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Power & Energy

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Hurricane Maria aftermath. The storm damaged the island’s already deteriorated electrical infrastructure. (Image credit Puerto Rico National Guard via Flickr)

 

Electricity is something most of us take for granted until it suddenly is shut off, and then it’s like our lives come to a screeching halt- no TV, no Wi-Fi, and no way to recharge mobile devices. While a power outage may leave us in the dark for a few hours or perhaps a few days, it’s nothing compared to what people are going through in Maria-ravaged Puerto Rico. The hurricane struck landfall on September 20th and not only destroyed homes and businesses, but the island’s already dilapidated electrical grid, so much so that nearly 88% of those living in Puerto Rico are still without power over a month later.

 

PREPA (Puerto Rico Electric Power Authority) is the island’s sole power company responsible for providing electricity to over 3-million people using coal, diesel, and heavy fuel oil as well as a smattering of wind, solar and hydro plants. It’s also $9-billion in debt with 58% of their annual budget going to fuel purchases alone to keep the power running, further adding to that debt. Most of Puerto Rico’s power plants can’t provide power to the masses, not because the plants were damaged themselves but because their electrical grid relies on power lines suspended from utility poles and it’s those poles that took the brunt of the hurricane-force winds.

 

A majority of them have been destroyed, which means most local districts and nearly all remote towns rely on generators to power them until the electrical grid can be repaired, however, that could take months or even a year or more to accomplish. This poses the question of whether or not they should rebuild an aging infrastructure? Doing so would be a costly endeavor (estimated in the billions) and redesigning a new electrical grid around fossil fuels would cost even more, especially with an island buried in debt. Perhaps Puerto Rico’s electrical grid solution lies in microgrids- a localized grouping of electrical sources that can operate connected to the national grid or independently, supplying centralized power to a single town.

 

Microgrids can tie alternative energy sources to the main electrical grid or become self-sustaining on its own. (image credit Junger via Flickr)

 

The practical solution would be to implement a green-energy platform, one that could sustain not only the national grid but one that could supply power independently in case disaster strikes, and it has over and over again for Puerto Rico- 54 hurricanes in total (tropical depressions included). Apparently, Puerto Rico’s governor Ricardo Rosello agrees as he stated in a recent Time article, “We can start dividing Puerto Rico into different regions... and then start developing microgrids. That’s not going to solve the problem, but it’s certainly going to start lighting up Puerto Rico much quicker."

 

A perfect example of microgrid integration and implementation is Kodiak Island off the coast of Alaska, which is one of the busiest commercial fishing ports in the nation and hosts the largest Coast Guard base in the US. Add to that a population of over 13,000 and the power requirements quickly add up. Kodiak’s power is generated from 100% renewable energy source, primarily hydro and wind, which saves them roughly $22-million per-year over using fossil fuels. Some businesses on the island, such as Kodiak’s fishing port have turned to their own mini-microgrids to supply backup power as well. The port recently turned to European renewable power provider ABB to integrate a battery backup solution that ties into the island grid but also maintains a steady supply of power using a unique flywheel system, which also facilitates the use of a massive electrical crane that would otherwise cause brownouts around the island.

 

According to ABB, their solution incorporates a pair of 1MW stabilization generators based on their spinning flywheel design and inverters to store short-term energy to absorb and/or inject both real and reactive power onto the microgrid. The same could be done with Puerto Rico as the island already has 21 hydroelectric plants positioned around the country as well as wind turbine generators. Not only that, Elon Musk is providing energy through Tesla’s Powerwall battery banks and solar panels, which are going up all over the island and are already powering a children’s hospital in San Juan.

 

Implementing solar, hydro and wind renewables and coupling them into area-specific microgrids is a feasible power alternative that Puerto Rico could sustain itself with, which would also serve to protect the electrical grid when hurricanes hit the Caribbean. No, it’s not a quick solution that will provide power to everybody in the short-term, but it’s certainly a better option than repairing a dilapidated outdated electrical infrastructure that will remain a risk the next time disaster strikes.   

 

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I want to share a project about building a battery backup supply for small electronics. With this backup supply, you can never run out of power.

There are a lot of electronics that need to be reliably on all the time. Alarm clocks are a good example of this. If the power goes out in the middle of the night and your alarm doesn’t go off, you could miss a very important appointment. The simplest solution to this problem is a battery backup system. That way, if the grid power drops below a certain threshold, the batteries will automatically take over and keep everything running until the grid power is restored.

 

Materials:

 

The Circuit

There are many different kinds of battery backup systems, and the type that you use is largely dependent on what you are powering. For this project, I designed a simple circuit that you can use to power low power electronics that run at 12 volts or less.

 

 

First, you need a DC power supply. These are very common and come in a variety of voltages and current ratings. The power supply connects to the circuit with a DC power connector. This is then connected to a blocking diode. The blocking diode prevents electricity from the battery backup system from feeding back into the power supply. Next, a rechargeable battery is connected using a resistor and another diode. The resistor allows the battery to be slowly charged from the power supply, and the diode provides a low resistance path between the battery and the circuit so that it can power the circuit if the voltage of the power supply ever drops too low. If the circuit that you are driving requires a regulated power supply then you can simply add a voltage regulator onto the end.

 

If you are powering an Arduino or similar microcontroller, you should keep in mind that the Vin pin and the DC power connector are already connected to an internal voltage regulator. So you can connect any voltage between 7V and 12V directly to the Vin pin.

