2021年3月30日 · A significant risk of damaging the load will exist if a non-conforming power supply delivers an output voltage that is greater than the legacy USB voltage of 5 V. Relationship Between USB Type-C, Power Delivery, and 3.1 Gen 2 The USB Type-C connector is closely associated with USB 3.1 Gen 2 and USB Power Delivery.

2013年12月18日 · A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0. As power is equal to current times voltage, all you have to do is multiply 5V with the current the device is drawing from the port.

2019年1月30日 · For USB 2.0 the spec says: • The voltage supplied by high-powered hub ports is 4.75 V to 5.50 V. • The voltage supplied by low-powered hub ports is 4.4 V to 5.50 V. USB Version 3.something introduces the availability of increased voltages (up to 20V). but a device has to explicitly request increased voltage, else they just get the same ...

2015年9月15日 · The higher voltage allows compensation for voltage drop to the device. If USB was 3.3v then if you had a long cable and poor connectors with 0.5v of drop then the device will only run at 2.8v. If the voltage is 5v the you still have 4.5v to work with and that is enough to run an LDO voltage regulator.

2017年7月14日 · Trying to connect multiple USB ports together to get more voltage or current is playing with fire. This would be especially so for putting USB ports in series to get more voltage, the ports almost certainly share a ground and connecting the ground of one USB port to the +5V of another USB port is just going to short circuit the power supply.

To measure the voltage then you either touch the meter probes onto the stripped ends of the wires or, if your cable end is a large connector, then touch the probes (without shorting them together) onto pins 1 and 4 of the connector.

2014年7月29日 · The QualComm QC (quick charging) method went a step further, and allows increasing the default USB voltage from 5V to 9, 12, 15, and 20V. After the device asserts some low-level signaling sequence on D+/D-, it then signals to the charger which voltage level it can accept by asserting certain DC combinations of voltages on D+ and D- wires.

2011年4月12日 · The USB spec lists a worst-case drop of 4.375 V at the device, after a bus-powered hub, with transient drops to 4.07 V. Keep in mind that not every USB host follows the USB spec, so it could be even worse. Wikipedia summarizes:

2015年3月12日 · This technology though does not use the Power Delivery specification as it uses the D+/D- lines of the USB 2.0 port to negotiate the voltage. Qualcomm Quick Charge 3.0 brings it one step further and now allow to "negotiate" any voltage from 3.7V to 20V by increment of 200mV. No data found so far about the current at each voltage.

The USB-IF has bumped up the maximum allowed current on USB-A over time and last I checked it allows a maximum of 2.4 amps. The voltage allowed on USB-A is 5 volts, at least according to USB-IF. There was the USB-PD 1.0 spec that allowed higher voltages on USB-A but I have not seen anyone actually use that spec in any devices available to the ...