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What Is a CCFL Inverter?

A LCD screen with CCFL inverter circuits.
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  • Written By: Geisha A. Legazpi
  • Edited By: Lauren Fritsky
  • Last Modified Date: 16 August 2014
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A cold cathode fluorescent lamp (CCFL) inverter is an electronic circuit that drives a CCFL, a gas-filled tube designed to produce light when the gas filling is ionized by electrical currents through the main terminals and through the gas inside the tube. The CCFL inverter is also used for advertisement boards and decorative lighting and is very common in vehicles that provide 12 volts direct current (VDC) from battery or 13.8 VDC when the engine is running. It generates high-audio frequency electrical energy using ferrite transformers that are more efficient at the given frequency of operation. Cold cathode devices do not require preheating unlike the hot cathode devices that make use of a directly or indirectly heated cathode. The CCFL may or may not have trigger terminals that initiate current from cold start.

An inverter is an electrical power conversion device that inputs direct current (DC) and generates alternating current (AC). The CCFL inverter is a special inverter that generates the higher AC voltage used by a cold cathode fluorescent lamp. In addition, the CCFL inverter also provides the needed current limit without which the CCFL will overheat and get damaged.

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The Royer oscillator generates a sinusoidal output used to energize a CCFL. It is a high-efficiency oscillator, making it a much-used circuit for battery-operated CCFL drivers. The Royer oscillator uses two main analog current control devices that generate AC through a transformer. Royer oscillators employ a feedback system that allows the main circuit to monitor the amount of power being fed into the CCFL. This way, there is a stable brightness level on the CCFL.

CCFL inverter circuits are used for indoor lighting and backlights in liquid crystal display (LCD) screens. The sinusoidal output in the CCFL inverter is clean and does not interfere with radio reception. For instance, if the CCFL inverter produces too much electromagnetic interference, it may interfere with electronic receiver operations such as for radio and television broadcast.

The various colors available for CCFL are made possible by different types of gases inside the CCFL tubes. Some CCFL tubes are gas-filled with an ultraviolet (UV)-producing gas like mercury vapor. The UV energy created then energizes a fluorescent coating on the inside of the tube to produce light.

Fluorescent tubes are available in cold cathode and hot cathode varieties. Early fluorescent tubes were preheated using a tungsten filament that may be temporarily preheated by a device known as a passive starter, which senses the voltage across the tube. If this is too high, the starter allows current to flow through it, causing a current flow through the filaments. This produces the preheating and eventual flow of current through the tube.

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