 

 

 

 

Choose the Resistor Value

The value of the resistor needs to be chosen carefully so that the battery isn’t over charged. To figure out which value resistor you should use, you first need to consider your power supply. When you are working with a non-regulated power supply, the output voltage is not fixed. When the circuit that it's powering is turned off or disconnected, the voltage at the output terminals goes up. This open circuit voltage can be as much as 50% higher than the voltage label on the housing of the power supply. To check this, take a multimeter and measure the voltage at the output terminals of the power supply while no other circuit is connected. This will be the maximum voltage of the power supply.

 

 

A NiMH battery can be safely charged at a rate of C/10 or one tenth of its capacity per hour. Once the battery is fully charged, however, continuing to apply this amount of current could quickly damage it. If a battery is to be continuously charged over an indefinite time period (such as in a battery backup system), then the charge rate needs to be very low. Ideally, you will want the charge current to be C/300 or less.

 

 

In my case, I'm using a battery pack that is made from AA NiMH batteries that have a capacity of 2500mAh. To be safe, I want the charge current to be 8mA or less. Given this, you can calculate what the value of the resistor needs to be.

 

 

To calculate the necessary value of your resistor, start with the open circuit voltage of the power supply, then subtract the voltage of the fully charged battery pack. This gives you the voltage across the resistor. To find the resistance, divide the voltage difference by maximum current. In my case, the power supply had an open circuit voltage of 9V and the voltage of the battery pack was about 6V. This gave a voltage difference of 3V. Dividing these 3 volts by the current of 0.008 amps gives a resistance of 375 ohms. So your resistor should be at least 375 ohms. I used a 1 kohm resistor to be extra safe. Keep in mind, however, that using a larger resistor will slow down the charging significantly. This isn’t a problem if the backup power system is very rarely used.

 

 

Using Your Battery Backup Power Supply

Using the battery backup circuit that I designed, you can plug your power supply into a female DC power connector. This is connected to the battery backup circuit. Then at the output of the battery backup circuit, there is a male DC power connector that can plug into the electronic device that you want to power. This simple plug-in design means that you don’t have to modify either the power supply or the appliance. If you have any questions about this circuit, or are having trouble getting it to work, please leave a comment below.

Telemetry in power systems has been around for quite a while, however it usually just showed up in high power environments like server farms. Power system telemetry is the communication between your system processing and the power supply devices. This communication can be used to control and / or monitor details about your power system. PMBus, Power Management Bus is an open standard for digital communication between power devices. The standard was created and is maintained by the System Management Interface Forum, LLC. For more details on the standard itself you can visit www.pmbus.org.

 

 

For the purposes of this blog, I’m going to talk about how it caught my eye for some of the Avnet designed products as well as provide links to a couple of videos that show the communication features in action.

 

Why PMBus?

 

As I mentioned, telemetry in power systems isn’t a new concept. What has changed, especially recently, is that adding the capability is no longer as cost prohibitive as it once was for lower cost systems. There is also growth in lower power level converters featuring this interface. Infineon for example has 2 devices that I’ve recently used, the first is the IRPS38060 which is a single channel 6A converter that was used on our Xilinx Kintex UltraScale KU040 development board.

 

Avnet KU040 Xilinx Kintex UltraScale board featuring Infineon IRPS38060

 

 

Our latest SOM (system on module) is the UltraZed, based on the Xilinx Zynq UltraScale+ family. This design features the IRPS5401 which is a 5 channel PMIC featuring 4 switching outputs and an LDO.

 

 

The most appealing part besides the technology is that you gain this functionality with a nominal cost adder. In the past when these features meant a serious cost premium it didn’t make as much sense for the masses. That roadblock has been seriously reduced with newer devices on the market. Why would you want this capability you may be asking? There are several benefits that may appeal to you.

 

Active margining

 

Active margining is typically more beneficial in high current systems. There are cases where margining (reducing the voltage by some small percentage, generally 5% or less) could save considerable power in your system. Margining can be made simple by sending commands to the regulators to lower or raise the voltage in question.

 

Real time monitoring

 

The most common reason a device fails from a hardware perspective is generally that the power system is compromised somehow. Whether it’s due to temperature, component aging or some other kind of degradation, a capacitor, magnetic component or a switching component are typically the weakest link. Maybe not in all cases, but in many cases you may be able to predict failures by monitoring the load profile of your system. For example in a motor control system, if you see the current demand increasing on a supply that is driving a motor maybe that is a flag for a technician to go and replace that board or motor before a failure occurs. Real time monitoring can be very valuable for high up time (always or nearly always powered) systems. Along with voltage and current measurements you can also monitor temperature. As the load and / or temperature increases, maybe you use that information to throttle back performance to lower the power demand or shut down the system before thermal overload kicks in.

 

Sequencing and Power Control

 

You may have entire sections of your equipment that do not need to be powered unless in use. Consider an IoT application such as a vending machine that sends inventory data. Does the cellular radio need to always be on for that? Probably not, maybe it only wakes up every so often to send data. This type of functionality would be useful in both low power battery applications where you try and squeeze as much run time out as possible and in high power systems where shutting down power to a motor bank could create dramatic savings in electrical power. You can also easily control startup and shutdown sequencing as well as slew rate control.

 

Want to know more?

 

I certainly didn’t cover all the potential benefits but what I've discussed should give you a taste of what is possible. Check out these videos that I created highlighting the functionality of the PMBus on two of Avnet’s products, the Xilinx Kintex UltraScale development board and the UltraZed SOM (system on module). These should give you a sense of how you can interact with the bus and the type of information and control you gain. PMBus compliance doesn’t require every device to support every command, but standardizes the commands and the hardware interface.

