TEXAS INSTRUMENTS - How a stand-alone active EMI filter IC shrinks common-mode filter size
Automotive on-board chargers and server power supplies are highly constrained system environments where
power density is a primary metric. It’s important to reduce the volume of the electromagnetic interference (EMI)
filter components so that the solution can fit into demanding form factors.
Common-mode (CM) filters for these and other high-density applications often limit the total Y-capacitance –
related to touch-current safety requirements – and thus require large-sized CM chokes to achieve a target corner
frequency or filter attenuation characteristic. The result is a compromised passive filter design with bulky, heavy
and expensive CM chokes that dominate the overall filter size.
With advances in passive components lagging behind high-speed power semiconductor devices as well as
circuit topologies, the volume of the passive filter is one of the limiting factors for increasing power density.
Practical filter implementations can occupy as much as 30% of the total volume of a power solution, as shown in
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