Question about charger / USB docking station
in [UK Mobile]
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From: jm on 8 Jan 2010 15:13 I bought a (third party) docking station for my HTC Touch Pro. It has two connections on the back, one for a USB cable to the PC for synching, and another 5V input for charging. I have a USB keyboard on my PC and I noticed that the three shift key status lights were illuminated when the PC was turned off, the charger is turned on and the docking station is connected to the computer using the USB cable. I can see that what is happening is the charging current is connected to the same point as the 5V power from the USB, and is flowing back down the USB cable to the other USB devices. Presumably it is not possible to have a blocking diode in the USB power circuit to prevent that from happening? Is this normal if you have a docking station with separate charging and USB inputs and is it likely to damage the computer? Am I supposed to use either the USB cable or the external charger, not both at the same time? Incidentally the USB cable came with the docking station and has a different connector from the one that plugs directly into the phone. So it is not a case of me using the wrong cable.
From: BORG on 8 Jan 2010 17:39 jm wrote: > I bought a (third party) docking station for my HTC Touch Pro. It has > two connections on the back, one for a USB cable to the PC for > synching, and another 5V input for charging. I have a USB keyboard on > my PC and I noticed that the three shift key status lights were > illuminated when the PC was turned off, the charger is turned on and > the docking station is connected to the computer using the USB cable. > > I can see that what is happening is the charging current is connected > to the same point as the 5V power from the USB, and is flowing back > down the USB cable to the other USB devices. Presumably it is not > possible to have a blocking diode in the USB power circuit to prevent > that from happening? > > Is this normal if you have a docking station with separate charging > and USB inputs and is it likely to damage the computer? Am I supposed > to use either the USB cable or the external charger, not both at the > same time? > > Incidentally the USB cable came with the docking station and has a > different connector from the one that plugs directly into the phone. > So it is not a case of me using the wrong cable. What did the instructions say ? I had one and it was either ither.
From: Denis McMahon on 8 Jan 2010 18:10 jm wrote: > I bought a (third party) docking station for my HTC Touch Pro. It has > two connections on the back, one for a USB cable to the PC for > synching, and another 5V input for charging. I have a USB keyboard on > my PC and I noticed that the three shift key status lights were > illuminated when the PC was turned off, the charger is turned on and > the docking station is connected to the computer using the USB cable. > > I can see that what is happening is the charging current is connected > to the same point as the 5V power from the USB, and is flowing back > down the USB cable to the other USB devices. Presumably it is not > possible to have a blocking diode in the USB power circuit to prevent > that from happening? > > Is this normal if you have a docking station with separate charging > and USB inputs and is it likely to damage the computer? Am I supposed > to use either the USB cable or the external charger, not both at the > same time? > > Incidentally the USB cable came with the docking station and has a > different connector from the one that plugs directly into the phone. > So it is not a case of me using the wrong cable. My PC supplies power to the USB ports when it's turned off, this means I can charge my mp3 player from the computer even when the computer is off. Are the shift status lights on when the new charger is disconnected? As far as I recall, the USB power spec provides for regulation and monitoring of the power on each outlet of a hub, so it shouldn't be possible for power to flow "back up the lead and into other USB devices." In fact I'm sure I've seen software apps that can display the power flows on each node. Rgds Denis McMahon
From: jm on 9 Jan 2010 05:32 On 8 Jan, 23:10, Denis McMahon <denis.m.f.mcma...(a)gmail.com> wrote: > Are the shift status lights on when the new charger is disconnected? No.
From: jm on 9 Jan 2010 05:33
On 8 Jan, 22:39, BORG <saerim...(a)gmail.com> wrote: > What did the instructions say ? There weren't any instructions. |