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您可以將USB 1.1集線器連接到牆上插座和充電設備嗎?

您可以將USB 1.1集線器連接到牆上插座和充電設備嗎?

Geoffrey Carr

讓舊硬件只是坐在周圍收集灰塵或擋住路徑是令人沮喪的,所以如果它可以重新利用並再次變得有用,那麼它就是令人高興的事。今天的超級用戶問答帖討論了為好奇的讀者重新利用舊的USB 1.1集線器設備的可能性。

今天的問答環節由SuperUser提供,這是Stack Exchange的一個細分,Stack Exchange是一個社區驅動的問答網站分組。

照片由Alexandros Kostalas(Flickr)提供。


超級用戶閱讀器user1049697想知道是否可以使用舊的USB 1.1集線器為他的設備充電:

I have an old USB 1.1 hub and I was wondering if it could be repurposed for something useful. Would it be possible to connect it to a wall charger that has a built-in USB outlet and use the hub to get 4 USB charging ports? Do USB hubs not work well when connected to wall outlets?

The image below shows a hub similar to the USB 1.1 hub I have:

(Update) I did try this with some devices and the results are as follows:

  • My old Android 2.3 device will charge, albeit very slowly.
  • My iPhone 5S will not charge at all.

是否可以使用舊的USB 1.1集線器為設備充電?



Unfortunately, it really depends on the specifics of the implementation of both the hub and the device.

The vast majority of simple hubs do not really implement any sort of power control. They will just connect the USB power lines directly to either their host or an external (regulated) power supply, which means you would effectively be sharing the capacity of the power source over all ports.

In practice, however, USB charging gets quite complex. The bottom line is that your USB 1.1 hub will probably charge your peripherals, but at a reduced rate. This is not because the hub is actively limiting the current output, but because peripherals will limit the current they draw unless they can positively confirm the host is capable of supplying that current (to prevent damage to hosts that cannot).

This reduced rate depends on the specific peripheral and the specific hub, but it likely ranges from 100 mA to 500 mA, which is far less than a modern smart phone’s maximum (over 1,000 mA).

To elaborate:

1. If the host implements some kind of power control, then the peripheral must initiate a data connection and negotiate properly. Even though this is technically required by the specs (except the newer battery charging specs), some peripherals might not do so. I imagine most smart phones will at least try, but there are many ‘dumb’ USB peripherals that will not.

2. In the case of a hub connected to a USB power supply without a proper host, it might not work at all.

3. Negotiation is as follows:

  • Each peripheral is permitted to draw one unit load without negotiation. Each peripheral should communicate with the host to request more units.
  • USB 1.1 and 2.0 define one unit load as 100 mA, with a maximum of 5 unit loads (500 mA).
  • USB 3.0 defines one unit load as 150 mA, with a maximum of 6 unit loads (900 mA).

4. Modern devices often need more power (smart phones often draw 1,000 mA – 2,000 mA).

5. There is a battery charging specification that deals with this. Read through the article “How USB Charges Just About Any Electronic Device” for details on how its negotiation and detection works, but that is not too important.

  • The charging limit is 1,500 mA, but only if the data lines are shorted together (or respond as if they have been). This is not the case with a data-capable host like a USB hub. There is an additional profile that deals with this, but a USB 1.1 hub probably does not implement it.
  • With a non-compatible host, most smarter peripherals will fail to detect a high-capacity source and will therefore fall back to charging at 500 mA at most. This means your USB hub will likely charge the device at a significantly slower rate than plugging the peripheral directly into the charger.

5. There are some other specs such as Apple’s protocol, Qualcomm’s quick charge protocol, etc. They all have their own detection and negotiation methods. They will also not work with a USB 1.1 hub.

6. There is a newer USB Power Delivery spec, but almost nothing implements it yet and it deals with all sorts of wacky things like different voltages.

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