This resulted in the Battery Charging Spec – BC 1.1 (later revised to BC 1.2). This interoperability issue, coupled with the rising popularity of battery-charging applications, gave the USB-IF enough reason to consider creating specifications for battery charging. However, due to the lack of a specification, interoperability was a major issue for first-generation USB battery chargers. As a result, USB-based charging products were created and launched in the market. In line with this functionality, USB 1.0 described a power source of 5 V 100 mA (0.5 W) while USB 2.0 described a power source of 5 V 500 mA (2.5 W).ĭespite there being no such guidelines in the specifications, designers figured out ways to use USB for battery charging.

Its purpose was solely to enable peripherals to power up. Power management in these initial generations was not intended for battery charging. Power management has been part of USB specifications since early generations. History of USB Power Delivery: A Secondary Function Gains Prominence This new USB power delivery specification allows power transfers of up to 100 W, along with other features and benefits. Almost at the same time as the USB 3.1 release, the USB Implementers Forum (USB-IF) released the USB Power Delivery Specification. However, this specification was only a precursor for what was to come. USB has always been positioned as an external bus for fast data communications, and has evolved in this way over the years. This specification introduced a mode called CDP (charging downstream port) that allowed for higher charging current (up to 1.5 A) compared to traditional USB.ġ. In fact, the first time a specification was made specifically for power delivery occurred only a few years ago in 2010: The Battery Charging Specification – BC 1.2 increased USB power delivery from 4.5 W to 7.5 W. With the focus on speed, power delivery was never the priority for USB.

However, another area of evolution for USB was sidelined earlier in its development-power delivery. 2), which again reemphasized the positioning of USB as a communications protocol. Moreover, each generation has been branded using terms such as “full-speed,” “Hi-speed,” “Super-speed,” and “super-speed+” (Fig. When observing how the standard has evolved over the years, one can notice a distinct bias toward increasing the speed of data communications (Fig. Since its early days, USB has been positioned as an external bus standard for fast data communications. This file type includes high-resolution graphics and schematics when applicable.

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