An AEF circuit for CM noise mitigation fundamentally either amplifies the apparent inductance of a CM choke or the apparent capacitance of a Y-capacitor over the frequency range of interest. A VSCI AEF circuit configured for CM attenuation uses an amplifier stage as a capacitive multiplier of the inject capacitor, C_INJ. This higher value of the active capacitance supports lower values for the CM chokes to achieve a target attenuation. More specifically, the amplified Y-capacitance enables a reduction of each CM choke inductance by up to 80% (while keeping the filter corner frequencies effectively unchanged), resulting in lower size, weight, and cost of the CM chokes.

Capacitive multiplication of the inject capacitance occurs over a relevant frequency range for low- and mid-frequency emissions, while not impacting the value at low frequency applicable for touch current measurement. The total capacitance of the sense and inject capacitors (highlighted in yellow in Figure 9-2) is kept less than or equal to that of the replaced Y-capacitors in the equivalent passive filter, which results in the total line-frequency leakage current remaining effectively unchanged or reduced.