23-02-13, 10:50 AM
courtesy of wikipedia (http://en.wikipedia.org/wiki/USB#Power):
I wonder what the schematic would be for a universal quick charger that would allow the full 1.5a for both Android and apple devices ?
Quote:The USB Battery Charging Specification of 2007 defines new types of USB ports, e.g., charging ports.[color=rgb(11, 0, 128)][51][/color][color=rgb(11, 0, 128)] As compared to standard downstream ports, where a portable device can only draw more than 100 mA current after digital negotiation with the host or hub, charging ports can supply currents above 500 mA without digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drop its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.[/color]
Charging ports exist in two flavors: charging downstream ports (CDP), supporting data transfers as well, and dedicated charging ports (DCP), without data support. A portable device can recognize the type of USB port from the way the D+ and D- pins are connected. For example, on a dedicated charging port, the D+ and D- pins are [color=rgb(102, 51, 102)]shorted[/color][color=rgb(11, 0, 128)]. With charging downstream ports, current passing through the thin ground wire may interfere with high-speed data signals. Therefore, current draw may not exceed 900 mA during high-speed data transfer. A dedicated charge port may have a rated current between 500 and 1500 mA. There is no upper limit for the rated current of a charging downstream port, as long as the connector can handle the current (standard USB 2.0 A-connectors are rated at 1500 mA).[/color]
Before the battery charging specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's [color=rgb(11, 0, 128)]iPod[/color][color=rgb(11, 0, 128)] and [/color][color=rgb(11, 0, 128)]iPhone[/color][color=rgb(11, 0, 128)] chargers indicate the available current by voltages on the D- and D+ lines. When D+ = D- = 2V, the device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device may pull up to 1000 mA of current.[/color][color=rgb(11, 0, 128)][52][/color][color=rgb(11, 0, 128)] When D+ = 2.8 V and D- = 2.0 V, the device may pull up to 2000 mA of current. [/color][color=rgb(11, 0, 128)][53][/color]
I wonder what the schematic would be for a universal quick charger that would allow the full 1.5a for both Android and apple devices ?
Opinions are like A**holes, Everyone has one. Some people seem to have more than one though which is a bit odd.