 

 

Are you having trouble choosing a power topology for your next project? I’ve recently written a blog covering how to choose a power topology for power hungry devices.  The various types of topologies are presented and examined in relation to a smart lock or heating, ventilation and air conditioning (HVAC) damper control system. As an example, I choose a specific part and walk through the design process of an actual system that was built and tested. 

 

Go here to read my blog!: https://e2e.ti.com/blogs_/b/powerhouse/archive/2017/08/09/power-topology-choices-for-power-hungry-devices?hqs=corp-e2e-null-e14powergroup-asset-blog-power-eu

 

If there are any related questions, I would be happy to try to answer them.

At some point in the product chain, almost all electronics require conversion from an AC source to a DC one. Whether your product ships with an external adapter, battery charger, or if you design your own offline (AC/DC) converter, that originating source power most likely comes from AC mains.

 

In many cases, it makes the most sense for engineers to buy off the shelf AC/DC converter solutions. There are many good options from manufacturers like Artesyn, Lambda, Bel Power and SL Power. These solutions can range from PCB mount to rail mount to fully enclosed external supplies. For those engineers who want to design their own chip down solutions, manufacturers like Infineon, ST Micro, Maxim, Microchip, Intersil, Rohm, OnSemi and many others provide conversion IC’s as well as reference material to help guide you in your design. You also need to consider the power needed from your supply. Designing a 5W converter isn’t nearly as complex as higher power designs. So how do you decide if you want to tackle designing your own or if you want to buy an off the shelf solution? Let’s take a look at some pros and cons to each.

 

The Case for Build 

The most compelling reason to try and design your own offline converter nine times out of ten is that you can do it for a lower cost than buying a module. You can also plan for procurement challenges by designing in as many second source capable components as you can. In a previous role I designed equipment in the telecom space. In that market every penny counts. Additionally, we designed for industrial environments and had plenty of in house expertise in not only circuit design, but design for compliance (regulatory, CE, UL, etc) testing… ah yes, compliance testing. Compliance is a huge part of the design process when dealing with hazardous voltages (not only AC/DC, but high voltage DC/DC). More on that to come. You also may have unique requirements that necessitate special features that you can’t get off the shelf or maybe a strict form factor that requires custom design. Bottom line, there are very valid reasons to design your own, however in my experience at least strongly considering a buy mentality is worth investigating. If you are comfortable designing your own custom magnetics, specifying the proper safety rated capacitors, meeting minimum creepage and clearance requirements and insuring that hazardous voltages aren’t exposed to where the user could touch them then maybe designing your own is the way to go. Like anything else it’s hard until you’ve done it. If any of the things I’ve mentioned in this section are news to you, it might be better to focus on the next paragraph…

 

Case for Buy 

In my opinion, the compliance and certification requirements would be reason 1A with safety being 1B. I should probably make safety number 1, but I’ve shocked myself plenty of times and I remember the pain from going through compliance testing more vividly. There are several topologies to choose from (flyback, forward, half-bridge, full bridge), regardless of topology they will all have to meet a variety of compliance standards to be sellable domestically and abroad. Depending on your market segment you may have slightly different or additional requirements, but in almost all cases you will have to pass some sort of regulatory standards. These include at a minimum safety and EMC - conducted and radiated electromagnetic emissions. Again, talk to your compliance engineer or your customers to figure out what standards you must comply with and make sure you plan for it from the outset of the design. The ease and peace of mind of buying a pre-certified and tested offline converter makes for a compelling argument. You don’t have to care about topology or cost involved in R&D and certification time and testing. Sure you will pay a slight premium but in a lot of cases unless you have a very high volume your per unit cost may actually be cheaper when you factor in time and engineering dollars. Another potential benefit from buying a power entry module or external adapter is that it might allow you to shrink your product or reduce thermal relief requirements by removing that heat from your core product.

 

So Now What?

 

Ultimately each designer needs to do the analysis and balance the risk, long term cost, upfront cost, engineering resources available and more to really decide which direction to go. I just encourage anyone considering designing their own offline power system to make sure they research the requirements outside of just design calculations that you will face before you can get your product to market. Also take a look at what precompliance testing you are able to perform yourself. You could potentially be looking at a hefty price tag if you submit your product for testing and it fails, requiring a second round. Avnet has application engineers around the world that can help you with this analysis and also help you find the resources you need to make an informed decision.

 

Here are some links that might be helpful to explore options -

 

AC/DC modules - http://www.newark.com/c/power-line-protection/power-supplies/ac-dc-converters 

AC/DC converters (chip down design) - http://www.newark.com/c/semiconductors-ics/power-management-ics-pmic/ac-dc-converters 

PWM controllers - http://www.newark.com/c/semiconductors-ics/power-management-ics-pmic/pwm-controllers

PFC (power factor correction) controllers - http://www.newark.com/c/semiconductors-ics/power-management-ics-pmic/power-factor-correctors-pfc

tesla-power-pack.jpg

Tesla Powerpack 2 system is scalable from 200 kWh to 100+ MWh. (Image credit Tesla)

 

Last September, Australians living in the southern half of the country got to experience what it’s like to live on the sun. To add insult to injury, they were also hit with a massive storm that knocked out power to 1.7-million homes. As a result, government officials began looking for ways to incorporate renewable energy sources and storage into the grid that could provide a security blanket in case large-scale power outages were to happen again.

 

One of the leaders in energy storage took notice and offered to provide the Aussies with an energy storage solution that will help with their storage problems. In fact, Tesla was awarded the entire energy storage component of Neoen’s Hornsdale Wind Farm, located near Jamestown. The $1.5-billion plan is expected to increase the power grid to an additional 500,000 homes as well as provide battery backup in case of outages.

