AC/DC adapters get their GaN shrink

The humble yet ever-present AC/DC wall-power adapter doesn’t get a lot of consideration from consumers. It’s one of those things that’s needed but is viewed as a necessary nuisance. I suspect that part of that is due to the fact that the adapter is a sealed box with an AC line cord and DC output cord, with no operational setup, no software, no upgrades, no security issues, nothing. It provides one vital and unambiguous function and stays in the background while doing so.

There’s certainly more to their story. These adapters—sometimes derisively referred to as “wall warts” —are something we absolutely need with us when using battery-powered devices at the office, home, or on the go. Being stuck without the right one can be frustrating or panic-inducing, depending on the situation. Forget about strangers asking if you can spare a dollar or two for coffee: instead, I’ve had them ask to borrow mine when on a longer-distance Amtrak ride.

Although adapters are usually viewed as single group, they really serve two distinct roles. First, there’s the recharging use where the connected item, such as a smartphone, will be used without the adapter most of the time. The adapter plays a critical but transitory role.

Second, there’s the operational role where the adapter is used full-time as the power source for the end-device. Based on a limited, non-scientific sample, I’m seeing more of this trend in consumer products, especially at the lower end of the product spectrum such as an entry-level turntable (record player) and rock tumbler (Figure 1).

Figure 1 (left) This Victrola Brighton record player, with an external 5 V/1 A AC-DC adapter, certainly won’t damage any eardrums; (right) the motor of this rock tumbler is powered by a 12 V/500 mA adapter. Sources: Amazon; Target

Using the adapter for DC power makes a lot of sense, as it totally gets the risky high voltage out of the box, so to speak. Doing so greatly simplifies obtaining the various safety-related regulatory approvals, since having only the low voltage in the box means that the complicated issue of line-volage electrical safety is avoided as long as an approved adapter is used (which is easy enough). Plus, it gives the OEM more flexibility in sourcing the power-supply functions, since alternate adapters are available from multiple sources.

How many AC/DC adapters are sold each year? Quick answer: I can’t tell. The many market report summaries at which I looked only call out OEM dollar volume, not units. Their numbers indicate a 2022 market of around $10 billion growing to $24 billion by 2032 with a compound annual growth rate (CAGR) of about 8%. I think I can say with confidence that the number of adapters shipped each year is many millions.

(Note: I rounded their numbers; these research firms have a fondness for providing market numbers and long-term forecasts to two and three significant figures. I assume that precision is used to imply accuracy, when instead a realistic level-of-confidence band—especially for forecasts—would be ±10% or ±20%. It’s yet another example of innumeracy.)

Pressures on adapters

Despite their humble place in the technology rankings, the pervasiveness of these adapters makes them worthy of serious attention, beginning with regulatory considerations. For example, they have been subject to ever-tightening regulations related to their efficiency. I won’t try to summarize the complicated standards which are a function of many factors including maximum output voltage, maximum output power, operating power level, and even define quiescent (standby mode) power, Figure 2. They are also subject to the usual EMI/RFI regulators, isolation (Class I or Class II—standard or reinforced), and more; adapters for medical uses have additional mandates.

Figure 2 This chart shows both the timing and technical complexity of the increasingly stringent efficiency standards for AC/DC adapters. Source: CUI

In 2023, another mandate for these lower-power adapters also received final approval. In the EU, they must use the USB Type-C connector, and so the proprietary Apple Firewire connector (as well as others) will no longer be allowed, Figure 3. The USB-C port will become mandatory for a whole range of electronic devices such as mobile phones, tablets, and headphones. In practical terms, this EU-centric standard will likely result in worldwide uniformity.

Figure 3 The USB Type-C charger (left) will be the EU (and beyond) standard for low-power connectors and will supersede Apple’s proprietary Lightning cable. Source: BBC

The objective of this one-size-fits-all charging port is clear enough: to reduce waste, trim needless clutter, and save consumers money. For many years, the primary to this commonality rule came from Apple, but they were eventually worn down and had little choice but to relent.

