Why are mobile computing and smartphone manufacturers applauding USB-C? This interface technology is an evolutionary step in USB’s long history, introducing the USB Type-C connector to enable one cable for both data and power. But USB-C also takes us back to the dawn of electricity, rekindling the question – should the world expect to work on DC power or on AC?
USB: Charge it up
Since its introduction in the mid 1990s, the USB standard has lived up to the ‘Universal’ part of its name, having been adopted as the default wired connectivity standard in consumer and industrial devices. Today, USB is by far the most common way to connect keyboards, mice, external memory, printers, phones and even industrial devices like oscilloscopes and test equipment.
Two key value propositions have made USB extremely popular. First, the interface is plug-and-play with built-in drivers, making it easy for even inexperienced users to get comfortable using it to connect equipment. Secondly, and perhaps more importantly, USB’s power delivery capability has made it the most popular way to charge mobile devices, including phones, wearables and personal portable devices like GPS trackers. The interface’s choice of 5V was ideal for single-cell lithium-based batteries and provided sufficient current to charge batteries in most portable devices. The USB interface was even co-opted and modified to create faster charging standards, like the QC standard from Qualcomm and Apple Fast-Charge.
AC versus DC
The electronics industry has seen numerous format wars, like Betamax versus VHS and MacOS versus Windows. The mother of all format wars was the ‘current war’ – whether it was better to deploy AC or DC to transmit electrical energy. Thomas Edison was firmly in the DC camp, while George Westinghouse and Nikolai Tesla favoured AC. As we all know now, AC won because the technology existed at that time to transmit electricity efficiently, by using transformers to raise the transmission voltage and minimise I2*R losses.
The irony, of course, is that most household appliances and electronics need electricity to be converted to DC: it wasn’t until the appearance of power semiconductors that efficient (and cost-effective) DC/DC conversion has been possible. As a result, consumers have been saddled with a slew of incompatible AC/DC converters. While there have been attempts, no DC standard capable of powering most household appliances has won mindshare or been considered ready for standardisation.
One of the many fascinating abilities brought out by the new USB-C standard is the ability to provide sufficient levels of power for most battery operated devices around the home, office, hospital or factory floor. The typical laptop draws 40W or less and, except for large TVs and DVR systems, USB-C’s 100W capability covers a substantial range of today’s power needs.
| “Intriguingly, AC wall sockets with the USB-C port embedded in them have started appearing. This represents the first standard high powered DC output from a wall socket.” Diwakar Vishakhadatta |
As more devices adopt the USB Power Delivery scheme, it opens up the possibility of a world where there will be fewer ‘power bricks’ to carry around to power our devices. We will, in the future, expect any OEM’s ‘wall wart’ to charge any phone – as long as the connector is a USB-C plug – and we will expect to use one OEM’s brick with another OEM’s device. The brick will simply negotiate the right voltage and current levels, and everything should work, as long as it has sufficient power delivery capability. Indeed, while simplifying consumers’ lives, this evolution can also reduce manufacturing costs and save on e-waste. In fact, bricks may become optional equipment on your purchases, because you’ll simply reuse your old brick. As automobiles and airplanes move to adopting the new interface, you won’t need to bring a power brick – you’ll simply charge your laptop or smartphone from the USB-C port.
Most intriguingly, AC wall sockets with the USB-C port embedded in them have started appearing. This represents the first standard high-powered DC output from a wall socket, allowing your device to plug in directly without an intermediate power conversion system. True, each device negotiates a specific voltage, so it is not a system for powering multiple outlets on one DC bus. Nevertheless, it is a significantly cleaner and more elegant solution to powering electronics. While AC still runs in the walls, we may finally have DC in the house after all! Edison would be pleased.
USB-C rules them all
There’s even more to USB-C with several technology improvements making it the most useful yet of the USB standards:
- Reversible, bidirectional connector: The Type-C connector is the most consumer-friendly cabling seen recently. It’s reversible and easy to use – instead of fumbling around to plug in your phone or ultrabook, the cable will slide right in, no matter what orientation. Physically, the Type-C connector is bidirectional (either end of the cable can be inserted into either device) and non polarised (it can go in either right side up or upside down). The connecting systems figure out the polarity as part of the negotiation process.
- It’s future proof: USB Type-C is the first USB connector that can connect everything. We complain about all the microUSB cables and accessories we have laying around, but Type-C will change all that. USB-C provides a truly universal connection for our mobile devices – no more Type-A, Type-B, micro USB 2.0, micro USB 3.0 connectors. Mobile products that don’t have USB Type-C are going to be the ones that stick out in the future.
- Faster data rates: The USB 3.1 standard allows for significantly improved data-rates; it now supports throughputs in excess of 10Gbit/s, with a combination of improved coding and separated and parallel Rx and Tx lanes. By making the interface configurable, based on the negotiations between both devices, the data lines can be repurposed and the interface can support standards like DisplayPort and Thunderbolt. Higher data rates will allow the user to stream to 4K displays and increase file throughput dramatically, compared to legacy USB data-rates.
- Higher power: Another key 3.1 spec improvement that hasn’t received the attention it should is the ability to transmit much higher power than before – up to 100W – and this can be bidirectional. The default is still 5V, but devices can negotiate up to 20V on the Vbus and allow devices to draw up to 5A. While the higher power ratings need special ‘electronically marked’ cabling, the raw ability to convey such high levels of power opens up new possibilities and has the potential to change how we use devices in our daily life.
- One cable to rule them all: Over the last 18 months, Apple introduced its 12inch MacBook with USB-C and Google’s line of Chromebook Pixel laptops, along with several Android handsets, have USB Type-C. Pay close attention as USB-C adoption rates soar and this new standard makes its way to other devices over the coming year. With USB Type-C plugs appearing in a variety of consumer and industrial battery powered devices, there just won’t be a need for the clunky Type-A connector anymore.
Conclusion
USB may seem like old news, but we work in an industry that continues to reinvent itself and USB Type-C is the perfect example of taking a good technology and making it even more useful. It’s good to see our buddy Edison back in the mix.
| Intersil |
