吸收电容对LED电源EMI的抑制实例分析

Case Study on Suppression of Absorption Capacitor to EMI of LED Power Supply

根据LED驱动电源的认证经验,其EMC测试项目中的电源端子骚扰电压和30~300 MHz辐射骚扰场强测试项目不容易合格,而且经过整改往往会增加电源成本。以一款单端反激式LED驱动电源为例,首先,介绍了单端反激式开关电源的工作原理;然后,探讨开关管MOSFET的漏极和源极并联小容量吸收电容后对驱动电源EMI的影响。通过对比测试结果发现,吸收电容的加入对原测试不合格的LED驱动电源起到了良好的EMI抑制作用,最终使得产品符合标准要求。此方法操作简单,成本低廉,为整改工程师提供参考。

From the experience of LED power supply certification, we found that the disturbance voltage at mains terminals and the 30-300 MHz radiated disturbance of EMI test items were not easy to be qualified, and the rectification would increase the power supply’s cost. In this paper,with a single-ended flyback LED power supply as an example, we firstly introduced the singleended flyback power supply principle. Secondly, a small snubber capacitance was added between the drain and source of MOSFET to restrain the power supply’s EMI level. By comparing the test results, it is found that the power supply, which was failed previously, met the standard requirements after adding the snubber capacitance. This method is simple and lowcost, and provides a reference for the rectification.