| General > General Technical Chat |
| Explain to me the (de?)-evolution of LED lightbulb technology |
| << < (4/15) > >> |
| TimNJ:
Here's an example of an circa-2013 LED bulb: Here's a slightly newer construction (circa 2016), less parts, but still generally high level of complexity: Now, LED bulb might just have a simple capacitive dropper like this one. Remind me what the downsides of these are again? Power power factor for one. Or some highly integrated constant current driver like this. But, as far as I know, these are linear constant current drivers, i.e. MOSFET/BJT operated in ohmic region to maintain constant current? Is it that LED efficiency has improved so much that burning a little power in the driver is less of an issue since the lumens per watt is better than it was before? |
| TimNJ:
And, adding the above point about linear constant current regulator. If it's effectively a linear regulator, then there's no real need (or less of a need) for EMI filter since there's likely no high frequency switching activity. |
| james_s:
--- Quote from: TimNJ on March 23, 2021, 12:36:51 pm ---My main point of curiosity is in understanding *what changed* between 2014 and now. What has gotten more efficient? The LEDs themselves? Why did the drive electronics go from complicated (50+ parts on the BOM) to completely minimalist (maybe 3-5 parts on the driver BOM). Did the ICs not exist yet? --- End quote --- The LEDs themselves mostly, they have gotten much more efficient. This enables them to be driven at much lower current, which simplifies everything else. The efficiency of an LED drops pretty dramatically as you crank up the current and the early ones had to be driven hard to get enough light out of them. This meant a mechanically complex design to deal with all the heat since almost none is radiated along with the light as with incandescent, instead it all ends up in the die itself. Then there are many new ICs that didn't exist before, and due to the lower power requirements enabled by newer more efficient LEDs the drive circuits can be simpler as everything runs at lower current. |
| james_s:
--- Quote from: TimNJ on March 23, 2021, 02:46:40 pm ---I love the filament bulbs, just wondering how we get away with a tiny 6x12mm or 8x12mm electrolytic cap in the base + some dinky looking diode bridge, while 5 years ago, the average LED light bulb had some monster 10x16mm cap, inductors, MOSFETs, all sorts of control stuff. We just don't need it anymore? Much better integration with new control ICs? In the early days companies were taking a much more old skool approach to doing constant current driver from mains? I've seen (I think electronupdate) do a filament bulb life test and they seem just as capable of lasting a long time, all things considered. I'm mainly just wondering where the heck all the control and power conversion circuitry went. --- End quote --- The filament bulbs have dozens of LED dies in series and drop close to the full line voltage across the LEDs at very low current, this makes it reasonable to use a simple linear regulator IC without crazy high losses. Compare this to an early bulb with perhaps 6-8 LEDs with a total forward drop of 30-40V being driven at 300-700mA, naturally it's going to require a more complex driver with bigger capacitors. A significant downside of many of the simpler bulbs though is that they flicker at line frequency, I find the flicker annoying and avoid those. |
| coppice:
--- Quote from: james_s on March 23, 2021, 05:08:48 pm ---The LEDs themselves mostly, they have gotten much more efficient. --- End quote --- They are not just more efficient. In 2014 Cree and one or two others had solved the problem of rapid ageing, while most makes were far dimmer after a few thousand hours. Now it seems most LEDs fade very slowly. |
| Navigation |
| Message Index |
| Next page |
| Previous page |