Equivalent Series Resistor (ESR) Value in Electrolytic Capacitors
Equivalent series resistor (ESR) in electrolytic capacitor is an interesting topic. Electrolytic capacitors can be found in many circuits in a circuit board but in today’s article I’m going to share with you about the electrolytic capacitors ESR found in the SMPS DC output line (filter circuit). I will not talk about ESR in details because there is already tons of information about ESR in the internet where you can refer to. In my previous article about different type of capacitors connected in parallel, I have explained about the function of this filter capacitor.
In order to test or to check the filter capacitor ESR, you need an ESR meter. In the market you can find many brands of ESR meters and comes with many different prices. One of the good features about ESR meter is that it can check the capacitor ESR while the capacitor is still in circuit (on board). Unless it is connected parallel with another filter capacitor or if the DC line is going to a low ohm component such as the heater circuit of CRT Monitor then you need to remove one of the leads and to test it.
If you found a capacitor with high ESR value or the capacitor already bulged, your next action would be to remove and replace with a known good capacitor and retest the equipment and hopefully the equipment will work again. This is a common procedure for troubleshooting and repairing electronic equipment. I myself also follow such procedures but what you need to pay attention is the brand of capacitors you are replacing.
From my repair experiences, I had encountered problem where the repaired set was returned for warranty claim because the capacitor that I have replaced became bulged after just couple of months only! A repeated call by customer means a lost time to you because you need to settle problem without getting any extra pay. If it happens few times to the same customer, you will be labeled as a non-professional repairer.
So, in order to solve the issue you really need a replacement capacitor with a good brand and are able to withstand higher temperature (105 Celcius). It is always a good idea to check the capacitor datasheet if you need more info about that particular brand of capacitor. For your information, there are certain conditions that can significantly affect the performance of a capacitor include high current, high frequency, and extreme temperatures but only frequency affects ESR.
In the above paragraph, I did not mention about using a super low ESR value capacitor. Basically low ESR capacitors mean it has:
- Less power losses across that capacitor
- Lower resistance thus lower heat generated from ripples (less internal heating problems means higher lifetime)
For your information, lowest capacitor ESR is not always a best choice to certain circuits such as the regulation feedback loop, Low Dropout Regulator (LDO) type of circuit, boost regulator circuit and etc. If a capacitor that has a bit lower ESR value than original is fine, but going ultra-low on a circuit may cause oscillation problem (instability).
Some says it is okay to replace with a very low ESR value capacitor but to some they will replace with the same type and brand of capacitor only. All electronics circuit design is eventually a compromise between theoretical perfection and practical real world working. This means if you have replaced the capacitor with a too low ESR value and the device have shown weird symptom (possible due to oscillation) then try replace with another capacitor (or original capacitor) that have higher value of ESR and do a retest. If all works fine then you should know what capacitor ESR value you should use.
Reliability of capacitor
Usually for branded capacitors, they will have longer service life and rarely bulge as compare to the non-branded one. When I searched for the price of a branded and a non-branded filter capacitor in my country local online website, this is what I have found:
Non-branded 1000uf 25 volt 105 Celsius- USD 0.15 each
Branded (Nichicon) 1000uf 25 volt 105 Celsius- USD 0.80 each
The above price is just a general guide and varies from country to country. I’m showing you how significant the price different between both kind of capacitors. There is no doubt that I will opt for the branded one to avoid repeated calls.
Repair tip- You can use a higher working voltage of capacitor for replacement. Example- for a 1000uf 16 volt, you can use 1000uf 25 volt as replacement in the filter output circuit. There are repair techs that used 2200uf 16v or 25 volt for replacement if the space is permitted.
Why there is more than one filter capacitor (Figure 2) connected parallel in the same DC line?
If you look at figure 1 below, you could see only one filter capacitor in the DC line (2200uf 16 volt):
Figure 1
Figure 2
Connecting more than one filter capacitor is actually to drastically reduce the total ESR value and to increase the total capacitance thus storing more current. If there is only one filter capacitor in the DC line, that particular capacitor would be working under stress but again it depends on the design. Now you have understood why certain power supplies have more than one filter capacitors in the DC line.
