In his fourth article on ballasts, Iain Mosely describes how the constant power operation inherent in a peak-current-controlled discontinuous mode flyback converter can deliver good drive characteristics for LED applications. For high brightness LED technology to succeed in replacing standard incandescent bulbs for high Volume markets, the cost of the drive electronics required to power the LEDs must be kept to a minimum. This article, the fourth in a series discussing LED ballast design, presents a solution that exploits a novel constant power flyback converter architecture. An ultra low cost 7W offline LED ballast that will run from 85?C265Vac at 50/60Hz. ![]()
The actual LED current is measured using a sense resistor and is used to control the duty Cycle of the primary side switching element. Although this gives excellent LED current regulation, the feedback circuitry requires an optocoupler, shunt reference, and sense resistor, all of which add cost and reduce overall efficiency.
+++++++
This article was published in the April 2008 issue of LEDs Magazine.
To read the full version of this article, please visit our Magazine page, where you can download FREE electronic PDF versions of all issues of LEDs Magazine.
You can also request a print copy of LEDs Magazine (available by paid subscription) and sign up for our free weekly email newsletter .Links:![]()
April 2008 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2004 2005 2006 2007 2008 2009 
The actual LED current is measured using a sense resistor and is used to control the duty Cycle of the primary side switching element. Although this gives excellent LED current regulation, the feedback circuitry requires an optocoupler, shunt reference, and sense resistor, all of which add cost and reduce overall efficiency.
+++++++
This article was published in the April 2008 issue of LEDs Magazine.
To read the full version of this article, please visit our Magazine page, where you can download FREE electronic PDF versions of all issues of LEDs Magazine.
You can also request a print copy of LEDs Magazine (available by paid subscription) and sign up for our free weekly email newsletter .Links:
2.0 plastic and wooden speaker
Speakers With Diaphragm,Mini Speaker With Usb Charger,Computer Woofer Speaker
Maikesen Technology Co., Ltd. , http://www.sz-speaker.com