 

australia-powerpack-blog.jpg

Tesla is pairing their Powerpack platform with the Hornsdale Wind Farm located near Jamestown. (Image credit Tesla)

 

According to Elon Musk, “This will be the highest power battery system in the World by a factor of 3!” The Hornsdale Wind Farm produces 315 megawatts while Tesla’s Powerpack will be capable of storing 100 MW/129 MWh of power in reserve. To put that into perspective, it’s enough reserve power to light up 30,000 or more homes during peak hours to help maintain reliable operation of the electrical grid.

 

Tesla states that “Upon completion by December 2017, this system will be the largest lithium-ion battery storage project in the world and will provide enough power for more than 30,000 homes, approximately equal to a number of homes that lost power during the blackout period.” Not only is it the world’s largest energy storage project, but it will also be completed in record time- in just a few months.

 

power-pack-pods.jpg

Each Powerpack 2 features 16 lithium-ion battery pods. (Image credit Tesla)

 

Although Tesla doesn’t specify what type of Powerpack they will use in the project, my money is on their 2nd generation storage solution- the Powerpack 2. Inside are 16 lithium-ion battery pods, each with their own DC-DC converter, making it easy to swap-out if they become damaged or fault in any way. What makes them a great solution for inclusion into an alternative energy power grid is their ability to charge/discharge instantly, providing frequency regulation, voltage control and spinning reserve to the grid when needed.

 

As far as when the Powerpacks will be integrated into the Wind Farm- Elon Musk pledged completion in only 100 days and will begin as soon as the contract is inked and will cost Tesla $50-million or more if they don’t deliver in the required time frame.

 

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Logitech Wireless Charging Pic.png

Logitech is launching two new wireless technologies that complicate the debate of wired vs. wireless mouses due to its reported impeccable performance. The Logitech G wireless mouse and charging pad which is available as a hard or cloth pad. (Photo via Logitech)

 

Are you adding wireless charging to all your designs? Maybe you should.

 

Recently, wireless charging has become an increasingly popular idea in providing unrestricted access to electronic devices, such as AirVolt’s wireless phone charging system, and now Logitech G is releasing a wireless mouse with a similar concept in mind. Constant, wireless charging for a wireless mouse. We are bound to see more of this type of technology added to all of our devices.

 

The two new technologies proposed by Logitech are dubbed Powerplay and Lightspeed; Powerplay refers to the wireless charging component, and Lightspeed technology pertains to the performance of the wireless signal connection to the mouse. Powerplay technology uses electromagnetic resonance which, according to the Logitech press release, is supposedly, “the world’s first wireless charging system for gaming mice,” and charges constantly, eliminating the need to dock the mouse to recharge. The Logitech G website says that the Powerplay charging system’s 275 x 320mm base “creates an energy field above its surface,” which allows it to charge the mouse while it’s in motion without interfering in the measurement and transmission of data. This technology accounts for one element of the argument against wireless gaming mice, which is that they may run out of battery at any given moment (and that they can run out of battery at all). The second issue that arises between wired and wireless mice is their connectivity and performance.

 

Logitech tackles this second issue with its Lightspeed technology, which is described as, “an end-to-end system optimization,” with a one-millisecond report rate that, “delivers competition-level responsiveness at speeds faster than many competitive wired gaming mice,” according to the Logitech press release. So, it appears that Logitech G has provided an answer to the debate between wired and wireless mice, but only through the combination of Lightspeed and Powerplay technologies.

 

Lightspeed wireless mice are available this June and the Powerplay technology isn’t available until August. The Lightspeed wireless G703 and G903 mice have a PMW3366 optical sensor, which is broadly considered the best gaming mouse sensor on the market, and they will be available for $99.99 and $149.99, respectively, and the Powerplay wireless charging system will be $99.99. So at minimum, this supposed ideal gaming experience would cost about $200. Even though the G903, the more expensive of the two mice, offers a more ambidextrous design, a customizable button layout, and additional mechanical features that improve the feel and responsiveness of the buttons, Logitech G seems to be offering a convenient and high-performing product either way.

 

 

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IC’s typically specify an accuracy range requirement for their power rails. For a very long time 5% was the norm. In a lot of cases that still stands true, but with higher performance, higher accuracy or higher power devices this requirement has pushed down to 3% or lower. In addition, limitations may be set on peak to peak noise, transient response requirements and more. So how do you design your system to meet these requirements?

 

Sources of Error

A good first step is understanding your sources of error and doing what you can to minimize them. For a design example, we are going to focus on meeting a 3% accuracy requirement on a core rail for an FPGA. In this example we are generating a 1V output requiring 3A of current. Your error sources can be broken up into two operating conditions, static and dynamic. Static sources are based on slow changing conditions during normal operation. Dynamic are error sources caused by large changes in operating conditions like transients (load steps). Under static operating conditions, the primary sources of error are power supply regulation and voltage ripple. Dynamic performance adds to that other variations such as transient droop and DC losses. Voltage ripple is the peak to peak variation you allow in your design based on the switching characteristics. The switching frequency, inductor characteristics and output capacitance characteristics all come into play when designing for your desired ripple. I won’t get into calculating that value here, but for our example we will use a target ripple variation of 0.5%.