Conclusion- You always has the choice of what brand of electrolytic capacitor you wanted to use. For your information my choice would be always the branded one so that I can avoid problem after the repair have been done. If the replaced branded capacitor has caused weird problems in the circuit then I will use a different capacitor ESR value and retest the set. Hope you have enjoyed the article and if you have any question related to this topic you can post it in the comment section below.
This article is brought to you by Jestine Yong. He is from Kuala Lumpur Malaysia and he loved electronics repair and blogging about electronics repair information. He is the author of the famous Basic Electronics Repair and SMPS Repair ebook . He is also a trainer and conduct electronics repair courses at Noahtech Electronics Training Center.
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You may also interested in his previous repair article on the Functions of RC Snubber Circuit in SMPS
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Albert van Bemmelen
September 29, 2021 at 1:22 pm
Nice article that reads like a good story but of course is about the well known problem that e-caps are known for.
Those preferable branded (Nichicon) e-caps are often also used to replace the old e-caps on the printed circuit boards in Tektronix oscilloscopes when engineers are replacing the already about 30 year old components. And only the best are good enough for our expensive and still perfectly working Tektronix devices!
Jestine Yong
September 29, 2021 at 1:49 pm
Hi Albert,
Thanks for sharing!
Jestine
Arun Kumar
September 29, 2021 at 2:46 pm
Simple explanation good
Jestine Yong
September 29, 2021 at 3:31 pm
Hi Arun,
Thanks.
Jestine
Yogesh Panchal
September 29, 2021 at 2:48 pm
Sir,
Thanks! for Informative Article.
Jestine Yong
September 29, 2021 at 3:30 pm
Hi Yogesh,
You are welcome.
Jestine
Mark
September 29, 2021 at 3:39 pm
Hey Jestine,
A great article, much appreciated.
Keep them coming! 🙂
Jestine Yong
September 29, 2021 at 7:30 pm
Hi Mark,
Thanks.
Jestine
Parasuraman S
September 29, 2021 at 4:17 pm
"All electronics circuit design is eventually a compromise between theoretical perfection and practical in real world working", that's the punch! Very informative article! Many thanks for sharing! Learnt a lot of new tips!
Jestine Yong
September 29, 2021 at 7:30 pm
Hi Parasuraman,
Glad that you liked it...thanks.
Jestine
Waleed Rishmawi
September 29, 2021 at 5:41 pm
not all branded name capacitors are good. I buy capaictors off the net and I see a lot of china made caparitos but most of time they work just fine. I keep a lot of good ones (more expensive) and use them only when the situation called for. have a blessed day and thanks for sharing. as always I get excited and I enjoy alot reading and learning from your artiles. keep up the good work and God bless.
Jestine Yong
September 29, 2021 at 7:26 pm
Hi Waleed,
Thanks.
Jestine
Babu M S
September 29, 2021 at 9:35 pm
Very informative article,Learned many things. Thank you very much for sharing.
Jestine Yong
September 29, 2021 at 10:05 pm
Hi Babu,
You are welcome.
Jestine
gerald guillermo
September 29, 2021 at 10:08 pm
thankyou very much sir jestine for untiring efforts inputs to our enlightment...
Jestine Yong
September 29, 2021 at 11:31 pm
Hi Gerard,
You are welcome.
Jestine
Eric Rice
September 29, 2021 at 10:35 pm
Thanks Jestine for that great article!
I do a lot of repair on older tube amps for musicians, which require a very high quality cap. Most modern amps are made in China and are built with cheap quality parts to keep costs down. Reworking the amps with “Audio” quality caps makes huge differences in the total quality of amps. I have discovered that there are three basic grades to caps: Audio grade being the best, Computer grade being the second, and General grade. Additionally you may see, Industrial grade or caps with no grade identified (usually being the cheapest). I have great confidence in Sprague and Nichicon caps as well as CDE for film type caps (715P & 716P).
Hope this helps if you’re working on audio circuits!
Again, thank you for such a good article Justine,
Eric
Jestine Yong
September 29, 2021 at 11:34 pm
Hi Eric,
You are welcome and thanks for sharing your knowledge about the capacitor grades
Jestine
Joven Urbano
September 29, 2021 at 11:09 pm
Very informative and well-explained. Thanks a lot!
