Analysis Of The USB Standard As A Power Supply

In the almost three decades of its existence, the USB standard has evolved from a data interface to a 240-watt power source. The paper presents the historical evolution of the USB standard by analyzing the characteristics of each power profile. The latest achievements of Power Delivery 3.1 are presented in the form of connecting power profiles, currents and nominal voltages needed for measuring current and voltage. Various small multimeters have been developed for measuring USB power delivery, of which the JT-UM25C was selected to analyze the practical representation of USB load measurement. The characteristics of the device and the related software were presented before the load analysis of three devices: BT headset, slow charging smartphone and fast charging smartphone. The individual measurements demonstrated the benefits of using a USB multimeter in determining the baseline required for regular assessment of the battery life of small devices. The USB multimeter was found to display incorrect battery capacity values when charging with gradually changing currents and voltages. Oscillograms, which give an accurate insight into the change in voltage and current over time, can only be created with a smartphone application. Regardless of the limitations, the USB multimeter gives a good insight into the state of the energy flow via the USB interface, which is why it is increasingly being integrated as part of USB power supply cables.