NCPRE | January Newsletter
Universal USB Charger

In this information-rich world, information is getting increasingly portable nowadays. With the huge demand to deliver global information in a timely and efficient manner, information sharing needs a portable platform for real-time response. Portable Electronic Devices (PEDs) including mobile phones, laptops, tablets and wearable electronic devices are the most promising ways that have facilitated the rapid growth of information sharing and processing.

The heart of these PEDs is their battery chargers, these battery chargers are simply AC to DC power converters also known as AC to DC adapters. Since, different PEDs require different voltage and power levels to charge their batteries, each PED needs a battery charger of its own kind. Also, various electronic devices like digital cameras, speakers, monitors, etc. need dedicated AC to DC adapters, which can meet their voltage and power specifications. In summary, the increasing numbers of PEDs and other electronic devices result in the manufacturing of a large number of AC to DC adapters and when discarded, flooding the earth with an enormous amount of electronic waste (e-waste).

E-waste is one of the fastest-growing waste streams, and its disposal is a challenge for the whole world. It is estimated that 50 million tons of e-waste have been generated globally in 2018, and half of this comprises of personal devices such as computers, laptops, smart phones, tablets and TVs. The discarded AC to DC adapters of these devices are also contributing to the global e-waste generation significantly. So, it is worthwhile to explore the concept of a universal USB charger (single USB charger for all PEDs), as it could be a step towards significant reduction of global e-waste generation.


USB STANDARDS AND SPECIFICATIONS

A USB specification is a set of protocols that defines both the data transfer rate and power transfer capability through a USB connector and port. Table below illustrates the evolution of USB specification in terms of their power handling capacity. The first version of USB specification, called USB 1.1, was brought into existence in the 1990s. USB 1.1 specification had a maximum transfer rate of 12 megabits per second (12Mbps) and maximum bus power transfer capability of 2.5 W (5 V, 500 mA).

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Table: Evolution of USB Specifications
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The next revision was USB 2.0, with a maximum transfer rate of 480 Mbps. The further revision (USB 3.1) has ramped up the data transfer rate to a greater extent, 5.0 gigabits per second (USB 3.1 Gen 1), 10.0 gigabits per second (USB 3.1 Gen 2) and 20.0 gigabits per second (USB 3.2). In addition to higher speeds, this specification has also increased bus power, offering 4.5W, compared to 2.5W that was available in USB 1.1 and USB 2.0. USB BC 1.2 is a special USB specification, introduced for a USB charger, a device with a dedicated charging port, such as a wall adapter or car power adapter, with a maximum power delivery of 7.5 W. USB Type-C is simply a new connector type for USB 3.1, which can carry a maximum current of 3 A, hence it can deliver maximum power up to 15 W. Since, the evolution of the first USB 1.1 till the USB Type-C specification, a nominal voltage of 5 V has been maintained and only the current has been incremented from 500 mA to 3 A, restricting the maximum power delivery up to 15 W. Hence, to increase the power delivery, recently a new USB specification has been introduced known as USB PD (power delivery). With USB PD, a huge jump in power can be achieved i.e. up to 100 W, because now the voltage can be increased to a level of 20 V and current can be increased up to 5 A. So, with the USB PD specification, high power consuming devices like monitors, tablets, and laptops can be powered through a USB charger. Therefore, with the arrival of USB Type-C and PD specification, the concept of a universal USB charger seems to be a legitimate possibility.


People Involved -

Alps

Ishtiyaque Ahmad

Alps

Prof B G Fernandes
bfg@ee.iitb.ac.in