Jestine Yong
September 30, 2021 at 10:40 am
Hi Joven,
You are welcome.
Jestine
Henrique J. G. Ulbrich
September 29, 2021 at 11:47 pm
Thanks for sharing. Your articles are very, very didactic. Just one question: your information about a capacitor having too low ESR causing instability and oscillation in the circuit. This is completely new for me!. Opposite of what I always knew. How can stability/oscillation occur in this condition?
Jestine Yong
September 30, 2021 at 8:37 pm
Hi Henrique,
You are welcome. As to your question, it depends on the circuit designs. Some circuits (especially LDO that has the control loop) tends to be more sensitive as compare to others because the circuit had been sort of like ‘tuned’ to work perfectly base on the component’s value given. Here is an example of a SMPS that has a shutdown problem. The cause was just a LED current limiting resistor value slightly out of tolerance and this DC line is linked to the regulation/feedback circuit. You may think the shutdown was caused by a bad filter cap, bad Optoisolator IC, bad TL431 IC and etc but the reality the resistor that was out of tolerance value. This means this SMPS design together with the regulation circuit is super sensitive, a slight value out in one of the components along the DC line or in the regulation circuit will cause instability thus shutting down the power supply. Being said that, in those sensitive circuits, the ESR value must be between a certain minimum and a maximum value and only the design engineers know about it.
Jestine
Prasanna
September 30, 2021 at 4:36 am
Thank Sir.very informative that article
Jestine Yong
September 30, 2021 at 10:38 am
Hi Prasana,
You are welcome.
Jestine
Rodger Hopkins
September 30, 2021 at 5:07 am
Jestine,
Nice article as always.
Jestine Yong
September 30, 2021 at 10:38 am
Hi Rodger,
Thanks.
Jestine
Anwar Y Shiekh
September 30, 2021 at 5:58 am
Given the work of disassembly, diagnostics, repair and testing I would not consider anything but top branded low ESR capacitors.
Jestine Yong
September 30, 2021 at 10:37 am
Hi Anwar,
I agree with your statement!
Thanks.
Jestine
Mihai
September 30, 2021 at 11:55 am
Hello sir,
Thank's for sharing.
Jestine Yong
September 30, 2021 at 1:44 pm
Hi Mihai,
You are welcome.
Jestine
ulises aguilar
October 1, 2021 at 9:00 am
Excellent Sir
Jestine Yong
October 1, 2021 at 11:34 am
Hi Ulises,
Thanks.
Jestine
Henry Mayanja
October 1, 2021 at 8:36 pm
Hello Jestine,
Excellent explanation, I have learnt a lot
Jestine Yong
October 1, 2021 at 9:13 pm
Hi Henry,
Thanks.
Jestine
Imoudu Onwumah
October 3, 2021 at 2:34 am
Good informative article!!,however I don't relay on testing e-cap with esr metre only,I always use capacitance metre also.Esr metre is not 100% reliable.
Humphrey Mndaka
October 5, 2021 at 2:01 am
Hi Imoudu,
Which model is your esr meter? Maybe faulty otherwise the best tester for capacitors over 1uF is ESR meter.
Regards Humphrey
Tito Kanshulu
October 8, 2021 at 8:04 pm
A very good article and full of well graded information Jestine. In our community here the market is full of China made non-branded e-caps and we don't have any option but to use them anyway. The article is a real eye opener Jestine. Thanks
Jestine Yong
October 8, 2021 at 10:49 pm
Hi Tito,
You are welcome.
Jestine
Humberto
October 12, 2021 at 11:26 pm
Didactical the information shown in the article. It's a pity in my country is impossible to shop in the stores electronic/electrical components due to absence of these kind of stores, impossible via on-line. But anyway the knowledge is Gold.
Gregory Brettell
January 27, 2022 at 6:48 am
Bad/faulty capacitors are in equipment everywhere!! ... sadly, the customer pays the price ... first, the initial purchase of the product, and then the repair bill.
I wish manufacturers had higher standards in quality control rather than trying to make an extra dollar by cutting costs on using cheap unreliable parts.
I still have a Sears transistor radio from the 1970's ... all original parts and still working (unlike most things you buy these days).
Thanks for the informative article!