Circuit Board Capacitor Filter for Common Mode Noise

The patent extracts the common mode coil from the common mode filter configuration, using only capacitors (first and second capacitors) to form the filter circuit. This extraction eliminates the need for the bulky coil component while maintaining noise filtering functionality through the capacitor-based design connected between power source terminal portions.

The patent changes the filtering mechanism from inductor-based (common mode coil) to capacitor-based (first and second capacitors). By changing the fundamental parameter of the filtering component from inductance to capacitance, the design achieves noise reduction without requiring the physical space of a coil, thus reducing the overall device size.

The patent introduces an intermediary structure: a conductor plate connected to the first and second capacitors, which mediates the electrical connection and provides a reference potential. This intermediary element enables the capacitor-based filter to effectively suppress common mode noise by providing a stable reference point, compensating for the absence of the common mode coil.

The first and second capacitors serve multiple functions: they act as filtering elements for common mode noise suppression, provide electrical connection between power source terminal portions, and establish reference potentials. This multi-functionality allows the design to achieve noise reduction without requiring additional dedicated components like the common mode coil.