The research on non flicker is the most intuitive from the perspective of power supply. In fact, it is about the issue of "frequency". Both ultra-high frequency human eyes and CCD probes do not feel it, while low-frequency human eyes and CCD probes will have a direct feeling. The way to achieve flicker free output is either to achieve ultra-high frequency DC output, or to truly remove or reduce the ripple content in the DC.

In 2014, the LED lighting market had already formed a booming trend, and constant current driving power supply, as the standard configuration for LED lighting fixtures, will be the most fiercely competitive market. Intelligence is not the current focus of competition in the market. From the perspective of traditional enterprise patterns, power supply manufacturers are still leveraging their competitive advantages in terms of price, delivery time, quality, and after-sales service to strive for development

Nowadays, people do not lack understanding of new technologies, making it difficult to choose suppliers that are suitable for them in the face of a variety of product technologies. Today, let's discuss the basic knowledge of the application of flicker free technology in the field of LED civilian lighting.

1. What is strobe?

Stroboscopic and stroboscopic effects are two mutually causal physical quantities that affect the depth of fluctuations in light flux and the magnitude of the resulting harmful effects (known as stroboscopic effects) of an electric light source. Stroboscopic refers to the depth of fluctuation in the luminous flux of an electric light source. The deeper the fluctuation of luminous flux, the more severe the flicker.

The flicker ratio is equal to the difference between the maximum and minimum light outputs within a switching cycle divided by the sum of the maximum and minimum light outputs. The flicker index is equal to the amount of excess light output in one switching cycle divided by the total light output.

The depth of fluctuation in the luminous flux of an electric light source is directly related to the technical scheme of the electric light source.

2. How to test strobe?

The human eye is not sensitive to flickering above 60Hz, and the output frequency of LED constant current power supply is generally 100Hz or above. When shooting with CCD photosensitive imaging (mobile phones, cameras), water ripples may appear due to different sampling frequencies. However, it is related to the preset frequency, photosensitive components, and shutter speed of mobile phones and cameras, so this testing method may not be accurate, but it is a simple testing method.

The traditional testing method is to rotate the black and white gyroscope under sunlight, and the pattern will form a stable circular shape. The color ring will not change with the rotation speed and direction. Under the tested illumination, rotate the black and white gyroscope and observe the phenomenon: if the color or circular structure of the pattern changes, it indicates the presence of flicker in the illumination, and the more obvious the change, the more severe the flicker. This method cannot make an accurate assessment of the depth of the strobe.

The most scientific testing method is to use a Light Flickering Analyzer, whose core is an ultra fast photometer with a sampling frequency of 10kS/s (tested 10000 times per second). Scan the emission curve of the luminescent object (similar to an oscilloscope) and calculate parameters such as scintillation index to obtain the depth of light fluctuation (light ripple coefficient).

3. What kind of flicker depth is acceptable?

There is no need for flicker, and it is developed specifically to meet the needs of the market. At present, there are clear technical requirements in the US regulations, but most markets do not have a unified standard to strictly require the flicker depth of light sources. At present, some customers require a fluctuation depth of less than 8%, some require a fluctuation depth of less than 5%, and some even require a fluctuation depth of less than 1%.

4. What is the technical approach to achieving flicker free technology?

LED lighting products are driven by AC-DC DC constant voltage or constant current power supply, and the light source itself will not affect the flicker characteristics. The presence or absence of flicker in the output light depends on the design scheme of the LED driver power supply.

It is worth noting that the presence or absence of flicker is not the basis for evaluating the quality, reliability, and quality of LED driver power supplies. It only makes the light quality of lighting products healthier. So, to achieve flicker free LED lighting products, the fundamental lies in the design of LED driver power supply solutions.

Under the current technological background, there are several technical approaches to achieve flicker free technology:

Option 1: Passive PFC+valley filling circuit

Option 2: Adopting a two-stage approach, active PFC correction+flyback converter

Option 3: BUCK circuit without PFC correction

Option 4: LED power supply DC end series connection ripple removal (no flicker) dedicated IC

Option 5: LED power supply DC terminal series linear constant current circuit