recently i had opted to upgrade my store with LED downlights of 14w each. problem i am facing is that drivers of these are going corrupt frequently. my electrician said , we can replace these drivers with a single power supply. can some one guide me how to calculate exact wattage for power supply and i wish to have 10 led's in a row to light up with single power supply.

  • Why not just use LED lamps in regular cans? MUCH simpler? Where are you located? – Speedy Petey Dec 11 '14 at 12:08
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    I think that's where the OP is starting from, and it's not working well. Which I'd take up with the maker of the LED downlights... – Ecnerwal Dec 11 '14 at 15:43

One problem with this approach is that LEDs are not incandescent bulbs.

LEDs (stripped of the on-board driver circuit which normally handles that part) are "current mode" devices - that is, an LED driver closely controls the current through the LED, and the voltage may vary. When driving multiple LEDs, they either need to be in series and driven off a driver with enough voltage capacity to run the whole string at the desired current, or you need multiple current controlling circuits.

You cannot simply say that the average voltage they use is 3, 12, 23, or 42 volts and supply that voltage to them in parallel; you must control the current, and if you don't, you'll almost certainly destroy them. If they happen to be 42 volts, running 10 in series is a bit challenging as you'd need a driver capable of supplying 420 (or 400-450) VDC at the appropriate current , while for 3V or 12V modules it's much easier to find drivers that might run 10 in series.

I'm not aware of LED fixture manufacturers providing the information about the drive requirements of the LED module - certainly none of the 3 fixture types I use has that information in the data sheets, as they are expected to be connected to mains voltage, and the manufacturer does not expect nor support modifying the fixture (including driver) as-built. As such you (or a good electrician who actually understands LEDs) would need to measure a "functioning" fixture to determine what the drive current and general voltage range are in order to choose a driver and wiring scheme sufficient to run 10 fixtures; Unless, of course, the driver modules you are replacing provide that information on themselves.

If you move back to the makers of the actual LED module, (or "light engine" as some call it) there's all sorts of drive data, but it's generally impossible to get a fixture maker to identify the module they use (and it may well change from time to time or batch to batch.)

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The lamps will draw more than their labeling since there are losses converting AC to DC for the LED's.

The previous poster's math is off but he is correct that the lower voltage means more losses over long distances.

200 watts would seem sufficient to run 10 - 14w lamps with added losses for rectification.

I suspect the drivers are going bad from heat generation. If they are surrounded by insulation they will run too hot and burn out. Try giving them some room to breathe.

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    If the fixture as built draws 14W, the LED module actually draws less wattage, since the drivers in the fixture (which take 14W at mains voltage) are doing the AC/DC conversion. My measurements of several LED fixtures suggests that the wattage labeling on fixtures is generally accurate for the mains input. – Ecnerwal Dec 11 '14 at 15:40

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