Influence of LED power supply ripple on LED lighting

In the traditional power supply, the large electrolytic capacitor is used to store energy, which provides the DC voltage to the switching stage. But the disadvantage is that it can not provide power factor correction, and electrolytic capacitor is also known as the bottleneck of life. Generally only for the following occasions 5W.

As the LED driver power supply will contain a certain amount of switching power supply ripple (ripple), then how to look at and deal with the LED power supply output ripple it? The lighting Research Council (LRC) study shows that the flicker of the LED lighting is related to the frequency, and the acceptance range of the stroboscopic effect is presented:

The results show that the output current ripple has no significant effect on the LED heating, and has no significant effect on the power conversion efficiency of LED lamps.

The output current ripple is closely related to the selected power supply topology. In the traditional power supply, the large electrolytic capacitor is used to store energy, which provides the DC voltage to the switching stage. But the disadvantage is that it can not provide power factor correction, and electrolytic capacitor is also known as the bottleneck of life. Generally only for the following occasions 5W. The output current ripple is closely related to the selected power supply topology.

In the traditional power supply, the large electrolytic capacitor is used to store energy, which provides the DC voltage to the switching stage. But the disadvantage is that it can not provide power factor correction, and electrolytic capacitor is also known as the bottleneck of life. Generally only for the following occasions 5W.

A new type of switching power supply with PFC function to improve the power factor, improve power efficiency and extend the life of the power supply. For example, single stage PFC correction constant current output (CC) topology can produce the highest conversion efficiency (>92%). However, the output ripple of this topology is high, and it is concentrated in the range of 120Hz (100Hz).

In order to reduce the ripple effect on the LED (flicker), some of the provisions of the provisions of the LED power supply ripple ratio, such as Japan, a certain standard ripple ratio is less than 4%. In addition, some specific applications (such as photography) also need to ripple control at a certain level.

Another method is to inject the primary side of the power supply IC feedback side, the output ripple can be reduced by about 25%, but the consequences of doing so is to reduce the PF (~0.7), the overall conversion efficiency of the power is not affected. Active ripple current filter (ARF) can be used to reduce the ripple to 8% or less, which is the electronic filter realized by the transistor. Due to the insertion loss of the filter, the conversion efficiency of the power supply will be reduced by about 5%.