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{{Short description, Electrical inverter A CCFL inverter is an electrical inverter that supplies
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which ...
power to a
cold cathode fluorescent lamp A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet ligh ...
(CCFL). CCFLs are often used as inexpensive light units in electrical devices that are powered by
direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...
sources such as
batteries Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...
. CCFL inverters are small, have switchover efficiency over 80%, and offer adjustable output of light. They are widely used for backlights for
LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...
s, or for rear lighting in advertising signs.


History

As for the inverter circuit of a cold cathode fluorescent lamp, a resonance type circuit has been widely used. This is sometimes referred to as the " Royer circuit". However the proper definition of the Royer circuit requires that the inversion of a switching operation be performed in a state in which the transformer is saturated. An inverter circuit which performs the inversion operation by utilizing resonance in the collector circuit of a transistor is preferably referred to as the " Baxandall converter" in distinction from a true Royer circuit.P.J. Baxandall,
Transistor Sine-Wave LC Oscillators
, ''International Convention on Transistors and Associated Semiconductor Devices'', 25 May 1959, fig 5, p. 751 The multilevel inverters are basically classified into three topologies namely, the flying capacitor inverter, the diode clamped inverter and the cascaded H-bridge inverter. All the topologies have same property of reducing the harmonics. The cascaded has the disadvantage to need separate DC sources but circuit layout is compact and voltage sharing problem is absent. The early designs of an inverter circuit for a cold cathode fluorescent lamp did not utilize the resonance method of a secondary circuit at all. Instead the so-called closed magnetic circuit type transformer having a small
leakage inductance Leakage inductance derives from the electrical property of an imperfectly-coupled transformer whereby each winding behaves as a self-inductance in series with the winding's respective ohmic resistance constant. These four winding constants also i ...
was used as a step-up transformer. The leakage inductance was such that it reduced the output voltage on the secondary side of the transformer. Since this was not desirable, it had to be made as small as possible.


See also

* Magnetic phase synchronous coupling *
Short-circuit inductance Short-circuit inductance of a real linear two-winding transformer is inductance measured across the primary or secondary winding when the other winding is short-circuited.Japan Industrial StandarC 5602-1986, pp 34, 4305/ref>This value is sometimes ...
*
Resonant transformer A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional part ...
*
Tesla coil A Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891. It is used to produce high-voltage, low- current, high-frequency alternating-current electricity. Tesla experimented with a number of differe ...


External links

# Jim Williams
"A fourth generation of LCD backlight technology: Component and measurement improvements refine performance"
Linear Technology Application Note 65, November 1995.


References

Inverters