As discussed in last month’s article, the Army is at the cutting-edge of developing and fielding more capable electric devices that provide our Soldiers better situational awareness. All of this is needed for future conflicts with near-peer adversaries and to maintain an unfair advantage on the battlefield. As the Army adopts ruggedized versions of commercial-off-the-shelf (COTS) devices, it is also looking at battery charging technology used in the consumer market. While most smartphones, notebooks, and tablet designs look like they have not changed much on the outside over the last few years, the same cannot be said for the electronics on the inside. While charging may have been the last area of focus, there have been tremendous improvements over the last couple of years with more coming soon. As the Army continues to evaluate newer COTS mobile devices for use on the battlefield, the battery charging technology used in these devices could be a benefit to the Soldier.
The following will cover several new technologies being integrated into mobile devices to support faster charging and could find their way onto the battlefield.
Faster USB Charging
Most of the COTS products being fielded by the Army use some type of USB connection. First introduced in the mid-1990s, this connector brought standardization to the industry. Since that time, many advancements around battery charging (BC) have happened. USB BC 1.0, which was originally released in 2007 and limited to 2.5 amps, has dramatically improved over the past 13 years. With the new standard being USB Power Delivery (PD) 3.0 with the capability to charge devices at 100 watts (Figure 1).
Driven by the demand for faster-charging solutions, the USB-PD and Programmable Power Supply (PPS) standard was developed by the USB Implementers Forum (USB-IF). Knowing that it is not enough for a charger to support just the wattage that a phone requires, it also needs to be able to provide power at the right voltage and current. Then, both the charger and the device need to be able to communicate the maximum they are capable of, or else they will default to a lower charging rate. USB-PD and PPS are now a standard that any manufacturer can use on any device with a USB port. It is capable of delivering up to 100W, so it is suitable for use with all kinds of devices beyond smartphones including some laptops, provided they have a USB-C port. USB-PD brings other benefits, too. The direction of the power is not fixed, so you will find portable battery chargers, for example, that have a USB-C port that can be used both to charge another device and to charge the battery pack itself. USB-PD also only provides the power the device needs, so the same USB-PD charger could charge a smartphone at top speed, but then also charge a laptop at its top speed. Knowing the importance of developing fast-charging solutions, Xentris Wireless was the first mobile device charger company to develop and receive certification for a USB-PD charger.
Phones, tablets and other small electronics have standardized on 5V USB power, but laptops are different. These larger devices accept 20V power from a supply that converts the high-voltage AC current coming from the wall into something palatable for a laptop. Almost all new laptops can be charged via USB-C and a power bank that has USB-C output and supports USB-C PD. Today’s Warfighter is equipped with a wider range of electronic devices when compared to the average consumer. From smartphones to tactical radios to rugged laptops, Soldiers today are equipped with mobile devices requiring various batteries with different voltage requirements. This has resulted in the Warfighter being burdened with carrying an assortment of dedicated batteries and chargers. As the technology of USB PD has developed, the mobile device industry has moved away from individual device chargers to an all-in-one solution. Addressing the needs of the consumer market, industry has developed high capacity, fast-charging power banks that handle everything from 5-volt smartphones and tablets to 20-volt laptops. As tactical radio manufacturers consider integrating PD charging into their devices, manufacturers will be able to support these multiple voltage requirements using a single design. By developing power requirements that support these different voltages from a single source, it could lead to eliminating the need for carrying device-specific spare batteries resulting in reducing the Soldier’s burden.
Fast Wireless Charging
Just as USB charging has dramatically improved over the last several years, so has wireless charging. With the Wireless Power Consortium’s (WPC) Qi becoming the world’s de facto wireless charging standard, all major device manufacturers now support this standard and has even now been adopted by Apple. This has resulted in some dramatic advancements. Though Qi wireless is primarily used to charge smartphones and wearables, wireless charging technology has now advanced to the point that charging larger devices, such as laptops and tablets, is now possible (Figure 2).
With charging speeds now 50% faster than just a few years ago, fast wireless charging can support the Army’s rollout of COTS-based devices that were designed to take advantage of the latest fast-charging. The benefits of offering the Soldier a fast charging, wireless charging solution includes fewer types of battery chargers to carry, no connectors or contacts that can fail in the field, and reduced wear and tear on the Soldier’s electronic devices. Just as wireless data transfer rapidly evolved to the point where it eclipsed Ethernet connections, the same is happening with wireless power.
Advantages of a Gallium Nitride (GaN) Charging – Lighter and Faster
Gallium nitride is a semiconductor material that first gained popularity in the 1990s through the manufacturing of LEDs. In 2010 the first GaN transistors became generally available. These devices were designed to replace power MOSFETs in applications where switching speed and power conversion efficiency are critical. These transistors, also called eGaN FETs, are built by growing a thin layer of GaN on top of a standard silicon wafer. This allows the eGaN FETs to maintain costs like silicon power MOSFETs but with the superior electrical performance of GaN. When compared to traditional silicon, the main benefit of GaN comes down to power efficiency (Figure 3).
This is because gallium nitride chargers do not require as many components as silicon chargers. This new semiconductor material has the potential to convert power up to 100x faster than old, slow silicon chips, which means smaller, lighter, faster chargers, and power adapters.
As GaN Systems, a manufacturer that specializes in gallium nitride, explained:
“All semiconductor materials have what is called a bandgap. This is an energy range in a solid where no electrons can exist. Simply put, a bandgap is related to how well a solid material can conduct electricity. Gallium nitride has a 3.4 eV bandgap, compared to silicon’s 1.12 eV bandgap. Gallium nitride’s wider bandgap means it can sustain higher voltages and higher temperatures than silicon.”
A higher bandgap efficiency means the current can pass through a GaN chip faster than a silicon one. GaN chargers are not only more efficient at transferring current, but this also means less energy is lost to heat. So, more energy goes to whatever you are trying to charge. When components are more efficient at passing energy to your devices, you generally require less of them. As a result, GaN chargers are noticeably smaller and weigh less while being 3x faster (Figure 4).
It has been estimated that GaN can conduct electrons 1,000 times more efficiently than silicon. As an early adopter, Xentris Wireless has been implementing this technology into its line of mobile charging devices. With GaN chargers being physically smaller than standard silicon-based chargers, Xentris Wireless consumers have benefited with a lighter and faster-charging solution. With this now-proven technology, the same opportunity exists to reduce the carrying load of Soldiers and enable them to charge their batteries faster.
With smartphones, tablets, notebooks and laptops requiring larger batteries to support power-hungry technology and advanced features, consumer device manufacturers have developed new methods for rapid charging to reduce charge time and eliminating the need for device-specific chargers by supporting multi-voltage output. The result has been less time waiting for devices to charge and less weight to carry for today’s mobile device user. These same charging technologies can be integrated into charging devices for our Warfighter. With Soldiers today carrying in excesses of 20 pounds of batteries for a typical 72-hour mission, large batteries aren’t the answer. The Army is focused on reducing the weight of these batteries but increasing the capacity. This will only shift the weight burden from one end to the other unless better charging technology is developed. By implementing fast charging technology, reducing the weight and size of battery chargers is possible and would be a tremendous advantage for today’s Soldier.