Electrolytic capacitor life

As we all know, a good LED could last very long up to 50,000 hours with with a good heat sink. But how is the LED driver electronics life? For common LED drivers there is at least one component is very weak. It’s the electrolytic capacitor.

High Bay LED Lighting Driver Heat Dissipation Temperature Test Report article gives some use useful information related to electrolytic capacitor life.

Typical temperatures for the how electrolytic caps are 85°C and 105°C. Usually the life time is 2000 or 3000 hrs at one of the above temperatures. This is how electrolytic caps are specified. But the cap’s life doubles for every 10°C below that temperature. So if you go 40°C below the specified temperature, you gain a factor of 2^4 = 16. 16× 3000 hours = 48,000 hours.

If your LED driver has caps at temperature 80 °C, the LED driver only can last about 2 years or less. After that time you can expect poor performance (lowered capacitance, increased ESR) or even capacitor exploding.

Gerald_G_Capacitors

14 Comments

  1. Tomi Engdahl says:

    Trading off lifetime vs. cost in LED light capacitor selection
    http://www.edn.com/blog/PowerSource/41629-Trading_off_lifetime_vs_cost_in_LED_light_capacitor_selection.php?cid=EDNToday_20120216

    IC family specifically says that the driver can be made with no electrolytic capacitors – in other words, with ceramics. But as Andy Smith points out, the company (Samsung) has a bill of materials budget that it has to meet, and quite likely the Samsung designers didn’t have the luxury of specifying ceramic capacitors for this product.

    However, electrolytic capacitors, when properly derated, can provide reliable performance.

    It isn’t management demanding low prices, it’s the customers. No one is going to sell LED dulbs with 2$ capacitors, insideas Ed suggested, since the final price to the consumer is unacceptable.

    The actual cost at the checkout includes tax, retail markup, internal distribution, import, export, transport, packaging, advertising &NRE, and factory markup, so the total BOM cost is going to be about 10% of the sticker price.

    Reply
  2. Fallon Brezenski says:

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    Reply
  3. Tomi Engdahl says:

    Consider Ceramic Caps for LED Lighting Systems
    http://www.digikey.com/us/en/techzone/lighting/resources/articles/consider-ceramic-caps-for-led-lighting.html

    Designing an LED lighting system is becoming a more complex task as designs incorporate electronics for LED dimming, color, wireless control, and system “intelligence.” While engineers typically pay more attention to their choice of power devices, drivers and thermal management circuitry, they should not lose sight of the need to select the right capacitor for the job.

    Despite their higher temperature stability and smaller size when compared to such capacitor types as film and aluminum electrolytic, too often designers have passed on the use of ceramic capacitors for LED lighting, largely because of their piezoelectric noise, which admittedly has been a cause for concern.

    This article will look at advances in ceramic capacitor technologies that provide reduced noise and DC smoothing in LED lighting circuits. Examples provided will include Murata’s GR3 and RDE series and AVX’s QM series.

    Ceramic capacitor makers agree that noise is one of the biggest issues for LED lighting designs, particularly as LED dimming becomes more popular. Ceramic capacitors operating with a pulse width modulation (PWM) dimmer circuit can cause acoustic noise and light flickering due to piezoelectric effects within the ceramic material. Another potential obstacle is the capacitive DC bias of the ceramic capacitors, which results in a lower capacitance value.

    That being said, it does not take a Ph.D. from MIT to conclude that ceramic capacitors exhibiting lower noise and a higher capacitance value under DC bias will prove attractive for LED lighting designs. Ceramic capacitor suppliers know this, too, and they have taken different roads to resolve these issues, either by using new dielectric materials or by designing new internal electrode structures.

    Since LEDs are robust devices, just about any circuit used with them will negatively impact reliability, so the goal is to select circuits that will have the least negative impact.

    Designers should always evaluate all capacitor technologies for LED lighting applications, whether they are going to be used in rectification circuitry, output filtering or noise suppression. Performance tradeoffs will be based on each application’s requirements.

    Looking at ceramic capacitors in particular, designers should not automatically discount them for use in PWM dimming control circuitry because of their piezoelectric noise. Advances continue to be made in capacitor technologies, opening the door to their use in this and other new applications.

    Reply
  4. Shiela Bagan says:

    Thanks a bunch for posting!

    Reply
  5. content says:

    I read this post great post

    Reply
  6. Tomi Engdahl says:

    Ensure long lifetimes from electrolytic capacitors: A case study in LED light bulbs
    http://www.edn.com/design/analog/4411475/Ensure-long-lifetimes-from-electrolytic-capacitors–A-case-study-in-LED-light-bulbs

    Hot LEDs and short-lived electrolytic capacitors

    I personally measured component temperatures as high as +130°C in light bulbs purchased at local retail stores. Now admittedly, these were early LED bulb designs. Manufacturers now understand that, even though these LED bulbs consume substantially lower power than those they would replace, they still must have good thermal engineering. This is the only way to get the lifetime of the electronics to match the lifetime of the LEDs themselves.

    I found it disturbing that many of these hot designs contained electrolytic capacitors which are notorious for a short lifetime at elevated temperatures. I expected that the lifetimes of these capacitors would severely compromise the lifetime of the products, and not allow them to reach the 30,000 to 50,000 hour capability of the LEDs themselves. With common electrolytics rated at 2,000 to 5,000 hours at +85°C, I vowed not to use an electrolytic in any LED bulb designs.

    In talking to LED bulb manufacturers at that time I found that many did not understand the limitations of electrolytic capacitors.

    It is important to understand both the “endurance” spec of electrolytic capacitors and how temperature affects it.

