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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Alex Eisenhut on October 14, 2014, 12:37:47 pm

Title: DC power supply design
Post by: Alex Eisenhut on October 14, 2014, 12:37:47 pm
Can someone tell me how to select the AC emergency capacitors after the bridge rectifier?
Title: Re: DC power supply design
Post by: lincoln on October 14, 2014, 11:56:54 pm
sure, select a value equal to 5/8 numble nuts by weight.

Title: Re: DC power supply design
Post by: T3sl4co1l on October 15, 2014, 03:13:15 am
The what?
Title: Re: DC power supply design
Post by: BradC on October 15, 2014, 04:24:02 am
Quote from: lincoln on October 14, 2014, 11:56:54 pm
sure, select a value equal to 5/8 numble nuts by weight.

No, no, no, no... not by weight.. by volume! Even a plumber should know that!
Title: Re: DC power supply design
Post by: Rerouter on October 15, 2014, 09:20:07 am
To give an actual answer, i am going to assume that you mean smoothing capacitors (or bulk storage capacitance) a general rule of thumb is about 1000uF per Amp of demand, in reality it varies a bit on how much headroom your supply has, e.g. if your rectified AC peaks at 24V DC, and your regulating down to 5V then it doesnt worry you if the voltage on the smoothing caps droops a few volts mid cycle, but if on the same supply you were regulating down to 19V, and burns a volt over the regulator itself it may become more of a concern and may need more smoothing capacitance to prevent any droops on the output,
Title: Re: DC power supply design
Post by: rob77 on October 15, 2014, 11:16:41 am
1000uF per ampere is the very minimum for a generic power supply. if you're designing some more serious audio stuff, then 2000-5000uF per ampere is what are you looking for ;)

and please don't use terms which are making no sense - no one on Earth (except you of course) knows what is an "AC emergency capacitor".
Title: Re: DC power supply design
Post by: mikerj on October 15, 2014, 11:31:24 am
Quote from: rob77 on October 15, 2014, 11:16:41 am
and please don't use terms which are making no sense - no one on Earth (except you of course) knows what is an "AC emergency capacitor".

The wording was intentional, read this thread (https://www.eevblog.com/forum/projects/tda-car-audio-chip-amp-purpose-of-output-caps/45/).
Title: Re: DC power supply design
Post by: T3sl4co1l on October 15, 2014, 03:34:59 pm
1000uF per amp is about typical at 25V supply.  Scale inversely with operating voltage.

Tim
Title: Re: DC power supply design
Post by: David Hess on October 19, 2014, 03:17:30 pm
For a 60 Hz AC input and full wave rectification, it is 8300 microfarad amps per volt of ripple.