High-end view:
FL7730 driver with power factor correction (PFC), TRIAC and analog dimming capability
FL7701 with drive soft start function to improve system reliability and optimize circuit design
development trend:
Fairchild offers a wide range of LED lighting solutions for medium and small power range LED lighting applications
Reducing costs, improving reliability and policy promotion will be the future direction of LED lighting development
If the LED lamp is likened to a "person", then the LED drive circuit is the "heart" of the entire LED lamp. This "heart" not only delivers energy to LED luminaires, but is also critical to the quality of LED luminaires. In terms of LED driver circuit design, the topic that everyone is most concerned about now is the dimming technology of LED lamps and the electroless capacitor driving scheme. Recently, the reporter interviewed Qian Jiafa, manager of Fairchild Semiconductor's technical marketing department, and learned about Fairchild's design ideas and latest products in dimming and electroless.
FL7730 driver embody TRIAC dimmer compatibility
LED lighting can replace ordinary light sources such as fluorescent and incandescent lamps and has developed into the most promising lighting solution. However, designers face some obstacles in the application of residential and commercial LED lighting up to 20W, including bulbs, downlights (GU10/E17, E26/27, PAR30/38) and tube/bar lights. Due to the compatibility of the dimmer, it is quite difficult to implement the LED dimming capability in a conventional TRIAC dimmer configuration. In addition, small space sizes are still a consideration.
To address these issues, Fairchild has just introduced two FL7730 single-stage primary-side regulation (PSR) controllers with power factor correction (PFC), TRIAC and analog dimming capabilities, and FL7732 control for non-dimming applications. Designed to achieve energy efficiency, high performance, compactness, ease of use, and lower system BOM cost. According to Qian Jiafa, manager of Fairchild Semiconductor's technical marketing department, Fairchild developed the FL7730 single-stage primary-side regulation (PSR) controller with a unique analog sensing technology that can be used from 0 to 100% of the light output. A flicker-free TRIAC dimming control is achieved. The FL7730 dimming voltage forms an internal CS compensation to reduce the regulated output current, and the dimming energy is compatible with more than 80% of the market's dimmer products.
Schematic diagram of single-stage PFC and PSR flyback scheme based on FL7730 driver
As a dimmable driver, the FL7730 improves overall system efficiency and is suitable for high-voltage or low-voltage line inputs. With low-voltage input, the efficiency is as high as 83%, while at high-voltage input, the efficiency is 85%. Boosting power factor and reducing total harmonic distortion (THD), this device features constant on-time control with an internal error amplifier and low bandwidth compensator. Accurate constant current accuracy/control (± 5%) accurately regulates the output current and is independent of input and output voltages, enabling designers to achieve higher and better illumination quality. The operating frequency of the FL7730 is proportional to the output voltage to ensure DCM operation with the best power factor/THD and a simpler design.
On the other hand, the integrated protection function of the FL7730 improves the reliability of the system. It features open/short LED protection, thermal shutdown, cycle-by-cycle current limit protection, and a longer system life expectancy. Electrolytic capacitors also reduce the number of external components and reduce costs.
Electroless Capacitor Drives FL7701 to Solve LED Lamp Life Problem
When talking about the impact on the life of LED lamps, Fairchild Semiconductor Technology Marketing Manager Qian Jiafa said that the life of LED lamps is mainly determined by its driver, and the life of the driver depends on the life of its internal electrolytic capacitors. About 5,000 hours, if this problem is solved, the life of the drive will be solved accordingly. Another influential factor is whether the overall circuit design of the LED luminaire is within a controllable range. Each part has its scope of application, and every detail adjustment is also very important. The internal structure of the circuit needs to be optimized and its reliability is guaranteed. For example, when the LED light is turned on, the brightness will drop immediately, which is actually a low-reliability performance. The intelligent non-isolated PFC step-down LED driver FL7701 from Fairchild has a soft-start function that improves system reliability and optimizes the design inside the circuit to help customers provide product performance and reduce costs. This drive eliminates the need for electrolytic capacitors for input, output, and IC VDD, and can replace large-volume transformers, thereby maximizing performance, meeting energy-saving regulations, and simplifying LED design with efficiencies of more than 85%. Minimize BOM for smaller lighting sizes. This also solves the life and reliability problems of LED lamps.
LED driver FL7701 with electroless capacitor solution
LED driver FL7701 with electroless capacitor solution (physical map)
Reducing costs, improving reliability and policy promotion will be the future direction of LED lighting development
Qian Jiafa finally said that this year's LED lighting application business focus is to provide a wide range of LED lighting solutions for medium and small power range LED lighting applications, this market prospect is very good. Of course, it will not give up the investment in high-power products. Fairchild's outstanding features in LED lighting solutions are the high integration of various components on a single IC, combined with efficient and advanced circuit topology, widely used in 1W or above power range lighting applications. Coupled with Fairchild's IC design, product reliability, heat dissipation, and small volume and after-sales experience, LED solutions have high power factor and low overall harmonic distortion, which can extend the use of luminaire systems. Lifetime and reduced cost during use can help designers meet demanding board space requirements, simplify product design and reduce overall bill of materials (BOM) costs, while meeting regulatory requirements in Europe and the US and helping customers improve their products Quality and performance. Under the current circumstances, LED lighting in the European and American markets has begun to become an important new trend of lighting. Similarly, in promoting the popularization of LED lighting, China has also done a lot of work on related policies, while urban lighting is most likely in China. One of the first popular LED lighting applications.
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