平面耦合EMI滤波器电容和电感的确定

Determination for capacitance and inductance of planar coupling EMI filter

EMI滤波器是抑制传导电磁干扰的重要手段,但分立元件型滤波器由于其自身的缺点性能受到限制,而平面耦合型滤波器能够很好改善传统分立元件型EMI滤波器的缺点。在介绍平面耦合型滤波器结构的基础上,指出电感和电容参数是该类滤波器的最重要技术参数。通过对滤波器元件数值计算模型的建立和论证,说明共模和差模电容可以通过解析表达式计算;差模电感,即共模模块形成的漏感也可以采用解析表达式确定。但是,各线匝的电感由于与频率密切相关,无法采用对应的解析表达式确定。

EMI filter takes an important role in suppressing the conducted electromagnetic interference. However, the performance of the discrete EMI filter is restricted due to its own shortcomings. Planar EMI filter can well overcome the shortcomings of the traditional discrete EMI filter. Based on the introduction of the structure of planar EMI filter, this paper pointed out that the inductance and capacitance parameters are the most important specifications of such type of filters. By the establishment and verification of the numerical calculation model of the filter components, the common mode and differential mode capacitance can be calculated by the analytical expression. Differential mode inductance （leakage inductance of common- mode module） can also be determined by analytical expressions. However, the inductance cannot be determined by the corre- sponding analytical expression due to the close relationship between the inductance and the frequency.