There’s nothing magical about the 100% number that damages diodes. However, there are reasons for running below 100% duty in order to increase the potential diode longevity.
A few things to consider:
- Diodes degrade from the moment you start using them. Even at lower duty loads. They are in constant degradation. The variable then is rate of degradation.
- Diodes themselves have manufacturing variance that can increase or decrease their actual working lifespan vs statistical life expectancy. DOA diodes are not unheard of.
- Calculated life expectancy of diodes is based on a very narrow set of conditions. Nichia, the premiere manufacturer of such laser diodes, calls for a recommended operating temperate range of 20-30 degrees C. Thats basically room temp and slightly higher.
- Heat is the single biggest factor in degradation and whether or not expected lifespans will be hit.
- Consumer modules are typically being driven harder than diode spec. And with designs that include dual-diodes or other elaborate designs heat dissipation becomes more difficult.
- Market forces are compelling laser module manufacturers for increasing performance at reduced costs. Most reviews are done within a short period after receipt of the laser. This isn’t necessarily conducive to a focus on reliability and longevity.
- Most laser manufacturers warranty their products for 1 year. If thought of as a consumable then there’s no need to hit the 70K hours mark or higher that the expected life expectancy of the diode is spec’ed to.
Having said that, the rationale for reducing the power level is to mitigate overdriving and easing the cooling burden in order to keep overall temperatures lower with the expectation that this will reduce degradation. This approach is true for pretty much all manufactured goods. Running things at less than 100% duty cycle increases longevity… or rather reduces the chance of premature failure.
To the extent that these laser modules are “made for it” to run at 100% power all the time is contingent on the quality of the design, the validation process, and how close your operating conditions conform to test conditions. Reports of premature failure are all too common. But then again, if all you care about is the ability to run at 100% power for <1 year then maybe that’s fine. It’s all a tradeoff.
Keep in mind also that if pressed, Neje themselves say not to run at 100% power continuously. There’s a different topic from someone who reported on this.