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

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The USB Power Delivery specification revision 3.Zero defines an optionally available Programmable Power Supply (PPS) protocol that permits granular control over VBUS output, permitting a voltage range of 3.3 to 21 V in 20 mV steps, and a current specified in 50 mA steps, to facilitate fixed-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 utilizing certified PD aware USB cables with normal USB Type-A and kind-B connectors to ship elevated energy (more than 7.5 W most allowed by the earlier USB Battery Charging specification) to devices with better power demands. Prior to the USB Battery Charging Specification, the USB specification required that units join in a low-power mode (a hundred mA most) and communicate their present necessities to the host, which then permits the device to modify into high-energy mode. As of USB Power Delivery specification revision 2.0, model 1.2, the six fixed power profiles for power sources have been deprecated. The first Power Delivery specification (Rev. 1.0) defined six fastened energy profiles for the ability sources. In addition to limiting the whole average energy used by the gadget, the USB specification limits the inrush present (i.e., low voltage duplex power cable the present used to charge decoupling and filter capacitors) when the system is first linked.

On Acer Inc. and Packard Bell laptops, sleep-and-cost USB ports are marked with a non-standard symbol (the letters USB over a drawing of a battery); the characteristic is known as Power-off USB. This may increasingly trigger issues with some computer systems, such as drawing a lot current and damaging circuitry. The surroundings of the put in wires determine how much current a cable is permitted to carry. Rubber-like synthetic polymer insulation is utilized in industrial cables and energy cables installed underground because of its superior moisture resistance. Cables intended for very versatile service or in marine functions may be protected by woven bronze wires. Since wires run in conduits or underground cannot dissipate heat as simply as in open air, and since adjacent circuits contribute induced currents, wiring regulations give guidelines to ascertain the current capability (ampacity). Because a number of conductors bundled in a cable can't dissipate heat as easily as single insulated conductors, those circuits are all the time rated at a decrease ampacity. Another type of high-temperature cable is mineral-insulated cable, with particular person conductors placed within a copper tube and the space stuffed with magnesium oxide powder. With some cables the person conductors are wrapped in paper earlier than the plastic jacket is utilized.

To stop loosening of the connections of individual conductors of a cable, cables should be supported close to their entrance to units and at regular intervals along their runs. PD-conscious gadgets implement a flexible power administration scheme by interfacing with the power source through a bidirectional knowledge channel and requesting a sure degree of electrical energy, variable as much as 5 A and 20 V depending on supported profile. On laptops, charging gadgets from the USB port when it's not being powered from AC drains the laptop battery; most laptops have a facility to cease charging if their very own battery charge 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 other jurisdictions now require the Protective Earth conductor to be insulated to the identical commonplace as the current carrying conductors with Green/Yellow insulation. When a gadget would not acknowledge the sooner-charging standard, generally the gadget and the charger fall again to the USB battery-charging normal of 5 V at 1.5 A (7.5 W). When a device detects it is plugged right into a charger with a compatible sooner-charging customary, the gadget pulls more current or the gadget tells the charger to extend the voltage or both to extend power (the main points differ between requirements).

The USB Power Delivery specification revision 2.0 (USB PD Rev. 2.0) has been launched as part of the USB 3.1 suite. USB devices are also required to mechanically enter ultra low-energy suspend mode when the USB host is suspended. Typically, this stuff contain no digital circuitry, and thus aren't normal-compliant USB devices. China are required to make use of a USB port as a power port for battery charging. Prior 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 3.0 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 information channel that reduces the possibilities for RF interference. The Mini-USB could not be modified and stay backward suitable to the existing connector as defined in the USB OTG specification. The usual 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 enhancements required by the USB Type-C customary rev. 2.1; present power modes are retroactively renamed Standard Power Range (SPR).