    Conversely, lifetime decreases by a factor of 2 for every +10°C increase in temperature. Therefore, at +100°C, the endurance of the 2,000 hour, +105°C-rated capacitor mentioned above would be 21/2 x 2000, or about 2800 hours. Even if you assume that, on average, the capacitor operates at +95°C, its lifetime only increases to 4000 hours. This is hardly the 30,000 to 50,000 hours desired for LED light bulbs.

    This is a good example of the importance of fully understanding the details of component specifications.

    Reply
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  8. Hausratsversicherung says:

    Sehr informativ, vielen Dank! :-) Schauen Sie doch auch mal bei meinem Blog vorbei, der sich mit dem Thema befasst.

    Reply
  9. Tomi Engdahl says:

    The case of the flat panel TV scream
    http://www.eetimes.com/author.asp?section_id=30&doc_id=1284996

    Sometime during the day the TV began to “scream”; a loud high-frequency buzzing coming from the speakers. They called the local cable company to come out and fix it (thinking it had something to do with the cable box). When the cable tech couldn’t fix it they called in a TV place to fix it. That person told them the panel couldn’t be fixed. Given that it is a waiting room they said replace it and put the old one aside to go in the trash.

    My wife (of 24 years) immediately thought “Mike can fix it” and asked if she could take it home. Her boss said “sure, but they said it can’t be fixed.”

    As soon as my wife told me the issue I had a pretty good idea what was wrong, but I had to open it up to be sure.

    I’ll give you the symptoms and if you’ve been around any piece of electronic equipment in the last 10 years you’ll most likely get it right away.

    The panel came on, the CCFLs lit and all controls worked. As it came on you could hear the “squealing” start and ramp up very fast to a high pitch.

    Look to the cap
    Having worked on SMPS and seen similar problems before I knew one of the power supplies had to be the culprit, and more to the point a filter cap had to be the source of the problem.

    A quick look around the boards and I found the culprit; two of the electrolytics on one of the supplies were bulging.

    I pulled the supply out and removed the caps.

    I replaced them

    I turned the panel on and presto, no noise. So, a panel that had been deemed “unrepairable” was now mine for the cost of about 40 minutes of my time and a couple of replaced caps.

    Reply
  10. Tomi Engdahl says:

    Safety warning: Arduino GSM shield may cause fires
    http://hackaday.com/2013/09/24/safety-warning-arduino-gsm-shield-may-cause-fires/

    Be careful with those Arduino GSM cards. As [James] reports, they may turn into fire starters. One person has reported a small explosion and fire already on the Arduino forums

    [James] states the problem is a tantalum capacitor used to decouple the GSM radio power supply from the main Arduino supply.
    Tantalum capacitors are great for their low ESR properties. However, they have a well known downside of getting very hot, or even exploding when stressed.

    It’s not the Tantalum Anode that is burning. The Manganese Dioxide used as a cathode in some Tantalum capacitors is the culprit.

    It comes down to voltage rating (or more aptly, derating). The Arduino GSM shield runs at 5 volts. The designers chose a 6.3V rated capacitor. While this close of a tolerance may be good enough for some types of capacitor, it is a no-go for a Tantalum cap with Manganese Dioxide.

    The dielectric material in these capacitors is so thin that the stress of a reflow oven cycle causes cracks. The cracks pass leakage current, and this sets the Manganese Dioxide on the path to destruction.

    What’s the solution? [James] suggests several options:

    1. Switch to a 10 volt part
    2. Switch to a safer Tantalum Polymer capacitor.

    Reply
  11. Tomi Engdahl says:

    What the cap?
    http://wtfmoogle.com/?p=3585

    when I start hearing this pop pop pop pop sound…
    No power necessary…. these spare caps blew by themselves…
    Yay for Truth branded caps!

    Reply
  12. aqualusso steam shower says:

    Adore this blogging site, amazing work

    Reply
  13. Tomi Engdahl says:

    Aluminum capacitor slideshow: Handling heat issues
    http://www.edn.com/design/analog/4439149/Aluminum-capacitor-slideshow–Handling-heat-issues?_mc=NL_EDN_EDT_EDN_analog_20150409&cid=NL_EDN_EDT_EDN_analog_20150409&elq=fb4444feb5e44abd9f6c75715c15c8e5&elqCampaignId=22468&elqaid=25263&elqat=1&elqTrackId=7f4dfca5c59e4786855a82eca4c0814a

    The lifetime of an aluminum electrolytic capacitor will be shortened as its temperature increases. For every 10 degrees C decrease in temperature at the hottest spot of the capacitor, its lifetime is essentially doubled, so the lifetime varies exponentially with heat.

    Let’s delve much more deeply into this issue with Vishay’s educational technical presentation

    Your system reliability will strongly depend on keeping the heat down in capacitors.

    Reply
  14. Tomi Engdahl says:

    Aluminum capacitor slideshow: Handling heat issues
    http://www.edn.com/design/analog/4439149/Aluminum-capacitor-slideshow–Handling-heat-issues?_mc=NL_EDN_EDT_EDN_weekly_20150416&cid=NL_EDN_EDT_EDN_weekly_20150416&elq=baa986391459406f89da378a9e63d81e&elqCampaignId=22580&elqaid=25391&elqat=1&elqTrackId=6b0bcb35649d43b4851e4f3d3bb40e58

    The following presentation is an excellent technical tutorial given by Vishay Product Marketing engineer, Theo van de Steeg on handling heat issues when working especially with aluminum capacitors.

    The lifetime of an aluminum electrolytic capacitor will be shortened as its temperature increases. For every 10 degrees C decrease in temperature at the hottest spot of the capacitor, its lifetime is essentially doubled, so the lifetime varies exponentially with heat.

    Reply

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