Pioneering solutions are overcoming the challenges of harnessing LED technology for use in backlighting, making the technology viable in more applications than ever before

None of the scientists involved in pioneering the world’s first visible-spectrum LED in 1962 can have dreamed of the types of application that would utilise their invention 48 years later. While the development of the LED heralded a breakthrough in scientific terms, there were a number of problems with their practical application. Early LEDs were costly, and their low brightness made them insufficient to illuminate an area, so their only real practical use was as indicator lights. Since then, LED cost and performance have both taken great strides, spawning a host of new applications in the automotive industry, lighting, and consumer products ranging from minituarised mobile phones to large panel LCD TVs.

One of these new applications is LED backlighting technology. Once the little brother of Cold Cathode Fluorescent Lamp (CCFL) technology, the increasing use of LED backlighting as a viable, and even preferable alternative to CCFL has been made possible by advances in technology which get around the ‘traditional’ problems of LED backlighting. With those obstacles removed, many manufacturers have opted to use LED backlighting in a number of different types of device because of the advantages it enjoys over alternative backlighting technologies: in terms of power consumption, LEDs are far more energy-efficient, and integrating an ambient light sensor can reduce energy consumption even further. Their life-cycle is potentially far longer, often measured in hundreds of thousands of hours, depending on physical operating factors such as temperature. They eliminate the use of mercury that is still a feature of some CCFL solutions, and also avoid the ‘flicker’ effect of CCFL, a known cause of eye-strain. The physical space required by an LED device is usually far less than the non-LED equivalent, facilitating demand for ever-smaller consumer electronic devices such as smart phones.

So it is not surprising that LEDs are replacing rival backlighting technologies in a host of products featuring display panels, from smart phones and tablet or notebook computers through to photo frames, TVs, computer monitors and personal navigation systems. To meet the growing LED lighting needs of various end backlighting applications, ON Semiconductor offers LED solutions to make customers’ applications more efficient. Here, we take a look at some of its solutions.

There are two alternative ways to achieve LED backlighting of medium to large panel screens: either by using Dynamic RGB LEDs, which are positioned behind the panel, or by using white edge-LEDs positioned around the rim of the screen which use a special diffusion panel to spread the light evenly behind the screen. This latter approach allows for extremely thin LCD TVs.  Featuring robust fault detection and prevention in every possible fault scenario, the CAT4026 is suitable for use in large LCD panels, such as large LCD TVs.

Another ON Semiconductor product, the CAT4106, is an integrated multi-channel LED driver and high power DC-DC converter suitable for powering backlighting applications up to a total of 6 watts (W) of LED output power, to maximize efficiency in general purpose LCD panels such as tablet and notebook displays, monitors, smaller LCD TVs, touch screens, medical and test equipment.

ON Semiconductor also offers the NCP1294 fixed frequency flyback pulse-width modulation (PWM) LED controller. The device contains all of the features necessary for basic flyback, forward or boost operation. This PWM controller has been optimized for high frequency primary side control operation.

Conclusion

Since the 1960s, the efficacy (measured in cost per lumen) and light output of LEDs has made great strides, in much the same way predicted by celebrated LED pioneer Dr. Roland Haitz (a trend sometimes referred to as ‘Haitz’s law’). This rapid development mirrors the progress made in other areas of semiconductor and materials technology. The combined effect of these advances is that LED technology has expanded into entirely new markets, including backlighting, in which innovations by pioneers such as ON Semiconductor have been eagerly welcomed by users keen to take advantage of the low running costs, efficiency and environmental sustainability that it offers today.

Courtesy: ON Semiconductor