Circuit for measuring current in class-d amplifiers

Details Circuit for measuring current in class-d amplifiers Circuit for measuring current in class-d amplifiers

1995-07-13

1997-05-13

Wieder, Kenneth A.

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

With coupling means

324117, 324726, G01R 3128

Patent

active

056296169

ABSTRACT:
A circuit accurately measures the current flowing in a load which is powered by a pulse-width modulated (PWM) arrangement. The current measurement circuit is transformer-coupled to the load. A first flux cancellation device produces a voltage which tends to reduce the flux in the transformer core to zero. A pair of peak detection circuits determine maximum and minimum voltages at the output of the first flux cancellation device, and another circuit measures the difference between the maximum and minimum voltages. This difference is a voltage which is proportional to the current flowing in the load. A second flux cancellation device includes an integrator which integrates the outputs of the peak detection circuits, and the output of the integrator is fed back to the first flux cancellation device. The second flux cancellation device compensates for flux creepage in the transformer, and tends to maintain the flux at zero, so that distortion is minimized, and so that one can use a small and inexpensive transformer.

REFERENCES:
patent: 4404623 (1983-09-01), Jourdan
patent: 4542440 (1985-09-01), Chetty et al.
patent: 4584635 (1986-04-01), MacInnis et al.
patent: 4912396 (1990-03-01), Groenenboom
patent: 5070292 (1991-12-01), Goff
patent: 5081409 (1992-01-01), Goff
patent: 5365422 (1994-11-01), Close et al.
patent: 5379209 (1995-01-01), Goff

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