Due to a range of advantages such as energy efficiency, safety, long lifespan, fast response time, excellent color reproduction, mercury-free composition, and compliance with environmental requirements, LED has replaced traditional CCFL backlighting and become the mainstream backlight source for LCDs. Nowadays, LED backlighting is gradually becoming the dominant choice in the application of large-sized LCD screens.

Small-sized LCD screens with LED backlighting are primarily used in mobile phones, digital cameras, and monochrome LCD modules used in industrial instruments. These screens have sizes ranging from 3 to 7 cm and typically require 3 to 6 white LEDs as backlight sources, which can be connected in series or parallel. If the same device utilizes white LED flashlights, a larger driving current is needed. Sometimes, the backlight brightness is adjustable by the user, requiring the driver to have a brightness adjustment function (i.e., changing the driving current). To meet this growing demand, many manufacturers of analog integrated circuits and power management integrated circuits have developed and produced various integrated circuits for driving LEDs. These circuits generally incorporate control functions for LED backlighting and LED flashlights, as well as switch control and multi-level brightness control functions. They are powerful in functionality and require fewer external components. Many LED driver chips belong to this category, and there are numerous vendors and product models available for users to choose from. For display devices larger than mobile phones and digital cameras, such as personal digital assistants (PDAs), portable media players (PMPs), electronic dictionaries, and handheld game consoles, the screen sizes can range from 9 to 10 cm, with some reaching up to 18 cm. Currently, achieving uniform illumination with LEDs is challenging for large screens. Therefore, regardless of size, it is not suitable to directly configure multiple LEDs as backlight sources. Instead, backlight modules are used, incorporating measures such as refraction and light guide plates to ensure uniform illumination from white LEDs, meeting user requirements. Manufacturers of PDAs and PMPs directly purchase these modules from backlight module suppliers instead of using a few LEDs to form the backlight source. However, in some designs, people still use more LEDs (e.g., 8 to 10 LEDs) as backlight sources for larger-sized LED LCD screens.

Medium-sized LCD screens with LED backlighting are mainly applied in portable DVD players, laptops, and car navigation systems, with screen sizes ranging from 7 to 12 inches. The LED backlight sources used in these devices are developed based on the LED backlighting solutions for small-sized LCD screens. They replace CCFL light sources with aluminum-based LED light bars, and the driving power supply should be compatible with existing CCFL backlight driving power supplies at the interface. Simple DC drivers (battery-powered, usually using 12V power) replace complex AC drivers. Although the comprehensive cost is slightly higher, it is comparable to traditional CCFL backlight modules. In this case, if multiple LEDs are still used to form an array, the series-parallel LED groups are typically treated as a whole, and their current is controlled and brightness adjusted through the driving power supply.

Large-sized LED backlight sources for LCD screens may require hundreds or more LEDs to be simultaneously illuminated to provide sufficient brightness. This necessitates higher voltage, larger current, more flexible control methods, and stricter requirements for driving power supply heat dissipation. It also places higher demands on the consistency of LED characteristics, wherein the current between the driver and LEDs must match and be shared. The LEDs used should undergo rigorous selection and classification based on their emission wavelength and brightness. When testing the optical characteristics and defining parameters of LEDs, a consistent rated current value is typically used as the basis, and an allowed range of forward voltage drops is provided. It can be anticipated that large-sized LED screen backlight sources will soon replace CCFL as the mainstream product. The application prospects of LED backlighting in laptops, monitors, and LCD televisions are promising. To reduce costs, LCD televisions adopt edge-lit backlight modules, although the quality is not as perfect as bottom-lit solutions and can only be considered a short-term solution for ultra-thin LCD televisions.