Maintenance-free mini devices through ultra low power

Portable devices operating for life without charging or changing a battery are the stuff of dreams of the medical industry, of measurement technology, of entertainment electronics and of sports and leisure. Ultra low power systems are making this a reality.

A patient with a heart pacemaker needs a new implant after 8.5 years to replace the flat battery. This is why researchers are frenziedly working on reducing the pacemaker’s energy consumption to a minimum. Components with extremely low power consumption are in high demand in medical technology as well as for numerous mobile applications such as remote controls, data loggers, portable measuring instruments and products for sport and leisure. Developers are thus increasingly working on low power and ultra low power systems.

The microcontroller, counting also among the highest consumers of power, is a key component in this respect. It captures measurement data, has a regulating algorithm and controls signals. Its power requirements and energy demand significantly affect the service life of its battery. The power consumption can be reduced to a minimum in sleep and deep sleep mode, i.e. with the CPU not in use. Power-On-Reset, Brown-Out-Detection and real time clocks are live in this operating mode. Analogue functions such as Brown-Out-Detection are now the main consumers of power.

If a function cannot do without the CPU, the computing time should be reduced to a minimum to save power. It is crucial to execute the commands fast. 32 bit architectures such as Cortex M3 and M0 not only distinguish themselves through higher computing power, but they also compute more efficiently than 8, 16 or even normal 32 bit CPUs.

The wake up time from sleep to active mode also affects the energy consumption. The faster a microcontroller wakes up, the greater its energy efficiency. Acceleration sensors changing the mode after detecting movement are also found in remote controllers or other portable devices.

Apart from the microcontroller, display elements included in many portable devices also count among the higher power consumers. Displays with minimum energy consumption in dynamic mode and requiring minimum power for the display itself are therefore decisive.

Ultra low power systems needing only renewable energy are almost perfect in this respect. Many mobile applications in the field of sport and fitness measuring instruments require no more than photovoltaic conversion of available sunlight. Sunlight is often not available enough as an energy source for industrial and medical equipment. Some ultra low power systems, however, need only artificial light sources to generate sufficient operating power. Other sources of energy include thermo-electric elements, piezo-electric foils and RF antennae.

New materials may also make a significant contribution towards minimum energy consumption. Researchers at Berkeley University succeeded in creating positive and negative charges in ferroelectric substances and maintain voltage without an external supply. Microcontrollers are based on traditional transistors which create too much heat to be further reduced in size or compacted. The first commercial products allowing further reduction of power, using ferromagnetic materials for example, are on the market already.