Blog #1: LED Life Booster/Extender

RE: Blog #1: LED Life Booster/Extender

robogary — Sun, 30 Jan 2022 17:26:54 GMT

Hi Karthik - Interesting idea.

I suspect the LED bulbs are PWM controlled and not straight flat DC and have switching loss content.

I am not an LED light bulb expert, but I could even imagine light bulbs being designed for 100W, and the 30W bulbs are exact same construction, just with the internal switching power supply phased back to a lower voltage.

If I could be so bold as to suggest some additions to your idea, one is to add junction temperature calculations if possible,

Another idea for your study is to see the impact of a dimmer switch on the LED bulb. Dimmers on incandescent bulbs are a no brainer as they put out alot of heat, and reducing voltage reduced the heat directly by reducing watts loss.

I dont know if LED bulbs would be hotter if dimmed, stay the same , or run cooler. There is a tradeoff there of I2R losses in heat for switching losses.

RE: Blog #1: LED Life Booster/Extender

Gough Lui — Sun, 30 Jan 2022 13:48:04 GMT

That seems like an interesting proposal, however, I'm not sure that this is the best idea.

One reason is that simply turning the second panel on while turning the first panel off is going to result in the panels being cycled. The thermal cycling causes expansion and contraction stresses on the panel PCB and LED packages which can cause failure by delamination of lenses or gold bond wires over time. As each panel is operating at the full drive current (presumably) while it is on, it is likely that the second panel will then come up to temperature and you may switch back to the first but it has not cooled down all that much which could lead to endless cycling?

Maybe it is best (from my experience) to run both LED panels in parallel (as you already have twice the LEDs you need) with the same drive current spread across the two. With now halved drive current and double dissipation area, the temperature will be much lower and you will actually gain an increase in light output as the LEDs running at lower currents usually are more efficient as they suffer less from internal resistive losses. If you are targeting the same brightness, then you can reduce the current slightly because of the increased operating efficiency.

Most LED torches, for example, use a thermistor or other "continuous" reading temperature sensor to adjust the drive current to target a particular maximum heatsink temperature to avoid overheating. As the thermal switches provide a discrete output, perhaps you can reduce the drive current based on reaching a temperature threshold, rather than switching between panels, as that may be more effective in protecting the LEDs but this will have an obvious effect on the output.

- Gough

RE: Blog #1: LED Life Booster/Extender

navadeepganeshu — Sun, 30 Jan 2022 12:05:32 GMT

Great plan [mention:be8e07385afe4f4ab960fa2baba6372b:e9ed411860ed4f2ba0265705b8793d05]! LED parts are tortured very much by their own heat....