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Embarking on the quest for high efficiency, low power

Posted: 04 Nov 2015     Print Version  Bookmark and Share

Keywords:consumer electronics  power  wireless  Power over Ethernet 

The proliferation of countless consumer electronics has spawned the problem of a more enduring, efficient and less-costly power system. Unfortunately, this dilemma that has been existing for a long time remains to be a headache for the industry.

We all know that every microwatt counts in consumer electronics, particularly in mobile devices. There is plenty of lip service paid to the need for more efficient power conversion and less power-hungry devices, but there is typically very little content devoted to digging into just what those needs mean and how we can achieve them.

Some interesting trends have emerged to meet the never-ending quest for higher efficiency and lower power. There is a recent trend to mitigate the unsightly "wall wort" or AC power adapter (even though it has seen significant improvement over the years through stricter efficiency standards, light-loading optimisation techniques, or and standby modes.

Another way to power devices is to simply take advantage of existing communication lines and integrate power delivery right alongside the data. In many devices and market segments, we have seen the maximum transmitted power creep from about 5W all the way up to 100W in several recent standards such as USB Power Delivery and Power over Ethernet (PoE).

With great power comes great...

While the extra power is great, it brings a host of challenges and implications for power integrity (PI), signal integrity (SI), intelligent power management, global system efficiency and potential design overprovisioning. SI is out of the scope of this blog, but most folks that have any experience with high speed data transfer are aware of the challenges around mitigating errors at multi-gigabit transfer rates. So one can only imagine how the typical PI challenges of voltage drop, regulation and electromagnetic compatibility (EMC) are compounded when high power is combined with high speed data in the same cable. PoE provides is a more extreme example, where one combines of this because one is combining some of the highest digital signal data rates (10+Gb) with the highest power (60W to 100W) and highest electrical potentials (-48V to 56V) in a single Ethernet cable and port.

It is great that there is increased flexibility for some devices to act either as power sourcing equipment (PSE) or a powered device (PD. The flip side of universal compatibility with increased power delivery is that lower power devices might need to be over-designed to handle the full power. For instance, a device that only requires 10W will dictate a larger, more expensive design if it wants to support a 100W standard and sit in the middle of bus requiring it to pass through the other 90W.

The growing trend of utilising wireless power transfer to charge devices is a real mixed bag. Convenience to the user certainly has its place, but it typically comes at the cost of other important factors that an end user may not be aware of, such as a major step backwards in global efficiency. Wireless power transfer also brings a whole host of engineering and safety concerns along with that convenience, including relying on a data bus to prevent items like your watch from turning into a heater and unknown long-term effects on the body of radio frequency high energy transfer at unprecedented levels.

- Brian Zahnstecher

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