AC Current sensing circuit
US4677536A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 17, 1986 |
| Grant date | Jun 30, 1987 |
| Priority date | — |
| Expiry date | Mar 17, 2006 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B70/10
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An alternating current sensing circuit for sensing the current supplied by a power supply of an electronic instrument includes an isolation transformer and at least one transistor connected across the secondary winding of the transformer. The isolation transformer provides galvanic isolation between the power supply and internal feedback circuitry that controls the power supply located within the instrument. The transistor clamps the secondary voltage on the transformer to a constant magnitude when the base-emitter junction is forward biased. In response to the sensed current, the secondary current of the transformer flows through the transistor when the base-emitter junction is forward biased to produce the constant secondary voltage. The secondary current provides a current sensing signal which is transmitted to the feedback circuitry. The low, constant secondary voltage enables the transformer to maintain its range of frequency response and thereby accurately transform the sensed current to a secondary current that provides the current sensing signal to the feedback circuitry.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.