power supply esr low advice

[goodguy]

Hi And thanks for reading this post.

I am building an amplifier power supply and am going to parallel connect the capacitors to take advantage of lower esr.

But what is the esr goes too low and the power supply begins to oscillate, what is an easy way to tell if that problem is occuring.

Will there be a buzzing sound coming from the capacitors or from the speakers. Or will the power supply simply oscillate and damage the amplifer without any warning.

Many thanks.

 

[mbz]

never mind.

 

[BinaryMike]

There may be only a couple of situations where very low capacitor ESR can cause oscillation: [1] At the output of certain voltage regulator ICs or circuits. [2] In a pentode tube amp without screen stopper resistors. In both cases, the oscillation is likely to be supersonic/RF and more damaging to tweeters than to woofers.

It's best to operate the equipment with a dummy load and check for oscillation with a wideband scope or spectrum analyzer if there's any doubt about stability.

 

[Hyperion]

But what is the esr goes too low and the power supply begins to oscillate

I think that would be a very rare occurrence indeed, the exceptions are well stated by the post above IMO.

 

[goodguy]

Thanks for the replies.

Sorry, i do not have that type of equipment. Have a general multimeter and esr meter.

Is there a value for esr when it is becomes unsafe to go any lower

I have paralled ten 100uf capacitors so should be decoupling the higher frequencies.

The esr in total is 0.0001 ohms

 

[triode17]

You may be looking at this wrong. ESR is tested at 100kHz. So a very low ESR should mean that high freqs. are going to be bypassed to ground. Plus, ten caps. in parallel?? Thats' overkill. Usually see two or four in parallel, not ten !!

 

[mbz]

Not sure why esr is given such a "hard time". Keep in mind that it's made up of fixed components like leed resistance
and also the non perfect weld of electrodes. Think there is also a frequency component due to non-perfect dielectric
behaviour. ESR is used to model the caps behaviour. If you think of esr simply as resistance that should be minimised
then connect a resistor in parallel (please don't) as has been suggested in some other threads, simply playing with
numbers.

ESR and tan delta are "measures" as to how close to ideal the cap is. Certainly pick lower esr caps over higher
(Nichicon KW over KG I&II) but having 10 caps in parallel, this was for improved ripple behaviour right?

My next rant will be on the futility of filter/coupling bypass caps.