: handheld (such as SFIM-300 spectrum). The flashing illuminometer), the desktop touch screen can be directly displayed (such as the LFA-2000 source strobe tester), and the desktop needs to be connected to the PC end plus software test (such as PM2000).

Ways to solve the strobo problem

Due to the characteristics of the electric light source, it is difficult to completely eliminate the stroboscopic light. To reduce the LED strobe, it is fundamentally dependent on the LED driver.

At present, the LED power supply can be achieved simply by satisfying the requirement of no stroboscopic.

There are roughly three ways:

1. Increase the output electrolytic capacitor;

2. Adopting a valley filling passive PFC scheme;

3. Adopt a two-stage solution (AC to DC, DC to DC).