Backup power switch
US4788450A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 11, 1987 |
| Grant date | Nov 29, 1988 |
| Priority date | — |
| Expiry date | Sep 11, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02J9/061
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A P-channel field-effect transistor includes an inherent junction diode. As it is normally used, the inherent diode is back-biased and therefore effectively out of circuit. An uninterruptible power supply arrangement including primary and backup voltage sources supplies uninterrupted power to a load by way of two or more P-channel field-effect transistors connected so that their inherent diodes conduct to provide an OR function, independent of field-effect operation of the field-effect transistors. A control circuit controls the gate voltage relative to the source voltage of each transistor to selectively short-circuit the inherent diode of that one transistor which is connected to the power supply which is to energize the load. This reverse-biases the other inherent diodes and effectively removes the other power supply from the circuit, so that power for the load is drawn only from the selected power supply, there is no diode forward junction potential reducing the load voltage, and no excess dissipation. Certain embodiments of the invention use commercially available integrated circuits to provide many of the required functions for the uninterruptible supplies.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.