Clearly you are not listening. I already said the voltage will drop and then rise as the capacitor charges, but the current will be constant until the voltage reaches the regulator voltage. All these references to all kinds of power supplies is senseless. We are only talking about the 5V2A supply recommended for the BBB, or the 5V4A supply suggested by the OP. If the power supply is spec’d at 2A, you are not going to get 10A because the power supply will protect itself and reduce the voltage to maintain the 2A limit. If this protection was not available, the power supply would just die. Your argument is this is a 10Watt supply, so if you drop the voltage to 0.1V, you can achieve 100A make no sense whatsoever. The maximum current is defined by the size of the wire in the coil or transformer and the size of the PCB traces. To prevent exceeding this max current, the regulator will reduce the voltage and maintain a constant current, thereby protecting the power supply from a dangerous failure.
Regards, John > On Jul 4, 2016, at 9:58 PM, 'Morgaine' via BeagleBoard > <[email protected]> wrote: > > John Syne writes: > > Nonsense. This is how the vast majority of power supplies work. The voltage > > ramps up while the current is maintained at it’s maximum current. When the > > voltage reaches the regulation voltage, the current is reduced. > > How? By magic? :P > > You appear to think that current limiting "just happens", without > understanding how it's actually done. It cannot be done without affecting > the supplied voltage, as that is core electrical theory. > > It doesn't matter how a PSU implements current limiting internally. It could > be manipulating effective internal resistance with linear devices, or it > could be altering buck/boost frequencies or duty cycles, or it could be > controlling linear or packetized charge injection into a capacitive tank, or > in a fun Heath Robinson world it could even be using stepper motors to switch > between transformer or inductor windings, but it really doesn't matter how. > Regardless of the internal technique in use, the end result is that when the > current limit is reached and fractionally exceeded, the PSU will always and > under all circumstances reduce the voltage supplied to the load that is > demanding the excess current. There is no alternative available in circuit > theory. > > And if the load keeps on demanding more current, that supply voltage will > keep on dropping, until it goes out of spec and then "bad things happen". > > You won't understand this until you check it out yourself --- easily done, > just grab a programmable PSU, set a current limit on it, watch the voltage on > a separate DVM, and reduce your load resistance to demand more current. Good > luck trying to keep the voltage fixed when you hit the current limit. Not > gonna happen. :-) > > Incidentally, it's very important that you try this and understand it. > Nothing in electronics will make any sense to you until this is fully > comprehended, as it's such a fundamental part of circuit theory. > > > -- > For more options, visit http://beagleboard.org/discuss > <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 [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/CAM0uzSuQY4gFZ%2Bt4BdrPg_0hUwj_BbW8c%2BOov0fznZyqXtfkpA%40mail.gmail.com > > <https://groups.google.com/d/msgid/beagleboard/CAM0uzSuQY4gFZ%2Bt4BdrPg_0hUwj_BbW8c%2BOov0fznZyqXtfkpA%40mail.gmail.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/BDEF82B0-502C-4CA5-B092-4EFC86B91A33%40gmail.com. For more options, visit https://groups.google.com/d/optout.
