| 摘要 |
An active EMI filter for reducing common mode noise current in a circuits, comprising: a transistor stage having two transistors coupled in series, a current sensor for sensing the common mode noise current, the current sensor having an output driving the transistor stage, whereby each of the transistors is driven in response to the common mode noise current, a capacitor coupling the transistor stage and the ground return line, the capacitor providing a cancellation current to cancel the common mode noise current, the current sensor comprising a current transformer having a primary coupled with the circuit having the common mode noise. The current sensor and the transistor stage may be coupled in a feed forward arrangement wherein the transistor stage and the current sensor have an amplitude gain of approximately unity; or in a feedback arrangement wherein the transistor stage and current sensor provide high gain.
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