 

Your power supply regulation error is actually the summation of several error sources. Some manufacturers will give a regulation accuracy, others will give a reference accuracy. You must read the datasheet to see what is provided and base your estimations on that information. More often than not, regulation accuracy tracks the internal reference accuracy. This accuracy is one of the contributing factors to the power supply regulation accuracy. You also have line regulation error (error created by variations to the input voltage) and load regulation error (error created by changes to the output load). These are typically very small, but still need to be factored in. Another source of error that often gets overlooked is the feedback resistor network. These resistors, used for setting the output voltage of an adjustable regulator, can contribute significant error into your system. The error created by the feedback resistors is represented by the equation here:

There is an app note available here that goes into detail on how this equation is derived if you would like to explore it – www.ti.com/litv/pdf/slva423

This diagram illustrates all of the error sources and how they combine to produce your total regulation error. The feedback resistors in this example are 0.1% accuracy. Using the equation above you can see how specifying lesser accuracy resistors can contribute significant error to your overall output.

You can see that just our regulation error without consideration of DC losses or transient response add up to 1.6%, leaving only 1.4% for other error sources. Take a look at the DC loss examples in the illustration. At low voltages even moderate current levels can create substantial DC losses either through filter beads or even through PCB traces.

Here is a model of a transient response. Note that your transient response has a lot to do with the equivalent series resistance (ESR) and the equivalent series inductance (ESL) of your capacitor network.

This diagram shows what happens to your output voltage during a load step. When the load current starts to increase you get an immediate drop across the ESL of your capacitor since the current through an inductor can’t change instantaneously. That voltage will then dip as the current increases based on the ESR of the capacitor. When the current stops increasing the voltage drop across the ESL will go away and your capacitor discharges. You see that the converter current (regulator output current) increases as the control loop catches up to the additional load requirement. The converter current will go higher than the load current as it provides current both to the load and to replenish the capacitors that were depleted during the load step. The capacitance network consists of your input and output bulk capacitance as well as your decoupling caps and board parasitics. Hopefully this illustration helps show why it is so important to design a complete decoupling network using low ESR devices.

 

Minimizing the Error

There are several things you can do to try and minimize your error. Use fixed output regulators which eliminate the feedback resistor error. Be sure to select devices that specify either output error or reference error of 1% or lower. Provide plenty of decoupling and bulk capacitance, using multiple devices in parallel to minimize ESR to minimize transient droops. Place your regulators as close as possible to their intended load and use wide traces or heavier copper weight to minimize impedance. Route your power planes carefully and avoid routing switching signals like clocks near or around your feedback loops. Be careful with current sense resistors and filter beads, be sure to calculate the voltage drop across their impedance at your expected load currents. Consider using regulators with remote sense, which detects the voltage at your load and can make adjustments to the output voltage to minimize error based on DC losses.

 

When designing to higher accuracy requirements be sure you take into account all of your error sources to try and avoid getting bitten when your prototypes come in. What techniques have you used to meet strict regulation requirements? Please feel free to provide additional suggestions or lessons learned from personal experiences below.

AirVolt Charger Pic.jpg

The wireless charging system featured on the crowdfunding site Indiegogo.com allows for greater ease and flexibility in the dreaded time spent charging phones. AirVolt’s wireless charging system uses radio waves and is comparable to wired-charging. (Photo via Airvolt's Indiegogo)

 

Mobile communication devices are becoming an essential part of life around the world, and in more developed countries, smartphones have become commonplace. Aside from the practical functional capabilities of calling, texting, and email, smartphones have become an even more attractive and dominating part of life through access to apps, games, and social media platforms. Whether people “need” their smartphones to post a “sick tweet” or actually need convenience and constant access to the functionality of their smartphones (e.g. calling, texting, email) for practical and important purposes such as for work, AirVolt’s wireless charging system provides significantly more flexibility and convenience than wired-charging (even a really long wire).

 

Business Insider reported a tweet from Pew Research Center demographer, Conrad Hackett, which showed some statistics about the percentage of people that have smartphones by country, and noted that the United States is on the high end at 72%. There seems to be a large and likely growing market for smartphone devices, and AirVolt is capitalizing on these users’ desire for convenience by providing a simple accessory that makes their devices of convenience more accessible.

 

The product’s Indiegogo crowdfunding page states that the system has an effective range that reaches up to 12 meters, and a standard range of 9 meters but notes that the charging efficiency diminishes after 9 meters. The AirVolt charging system uses a transmitter that creates “one-type radio waves,” and the antenna that is inserted into the phone converts these transmitted radio waves into energy for the phone’s battery, and are only 10-15% less efficient than charging directly with a standard 5V charger. The page states that “Charging the smartphone at an average of two and a half hours using a wire, it will take you three hours if you use AirVolt instead,” and the longer charge time is compensated for by the convenience provided by the wireless system. There is also a feature called the “Power bank” that can be initiated by pressing the button on the transmitter and allows the phone to be charged even when the transmitter isn’t plugged into an outlet. The power bank feature is good for one full charge cycle and provides further flexibility in enabling access to smartphones and their various essential and/or trivial functions.

 

Saying only “Radio waves” it a bit of a black box description of how it works. However, based on the 9m distance, I assume it used Magnetic-Resonance power transfer. Like Witricity, for example. But, Airvolt seems to be offering a lower power option, less than 5W here.

 

AirVolt also intends to develop an app that will provide additional capabilities such keeping the battery in the 20-80% range, sequential charging, and turning off radio wave transmission at full charge, but it is clearly stated that the system can still function without the app. The Indiegogo page seems to suggest the retail price of a single radio transmitter and complementary antenna will be $50, and as more transmitters and antennas are purchased, the price drops to the extent that five transmitters and ten antennas would cost $360. AirVolt estimates that their product should be out for delivery in January 2018, and the latest possible date of delivery is February 2018. Assuming the system functions properly, it will undoubtedly provide a significant convenience and enable more consistent access to smartphones, but whether it will have positive societal and cultural implications for an already technology-obsessed generation remains to be seen.

