Without light, and LCD screen might as well be a paperweight. Many LCD screens use a cold-cathode fluorescent lamp that requires an inverter. Commonly known as a CCFL inverter, this component prepares the power connection of the DC power supply to work with the AC power requirements of the lamp.
The Inverter's Role
When a computer is plugged into the wall, it converts the power outlet's AC waves into DC. This works well for digital components, such as the motherboard, but it doesn't work for fluorescent bulbs. The inverter intercepts that DC power, and converts it back to AC power for use by the bulb that lights the screen.
Troubleshooting the Inverter
When the inverter breaks, it will look like the LCD has shut off. Looking closely, however, you'll still see that the display is still working, as images are still being rendered but are not illuminated. Many LCD fluorescent bulbs are integrated onto a circuit with the inverter, requiring one to be replaced along with the other. If you are not comfortable dismantling your LCD screen, it's often more cost effective to replace the whole LCD than to change the LCD inverter unit.