Active EMI filter having no inductive current sensing device

DETAILED DESCRIPTION The proposed topology has a voltage input instead of a current sensing device to capture the common mode noise current to be canceled.
Instead of current sensing as in the prior art, an error amplifier senses the voltage difference between one of the AC lines and ground.
The amplifier has a certain amount of impedance, which induces a voltage due to the noise current.
The error amplifier creates a canceling current by amplifying the voltage difference between the line and ground.
The canceling current is supplied to the ground line to compensate for the common mode noise current.
The amplifier has three inputs, the voltage input and two current inputs.
The second input detects current at the output isolation capacitor.
The third input is provided for improving high-frequency response.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.