USB powered - how does it work?

Question

Electronics

1. Does the voltage of the chargers sag when powered? (So that you can judge the maximum power by the drawdown)
   
2. As far as I know, phones suck 0.5A, and they start taking more when the data contacts close (d + and d-) - and if they are opened, then what - immediately the power is limited to 0.5A?
   
3. What if the mains charger is designed for 0.5 or 1A, and try to take more from it (2 or 3A for example) - will it burn out (overheat to a state of corruption) or should they be designed for this?
   
4. In mains chargers, there are probably rarely fuses (and if there are, then on a short circuit), but in "portable chargers" for what max. current usually protection? For example, if they are designed for 2A, then maybe they are already cutting off power at a current of more than 2.1A?
   
5. What is the max. voltage and current for microUSB contacts - what do you think? (By the way, male and female seem to have different resistances)
   
6. Do all mobile devices support data transfer while charging? (and by the way, do you know where to buy hubs for this? to charge the host when the mouse is connected)
   

Answer 1

1. Yes, it sags. But it depends on the design scheme and the wire used.
2. Not necessarily, a personal matter of the manufacturer, this requirement is not described by standards.
3. Nothing will happen, he just won't give out more than his face value. And it will burn or not, it depends on the execution scheme and the level of "Chinese".
4. You cannot take more current from the source than it can give. The fuses are for short circuit protection, it is not needed from the rest.
5. Do not use them for purposes not intended for them. 5v / 1-2A is their rating. And again, everything will depend on what quality the connector will be - poor contact, for example, these are drawdowns and heating = failure.
6. Depends on the manufacturer, not described by standards. But most support it because nothing prevents it.

Answer 2

1. The charger itself (or any other device with a USB host) sags when more current is taken from it than it can give. In normal mode, the voltage at the charge output is maintained at 5.0v - 5.2v
. But at the other end of the cable, a drawdown is already possible! The higher quality wires and connectors they use, the lower the voltage drop. (that is why it will not be possible to squeeze out 2A using a bad cable - the voltage will drop, the phone will see this and moderate the appetite)
2+3. The USB standard (up to 2.1 inclusive) obliges device manufacturers to consume no more than 0.5A during operation. In USB 3.0, this threshold is raised to 1A. Moreover, a USB host is not required to support devices with a consumption of even 0.5A - according to the standard, upon initial connection, the device reports what current it needs to work, and the host answers if it can provide it. According to the standard, during initialization, the device should not consume more than 0.1A
This is where the phone industry and the microUSB charging port standard come into play. When the USB standard, intended for communication, began to be used "stupidly" to provide power to devices, confusion began. If, when connected to a PC, the phone could "ask" how much current it could give out, "stupid" charges did not support any initialization and connection establishment, and it was possible to take from them ... but how do you know how much ampere you can take from charging? What current does the phone consume when 5 volts is plugged in ?? And in general, what if this is not a stupid charge, but a cable with broken data buses connected to a PC, from which you can not take more than 0.5A ???
In general, they came up with the idea of ​​checking whether the data buses are closed, and if they are closed, take, for example, 1A. In other manufacturers, the same Apple, charging applied a certain voltage to the data bus, which the phone determined, recognized the charge as “its own” and consumed, for example, 2A.
Then Qualcomm came up with QuickCharge, made smart charging and put as many as 9 volts through the cable instead of 5 volts. In new versions, the voltage rose to 12, and then to 20 in general. And all this via USB ... Something got me in the wrong place. What's the next point?
4. I didn’t see any fuses in the chargers. Usually the voltage sags, up to four volts. At this voltage, the phone can no longer take a lot of amperes and automatically reduces the current consumed.
5. The standard voltage at which devices can theoretically be charged is in the range of 4.0-5.5 volts (I have a charger with 5.5). With QuickCharge 3.0 - voltage up to 20 volts. Depending on the quality of the cable, up to 2 amps can flow through it. Well, a maximum of 3, it's no longer worth it - the contact point will overheat and everything will melt nafig.
6. In what direction? Charging is generally a by-product of the USB standard. If you are talking about connecting the phone to a PC, at which it is charging, this usually always works. If OTG - on my phone I managed to make it charge at the same time. But not always. In this mode, according to the USB standard, the phone must serve as a power source, and not vice versa, be charged from the device connected to it.

Answer 3

Or via transform if you don't care about dinosaur support, something like this codepen.io/anon/pen/pRKaww

Answer 4

codepen.io/Geyan/pen/zNapqB?editors=1100 like this - just fix the colors

Answer 5

Approximately this can be done.
https://jsfiddle.net/btj2p7x1/
The very essence is clear, then on your own;)