Internet of Things (IoT) is the world where everything is virtually equipped with one or more small operating systems or smart sensors. Recording, monitoring and measuring more and more things? It remains to be seen whether this development can be regarded as positive or negative. The fact is, the number of applications is – surprise surprise – expected to increase significantly – as in earlier years. The efficiency of this sensors is that through networked servers, applicants will receive direct information that will help in task coordination and maintenance.
It might not be too difficult to answer the question how this issue is linked with the topic of sustainable urbanization. The first thing that you probably think of, if you do a brief brainstorming session, is air pollution monitoring at various locations in the city. But of course, there are more usage possibilities, such as in the field of water quality management, occupancy control for parking lots, urban gadgets, the wireless future of urban mobility, watering systems for professional urban farms, urban drones, autonomous vehicle mobility, or even common bike-sharing schemes.
Power Converters are Only Efficient Within Narrow Current Ranges
Especially when it comes to systems without a permanent power supply, such as drones, sensors should consume as little power as possible in order to extend battery life or run self-sufficient with renewables. Commonly, the energy demand of sensors is low. Measurements, little calculations or automated comparisons are hardly worth mentioning. The energy consumption is higher, however, when it comes to transmitting data to a remote receiver. This, in turn, means that a power converter, able to provide different currents, is needed. The operation of this power converter is that it takes input voltage and converts into output voltage. Only within narrow current ranges, these energy converters are considered to be very efficient.
MIT’s New Power Converter Halves Quiescent Power Consumption
This limitation of the power converter has led the scientists of MIT’s Microsystems Technologies Laboratories (MTL) to develop an improved converter. The new converter is designed to keep up its efficiency in currents that range from 500 picoamps to 1 milliamp, which is a very wide span and encompasses an increase of up to 2,000,000-fold. With this improvement, the power converter will be 50% more efficient regarding the quiescent power consumption as compared to its existing counterparts at this current level and focuses on sensors associated with Internet of Things as well as wearable designs.
Scientists agree on the fact that the system allows sensors to operate at even low temperatures which will add into the life of its battery for months or make energy harvest from the surroundings.
“Typically, converters have a quiescent power, which is the power that they consume even when they’re not providing any current to the load,” says Arun Paidimarri, who was a postdoc at MTL when the work was done and is now at IBM Research. “So, for example, if the quiescent power is a microamp, then even if the load pulls only a nanoamp, it’s still going to consume a microamp of current. My converter is something that can maintain efficiency over a wide range of currents.”
“It’s Based on These Packets of Energy”
The step-down converter of the MIT scientists has an input voltage ranging between 1.2 to 3.3 V and an output with 0.7 to 0.9 V. Paidimarri adds: “In the low-power regime, the way these power converters work, it’s not based on a continuous flow of energy. It’s based on these packets of energy. You have these switches, and an inductor, and a capacitor in the power converter, and you basically turn on and off these switches.” If the output voltage falls below this threshold (in our example 0.9 volts), the controllers will switch and an energy packet will be released. Soon after this, another operation is performed and another packet will be released.
When there is low power, this power converter will not work on a continuous flow of energy. Rather it will operate on these energy packets. When the converter cannot detect any active devices, the controller is programmed to release 1 to several hundreds of energy packets every second. However, if the converter is providing load even to an electric motor of a drone, it will have to release a million energy packets every second.
This power converter also has a variable clock which operates switch controllers at a broad range of rates. This means that it needs more complex circuits that have the capability of monitoring the output voltage of the converter. These circuits also include an element called voltage divider capable of tapping off some current from output voltage for measurement.
This voltage divider in the power converter is surrounded with a block of additional circuitry elements. Through this element, the divider can be accessed but, only for a fraction of a second that is required by a measurement.
This power converter will raise the bar in low-power DC-DC converters along with efficiencies that can be achieved at low current levels. The project is currently being funded by Shell and Texas instruments whereas; the prototype chips are manufactured in Taiwan Semiconductor Manufacturing Corporation.