Power category

The behavior of electro-magnetic radiation of power inductors in power management

Application note form Würth Elektronik about EM radiation radiated from inductors in DC-DC converters.

This Application Note focuses on the Electro-Magnetic (EM) radiation behavior of power inductor(s) in DC-DC converters, which is dependent on several parameters such as ripple current, switching frequency, rise & fall time of a switching device, the core material and its permeability and suggests several design tips to mitigate these EMI effects.

The behavior of electro-magnetic radiation of power inductors in power management – [Link]

1kW bidirectional DC-DC converter with credit card footprint

Diamond Electric in Japan has designed a 1kW isolated bidirectional DC-DC converter (IBDC) inverter using gallium nitride (GaN) devices that is the size of a credit card. by Nick Flaherty @ eenewseurope.com:

The technology can substantially reduce the weight and size of DC-DC converters for rechargeable batteries in electric vehicles (EVs) and smart grids as well as uninterruptible power supplies (UPS).

The IBDC combines both charger and discharger circuits with a patented control architecture with switching up to 2MHz and a current range of -3.7 to +3.7A for the 270V to 330V input and output. This has enabled smaller magnetics for a footprint of 93.5 mm x 60 mm x 10.5 mm, excluding the control circuit and heatsink, a quarter the size of the existing designs.

As well as enabling the higher frequency, the use of GaN power devices allows a conversion efficiency of 95%.

1kW bidirectional DC-DC converter with credit card footprint – [Link]

PowerSpot Far Field Wireless Charger Will Charge Devices Up to 80 Feet Away

Over the last few years, there has been an unprecedented growth in the consumer electronics industry. The smartphones, fitness trackers, Smart homes devices, wearables, earbuds, VR/AR, and much more have fostered this growth.

The Smartphone proliferation has been a key factor in the global consumer electronics market size, smartphones have become way better, faster and even cheaper. The Internet of Things (IoT) has promised us more incoming and it’s estimated that we will have up to 21 billion connected devices by 2020. Technological advancements like the emergence of 4G and 5G technologies are expected to drive this demand. Despite all these advances in technology, one function remains chained to the wall – Power.

The laptops, tablet, phones, smart hubs, fitness trackers and others still require being powered. Even, though they are mostly battery powered and could last for a couple of days (without much activity), they all still need to be tied to a plug socket for hours to be recharged. Power has been a major source of concern and people have been dreaming about the potential of wireless charging their devices.

Powercast PowerSpot Transmitter

Wireless charging has been an interesting topic in the past few years with major advancement made in wireless charging smartphones up to a few centimeters using charging platforms. Like Energeous Wattup that charges up to 3 feet away, Powercast has introduced PowerSpot – a system that will allow devices to be wirelessly charged at up to 80 feet away.

Powercast a leading provider of RF-based wireless power technologies, has unveiled the PowerSpot. Similar to Wi-Fi, devices charges in the range of the PowerSport 3W transmitter, and will automatically turn off when full. PowerSpot charging technology needs no charging platform or direct line of sight as we have seen in Qi charging platforms and has already received approval from both the U.S.-based FCC and Canada-based ISED.

Powercast’s transmitter uses the 915 MHz ISM band to send power to a Powercast receiver chip called “The PowerHarvester” in a device, which converts the transmission to DC to “directly power or recharge” an enabled device at up to 80 feet for devices with low power need. The PowerSpot transmitter uses Direct Sequence Spread Spectrum (DSSS) modulation for power and Amplitude Shift Keying (ASK) modulation for data and includes an integrated 6dBi directional antenna with a 70-degree beam pattern.

PowerSpot charging zone

Game controllers, smartwatches, fitness bands, or headphones will charge best up to two feet away; with keyboards and mice up to six feet away. TV remotes and smart cards charge well up to 10 feet away; with low-power devices like home automation sensors getting sufficient charging power up to 80 feet away.

Powercast is expecting a $100 retail on the transmitter with a projected $50 average price when it reaches mass production. It will be available in the 3rd quarter of 2018 or early 2019.

Could Sodium-ion Batteries be a Replacement for Li-ion Batteries?

Batteries made by Tiamat, a sodium battery startup spun off from the National Center for Scientific Research in France.