 

The low budget official videos and grammar errors in the Indiegogo page does not give me a lot of confidence that the product will actually ship. Everything is a sort of "take our word for it, it totally works!"

 

 

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I think we all live with some level of tunnel vision. We live locally and too often are unaware of what is going on in the wider world despite our access to the reportage of world events.

 

I thought about my own tunnel vision of the wider world when I did my typical Saturday morning thing: got a cup of coffee from my local Starbucks and read in the New York Times the story: India, Once a Coal Goliath, Is Fast Turning Green.

 

The gist of the story is that India WAS planning on building a whole lot of coal-fired plants but are cancelling many of them because (a) their current plants are operating at only 60% capacity and (B) they are relying more on renewables such as solar power.

 

India, so says the story, is also decreasing its annual coal production from 660 million tons to 600 million tons -- down 10%.

 

Clearly, the world is embracing renewable energy technology. It appears to be making sense in India. It even makes sense to the mayor of Pittsburgh in the U.S. In another story, it says that  Pittsburgh already has 13,000 jobs in the renewable energy industry. Says the story, "Pittsburgh today is increasingly rebuilding around greener medical complexes, research university and tech offices." Less need for coal, for sure.

 

I haven't been to Pittsburgh since I worked for Eaton Corp. as a field engineer about 20 years ago. And I have yet to visit India. But this morning over a cup of coffee at my local Starbucks, my world view just got a wee bit bigger.

The term PMIC (Power Management IC) gets thrown around a lot when discussing power. In my experience it could mean anything from a dual output power regulator, to a full featured device with a dozen outputs, reset controllers, GPIO and more.

 

So how do I know what I’m looking for and where to go for information? Well, the answer to that question isn’t always easy. It varies by manufacturer based on how they categorize these devices on their websites which sometimes makes it difficult to locate a part that may be perfect for your needs. Let’s take a step back and talk about defining your power requirements first. Rarely if ever do modern designs consist of a single supply outside of perhaps some wearable or low power battery driven devices. That means when you are talking about your power needs, you aren’t talking about a simple Vin and Vout, you are talking about a system Vin, multiple outputs, possibly multiple power modes, sequencing requirements and more.

 

It’s not until you really dig into the system level requirements where you see that a PMIC that may have been conceptualized and designed as a companion to a specific processor family, for example, actually fits a tremendous number of applications when you look at the ins and outs in their simplest forms.

 

da9062.PNGTake for example the DA9062 from Dialog Semiconductor. I’m not sure what this device was initially designed around, but after looking at the system requirements for one of Avnet’s upcoming designs I found that it was a near perfect fit for what we needed. I was able to combine multiple devices into a single part, in a smaller footprint and at a lower cost by approaching my power architecture selection from a system level rather than a point of load (POL) level.

 

Look at it the way you select a processor. You may not use EVERYTHING in the processor, but you have a list of things you need and you find a single device that does most, if not all of those things for you. Back to my DA9062 example. We needed 4 DC outputs, as well as a DDR3 termination regulator and a push button reset controller. The DA9062 provides 4 switching outputs, one that can be configured as a termination regulator, 4 LDOs, 5 GPIOs, an RTC and a backup battery charger. Honestly did I need all those features? No, but I was able to use 3 switching outputs, utilize the 4th as my termination regulator, operate 2 of the LDOs in parallel to get enough current for my 4th DC output, then configure the GPIO pins to handle my push button debounce input and reset control. I was also able to use footprint capability to add an RTC to the system if desired. I didn’t fully utilize the device, but I didn’t need to and I still got all the functions I needed at a much lower cost and smaller footprint than if I had used discrete devices.

2.PNGThat specific device is admittedly targeted at lower power applications. In contrast, let’s look at the higher power UltraZed SOM that was recently released by AVNET. This SOM (System on Module) basically contains  a complete Xilinx Zynq UltraScale subsystem that customers can define custom carrier cards around to provide their application specific circuitry in a production ready package. For this SOM, I decided that I wanted to support all the power modes of the Zynq UltraScale device. I also wanted to include PMBus communication capability for real time monitoring and control. Having had a good experience on a previous design using Infineon’s IRPS38060 single channel PMBus regulator, I looked at their 5 output PMIC based on the same architecture of the single channel device. The IRPS5401 provides 4 switching outputs as well as an LDO, all accessible through the PMBus I2C hardware interface. The UltraZed requires 14(!) supplies to meet all of the various requirements to support power modes and our use cases. Four of these rails provide power to individual devices and/or weren’t required for power mode support so these are powered by lesser featured devices. The main ten rails though, are powered by two IRPS5401 PMICs that were then tied back to the Zynq UltraScale SoC. By doing so, the Zynq UltraScale can now send PMBus commands to turn off/on supplies, control slew rate, read real time voltage and current (meaning power too), temperature as well as read error flags such as overcurrent warnings, errors, etc.

 

Again the integration level of these devices allowed us to cram the very full featured UltraZed SOM with its 14 power supplies into the footprint about the size of a business card.

som.PNGWhile not as full featured as the PMBus enabled Infineon device, the Dialog device also features an I2C interface (although not PMBus compatible) that can be used in circuit to enable/disable supplies, read fault registers and more. Point being, when you start looking at defining your power architecture be sure to consider it from the system level. You may find that there is a PMIC out there that does everything you need (and more) for less real estate and a lower cost than the solution you were considering piecing together.

