Circuit for measuring current in class-d amplifiers
US5629616A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 13, 1995 |
| Grant date | May 13, 1997 |
| Priority date | — |
| Expiry date | Jul 13, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R31/2825
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.