USB Port and power delivery: An overview of USB port interoperabiliy

This paper discusses the interoperability between the computer USB port and handheld devices including power banks, cell phones and tablets. According to USB power delivery standard, a USB2.0 port can supply a maximum current of 0.5A at 5V [1] and a USB3.0 port can supply a maximum current of 0.9A at 5V [2], but the test results indicate that some of the handheld devices can draw 2.5A or more current through their USB ports depending on the design. (There are other requirements and standards specifically addressing USB product safety, but this paper focuses on interoperability related to USB power delivery standards.) Some consumers have reported damages to their computers when charging power banks through the computer USB port. And therefore it is beneficial to investigate if overloading is an issue. This paper provides an overview of the computer USB port power management and handheld device power management. This paper also proposes a solution based on the test results and circuit analysis.