What about size?

While regulators may be concerned mostly about efficiency, users also want an adapter which is smaller and lighter. That’s especially the case if they need to carry it, but it is also an issue for relatively fixed settings such as the crowded confines of an ambulance or hospital crash cart with all of its electronics.

There’s major news in the size area as well, with the increased availability of switching devices based on gallium nitride (GaN) materials and processes, thus allowing for more efficient, smaller adapters with reductions in size of up to 50%. Texas Instruments (TI) has just introduced a family of low-power GaN devices specifically targeting these adapter applications (although they are obviously not limited to that role only). The devices are designed to help improve power density, maximize system efficiency, and shrink the size of AC/DC consumer power electronics and industrial systems.

TI maintains that new devices will help engineers to develop smaller, lighter AC/DC solutions, achieve up to 95% systems efficiency, and reduce the size of a typical 67-W power adapter using silicon materials by up to 50%, Figure 4.

Figure 4 AC/DC adapters based on GaN switching devices such those in the newly introduced TI family should reduce the size of the adapters by half. Source: Texas Instruments

The portfolio is optimized for the most common topologies in AC/DC power conversion such as quasi-resonant flyback, asymmetrical half-bridge flyback, inductor-inductor-converter, totem-pole power factor correction, and active clamp flyback.

The three GaN devices from TI—LMG3622, LMG3624 and LMG3626—are housed in 8-mm × 5.3-mm 38-pin, quad flat no-lead packages. To simplify design-in, each incorporates the requisite driver (always appreciated) as well as high-accuracy integrated current sensing, which eliminates the need for an external shunt resistor, Figure 5. (For those who don’t need the internal current sensing, pin-to-pin compatible devices without integrated current sensing are also available.)

Figure 5 Like other members of the GaN family, the LMG3622 includes both the switch driver and internal current sensing. Source: Texas Instruments

Much-smaller adapters are already on the market; I can’t say if they use the TI GaN devices. For example, XP Power recently introduced the AQM200 series of 200-W external power supplies, with 12-V to 48-VDC output. These are fully approved to the many international medical safety standards, in sealed IP22 cases with two means of patient protection (2×MOPP) ratings. Using GaN devices, the units measure approximately 166 × 54 × 33 mm (roughly 6.5 × 2.2 × 1.3 inches) which is about half of size of their non-GaN units, Figure 6.

Figure 6 The AQM200 family of 200-W external power supplies (with 12 V to 48 VDC outputs) is not only half the size of similar adapters, but also meets the additional medical-supply mandates including a 2xMOPP rating. Source: XP Power

External AC/DC adapters may not be glamorous, but they are an important if underappreciated consumer product used in countless charging and operational situations. By reducing their size and weight, as well as improving their efficiency, they will likely be increasingly used for many expected and unexpected applications. It’s these invisible improvements that can make a big difference with unexpected consequences and implications.

Bill Schweber is an EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features.

References

Market size

Allied Market Research, “AC-DC Power Supply Adapter Market, 2022-2031” 10 B to 24 B, 8%
Future Market Insights, “AC DC Power Adapter Market Snapshot (2022 to 2032)”
Spherical Insights, “Global AC-DC Power Supply Adapter Market Insights Forecasts to 2032”
Transparency Market Research, “AC-DC Power Supply Adapter Market”

Standards & efficiency

CUI, “Efficiency Standards for External Power Supplies”
European Union, “Common charger: EU ministers give final approval to one-size-fits-all charging port”
BBC, “December 2024 set as date for universal phone charger in EU”

GaN devices and adapters

Texas Instruments, “The benefits of low-power GaN in common AC/DC power topologies”
Texas Instruments, “LMG3622 650-V 120-mΩ GaN FET with integrated driver, protection and current” sense emulation
XP Power, “AQM200 Series AD-DC Adapters”
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