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pgola4u
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Join Date: Jun 2011
Location: Haridwar (India)
Posts: 18

3W LED Driver Design Problem

07/15/2013 11:00 AM

hello every one, i have working on 3W LED driver which use a chines IC AM12A, this offline smps primary switcher IC, same as ST Viper12A, as i found during my study, but when i remove the AM12A and use ST Viper 12A, the LED start blinking, i uses 3 nos. 1watt power LEDs in series, the driver has o/p volatge 10-12V, and o/p amp- 350mA. i have checked the circuit many time also pin configuration of both IC but, driver not working with ST Viper12A, Please give your valuable suggestions, how i can rectify this i only want to use ST viper12A in circuit, because that easily available... thanks w8 for help...:-)

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SolarEagle
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#1

Re: 3w LED Driver Design Problem

07/15/2013 11:50 AM




http://designs.digikey.com/library/4294959899/4294959898/348

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pgola4u
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Join Date: Jun 2011
Location: Haridwar (India)
Posts: 18
#2
In reply to #1

Re: 3w LED Driver Design Problem

07/16/2013 1:01 AM

Thanks a lot sir... i check this schematic with mine see what are the difference....

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Winfield Hill
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Join Date: May 2010
Location: Cambridge, MA
Posts: 390
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#3
In reply to #1

Re: 3w LED Driver Design Problem

07/16/2013 6:07 AM

Whoa, this ST appnote an2961 eval schematic and configuration is quite different from the suggested schematic in the VIPer22A datasheet (the 12A is similar to the 22A). The datasheet describes a conventional flyback circuit, with an isolated output. In it the VIPer22A smps controller IC operates from the most negative-rail point, in a conventional way.

OTOH, this appnote describes a buck configuration, with the VIPer22A smps IC acting as a flying hi-side switch, with a flying power supply. A bipolar transistor's VBE acts as a current sensor. And as they warn you, it's not isolated, which means the circuit rides the AC power-line bridge-output negative half-cycle. Whatever you do, don't ground the spot where they show a ground symbol!

This is not the easiest circuit to use, to learn with, or to explore the operation of VIPer22A, etc., and it's certainly not the safest either. Whoa, Keep one hand behind your back at all times!

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ci139
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Join Date: Feb 2012
Posts: 595
#4

Re: 3W LED Driver Design Problem

07/16/2013 7:40 AM

?maybe "thermal" engages
this sounds hard to tune up http://www.powerint.com/en/design-support/parametric-search#6500
a bit better integration http://www.ams.com/eng/Products/Power-Management/LDOs
((donno if4 any 'elp))

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