Archive : 13 February 2017 год

Cell phones and other devices could soon be controlled with touchless gestures and charge themselves using ambient light, according to researchers at the University of Illinois and Dow Electronic Materials.

Made of nanorods arranged in a thin film, LEDs arrays that can both emit and detect light could enable new interactive functions and multitasking devices.

The 5nm nanorods are made of three types of semiconductor material. One type emits and absorbs visible light. The other two semiconductors control how charge flows through the first material.

According to the team, the LEDs switch so fast between emitting and detecting light that the display appears to stay on continuously – at rates three orders of magnitude faster than standard display refresh rates.

The researchers demonstrated pixels that automatically adjust brightness, as well as pixels that respond to an approaching finger, which could be integrated into interactive displays that recognise objects or respond to touchless gestures.

They also demonstrated arrays that respond to a laser stylus, which could be the basis of smart whiteboards, tablets or other surfaces for writing or drawing with light, and claim the LEDs can convert light to electricity.

“The way it responds to light is like a solar cell,” Professor Moonsub Shim from the University of Illinois said. “We still have a lot of development to do before a display can be completely self-powered, but we think that we can boost the power-harvesting properties without compromising LED performance.”

Nanorod LED displays can also interact with each other as large parallel communication arrays. Two LED arrays facing each other could potentially communicate with as many bits as there are pixels in the screen.

Author
Peggy Lee

Source:  www.newelectronics.co.uk

To resolve the problem of counterfeit wireless chargers - which could cause power surges that fry a device’s circuitry – researchers from MIT’s Microsystems Technology Laboratories have built a chip that blocks attempts to wirelessly charge a device’s battery unless the charger first provides cryptographic authentication.

The same technology also solves another problem with wireless chargers. When two devices share a single charger, if they are different distances from the charger’s electrical coil, their charging rates can vary, to the extent where one device might charge fully while the other remains virtually uncharged.

In the same way that the researchers’ chip can block power transfer from an unauthorised charger, it can slow the power transfer to a device nearer the charging coil, ensuring more equitable charge rates.

In a wireless charging system, both the charger and the target device contain metal coils. An alternating current passing through the charger’s coil produces a magnetic field, which induces a current in the device’s coil. The rate at which the current in the charger alternates defines a frequency, much like the frequency of a radio transmission. The device’s coil must be ‘tuned’ to the transmission frequency in order to receive power.

The MIT researchers’ created a more compact and efficient circuit for tuning the frequency of the receiving coil. Instead of a single coil attached to a bank of capacitors, the MIT researchers’ design uses a pair of coils attached to one capacitor each - no switches required.

In the researchers’ chip, the main coil is much larger than the auxiliary coil. When a current is flowing through the auxiliary coil, it produces a magnetic field that changes the tuning frequency of the main coil.

When the resistance in the auxiliary coil’s circuit is high, the magnetic field is weak, and the detuning is less drastic. That permits other, more distant devices to harvest more of the power transmitted by the charger coil.

The chip also uses an authentication technique called elliptic curve cryptography. Using publicly available information, the chip can generate - and verify the response to - a question that only a charger with valid private information can answer. The chip doesn’t need to store a secret key of its own.

Elliptic curve cryptography is a well-established technique but the team found a way to simplify the encryption circuit so that it takes up less space on the chip and consumes less power.

Author
Peggy Lee

Source:  www.newelectronics.co.uk

Starting from a few specifications, such as required power or the entry and exit voltages, SmartCtrl – a program developed by the Universidad Carlos III de Madrid (UCM) – is said to provide those designing electronic power converters with a predefined map of solutions.

This, say the developers, accelerates design work as engineers don’t need to resort to complex mathematical calculations. “The designer is provided with automatic code generation, which will give them a solution that is directly embeddable in their system,” said UCM Professor Antonio Lázaro.

According to Power Smart Control – the company set up to market the software – the solutions map helps the user to choose the crossover frequency and phase margin, adding the software presents a stable solutions space for every type of regulator, with inductor current and voltage ripple plotted and the modulating signal output ripple shown.

Predefined topologies in the package include: forward converter; flyback converter; buck converter; boost converter; and buck-boost converter. For each predefined topology or generic converter, users can choose between: voltage mode control; average current mode control; and peak current mode control.

Said to be suitable for use in sectors ranging from aerospace to communications technologies and transportation, the software is based on the design of control systems for power converters. However, the collaborators say the program will be extended to address the control of power inverters and rectifiers, as well as the the digital implementation of controls in SoC platforms.

“Power electronics is going to enable the technological development of other disciplines, such as electric transport, renewable energies, communications and even electromedicine,” Prof Lázaro added.

Author
Graham Pitcher

Source:  www.newelectronics.co.uk