Wireless power. It’s less sci-fi sounding than it once was, thanks to induction charging like that based on the Qi standard, but that’s still a tech that essentially requires contact, if not incredibly close proximity. Magnetic resonance is another means to achieve wireless power, and perfect for much higher-demand applications, like charging cars. But there’s been very little work done in terms of building a solution that can power your everyday devices in a way that doesn’t require thought or changing the way we use our devices dramatically.
Cota By Ossia Aims To Drive A Wireless Power Revolution And Change How We Think About Charging - [Link]
Which are the key parameters for MOSFETs in typical DC/DC converter applications. by Publitek European Editors:
The silicon MOSFET has become a key component in the design of DC/DC converters, providing the high-speed switching and current-handling capability needed to implement high-efficiency, pulse-width-modulation-based control strategies. The drive towards higher efficiency is placing more intense demands on MOSFETs, particularly in designs that have constraints on size, reducing the amount of space that can be given over to heatsinks and other cooling assistance.
The trends are pushing towards the use of MOSFETs that offer reduced Rds(on), as well as offering low switching losses through good charge-storage characteristics. This article will examine a number of the key parameters for MOSFETs in typical DC/DC converter applications.
MOSFETs Target the Major Efficiency Losses in DC/DC Converters - [Link]
by Jon Gabay,
Low-power microcontrollers have done much to improve longevity in energy-harvesting systems. Clever architectures and use of low-power modes lets micros draw nanoamperes of current while preserving registers and configuration data. This allows designers to use smaller and less dense energy storage solutions that were not feasible in the past. Nevertheless, energy storage, which plays a key role in ambient-energy-harvesting systems, is still needed in most cases as a power buffer to store enough energy to provide the power bursts needed to acquire and transmit data during peak demand, particularly if data is going to be transmitted across a wireless network. These energy storage devices generally take the form of either a battery or a supercapacitor (supercap).
Supercapacitor Options for Energy-Harvesting Systems - [Link]
Linear Technology announced the LTC3330, a complete regulating energy harvesting solution that delivers up to 50mA of continuous output current to extend battery life when harvestable energy is available. The IC requires no supply current from the battery (Iq=0) when providing regulated power to the load from harvested energy and only 750 nA operating when powered from the battery under no-load conditions.
What are the key needs of an Energy Harvesting (EH) power supply? Well, first of all, battery redundancy power needs to be available at times when the ambient power is not available. Of course, we want to extend battery life by harvesting ambient energy from thermal, vibration, solar, etc. To make the front end of our power supply more versatile, it would be useful to be able to convert both AC (piezo, magnetic, etc.) or DC (solar) energy transducers with a fairly wide voltage range and also to have an input prioritizer that could decide whether to use the energy harvesting input or the battery input.
LTC3330 – LTC nano-power buck-boost DC/DC - [Link]
Debraj built an electrical dummy load to test his power supply:
Recently, I purchased a power supply that claimed a max current of 2A and 0~15V. So I wanted to test it. I had a 36 watts bulb (used in motor cycles), but that was too much. Then, I thought of the dummy load that is explained by Dave in his video blog. My version is similar, but I changed certain components to my liking (and what ever was already available with me)
Dummy electrical Load - [Link]
Abel Raynus writes:
Rechargeable NiCd (nickel-cadmium) cells are widely used in consumer devices because of their high energy density, long life, and small self-discharge rate. As a part of one project, I needed to design a reliable and inexpensive charger for a battery pack containing two NiCd AA-size 1200-mAh cells. In the process of the charger design, I needed to solve two main problems: first, setting a proper charge-current value, and second, stopping the charging process when the cell is full to avoid overcharging. This Design Idea describes a way to overcome both problems.
Charge a nickel-cadmium cell reliably and inexpensively - [Link]
by Fran Hoffart:
A circuit that properly charges sealed lead-acid batteries ensures long, trouble-free service. Fig 1 is one such circuit; it provides the correct temperature-compensated charge voltage for batteries having from one to as many as 12 cells, regardless of the number of cells being charged.
The Fig 1 circuit furnishes an initial charging voltage of 2.5V per cell at 25°C to rapidly charge a battery. The charging current decreases as the battery charges, and when the current drops to 180 mA, the charging circuit reduces the output voltage to 2.35V per cell, floating the battery in a fully charged state. This lower voltage prevents the battery from overcharging, which would shorten its life.
Charger extends lead-acid-battery life – [Link]
By Steven Keeping
Switching DC/DC voltage converters are popular because they provide efficient power conversion that can exceed 90 percent. That is an advantage both when input power is at a premium and when it is difficult to get the heat out (common challenges for engineers designing compact portable products).
With key power component manufacturers offering products that appear virtually identical on the specification sheet, it is tempting for an engineer to just pick a switching converter with the highest peak efficiency from a shortlist that meets their product’s general requirements. However, that would be a mistake because apparently identical converters can offer markedly different performance.
This article considers the major implications for power dissipation and associated heat rise that just a few percentage points difference in efficiency can make. The article then leads on to discuss how, depending on the load pattern, a converter with lower peak efficiency, but a flatter efficiency curve, could well be the better choice for a particular application.
Selecting the Right Voltage Converter Is Not Just About Peak Efficiency - [Link]
Joohansson @ instructables.com writes:
The reason for this project was to solve a problem I have. I sometimes do several days of hiking/backpacking in the wild and I always bring a smartphone with GPS and maybe other electronics. They need electricity and I have used spare batteries and solar chargers to keep them running. The sun in Sweden is not very reliable. When you need it as most it´s either raining or other circumstances that makes it impossible to charge with solar panels. Even when it´s clear weather it simply take too long to charge. Batteries are good but heavy. I have looked for alternatives but they are either very expensive or too large.
Smartphone Charger Powered by Fire - [Link]
Dimitar Kolev writes:
I test both, just with one LED for now (like 15mA) – they was working quite OK for distances up to 1-2cm, just some paper and thin air between TX and RX coils. With appropriate ferite it seems distance and coupling can be even better.
Just to fire further my interest, chip labels on board were erased, but fortunately I found a good picture where most of the labels were visible. Unfortunately no results after some googling, but finally I think I found the manufacturer of chips and some other wireless power/charging modules – it should be Elecoteq Electronics Website is only in Chinese, so I read what I can via Google translate. I found no datasheets, but for one there was some basic description
Wireless power and charging test and some reverse engineering - [Link]