[sdiy] Re: Bypass caps

[James Patchell]

Power One Supply don't current limit...they fold back.  This is because 
those things are generally pretty beefy....A power supply with a standard 
current limit will eventually charge capacitors up.  On the LM723, it seems 
like I remember you can set it up to either current limit or fold back....I 
just checked the data sheet...and yes, you can make either a fold back or 
standard current limit regulator with it.

The LM78xx regulators only have current limit.


At 03:39 PM 12/6/2005 -0800, Harry Bissell Jr wrote:
>No it does not. I'm using the standard "PowerOne" type supply...
>if it gets an overcurrent, it shuts down the output and remains latched
>off until power is reset.
>
>If you power off, then on again quickly, it will start because the caps
>are not 'all the way' discharged and the current spike is less...
>
>that is still ugly...
>
>H^) harry
>
>Seb Francis <seb at burnit.co.uk> wrote:
>>surely having a current limiting PSU (e.g. with an LM 723) would just
>>bring the voltage up as the caps charged?
>>
>>seb
>>
>>
>>Harry Bissell Jr wrote:
>>
>> > Just for the record (and noobs)
>> >
>> > another solution is to either
>> >
>> > Power one half the rack, then after a time delay
>> > of a second or so... power the other half using a relay.
>> >
>> > ~or~
>> >
>> > Power the whole system through some series resistors that limit the
>> > inrush current, then short across those resistors after a one second
>> > delay.
>> >
>> > This is how I did my system... but the 'brute force' larger supply is
>> > a valid option
>> > too. Its more size and weight, less complexity.
>> >
>> > Engineering... ~make the choice~
>> >
>> > H^) harry
>> >
>> > */Tim Daugard /* wrote:
>> >
>> > From: "harrybissell"
>> > .
>> > >
>> > What price failure ? More time is wasted by NOT using sufficient
>> > bypass caps than is saved by not designing them in (in small
>> > production runs). It is really hard to OVERDO the caps, unless the
>> > power supply is unable to start because of the peak current :^P
>> > >
>> >
>> > Which happens, my system reached the point where the power supply was
>> > ad! equete for steady stae use, but couldn't power up the system. I had
>> > to unplug one row of modules from the power chain until the system
>> > powered up. When all the other modules had charge their caps, the last
>> > chain got pluged in. I finally solved that problem by putting in an
>> > upgraded power supply - two modules wide with 3X the current
>> > capability.
>> >
>> > Tim Daugard
>> > AG4GZ 30.4078N 86.6227W Alt: 12 feet above MSL
>> > http://home.sprintmail.com/~daugard/synth.htm
>> >
>> >
>> >
>> >

         -Jim
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