In early 1990s lithium-ion batteries started gaining popularity as a substitute for nickel-cadmium batteries. They have higher energy density, low self- discharge, and low maintenance, but it was soon found that they have short life span, unstability which causes security concerns and creates the need for protection circuits (to maintain it within safe limits), and are really expensive to produce. Lithium is scarce (or is soon going to be), only 0,06% of earth crust is made of this material and its mainly found in South America. A start up called Tiamat formed by scientists at several French universities proposed an alternative to lithium-ion batteries, they developed the first sodium-ion battery in industry standard 18650 cell size.

Unlike Lithium, sodium makes up 2.6% of earths crust which makes it the sixth most abundant element. As a raw material sodium sells at about $150 a ton compared to $15,000 a ton for lithium. Sodium batteries are cheaper to produce than lithium batteries, leading to a lower selling price. Also, the lifespan is about ten years compared to lithium which is 4 years and Sodium-ion batteries can last for up to 5000 charge/discharge cycles. Tiamat batteries are not a fire hazard, and provide more stability for a cheaper price.

Scientists want to use these batteries mainly for mass storage of interment renewable energies such as solar o wind. Tiamat is not looking to make Li-ion batteries disappear, instead they want to focus on their long lasting power, and use it for stationary storage. This type of battery could be used in electric cars to allow lasting trips with short recharge time. Production has not started, but when it is approved, and they start to sell France could become a leader in this type of technology. This startup has the support of RS2E (Réseau sur le stockage électrochimique de l’ énergie) a French research network dedicated to energy storage devices, and they plan to launch the product on 2020.

Nowadays, lithium batteries are used mainly for smartphones, laptops, and cars that means that if a new technology was going to replace them, a much better alternative would be needed. Even when sodium batteries are cheaper and safer they still have performance issues that could affect their sales, but as Tiamat said they are not looking to replace these and their market is completely different. For now, the cells produced offer only about half of the energy density of Li-ion and are yet to be improved in many aspects.


WattUp – RF based Wireless Charging at a Distance

WattUp Far Field Transmitter

Recently, many big companies such as Samsung have developed wireless chargers which work by induction. These chargers usually consist of a station which needs to be in contact with the device in order to charge. The station defeats the purpose of being able to move and walk while still charging the device. Energeous, a global leader in RF- based wireless charging, created the award-winning device WattUp in order to give mobile power to everyone.

The WattUp transmitter converts electricity into radio frequencies, then beams the energy to nearby devices that have the right receiving equipment. This system has proved to be more practical than induction since it can work from up to 3 feet away. Energeous wants to make a wire free charging ecosystem by taking into advantage the fact that the transmitter can charge multiple devices at a time, and as WIFI it would be able to charge your phone even if you are Samsung and the transmitter is Apple. All kind of devices can be charged using WattUp including (but not limited to) cameras, smartphones, tablets, wearables, and toys.

The receiver uses multiples antennas to collect the micro energy beams created by the transmitter (which makes it safe because power is received in small amounts). There is also an application available in which you can control the devices that are receiving power, how much power for each one, and even what times you want it charging. For example, you can prioritize cellphone charging in peak hours of use and leave other electronics to charge at night just with the click of a button.

The WattUp has already been FCC (federal communications commission) approved, and Energeous offers a variety of prices depending on the range of the transmitter, but it is still not available in the market. The company will be in CES 2018 showing their product, this event will take place on January 9th– 12th in Las Vegas.

Wireless charging not only benefits consumers, but also offers real benefits in terms of efficiency, productivity, and safety in industrial applications. Moreover, cables require maintenance and are easily damaged which makes them unreliable and expensive to maintain. In hospitals there is a constant need for big equipment that uses battery packs or cables, but to maintain a sterile environment WattUp could be a good alternative. Furthermore, in the future this technology could be used to power electric cars avoiding the need for charging every 10 to 40 miles.


Improving Wearables with Flexible and Rechargable Battery

The stretchable batteries were printed on fabric for this demonstration. They make up the word NANO on the shirt and are powering a green LED that is lit in this picture. (Image courtesy of Jacobs School of Engineering/UC San Diego.)

Nowadays, there is a lot of technology that implements wearables in fashion, medicine, worker safety, accessories and much more. Many wearables are coupled with uncomfortable charging cables that are irritating for users to handle, some even have big batteries that make wearables a burden instead of an advantage. Statistics show that people tend to abandon this devices after only 6 months of buying them, and battery life and portability is one of the issues. Addressing portability, the nanoengineers at the university of California San Diego have developed a new material that allows the creation of flexible, stretchable, and rechargeable batteries which can be printed into clothes.

