Types of capacitor should be used

Thread Starter


Joined Nov 8, 2011
I found the following electroylic capacitors get very hot and have smell coming out, the related areas for that capacitors are working at +90VDC and at frequency 20KHz.
- 1uf, 400V
- 10uf, 400V

I checked that there is no wrong polarity connection mistake involved and think that the type of capacitor I used is not suitable. What is the meaning for ESR for capacitor, are there such reading marked on capacitor for the distinction?



Joined Dec 26, 2010
It is also might be that the ripple current (the AC component of the current) is really too big even for the best electrolytic capacitors. Depending on what your circuit is, this might a design issue or the result of a component failure.

If you post a schematic, somebody may be able to advise you further.

Thread Starter


Joined Nov 8, 2011
Where can I buy ESR capacitor? I already bought a 1uF 400V capacitor of audio use type, there is no such ESR marking on it but it's price is five times the general capacitor of same rating. However, same high temperature and smelling happened when using. Can I use polypropene or mylar type or etc. instead of electroylic type? Of course, I don't prefer these because their sizes are much bigger bigger than the space available in the populated circuit board.

P.S it is used in floating voltage supply in high side gate driver, so its voltage is shifted +90v to 0 at frequency 20KHz.



Joined Feb 19, 2009
If you bought an "audio grade" capacitor, take it back.

They are generally dressed up standard capacitors, with average specs, but specially plated and had a virgin's tear land on it during a full moon in February.

Digikey sells Low ESR capacitors, I'd suggest Nichonon or Panasonic lines

Mouser also carries those brands.


Joined Oct 26, 2011
Low ESR capacitors have current ratings at 120hZ and 10kHZ or 100kHZ indicated on the datasheet--in some applications, it requires parallel capacitors to increase the current rating.

New observation:
It appears that capacitors of this DC voltage rating (>150VDC) are not specified in terms of ESR, but current rating only.

I did a quick search on DigiKey's search engine and located this 10uf 250V radial capacitor with a current rating of 350mA @ 100kHZ that was designed for nasty ballast applications--it may possibly work???



The 450V version has a current rating of 450mA--higher probably due to increased surface area that enhances cooling.