The purpose of the laptop inverter

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The purpose of the laptop inverter
The inverter supplies power to a laptop's LCD backlight lamp (Laptop image by Marek Kosmal from Fotolia.com)

The inverter is part of a laptop's display assembly. Also known as inverter board, screen inverter or LCD inverter, the device is a small green board attached to the base of the LCD panel. In a laptop computer, the LCD screen relies on a backlight source to uniformly light up the screen, and the inverter acts as the power supply for this lighting source.

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Arrangement

A laptop's display assembly consists of the LCD screen with its mounted backlight source, the video cable and the inverter. You may access the board by removing the plastic frame bordering the LCD panel, known as the screen bezel, and prying the ends loose to raise the inverter from its position. In most models, the inverter is a narrow strip of PCB (printed circuit board), and depending on manufacturer and model, may or may not be encapsulated in a plastic outer layer. The inverter board has connectors on either end, and wires connect the left side to the video cable (LCD screen cable), and the right side to the mounted backlight lamp.

Inverter Malfunction

When the inverter malfunctions, or when its connecting wires are damaged, the LCD screen goes dark frequently, or does not light up at all. This happens because the inverter is unable to convert low-voltage DC power from the laptop's motherboard and supply the LCD backlight with high-voltage AC power. Without this power input, the backlight lamp is unable to light the LCD screen and as a result, the screen becomes dim. Even when the inverter works properly, the LCD screen may not light up due to damaged or loose wiring.

Diagnosis

Diagnosing laptop LCD problems entails checking the inverter board, the backlight source and the screen itself. Since symptoms of inverter failure and backlight lamp failure are similar, it is often difficult to ascertain which component is damaged. For example, when the screen does not light up sufficiently, it may either be due to a worn out backlight lamp, or a malfunctioning inverter board.

It is easier to determine whether the laptop's display problem is due to the back-light-inverter combination, or a motherboard related issue; if the computer is able to display images on an external monitor, the problem is with the display assembly and not the motherboard's video card.

Determination

An inverter can be checked to determine whether it is receiving power from the motherboard by using a multimeter. The positive and negative leads of the meter are connected to corresponding pins on the board and the reading is observed. Testing the inverter board is an involved process and should only be done by skilled professionals. If the board is accidentally shorted, it may damage both the inverter and the motherboard.

Replacement

Since inverters are not universal, not all laptops will work with all types. A laptop will only accept an inverter board that is compatible with its motherboard and backlight lamp. Replacing the unit entails ordering for a compatible inverter from the manufacturer by referring to the component's model number. If an unsupported type is connected, it might damage the backlight lamp and the motherboard.

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