| 摘要 |
A motor drive including an input for alternating current, a rectifier circuit, an inverter, an output which provides the controlled alternating current to drive a motor; and an active EMI filter for eliminating common mode noise in the motor drive which employs a magneto-resistive sensor. In the filter, a pair of lead frame bars which are connectable to the current path of the motor drive and an MR sensor in the form of a Wheatstone bridge are fabricated on a semiconductor die, with the bridge in contact with and straddling the lead frame bars. The bridge elements are so oriented that opposed elements in the bridge are responsive to changes in magnetic flux in a first sense to exhibit an increase in resistance, and adjacent elements in the bridge are responsive to changes in magnetic flux in a second sense opposite to the first sense to exhibit an increase in resistance. This allows the lead frame bars to be connected in such a manner that the common mode noise signals in the motor drive current path cause flux variations which reinforce the sensor output, while flux variations associated with other signals tend to cancel.
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