DC DC Converter operating life

Discussion in 'General Electronics Chat' started by Convex, Apr 12, 2015.

  1. Convex

    Thread Starter New Member

    Apr 12, 2015
    What is the typical operating life of a DC DC converter? Are there any particular types that last longer?

    The particulars of the DC DC converter that I might desire are: ~20-200 W, ~24-48 V input, ~14 V output. I'm just mentioning that in case high power converters tend to have a lower life.

    The potential application here is to use an ultracapacitor bank to power a light. The output voltage of the ultracapacitor bank would vary with its state of charge, so a DC DC converter would be needed to maintain a constant voltage into the light source.

    The idea is that both the light and the ultracapacitors could last for 10 years or more, but I am not sure if DC DC converters typically last this long (especially when in use for 12-24 h a day)...

    Does anyone know? Or has anyone operated a DC DC converter for so long that they can confidently say that they do not have life issues?

    I know quite a bit about ultracapacitors, but very very little about electronics.
  2. paulktreg

    Distinguished Member

    Jun 2, 2008
    The datasheet may give you a MTBF (Mean Time Before Failure)?
  3. Convex

    Thread Starter New Member

    Apr 12, 2015
    Roderick Young likes this.
  4. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    Although small converters like the 15 W datasheet usually are more reliable than higher power models, I've seen 1 million hour MTBF numbers for decades, and none of them are true. They are based on a set of calculations, which are based on a set of assumptions and conditions, which are usually secret and never identical to your particular application. So while they are useful in weighing the relative merits of two similar, competing products, they can not be used to predict demonstrated reliability of an individual unit unless your operating environment happens to be almost identical to Belcore or MIL specs.

    Still, there are techniques that can be applied to circuit design and component selection that will (statistically) increase the long-term reliability. Some are general industry rules of thumb, some are in company requirements documents, etc. Things like:
    Never operate a capacitor at more than 50% of it's rated voltage.
    Same for transistors.
    Never operate a capacitor at more than 25% of its rated ripple current.
    Never operate a resistor at greater than 50% of its rated power.
    Same for connector pins.
    Same for transistors.
    Never operate an IC within 20 degC of its rated temperature (40 degC is better).

    I'm sure many of the more experienced designers on this forum have their own lists of do's and don'ts.

    In terms of the operating environment, two things reduce the long-term reliability of an embedded power supply more than any others: power-on cycles and heat.

  5. ian field

    AAC Fanatic!

    Oct 27, 2012
    SMPSU life seems to depend more than anything, on where the manufacturer got the electrolytic capacitors.
  6. Convex

    Thread Starter New Member

    Apr 12, 2015
    Thanks for those additional points. It's very valuable as I have not heard these things before. I have also noticed the higher power converters have fans, which would probably limit lifetime to a lot below the mtbf rating. On the electrolytics, I just happened to have watched a vid where the buyer (an electrical engineer) peeks into his computer power supply and manages to ID the caps in there (panasonic) - which he gave the tick of approval to.
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    On the contrary. Without the fans to remove heat the converter lifetime would be very short.