The increase in luminous efficiency, the extension of service life, and the growing demand for wide color gamut have pushed LEDs to replace cold cathode fluorescent lamps (CCFLs) as backlights for liquid crystal display (LCD) flat panel TVs. In order to provide sufficient brightness for large-size LCD TVs, LED backlights require many LED arrays.
According to its arrangement, the LED backlight unit (BLU) can be divided into two types: edge-lit LED BLU and direct-light LED BLU, as shown in Figure 1 and Figure 2. In edge-lit LED BLUs, high efficiency, high step-up ratio DC-DC converters are required to drive LED strings in series. Cascaded DC-DC converters can meet these requirements, but they also present some challenges, such as additional complexity and higher costs. This article describes a voltage doubler boost converter that solves the above problems.
Sidelight LED backlighting power requirements
The BLU in LCD TV has a large impact on the total cost of the application because it can account for 30-40% of the total LCD TV cost and plays a decisive role in the final angular luminance, contrast and brightness.
As a BLU light source, LEDs are rapidly emerging in the LCD industry as a replacement for CCFL and are expected to maintain steady growth in the next few years. LEDs outperform CCFLs in terms of color performance and product life because they have RGB wavelengths that do not overlap with the actual RGB wavelength peaks. LEDs are also easy to miniaturize and have excellent seismic resistance. But LED also has a disadvantage, that is, its cost is higher. Due to the cost advantages of edge-lit and the development of optical film technology for different types of metering, the edge-lit LED BLU is currently used in LCD flat-panel TVs.
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