You know that you are nit picking right now. The requirements are clear, 5V2A. Test any of these supplies, and see what happens to the supply when you try to take 3A, it won’t and it will current limit at close to 2A. For UL requirements, they all have short circuit protection, which is a safety requirement. Most of these supplies are based on switchmode technologies and hence naturally current limit. This is just common sense, and so why do you expect Gerald to specify every detail. The documentation he compiled is very detailed so I would cut him some slack here.
Here is the recommended power supplies: http://elinux.org/Beagleboard:BeagleBone_Black_Accessories#Power_Supplies Here is what is described on the BeagleBoard FAQ What power peripherals are required/desirable? • There are several ways to power a Beagle. The option exists to feed the on-board regulators through either the 5V barrel connector input or USB input. When powered up over USB, the regulators are somewhat limited in what they can supply the system. Power over USB is sufficient as long as the software and system running perform some management to keep it under the USB current limit threshold. For simplicity and maximum capability, powering over the 5V barrel connector is typically recommended. • The power adapter is required to provide 5V over a 5.5mm outer diameter and 2.1mm inner diameter barrel connector (a barrel connector length of 9.5mm is more than sufficient). The recommended supply current is at least 1.2A (or 6W), but at least 2A (or 10W) is recommended if you are going to connect up anything over the USB. The actual power consumption will vary greatly with changes on the USB load. Regards, John > On Jul 5, 2016, at 4:42 PM, Harvey White <ma...@dragonworks.info> wrote: > > On Tue, 5 Jul 2016 16:00:05 -0400, you wrote: > >> On Mon, Jul 4, 2016 at 9:14 PM, 'Morgaine' via BeagleBoard >> <beagleboard@googlegroups.com> wrote: >>> John Syne writes: >>>> >>>>> a power supply that is spec’d at 4A should not shutdown when it sees a >>>>> 4A load, but rather, it should current limit at 4A. If the power supply is >>>>> spec’d at 4A, then 4A should not be treated as a short circuit. >>> >>> >>> That's impossible. You can't recommend that fundamental electrical laws be >>> overridden. :P >>> >>> If a PSU current limits at 4A, it can do so only by reducing its output >>> voltage. This may then drop below specification for its load and this can >>> have very bad consequences such as non-stop rebooting. There is no way for >>> the voltage to be maintained above its minimum spec while still providing a >>> current limit. >> >> Yes, but remember that the problem here is a startup inrush current, >> which would be handled properly by current limiting. After all, that's >> what the 2A current supply is doing: essentially, it soft-starts, >> providing limited current charging the input caps, while ramping up >> the voltage. Once the caps are charged and the supply voltage >> stabilizes at the nominal value, the system progresses to boot. > > Your discussion makes the assumption that the power supply provided or > specified is current limited at the maximum output current. I > (without looking at PS specs) have no such assurance. > > *with* such limiting, behavior is one way. Without that limiting, > behavior is quite something else. > > I don't remember (particularly...) that the power supply specification > mentioned current limiting. I thought that I had read only a voltage > tolerance. People on this forum have mentioned using a particular > supply (not model number, simply rating). The normal problem I have > seen was the current supply rating, so that the BBB could boot as well > as have sufficient power to drive such things as hard drives. > > It seems to me that this does not address the *maximum* current of the > supply, nor does it specify what kind of supply is expected to supply > that maximum. > > If this current capacity (as in surge current or current limiting) is > a difficulty, then perhaps it needs to be addressed. I have not seen > (nor particularly searched for....) such limitations. > > *if* they are important, then they need to be mentioned. If they are > not, then perhaps that needs to be mentioned as well. > > Harvey > > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to beagleboard+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/a3honbps1s8gtaspjnfhphdnfdo76n8cfv%404ax.com. > For more options, visit https://groups.google.com/d/optout. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/3BCC8D0D-6C76-49E2-80B4-12BE663EE859%40gmail.com. For more options, visit https://groups.google.com/d/optout.
