What Is a CCFL Lamp
A CCFL Lamp is a fluorescent lamp, shortened for Cold Cathode Fluorescent Lamp.
While ordinary fluorescent lamps heat their filaments to emit thermal electrons, cold cathode tubes emit electrons without heating their electrodes. Therefore, cold cathode tubes operate at lower temperatures and have a longer life.
In addition, since there is no need to build a filament into the tube, the tube can be made thinner. Fluorescent lamp tubes range in diameter from 15 to 38 mm, while cold cathode tubes are 3 to 5 mm in diameter.
CCFL Lamps cannot be used with standard 50 or 60 Hz commercial AC and require a dedicated power supply that provides high-frequency power.
Applications of CCFL Lamps
CCFL Lamps have more than 30 years of history and have long been used for LCD backlighting, advertising signboards, guide lights, and lighting because of their easy dimming, energy savings, and long life.
In recent years, there has been a shift from CCFL Lamps to LEDs due to the superiority of LEDs over the advantages of cold cathode tubes. LEDs have already completely replaced LCD backlights, and an increasing number of manufacturers are discontinuing the production of cold cathode tubes.
However, CCFL Lamps have advantages not found in LEDs, such as the ability to diffuse light over a wide area and output even, even light, and the ability to produce eye-friendly white light that is close to natural light.
Principle of CCFL Lamp
A CCFL Lamp consists of a long, thin glass tube filled with argon gas and mercury vapor, phosphor coated on the inner wall of the glass tube, and electrodes placed at both ends of the glass tube.
The basic principle of operation of a CCFL Lamp is the same as that of a general fluorescent lamp: electrons emitted from the electrodes combine with mercury ions filled in the glass tube to emit ultraviolet radiation, which excites the phosphor on the inner wall of the tube to emit visible light.
The only difference is the method of electron emission. While ordinary fluorescent lamps emit thermal electrons by passing an electric current through a filament coated with electron-emitting material, CCFL Lamps emit secondary electrons by ion bombardment of argon.
When a high voltage is applied to the metal electrodes of a CCFL Lamp, electrons in the tube are pulled by the positive electrode and move within the electric field, colliding with argon. The argon cations ionized by this collision collide with the negative electrode, emitting secondary electrons.
Since a high voltage must be applied to the CCFL Lamp to emit secondary electrons, an inverter circuit is used as the power supply.