Antifuse
An antifuse is an electrical device that performs the opposite function to a fuse. Whereas a fuse starts with a low resistance and is designed to permanently break or open an electrically conductive path (typically when the current through the path exceeds a specified limit), an antifuse starts with a high resistance--an open circuit--and programming it converts it into a permanent electrically conductive path (typically when the voltage across the antifuse exceeds a certain level).[1] This technology has many applications. Antifuses are best known for their use in mini-light (or miniature) style low-voltage Christmas tree lights.
Christmas tree lights
Low-voltage lights cannot handle the full voltage typical to a residential circuit and are wired in series, unlike the larger, traditional, C7 and C9 style lights which are wired in parallel and are rated to operate directly at mains/residential voltage. Since a blown bulb in a series circuit would open the entire circuit, a series string would be rendered inoperable by a single lamp failing.[2]
Because of this, each
As more bulbs fail in the string, a higher and higher voltage is applied across the remaining bulbs. Often a special bulb with no antifuse and often a slightly different rating (so it blows first as the voltage gets too high) known as a "fuse bulb" is incorporated into the string of lights to protect against the possibility of severe overcurrent if too many bulbs fail.
Antifuses in integrated circuits
Antifuses are widely used to permanently program
Certain
Dielectric antifuses
Dielectric anti-fuses employ a very thin oxide barrier between a pair of conductors. Formation of the conductive channel is performed by a
Amorphous silicon antifuses
One approach for the ICs that use antifuse technology employs a thin barrier of non-conducting
Amorphous silicon is a material usually not used in either bipolar or CMOS processes and requires an additional manufacturing step.
The antifuse is usually triggered using an approximately 5
Zener antifuses
Zener zap is frequently employed in
Street-lighting (obsolete)
In a similar fashion to that of Christmas tree lights, before the advent of high-intensity discharge lamps, street light circuits using incandescent light bulbs were often operated as high-voltage series circuits. Each individual street-lamp was equipped with a film cutout; a small disk of insulating film that separated two contacts connected to the two wires leading to the lamp. In the same fashion as with the Christmas lights described above, if the lamp failed, the entire voltage of the street lighting circuit (thousands of volts) was imposed across the insulating film in the cutout, causing it to rupture. In this way, the failed lamp was bypassed and illumination restored to the rest of the street.
Unlike Christmas lights, the circuit usually contained an automatic device to regulate the electric current flowing in the circuit, such as a constant-current transformer. As each series lamp burned out and was shorted out, the AC current regulator reduced the voltage, which kept each remaining bulb operating at its normal voltage, current, brightness, and life expectancy. When the failed lamp was finally replaced, a new piece of film was also installed, again separating the electrical contacts in the cutout. This style of street lighting was recognizable by the large porcelain insulator that separated the lamp and reflector from the light's mounting arm; the insulator was necessary because the two contacts in the lamp's base may have routinely operated at a potential of several thousands of volts above ground/earth.
The same mechanism (a film-disc cutout) is used broadly in applications where series lighting is desired,[8] such as airfield runway and taxiway lights.[9][10]
See also
- Crowbar (circuit)
- Diac
- Lightning arrester
- Transient voltage suppression diode
- Varistor
References
- ISBN 978-1-4020-6100-4.
- ^ Wood, Daniel (16 December 2015). "How Do Holiday Lights Work?". Department of Energy.
- ^ Brain, Marshall (26 March 2014). "How Christmas Lights Work". HowStuffWorks. Archived from the original on 26 March 2014. Retrieved 2023-09-23.
- .
- ISSN 0741-3106.
- ISBN 978-1-4419-7595-9.
- ISSN 1065-514X.
- ^ "Film Disc Cutouts - Meridian Electric". www.meridianelectric.net. Retrieved 2023-09-24.
- ^ Philips, Cecil B. (1975). Evaluation Of Taxiway Centerline Lighting For Runway Exits And Taxiway Intersection. William J. Hughes Technical Center. p. 3.
- ^ "Advisory Circular 150/5345-46B". Federal Aviation Administration. September 1998.
External links
- Information on use of antifuses in Christmas lights (They avoid use of the term antifuse presumably because of their non-technical audience.)
- More information on the types of Christmas lights
- Historical page on Series Operation of Street Lamps