 

-- written by Chris Ammann, AVNET

I'm reviewing a Gallium Nitrate step-down converter for Point of Load (PoL) high power conversion.

This design is intended to deliver low voltage (0.5 - 1.5V) at a power hungry point of load. It can source 50A. With a switching frequency of 600 kHz, the footprint can stay small.

 

Part 1 gives a high-level overview of the design. The converter is interesting for more reasons than just being GaN. There are a few advanced switch-mode conversion patterns used in the evaluation kit.

One of the specifics of this design is the Current Doubler at the secondary stage.

 

In this design, the output current is divided over two inductors that each take half the current. Rectifying is done by two transistors (in our design: 2 times 2 GaN FETs) that are driven by the same PWM signal that drives the primary side half-bridge.

A few advantages of this design:

  • simpler transformer: no need for a center tapped design.
  • current shared over 2 inductors, so they can be smaller and heat isn't concentrated on a single spot.
  • significant part of the output current is canceled because current in the two sides of the output is (almost) inversed and a significant chunk cancels itself out -> smaller output capacitor needed.

There are more advantages and trade-offs with this design. It requires current control instead of voltage contrlol. You have to use phase-shift controlled PWM; Duty-cycle controlled PWM won't do.

There's a document available on the ti site that explains the design in depth.

RIGOL Print Screen11-2-2017 12_50_21.502.png

image: phase-shifted HI and LO control signals.

 

Here's the effect of the ripple canceling with a current doubler:

The two secondary sides are in essence two switching converters that run interleaved. Not exactly 180°. The controller uses phase shifted PWM to drive the two sides and the current that runs trough both inductors is a saw-tooth, not a 180° mirrored triangular signal.

So even though the cancellation isn't perfect, a significant amount of the ripple disappears because of the signals being fairly close to inverse. That allows us to reduce the output filter capacitors.

 

 

A second win is that the resulting ripple current has double frequency. So that allows us to reduce the capacity once more.

In TI's evaluation kit, the two output transistors are each a pair of EPC2023 GaN transistors. They are driven by the same signal that drives the LMG5200 GaN Half-bridge on the primary:

A somewhat simpler design is documented with a wealth of oscilloscope captures of the operation, control signals and the current doubling and canceling.

 

 

Blog Posts
GaN Point of Load converter 48V to 1V 50A - part 1: Design Overview
GaN Point of Load converter 48V to 1V 50A - part 2: Current Doubler
Related Blog
Checking Out GaN Half-Bridge Power Stage: Texas Instruments LMG5200 - Part 1: Preview

I'm reviewing a Gallium Nitrate step-down converter for Point of Load (PoL) high power conversion

 

IMG_7659.JPG

 

This design is intended to deliver low voltage (0.5 - 1.5V) at a power hungry point of load. It can source 50A. With a switching frequency of 600 kHz, the footprint can stay small.

 

 

A 48V DC power bus is common in industrial environments. That voltage often needs to be converted to other levels.

For high-performance processors, FPGAs and application specific ICs, this can be as low as 0.5V or 1V,  with a current draw of many amps.

The evaluation kit here (LMG5200POLEVM-10), that I got for review from TI almost a year ago, is intended for such applications - located close to the low voltage load.

 

GaN Power Stages

 

This isn't the simplest circuit. It consists of a half-bridge Buck converter, a transormer (a funny one) an output rectifier with filtering.

 

Primary Side

 

source: Using the LMG5200POLEVM-10 48V to Point of Load EVM

 

The half-bridge on the primary side is a GAN device that I've extensively reviewed in previous blogs: LMG5200. Check the blogs for details.

For this design, it's essential to understand that it is used as a typical Buck and that it switches at high frequencies.

We'll visit this component again when we check the PWM controller (it's a smart one with i2c interface) that is the brain of the converter.

 

Transformer

 

It's built from PCB traces, with a ferrite core over it. SO no wires in this transfo, just a single PCB trace on each side of the board.

edit: This is a 10 layer board. The Transfo has a 5:1 ratio. Check the comments below.

 

Top copper side of the PCBBottom copper side

Surrounded by a ferrite core

(two half cores that connect trough rectangular openings in the PCB)

 

10 layer board

Layers 1,4,5,7,10 dedicated to the secondary side (each one turn in parallel) and the other to the primary side (one turn each in series).

 

 

The stacking goes S PP SS P S PP S (S=secondary P= primary).

 

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source: Using the LMG5200POLEVM-10 48V to Point of Load EVM

It's crazy that you can transfer 75 Watt with this construct, isn't it?

 

Secondary side

 

This is a GaN transistor based rectifier and an LC filter to smoothen the output.

The gates of these transistors (in reality Q3 and Q4 in Figure 1 each are constructed with two discrete GaN FETs) are driven with the same signal that drives Q1 and Q2 on the primary side.

 

Core of the power circuit. Additional decoupling and filter caps not shown here.

source: Using the LMG5200POLEVM-10 48V to Point of Load EVM

 

 

 

There's no heat sink required. When the output current exceeds 20A, active cooling (a fan) is needed.

 

In the next blogs, I'll check out additional circuits on the development kit: the step-down controller and the on-board 10A pulsing(!) test load.

I hope that someone with sound electromagnetic knowledge chimes in to discuss the PCB transfo (the core is ER18-3.2-10-3F45-S from Ferroxcube).

