 greenpowerZONE Products for the week of November 6, 2006
STMicroelectronics Says....
One-Chip Electronic Ballast Lets Fluorescent Lamps Shine Brighter, Use Less Power
STMicroelectronics has introduced a single chip (Combo IC) which integrates a Power Factor Corrector (PFC) with a half-bridge controller and all the relevant drivers and logic for an electronic ballast IC for fluorescent lamps. Combining these functions on a single IC allows ST's new L6585 to generate more light from less energy, while ensuring full compliance with safety and power consumption regulations.
The L6585 one-chip solution, in fact, is the first on the market to enable EOL (End-of-Life) detection in either "lamp-to-ground" or "block capacitor-to-ground" ballast configurations. For the first time, manufacturers can choose how to design their application to simplify board qualification and easily pass ballast security tests.
Unlike previous solutions that require a Combo IC and several external components to feature EOL detection and the specific protections required by the new types of fluorescent lamps, the L6585 ensures all these necessary functions, thus eliminating the need for external circuits, drastically reducing design time and complexity, dramatically lowering costs, and increasing reliability.
The L6585 IC offers independently programmable pre-heating and ignition duration as well as the half-bridge frequencies for each operating phase. As a result, this one IC can serve many different lamp types.
The Combo IC enables high levels of protection on both the PFC and Half-Bridge sections of the device. In addition to the capability of limiting the voltage applied to the lamp and controlling current levels during the ignition and run-mode phase, the L6585 increases ballast reliability by avoiding the capacitive mode in the half-bridge section through the over-current protection.
Other major benefits of the L6585 are the detection of over-voltage and feedback disconnection on the PFC, which stops the IC to avoid ballast damage, and the highly linear multiplier that allows wide-range-mains operation with an extremely low Total Harmonic Distortion (THD).
Lamp management is also simplified by the automatic re-lamp feature, which allows operators to replace lamps without needing to power off all the other lamps.
EN-Genius Says...
 ST's L6585 integrated electronic fluorescent ballast and power factor correction circuit is a great example of an electronic product that makes sense both economically and ecologically. Its efficiency, tight power factor correction (0.99) and low standby power round out a list of must-have features for a high-efficiency ballast, but ST has added a bunch of clever improvements that set it apart from the excellent devices produced by Philips and other competitors.
Combining the PFC controller and ballast controller (see Fig. 1) is not unique to the L6585, but ST's designers have taken advantage of the tight coupling between the two elements to deliver better power management and some truly innovative techniques for handling the less-than-ideal characteristics the fluorescent tubes display as they age. For one thing, the ballast controller's end-of- life sense circuit looks at the dc component of the filament voltage which grows as the tube ages and shuts down the lamp when the voltage grows too high. This protects both the drive circuit from frying and the tube from overheating or even melting down. And as the release above explains, it can work with both capacitor-to-ground (used in Europe & China) and lamp-to-ground (used in US) configurations.
The L6585 has several other nice protection features, including a circuit in the PFC section that guards against boost inductor saturation that can occur due to a short or other over-current fault. This and an open-output sense circuit (to prevent destroying the power transistor under open loop conditions) makes the device much less prone to catastrophic failure without having to add many external sense components.
Thanks to its programmability and ability to detect and signal a lamp fault, the L6585 is a great candidate for smart lighting applications. To this end the chip's designers have worked with other ST groups to develop microcontroller-based lighting reference designs that support DALI or other lighting control protocols using either power line modems or ZigBEE wireless networks. So, besides being able to manage a large building's lights from a central point, operators will also be able to know when and where the building's lamps need service. There is even a reference design in the works for a universal fluorescent ballast that drives any type of tube. Once done, it will allow the microcontroller to sense the type of lamp being placed in the socket so that it can set the proper start-up and drive parameters under software control. This, and the device's wide operating voltage (85 Vac - 265 Vac) should make it possible to produce extremely efficient fluorescent lighting products that could be sold worldwide to work with whatever lamps and power sources are available.
Offered in the SO-20 Pb-Free EcoPak the L6585 costs $1.40 in 10-k piece lots. It is sampling now with volume production slated for January 2007.
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