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Electrical devices powered by a DC adapter have specific in/out voltage/current values, so as an example what will happen if we used an adapter with 9v/1A output for a 5V/0.5A device?

Consider all cases either the output voltage/current of the adapter is lower or higher than the input voltage/current of the device. What will be the effect of each case and why?

As a real example, I have a power bank with Micro-USB input: DC 5V 2A and USB-C-Input (PD): DC 5V 3A, 9V 2A, 12V 2A, 14.5V 2A. I think I charged it with micro-USB from a DVB USB port used for connecting external HDDs, for recording, etc. After this, the power bank can be charged but it can not charge other devices. Is the USB port have any possible effect!!

Thanks

alsadk
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  • Is this homework? – Andy aka Sep 24 '20 at 15:45
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    @Andyaka no, it appears to be a user question prompted by the failure of a device the asker may have misued. It's somewhere between an off topic usage question, an off topic repair question, a duplicate of the canonical power supply ratings question, or an example of USB PD confusion... – Chris Stratton Sep 24 '20 at 15:48
  • @ChrisStratton the middle para seems to imply it is homework. – Andy aka Sep 24 '20 at 15:50
  • Using a voltage that is higher than the rated voltage for the device will cause the magic smoke to come out... – Vance Sep 24 '20 at 15:51
  • @Andyaka No its not – alsadk Sep 24 '20 at 16:03
  • @ChrisStratton This is always have been a question when I am trying to find the right adapter with no luck. Recently I had the power bank problem and I need to know the effect. – alsadk Sep 24 '20 at 16:05
  • @Vance What about using lowe voltage like using 5V for a device needs a 9V?! – alsadk Sep 24 '20 at 16:06
  • @alsadk the traditional power supply selection situation is described here: https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings Some things such as USB-PD are more complex situations as they can "negotiate" to work at various supply points. Questions on this site must be narrowly specific with full details provided, questions on the *usage* of products are generally off topic here as it is typically not possible to provide sufficient detail to have an answerable *engineering* question. – Chris Stratton Sep 24 '20 at 16:11
  • @ChrisStratton Thanks for the link I do not need to have an answer for a specific device I just need to know the concept. You can think about the power bank as an example. – alsadk Sep 24 '20 at 17:24
  • Does this answer your question? [Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings) – JRE Sep 24 '20 at 17:39
  • Questions here have to be specific, yours is too broad covering too many situations to be answerable. If you'd really read the linked canonical question you'd start to understand. – Chris Stratton Sep 24 '20 at 19:58
  • @JRE This is informative but my question here is: "What if a power bank rated at 2A input connected to a USB port 0.5-0.9A output should this harm the power bank or the USB port?" by reading the answers I am still confused – alsadk Sep 25 '20 at 09:04

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In general the effect depends on the device and power supply.

In general, connecting a 9V supply to 5V device could damage it immediately, or in long term, but it is impossible to say without seeing the schematics of the device how much excess voltage it can handle.

However, you are using USB devices, so the above does not apply.

In this case you simply used device with 5V USB output to a device that can take 5V USB input but also other voltages.

USB devices communicate which input and output voltages are supported, so a USB charger able to output more than 5V will output only 5V unless the charged device communicates and asks for higher voltage.

Justme
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  • Ok what about the current what's the effect of using a USB port to charge a power bank that needs a 2A not 0.5A that the USB port support? – alsadk Sep 25 '20 at 07:11
  • Again, USB is a special case and it depends on both devices how they are made. The 0.5A source port may have active overcurrent detection and shut down, or have a resettable thermal fuse (polyfuse) or plain old fuse that can blow and the port will become unusable. The device that is rated to consume 2A, it can be properly made and it may detect to what kind of port it is connected to and charge its batteries with current that is available, i.e. 0.5A data port or 2A charger. Or it might be dumb device and try pulling 2A which may break ports and chargers that cannot provide 2A. – Justme Sep 25 '20 at 08:09
  • So 0.5A does not affect the power bank but it might break the charger, not the power bank? – alsadk Sep 25 '20 at 08:26