The Trouble With USB Universal Charging

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The recent announcement by the GSMA of broad support behind a USB-based universal mobile phone charging system raises hope of a universal charging solution, but also raises many problems that few have discussed.

The first question is who is driving this standard, and what is it called? The Open Mobile Terminal Platform has a specification titled Common Charging Solution. The GSMA references this in their GSMA Universal Charging Solution, but doesn’t define the relationship between the two. And then there is the USB Implementor’s Forum’s USB 2.0 Battery Charging Specification. All three organizations use different names, but are they really the same thing? And specifications are notoriously difficult to read, but the OMTP one is one of the most obtuse and under-specified I’ve read in years.

I am a huge fan of the concept of a universal charging connector, but there are many problems I see with the current state of the above efforts.

No Support for Drop-in Chargers

First, the selection of the Micro-USB connector is troubling. Yes, it’s smaller than the Mini-USB connector, and was designed for a higher number of mate cycles (up to 10,000!). But it was also designed to have higher retention than Mini-USB, and nothing in its design addresses blind mating. In fact, the specification adds an option for a latch.

So this universal charging specification is one step forward and at least one step backward. A charging adapter that doesn’t support the kind of low-force, drop-in chargers that have been made ubiquitous by the iPhone relegates users to having to once again fish out the charging cord that has dropped down below the desk or nightstand before they can get their nightly recharge.

No Rules for Charging Status

All of these specifications are lacking guidelines for how to indicate the charging status of a phone or the capabilities of the USB host or charger. Standard USB can only supply enough power for a very slow trickle charge, 100 mA or 500 mA. The USB 2.0 Battery Charging Specification provides for a way to provide up to 1500 mA (1.5 amps) for charging, but there are no rules for how to indicate that a USB port or USB charger is capable of this increased power delivery, which is needed to provide fast charging. There needs to be an icon on or next to a USB port to indicate it is capable of this, and a light or other indicator when it is actually in this mode.


How many people commenting on the OMTP/GSMA USB charging efforts have read the USB 2.0 Battery Charging Specification? The specification is extremely complex (as it needs to be, since it is adapting USB for a purpose it was not initially designed for), and based on the past incompatibilities between mobile phones that used USB charging (think charging a Motorola Razr V3 with a Blackberry charger, or a few other combinations), I expect that there will be numerous USB chargers and mobile phones that incorrectly implement the spec. The result will be chargers that don’t charge all phones, phones that can’t be charged by all chargers, and perhaps worse.

What about GreenPlug?

And then there is GreenPlug. This group is on a parallel track to implement universal USB charging, but with a technology that requires an enhanced USB connector and plug with additional pins and logic.

In the year plus GreenPlug has been around, I have not seen any devices ship that use its technology. OK, so there’s one charger, but where are the end devices implementing it? Although it seems reasonable that the new OMTP/GSMA initiative will get significant traction, the existence of multiple competing methods and poorly written specifications will continue to cause incompatibilities among “universal” USB charging solutions.

What Next?

Complete failure of the USB charging initiatives is unlikely, but it is clearly not a great solution. Improvements can and should be made to the standard, but I think it is already time to look forward and begin designing a better replacement. Perhaps one that can solve some additional end-user problems, and not just provide another way for the industry to save cost by providing inferior technology.

Author: Peter Sheerin

Peter Sheerin is best known for the decade he spent as the Technical Editor of CADENCE magazine, where he was the acknowledged expert in Computer-Aided Design hardware and software. He has a long-standing passion for improving usability of software, hardware, and everyday objects that is always interwoven in his articles. Peter is available for freelance technical writing and product reviews, and is exploring career opportunities in interaction design. His pet personal project is exploring the best ways to harmonize visual, tactile, and audible symbols for improving the effectiveness of alerting systems.

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