 

Blog Posts
GaN Point of Load converter 48V to 1V 50A - part 1: Design Overview
GaN Point of Load converter 48V to 1V 50A - part 2: Current Doubler
Related Blog
Checking Out GaN Half-Bridge Power Stage: Texas Instruments LMG5200 - Part 1: Preview

3906 (1).jpg

A small Normandy village spent $5.2 million to build a solar panel road that will help power the streetlights. The solar panel road will be used by 2,000 motorists a day (via Christophe Petit Tesson/EPA)

 

Every year different towns and cities work to incorporate solar power into their transportation systems, like Santiago, Chile wanting to power its Metro system on solar energy. Now, a town in France is claiming to have the world’s first solar panel road. Tourovre-au-Perche, a small Normandy village, now has a 1km route covered with 2,800 square miles of solar panels that will help power the street lights. The new road, made by Colas, was officially opened by French Ecology Minister Segolene Royal.

 

The power generating road, which looks like a gothic version of the Yellow Brick Road, is comprised of 30,000 square feet of solar panels covered with a clear silicon resin making sure they can handle the impact of vehicle traffic. It took five years to develop and it wasn’t cheap: it took about $5.2 million to produce and install.

 

It’s exciting to think of street lights incorporating solar energy to help create a cleaner planet, but the new road is still in the testing phase. For two years it will be used by about 2,000 motorists a day to see if it can create enough energy to power the street lights in this village, which consists of 3,4000 residents. It’s a fairly small town, but if the road proves to be successful, perhaps it won’t be long until we see larger towns and cities using the same methods.

 

The solar powered road, dubbed Wattway, will face some limitations the biggest one being Normandy doesn’t see a whole lot of sunshine. The region’s political capital, Caen, gets about 44 days of sunshine a year when compared to 170 days a year in Marseilles. Another issue is the position of the panels. Since the panels sit flat on the surface, there’s a chance they’ll be less efficient than those set at an angle.

 

And while you can commend France for wanting to promote clean energy, you have to think of the cost. Critics are already pointing out how it’s not necessarily the most cost effective use of the public’s money. The panels themselves are expensive to produce on a massive scale and the upkeep may prove to be costly as well. Still, Royal remains hopeful and wants to install more of these solar roads all over the city.

 

Colas, in the meantime, has plans for other solar paneled roads. They want to install more of these roads in France and half of them aboard. For now, we have to wait and see how efficient the new road actually is. It does make you question whether solar panel streetlights would be better and cheaper than these roads.

 

Have a story tip? Message me at: cabe(at)element14(dot)com

http://twitter.com/Cabe_Atwell

This series of blogs describes the design of a GaN BoosterPack and its LabVIEW integration.

The LMG5200 is a GaN Half Bridge that can manage 80V and 10A. This BoosterPack allows you to evaluate the performance of the device. You can change its operating parameters via software and via the on-board rotary encoder.

 

The GaN BoosterPack is designed to be used with a Hercules LaunchPad.

The LaunchPad delivers the complementary signals required to drive the LMG5200 GaN Half Bridge.

The project comes with firmware that allows you to change the driver signals to your needs.

You can change duty cycle, frequency, deadband from LabVIEW or other lab automation software that supports USB and SCPI.

There's stand-alone firmware that changes the duty cycle when you rotate the rotary encoder on the BoosterPack, if you prefer that.

 

All schematics, PCBs, BOM and source code is attached to the blog posts.

 

{gallery} GaN BoosterPack

hercules GaN FET half-bridge TMS570LS43x texasinstruments

Hercules LaunchPad: proto setup

LabVIEW: test SCPI firmware

LabVIEW: Control software design

Hercules LaunchPad: First tests with a modded LMG5200 evaluation module

LMG5200 Hercules BoosterPack schematic

GaN BoosterPack: first schematic

GaN BoosterPack: KiCad 3d viewer

LMG5200: Layout Guidelines

GaN BoosterPack: one of the evaluation kit (reference design) PCB layers

boardbottom.png

GaN BoosterPack: KiCAD view of an internal PCB layer

GaN BoosterPack: Custom KiCAD footprint for LMG5200

GaN BoosterPack: Seeed Studio PCBs

20161210_174650.jpg

GaN BoosterPack: Device under test

 

Related Blogs

Hercules LaunchPad and GaN FETs - Part 1: Control Big Power with a Flimsy Mouse Scroll Wheel
Hercules LaunchPad and GaN FETs - Part 2: Make a BoosterPack
Hercules LaunchPad and GaN FETs - Part 3a: BoosterPack Layout - Reference Design
Hercules LaunchPad and GaN FETs - Part 3b: BoosterPack Layout - my version
Hercules LaunchPad and GaN FETs - Side Note A: BoosterPack Layout - Custom KiCad Parts
Hercules LaunchPad and GaN FETs - Side Note B: Look at the PCB
Rotary Encoders - Part 1: Electronics
Checking Out GaN Half-Bridge Power Stage: Texas Instruments LMG5200 - Part 1: Preview
Rotary Encoders - Part 4: Capturing Input on a Texas Instruments Hercules LaunchPad with eQEP
Vintage Turntable repair: Can I fix a Perpetuum Ebner from 1958 - part 4 - Hercules LaunchPad Enhanced PWM try-out

 

 

 

Related Blogs : Smart Instrument with SCPI

Create a Programmable Instrument with SCPI - Part 1: Parser Library
Create a Programmable Instrument with SCPI - Part 2: Serial over USB
Create a Programmable Instrument with SCPI - Part 3: First Conversation *IDN?
Create a Programmable Instrument with SCPI - Part 4: Error Handling by Default
Create a Programmable Instrument with SCPI - Part 5: First Hardware Commands
Create a Programmable Instrument with SCPI - Part 6: LabVIEW Integration
Create a Programmable Instrument with SCPI - Part 7: Talk to Hardware Registers