Axelson, Jan. "USB 3.0 Developers FAQ" > 자유게시판

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The USB Power Delivery specification revision 3.0 defines an non-compulsory Programmable Power Supply (PPS) protocol that permits granular management over VBUS output, allowing a voltage range of 3.3 to 21 V in 20 mV steps, and a present specified in 50 mA steps, to facilitate constant-voltage and constant-current charging. In July 2012, the USB Promoters Group introduced the finalization of the USB Power Delivery (USB-PD) specification (USB PD rev. 1), an extension that specifies using certified PD conscious USB cables with standard USB Type-A and kind-B connectors to ship increased power (greater than 7.5 W maximum allowed by the previous USB Battery Charging specification) to units with larger power calls for. Prior to the USB Battery Charging Specification, the USB specification required that gadgets join in a low-power mode (one hundred mA maximum) and talk their current requirements to the host, which then permits the system to switch into excessive-power mode. As of USB Power Delivery specification revision 2.0, model 1.2, the six mounted power profiles for power sources have been deprecated. The first Power Delivery specification (Rev. 1.0) outlined six fastened energy profiles for the facility sources. Along with limiting the total common power used by the system, the USB specification limits the inrush current (i.e., low voltage duplex power cable the present used to cost decoupling and filter capacitors) when the device is first connected.

On Acer Inc. and Packard Bell laptops, sleep-and-charge USB ports are marked with a non-customary image (the letters USB over a drawing of a battery); the feature is named Power-off USB. This will likely cause problems with some computers, similar to drawing a lot present and damaging circuitry. The atmosphere of the installed wires decide how a lot present a cable is permitted to hold. Rubber-like synthetic polymer insulation is used in industrial cables and energy cables installed underground due to its superior moisture resistance. Cables intended for very flexible service or in marine applications may be protected by woven bronze wires. Since wires run in conduits or underground can not dissipate heat as easily as in open air, and since adjoining circuits contribute induced currents, wiring laws give guidelines to establish the present capability (ampacity). Because a number of conductors bundled in a cable cannot dissipate heat as easily as single insulated conductors, these circuits are always rated at a decrease ampacity. Another type of excessive-temperature cable is mineral-insulated cable, with individual conductors positioned inside a copper tube and the space filled with magnesium oxide powder. With some cables the individual conductors are wrapped in paper before the plastic jacket is applied.

To forestall loosening of the connections of particular person conductors of a cable, cables must be supported close to their entrance to units and at regular intervals along their runs. PD-aware devices implement a flexible power administration scheme by interfacing with the power supply by way of a bidirectional information channel and requesting a certain level of electrical energy, variable up to 5 A and 20 V depending on supported profile. On laptops, charging gadgets from the USB port when it isn't being powered from AC drains the laptop computer battery; most laptops have a facility to stop charging if their own battery cost level gets too low. USB IF Compliance Updates. Universal Serial Bus Cables and Connectors Class Document (PDF), Revision 2.0, USB Implementers Forum, August 2007, p. Cables insulated with compressed mica flakes are sometimes used. Most different jurisdictions now require the Protective Earth conductor to be insulated to the identical normal as the present carrying conductors with Green/Yellow insulation. When a device does not acknowledge the faster-charging normal, usually the device and the charger fall again to the USB battery-charging normal of 5 V at 1.5 A (7.5 W). When a system detects it's plugged into a charger with a appropriate sooner-charging customary, the system pulls more present or the system tells the charger to extend the voltage or both to extend energy (the main points differ between standards).

The USB Power Delivery specification revision 2.0 (USB PD Rev. 2.0) has been released as part of the USB 3.1 suite. USB devices are additionally required to robotically enter extremely low-energy suspend mode when the USB host is suspended. Generally, these things include no digital circuitry, and thus are usually not normal-compliant USB units. China are required to use a USB port as a power port for battery charging. Previous to Power Delivery, cell phone vendors used customized protocols to exceed the 7.5 W cap on the USB Battery Charging Specification (BCS). In May 2021, the USB PD promoter group launched revision 3.1 of the specification. USB 3.Zero Promoter Group. Howse, Brett. "USB Type-C Connector Specifications Finalized". It covers the USB-C cable and connector with a separate configuration channel, which now hosts a DC coupled low-frequency BMC-coded data channel that reduces the prospects for RF interference. The Mini-USB couldn't be modified and stay backward compatible to the prevailing connector as defined within the USB OTG specification. The standard is designed to coexist with the previous USB Battery Charging specification. Higher voltages require electronically marked EPR cables that assist 5 A operation and incorporate mechanical improvements required by the USB Type-C standard rev. 2.1; existing energy modes are retroactively renamed Standard Power Range (SPR).