Comparison between Self-powered hub and Bus-powered hub

here are many request from customer to explain the behavior of two kinds of hubs: Self-powered hub and Bus-powered hub.

Some issues are due to this behavior.



For example,

When USB Cabel is connected or disconnected to the certain hub, Other USB device ( Keyboard, Mouse,etc) does not work normally.

The reason for this issue is following:
When the device turns on charging, it request 500mA from the USB, so other devices which attached to 'bus-powered' hub (which does not connect to power source) are not able to work well.



Here is the comparison between Self-powered hub and Bus-powered hub



A bus-powered hub is a hub that draws all its power from the host computer's USB interface. It does not need a separate power connection. However, many devices require more power than this method can provide, and will not work in this type of hub.

USB current (related to power) is allocated in units of 100 mA up to a maximum total of 500 mA per port. Therefore a compliant bus powered hub can have no more than four downstream ports and cannot offer more than four 100 mA units of current in total to downstream devices (since one unit is needed for the hub itself). If more units of current are required by a device than can be supplied by the port it is plugged into, the operating system usually reports this to the user.

In contrast a self-powered hub is one that takes its power from an external power supply unit and can therefore provide full power (up to 500mA) to every port. Many hubs can operate as either bus powered or self powered hubs.

However, there are many non-compliant hubs on the market which announce themselves to the host as self-powered despite really being bus-powered. Equally there are plenty of non-compliant devices that use more than 100 mA without announcing this fact (or indeed sometimes without identifying themselves as USB devices at all). These hubs and devices do allow more flexibility in the use of power (in particular many devices use far less than 100 mA and many USB ports can supply more than 500 mA before going into overload shut-off) but they are likely to make power problems harder to diagnose.
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-Quoted from open-site wiki, http://en.wikipedia.org/wiki/USB_hub.
For more details, you can refer to USB standard 2.0.
Please remind this:
"
However, there are many non-compliant hubs on the market which announce themselves to the host as self-powered despite really being bus-powered.
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In my office, I also confirmed my hub(D-Link) after taking off power cable, still recognized as 'self-powered' to host PC.

To check your hub is either self-powered, or bus-powered, you can check, Device Manager -> View ->Device by connection , and then right click on 'USB Root Hub' and then click 'Properties', click the tab, 'Power'. you can see how host recognize the hub.