High-tech trick: noise suppression method for thyristor dimming

SCR is a very important part in LED lighting design. With the increasing use of thyristor dimming in the lighting market, it is inevitable that there will be problems with excessive noise. This article mainly explains the noise suppression method of thyristor dimming, which can be controlled within one meter and is difficult to detect.

When using the isolated flyback ICMP4033, the use of thyristor dimming will reveal noise, the transformer has been immersed in the paint, and after the differential mode inductor is removed, there is still noise. What is this?

The first thing to be clear is that it is almost impossible to completely eliminate the noise in the thyristor dimming. But this does not mean that noise cannot be suppressed. The noise can be controlled to a level that is difficult to detect within 1 meter by a certain method. Here, it is necessary to consider the impact current of the AC at a phase angle of 90 degrees after the phase change of the dimmer. The use of a reasonable RC damping circuit (R7 & C1 in Figure 1 and R1 added in the LN circuit) will be improved. The differential mode inductor and the post-bridge LC filter inductor in Figure 1, as well as the transformer need vacuum impregnation, may even require secondary impregnation to improve. PI's LYT series of original DATASHEET has some details for reference. This article introduces the readers to the ideas and methods of thyristor dimming noise suppression. There are many ways to suppress noise in the circuit design process. Xiaobian will continue to collect more relevant knowledge for readers. I hope everyone can gain something after reading this article.