Products, Materials + Tools | Mar 09, 2012

Fairchild Semiconductor’s FL77xx series LED LED Driver Offers high Reliability and Accurrat Current Control

LED lighting has evolved into a promising solution for replacing conventional lighting sources, such as fluorescent and incandescent lights. However, designers face several obstacles in residential and commercial LED lighting applications up to 20W including bulb, down lighting (GU10/E17, E26/27, PAR30/38) and Tube/Bar. Implementing dimming capabilities in a conventional TRIAC dimmer infrastructure is challenging because of dimmer compatibility. Additionally, small space requirements remain a consideration.

To help designers address these challenges, Fairchild Semiconductor (NYSE:FCS) developed the FL7730 single-stage primary side regulation (PSR) controller with power factor correction (PFC), TRIAC and analog dimming compatibility, as well as the FL7732 for non-dimming applications.

The FL7730 is an active PFC controller for single-stage flyback topology application. The device supports both TRIAC and analog dimming. Implemented with Fairchild’s unique analog sensing technology, the device can achieve TRIAC dimming control without flicker over the full range of 0 to 100% light output.

The FL7730 and FL7732 combine primary-side regulation and a single-stage PFC topology to minimize total bill-of-material (BOM) count, such as an input electrolytic capacitor and feedback circuitry, therefore allowing for a more compact, longer life, and lower system cost design.

To improve power factor and THD, both devices feature constant on-time control with an internal error amplifier and low bandwidth compensator. Precise Constant Current accuracy/control (± 5 percent) regulates accurate output current, independent of input and output voltage, allowing designers to achieve high and improved lighting quality. Operating frequency is proportionally adjusted by output voltage in both devices to guarantee DCM operation with optimized PF/THD and simpler design.

Excellent PF (≥0.9), low total harmonic distortion (THD) (Class C) and power efficiency of up to 85 percent for the FL7730 – greater than 85 percent for the FL7732 in non-dimming applications – allows these devices to meet worldwide energy saving regulations.

In an introduction interview about the FL77xx series LED drivers for replacement lamps with LED professional , Brian Johnson pointed out "an accurate everage current is essential for homogenious light in a room where several LED luminaires are installed and should deliver the same illumination level. That means that the power, respectively current should be similar from lamp to lamp." He added "esepecially achieving a good accuracy without sacrifying other relevant parameters is quite challenging for replacement lamp drivers. While we publish a 5% accuracy in the datasheet we consistently measure below ±3% current accuracy, which is an absolutely world-leading value. This accuracy can be mentained over the whole flicker-free dimming range from 0-100% with the FL7730"

Coming back to the other relevant parmeters for LED drivers Brian explains "Infineons new FL7730 dimming capable driver IC has a high PF of more than 90 with 85% efficiency. The non-dimming FL7732 even exceeds 85% efficiency. Both drivers, what is very relevant in respect to lifetime issues, offer primary side regulation eliminating the need for optocouplers and even more important have no need for an electrolytic capacitor."

As if it was given anyway, he explains " of course there are also safety features included in our driver design, open-circuit protection and short-circuit protection as well as thermal shut down.To ease the electronic designer's live," he continues, " we implemented a frequency hopping function that reduces EMI significantly. Not to forget, the device offers a low THD." Than Brian Johnson summarizes and closes "we developed this two devices to cut down the major challanges of electronic designer with their task to develop solutions for replacement applications."

Fairchild offers a total solution portfolio for low- (<20W), mid- (20W to 50W) and high- (>50W) LED driver applications. Our highly integrated PWM and PFC controller solutions reduce component BOM counts to enable smaller lamp sizes and eliminate design complexities, while improving overall lighting efficiency. Fairchild’s extensive product portfolio ranges from discrete devices to integrated solutions that contain PFC controllers, high voltage gate drivers and MOSFETs. With a commitment to energy savings and meeting the most stringent regulations, Fairchild has developed innovative products that maximize performance while reducing board space, design complexity and system costs. In addition, Fairchild’s Global Power ResourceSM Center comprised of online tools, FAEs and regional centers staffed by power engineers, is the industry standard for customer design support.

To contact Fairchild Semiconductor about this product, please go to: http://www.fairchildsemi.com/cf/sales_contacts/.
For information on other products, design tools and sales contacts, please visit: http://www.fairchildsemi.com.

About Fairchild Semiconductor:
Fairchild Semiconductor – global presence, local support, smart ideas. Fairchild delivers energy-efficient, easy-to-use and value-added semiconductor solutions for power and mobile designs. We help our customers differentiate their products and solve difficult technical challenges with our expertise in power and signal path products. Please contact us on the web at http://www.fairchildsemi.com.

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