Street LED Light & Power Driver - Surge and Over Voltage/temperature Protection Solution

Perhaps I'm reading this wrong, but LED's do not have the same inrush current problem that is inherent with incandescent lighting. There is no filament, no dramatic change in resistance with temperature, and nothing to produce current spikes in the LED driver, which should be in saturation anyway.

Nope. Not without a clearer description of what you have to work with and what failure mode you're trying to avoid.

Well, maybe a few hints. If you suspect overvoltage spikes, measurements with an oscilloscope or power line recording monitor will be helpful to determine how much protection is required. If it's a low energy short duration spike, a simple MOV (metal oxide varistor) should be sufficient. If it's a high energy spike, with longer duration, you'll need some kind of LC filter in addition to the MOV. If the input voltage varies substantially for longer durations, such as in automotive applications, find a better protected voltage regulator.

Dear Jeff,

Thank you for your kindness of technological information. We are not the LED light designer, just the circuit protection component ma nufacturer. For years, our factory has designed the components for protecti ng LED and power driver from abnormal circuit. Our designs would involve th e over current, over voltage and surge protection. MOV for small over-volta ge protection, TRXF(built-in with thermal fuse and RXF) for over current pr otection, SPD for high spike surge protection.

Personally speaking, I would like to get more knowladge of LED/power driver 's protection.

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First of all, if you expect to reach the 30,000-100,000 hour life time as some manufacturers claim, you need to run the LED below Imax/3 i.e. a 1 A (3 W) LED should be run at 350 mA or less. For white LEDs with phosphors, the light output degrades very fast when driven with Imax or even above.

Running well below rated current greatly simplifies the thermal design, especially lowering the temperature different between junction and LED case.

An additional advantage of running well below Imax is that the efficiency drops significantly when approaching Imax, the best performance is around Imax/2 or Imax/3. To get the same light output, running well below Imax will require more LEDs, but not as many as one might expect, i.e. two LEDs at Imax/3 will nearly as much light as one at Imax, especially when considering the situation after 10,000 or

For traffic lights (and other lights with frequent cycles), use a heavy metallic block as heatsink, so that the LED case temperature remains nearly constant (but elevated). The thermal resistance from heatsink to air with _average_ power consumption will then determine the case/heatsink temperature. The junction to case thermal resistance will then determine the junction temperature variation during OFF/ON./OFF.

At least in Europe, mains connected devices should be tested for 1500 V and devices in main distribution panels at 2500 V. I guess street lights might need that higher rating.

For a Class-II (double insulated) case would be simpler, since you only have to protect against differential overvoltages and let the whole electronics and LEDs jump at some unspecified voltages against ground, just use sufficiently insulation against anything grounded.

For a grounded Class-I you would also need additional overvoltage protection against common mode voltages.

Surreptitious spam, I think.

On Wednesday, July 29, 2015 at 2:59:03 PM UTC+8, snipped-for-privacy@downunder.com wro te:

ts and the power driver. But the surge and over voltage, frequent inrush st art-up current will always harm the life of each LED and the driver.

Thanks. Our Thermal protected MOV has the over voltage protection function. The therminal protection could present MOV fire while MOV failure. Like as our TFMOV10S- TFMOV20S series, the Imax is from 2KA-15KA.They are q uite enough to protect the LED circuit during designing.

According to our Surge Protective Device, we offer differential and common mode protections that installed inside or outside LED power supply. While t he in series with MOVs overheating during the abnormal circuit happened, th e interal thermal cutoffs will cutoff at its set fusing temperature. So the y could disconnect the circuit and stop MOV over heating or getting fire. The SPD is also good for protecting lightning hitting.