This material named SIS can be expanded twice its size in any direction without any damage. SIS is made from a hyper elastic polymer material made from isoprene and polystyrene. The ink used to print the batteries is made with Zinc silver oxide with bismuth (to make it rechargeable). The whole flexible battery is made from both SIS and the ink.  When zinc battery runs out, their electrodes react with the liquid electrolyte inside the battery which eventually shorts circuits the battery, bismuth prevents this from happening and ensures battery durability.

The prototype has 1/5 the capacity of a hearing aid rechargeable battery and it´s 1/10 as thick. It costs only $0.5 USD to produce and uses commercially available materials which makes it cheaper and smaller, but not as efficient as a common wearable battery. Two of these batteries are needed to power a 3 v LED, so a lot of them would be needed to power a bigger device.

The engineers are working towards improving performance to make them a good choice for wearable developers. They also want to extend their work towards lithium ion batteries, supercapacitor, and photovoltaic cells. Commercially, the short-term objective is to replace coin batteries for printable batteries which have a competitive price.

When performance is improved these batteries could power all kind of wearables for medical purposes such as shirts that can detects fever, or glucose sensor in diabetic patients. Also, for recreational purposes such as a sweatshirt with LEDs to run during night, or a shirts that detects movement and helps you with your movements while playing golf. Engineers for this project should consider implementing wireless charging to make it even more comfortable for the user by ending the need of cables and small connectors which are a nightmare for most of the people.


USB To 12V Boost Converter

This project provides 12V output from any USB power source, like PC USB port, USB adapter or power banks. LM2577ADJ boost converter IC is the heart of the project. The IC can handle load up to 800mA, it’s advisable to use only 200mA load on output to be on the safe side. The LM2577 are monolithic integrated circuits that provide all of the power and control functions for step-up (boost), fly back, and forward converter switching regulators. The device is available in three different output voltage versions: 12V, 15V, and adjustable. Requiring a minimum number of external components, these regulators are cost effective, and simple to use. Listed in this data sheet are a family of standard inductors and fly back transformers designed to work with these switching regulators. Included on the chip is a 3.0A NPN switch and its associated protection circuitry, consisting of current and thermal limiting, and under voltage lockout. Other features include a 52 kHz fixed-frequency oscillator that requires no external components, a soft start mode to reduce in-rush current during start-up, and current mode control for improved rejection of input voltage and output load transients.

USB To 12V Boost Converter – [Link]

Wireless power in AA battery format

Ossia has created the world’s first wirelessly-powered alternative to disposable AA batteries. The “Forever Battery” puts a long distance wireless power receiver into an AA battery format. The technology can receive up to 4W from a nearby RF transmitter (Cota transmitter), and includes a data link. [via]

Forever Battery bridges the gap between the battery-wire age and the wireless power era,” said Mario Obeidat, CEO of Ossia. “When people see how Cota Real Wireless Power can be implemented in a AA battery, they will start to see the vision of Cota everywhere. The Forever Battery will create awareness of Cota and provide confidence that devices will be powered when it matters.

Programmable Power Supply Using OPA548

Project provides 1.2 to 20V DC output with current limiter adjustable to 0-5A. I have tested the circuit with 250mA output without a heat sink. Project is capable to drive 3A continues load and 5A peak, large size heat sink required for full load. The tiny power supply based on low cost OPA548 high-voltage and high-current operational amplifier is ideal for driving a wide variety of loads. The project provides excellent low-level signal accuracy and high-output voltage and current. The circuits operate with single supply 24V DC and logic supply 5V DC. The IC is internally protected against over-temperature condition and current overload. Trimmer potentiometer PR1 sets the output voltages, PR2 helps to set the current limit 0 to 5Amps.

Programmable Power Supply Using OPA548 – [Link]

Grid-connected solar microinverter reference design

A PDF from Microchip on the theory behind inverter design connected to grip power.:

There are two main requirements for solar inverter systems: harvest available energy from the PV panel and inject a sinusoidal current into the grid in phase with the grid voltage. In order to harvest the energy out of the PV panel, a Maximum Power Point Tracking (MPPT) algorithm is required. This algorithm determines the maximum amount of power available from the PV module at any given time. Interfacing to the grid requires solar inverter systems to abide by certain standards given by utility companies. These standards, such as EN61000-3-2, IEEE1547 and the U.S. National Electrical Code (NEC) 690, deal with power quality, safety, grounding and detection of islanding conditions.

Grid-connected solar microinverter reference design – [Link]