Invention Grant
- Patent Title: Common-mode current cancellation with switching waveforms from isolated applications using a variable capacitor network
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Application No.: US15827588Application Date: 2017-11-30
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Publication No.: US10069400B1Publication Date: 2018-09-04
- Inventor: Larry D. Morgan, Jr. , Raymundo J. Medina
- Applicant: NATIONAL INSTRUMENTS CORPORATION
- Applicant Address: US TX Austin
- Assignee: NATIONAL INSTRUMENTS CORPORATION
- Current Assignee: NATIONAL INSTRUMENTS CORPORATION
- Current Assignee Address: US TX Austin
- Agency: Meyertons Hood Kivlin Kowert & Goetzel, P.C.
- Agent Jeffrey C. Hood
- Main IPC: H02J1/02
- IPC: H02J1/02 ; H02M1/12 ; H02M1/14 ; H02M1/00 ; H02M7/538 ; H02M1/44 ; H02M3/337 ; H02M3/07

Abstract:
A residual current (e.g. common-mode current) may be present in an isolated subsystem. The isolated subsystem may include the secondary winding of a transformer while a first subsystem may include the primary winding of the transformer. The first subsystem may also include a compensation circuit. A driver circuit may generate drive signals provided to the primary winding of the transformer and also to the compensation circuit. The compensation circuit may include a variable capacitor network (e.g. a variable capacitor diode network) that receives the drive signals and also receives a bias voltage, and generates a cancellation signal according to the drive signals and the bias voltage. The compensation circuit may provide the cancellation signal to the ground plane of the isolated subsystem through a capacitor that couples the variable capacitor diode network to the ground plane, in order to reduce or cancel the residual current present in the isolation subsystem.
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