High Tech Goes Low Power

As electronic components become more sophisticated and less costly, the demand for smart sensors, wearable devices and ubiquitous communication tools continues to grow, increasing the need for electricity to power them. According to the Intergovernmental Panel on Climate Change, information and communication technology (ICT) could account for more than one-fifth of the world’s energy consumption by the end of this decade. At the same time, the world is trying to cut down on energy consumption in order to curtail climate change, decrease the number of spent batteries in the waste stream, and reduce the cost of replacing batteries in remote sensors. In the U.S. alone, more than three billion batteries make their way into landfills every year. Over 90 percent of all lithium-ion batteries—considered hazardous waste, due to their lead, cobalt, copper and nickel content—are thrown away rather than recycled at the end of their usable lives.

Fortunately, the electronics industry is providing a plethora of ultra-low-power components, longer-lasting batteries, and innovative devices that generate electricity by harvesting free ambient energy. With this hardware and a little ingenuity, engineers can design high-tech products with minimal energy requirements.

Amplifiers Go Digital…

In audio applications, engineers can minimize power consumption by designing with class D amplifiers. These highly efficient power boosters convert the incoming analog waveform into a PWM signal whose overall duty cycle is proportional to the signal’s amplitude, with the width of each pulse representing the instantaneous signal level at the time of sampling. Since these are switching amplifiers, they consume power only during the brief instant that the digital output changes state, and use virtually no power when the output pulse is in the high or low state. Unlike their analog counterparts, whose efficiencies struggle to reach 70 percent, class D amplifiers can easily achieve 90 percent efficiency or higher, making them ideal for audio applications with ultra-low-power requirements.

Just as the op-amp provides a customizable building block for analog amplifiers, an IC-based class D amplifier gives engineers a functional amplifier that’s already optimized for low power consumption, minimal distortion and EMI, good thermal performance, and a tiny footprint. Some even offer the added benefit of an integrated DSP, which lowers the cost, size and weight of a product.

…While Computers Go Analog

Just when you thought everything was going digital, analog designers say, “Not so fast.” Digitizing makes for a more efficient amplifier, but certain computations are better suited to the analog world. The human brain, the world’s most proficient neural network, draws less than 20 watts of power while processing analog information. And unlike its silicon counterpart, carbon-based gray matter is very effective at pattern recognition, having the ability to identify objects and sounds with little effort.

Devices that rely on pattern recognition, such as smart doorbells, voice-assistant speakers and security cameras, spend most of their lives in standby mode, waiting for an appropriate stimulus to wake them. In some cases, like a smart speaker, the device is designed to react to a human voice and ignore other random noises. Nonetheless, all audio waveforms must be analyzed, and that requires waking the MCU every time a sound is detected and running a machine learning (ML) algorithm to perform pattern recognition, all of which expends computing capacity and electrical energy.

A number of IC makers are now producing programmable analog chips with ML capabilities that do preliminary computations on analog quantities prior to the data being digitized. These use a tiny fraction of the power used by digital microcontrollers performing the same ML functions, significantly increasing battery life. The chips can be programmed to accommodate different sensors and identify certain features of the waveform using their version of an analog neural network. When an appropriate signal has been identified, the analog device brings the digital microcontroller out of standby mode for processing.

Ultra-Low-Power Microcontrollers

Given that ICT products nearly always have a microcontroller inside, it’s not surprising that a 2022 report by KVB Research predicted that the ultra-low-power microcontroller market will reach $7.9 billion by 2027 with a CAGR of 10.3 percent. The report cites many reasons for this growth, including climate change, wearable electronics, remote controls, building automation systems, and wireless sensors.

Every microcontroller maker offers a series of ultra-low-power MCUs, and some take it to the next level by incorporating energy-harvesting control units, which extend battery life or eliminate the need for a battery altogether. These draw minimal current in both active and standby modes, making them suitable for wearable electronics, IoT applications, smart buildings and remote sensing applications. Look for a model whose evaluation kit features an energy harvesting device (like a solar panel) and a supercapacitor.

Energy Harvesting

Now that you’ve minimized the power consumption requirements, let’s look at a few ways to harvest the energy needed to operate the device without the need for batteries or a power outlet.

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Diana TaiJune 21, 2023