Editing Compact fluorescent lamp (section)

== Pattern ==
There are two types of CFLs&nbsp;— integrated and non-integrated lamps, where CFL-i denotes an integrated ballast and CFL-ni denotes a non-integrated ballast. Integrated lamps combine the tube and ballast in a single unit. These lamps allow consumers to replace incandescent lamps easily with CFLs. Integrated CFLs work well in many standard incandescent light fixtures, reducing the cost of converting to fluorescent. [[3-way lamp]]s and dimmable models with standard bases are available.

Non-integrated CFLs have the ballast permanently installed in the [[Light fixture|luminaire]], and usually only the fluorescent tube is changed at its end of life. Since the ballasts are placed in the light fixture, they are larger and last longer compared to the integrated ones, and they do not need to be replaced when the tube reaches its end-of-life. Non-integrated CFL housings can be both more expensive and sophisticated. They have two types of tubes: a bi-pin tube designed for conventional ballast, e.g. with G23 or G24d plug-in base, and a quad-pin tube designed for an electronic ballast or a conventional ballast with an external starter. A bi-pin tube contains an integrated starter, which obviates the need for external heating pins but causes incompatibility with electronic ballasts.
Non-integrated CFLs can also be installed in a conventional light fixture using an adapter containing a built-in magnetic ballast. The adapter consists of a regular bulb screw, the ballast itself and a clip for the lamp's connector.

[[File:Kompaktleuchtstofflampe.jpeg|thumb|upright|Non-integrated bi-pin double-turn CFL with G24d plug-in base]]
[[File:Elektronstarterp.jpg|thumb|An electronic ballast and permanently attached tube in an integrated CFL]]
CFLs have two main components: a magnetic or electronic ballast and a gas-filled tube (also called bulb or burner). Replacement of magnetic [[Electrical ballast|ballast]]s with electronic ballasts has removed most of the flickering and slow starting traditionally associated with fluorescent lighting, and has allowed the development of smaller lamps directly interchangeable with more sizes of incandescent light bulb.

Electronic ballasts contain a small circuit board with a [[bridge rectifier]], a filter [[capacitor]] and usually two switching [[transistor]]s, which are often [[insulated-gate bipolar transistor]]s. The incoming AC current is first [[rectification (electricity)|rectified]] to DC, then converted to high frequency AC by the transistors, connected as a resonant series DC to AC [[inverter (electrical)|inverter]]. The resulting high frequency is applied to the lamp tube. Since the resonant converter tends to stabilize lamp current (and light emitted) over a range of input voltages, standard CFLs respond poorly in dimming applications and will experience a shorter lifespan and sometimes catastrophic failure. Special electronic ballasts (integrated or separate) are required for dimming service.

CFL light output is roughly proportional to phosphor surface area, and high output CFLs are often larger than their incandescent equivalents. This means that the CFL may not fit well in existing light fixtures.
To fit enough phosphor coated area within the approximate overall dimensions of an incandescent lamp, standard shapes of CFL tube are a helix with one or more turns, multiple parallel tubes, circular arc, or a butterfly.

Some CFLs are labeled not to be run base up, since heat will shorten the ballast's life. Such CFLs are unsuitable for use in [[pendant light]]s and especially unsuitable for [[recessed light]] fixtures. CFLs designed for use in such fixtures are available.<ref>[http://members.misty.com/don/cfapp.html#r What Compact Fluorescents to Use Where]. Accessed 1 January 2008.</ref> Current recommendations for fully enclosed, unventilated light fixtures (such as those recessed into insulated ceilings), are either to use "reflector CFLs" (R-CFL),<ref name="DealerGuide">{{cite web |url=http://www.energystar.gov/ia/business/small_business/BM31jan22.pdf |title=A Dealer Guide to Energy Star: Putting Energy into Profits |access-date=2007-10-09 |archive-url=https://web.archive.org/web/20170430211128/https://www.energystar.gov/ia/business/small_business/BM31jan22.pdf |archive-date=2017-04-30 |url-status=dead}}</ref><ref>{{cite web|title=CFL Reflector Products |publisher=Pacific Northwest National Laboratory |date=2007-10-02 |access-date=2007-12-24 |url=http://www.pnl.gov/rlamps/ |url-status=dead |archive-url=https://web.archive.org/web/20071221002446/http://www.pnl.gov/rlamps/ |archive-date=December 21, 2007}}</ref> [[cold-cathode fluorescent lamp|cold-cathode CFL]]s or to replace such fixtures with those designed for CFLs.<ref name="DealerGuide" /> A CFL will thrive in areas that have good airflow, such as in a table lamp.<ref>{{cite web|url=http://www.lrc.rpi.edu/resources/newsroom/pr_story.asp?id=162 |title=Press Releases {{pipe}} LRC Newsroom |publisher=Lrc.rpi.edu |date=2009-03-16 |access-date=2012-07-15 |url-status=dead |archive-url=https://web.archive.org/web/20120724011821/http://www.lrc.rpi.edu/resources/newsroom/pr_story.asp?id=162 |archive-date=2012-07-24}}</ref>