power Related Articles

This article is mainly to talk about the latest development of electric vehicle power management technology. Electric vehicle systems consist of electric motors, power converters, and energy storage devices such as lithium-ion batteries. This new architecture system must be optimized to maximize system efficiency, enabling the car to achieve maximum travel distance on a single charge. These developments in electronic technology have created conditions for reducing the emissions from transportation. Save our planet and keep the earth away from pollution! This is a consensus voice among scientists and people of insight around the world to reduce greenhouse gas emissions. Vehicles powered by fossil fuel combustion engines are the culprit. Although there are many alternative technologies to promote car travel, the only feasible solution at present is: electric cars.   Catalog   I Electric vehicles (EV) and hybrid electric vehicle (HEV) II Silicon carbide (SiC) power supply for electric vehicles III GaN power supply for electric vehicles IV Utilizing hybrid vehicle transmission system to reduce greenhouse gas emissions V Automotive inverter VI Dual-voltage battery system VII Delphi integration and wiring VIII Electric wheel drive system IX Conclusion FAQ I Electric vehicles (EV) and hybrid electric vehicle (HEV) An electric vehicle (EV) runs on a battery, as does a hybrid electrical vehicle (HEV), except that it also uses a fossil-fueled internal combustion engine as an aid. The technologies that power these cars need to be successful and have a bright future. Energy efficiency is the key. Therefore, intelligent power management mechanisms are needed to maximize the efficiency of converting battery energy into wheel mechanical driving force, thereby increasing single-charge charging. Travel distance, while not increasing carbon emissions, is ideally a significant reduction in carbon emissions. This video describe the operational characteristics of a hybrid vehicle drive train: Introduction to hybrid-electric vehicle energy monitor   II Silicon carbide (SiC) power supply for electric vehicles The weight, size, and cost of an electric vehicle, and the distance travelled by a single charge, are directly related to the efficiency of the power conversion system. SiC power components are ideal for working in the high temperature environments that are common in automobiles. Let us take a closer look at the role of silicon carbide power components in improving system efficiency. Lighter weight means longer mileage. A typical way to reduce the weight, cost, and size of a power conversion system is to increase the switching frequency of the switching regulator. We know that the size and weight of active components such as inductors, capacitors, and transformers can be reduced when operating at higher frequencies. Embrace the silicon carbide (SiC) solution. Although silicon (Si) power devices can also operate at high frequencies, the advantage of SiC is the ability to handle much higher voltages than Si. SiC is a wide band gap semiconductor device, and a wider band gap means a higher critical electric field (a critical electric field is a blocking voltage in an off state). The high voltage capability of wide bandgap (WBG) SiC devices allows them to have lower on-resistance, resulting in faster switching speeds and unipolar operation. Part of the principle is that their carrier frequencies need to be accelerated to much higher speeds (more High kinetic energy) to overcome wider band gaps. Although gallium arsenide (GaAs) and gallium nitride (GaN) also have high critical electric fields and are also improved devices for high-power solutions, SiC has other advantages, such as higher maximum operating temperatures. High Debye temperature, high thermal conductivity (in polycrystalline SiC), rapid switching and high resistivity saturation with low resistivity in the electric field, facilitated generation of lower silica (SiO2) The production cost, as well as the higher threshold energy brings more robust radiation resistance. SiC devices have many key applications in electric vehicles. The existing electric traction drive can convert 85% of the electrical energy into mechanical energy to drive the wheels. This efficiency is quite high, but SiC can also help improve efficiency. The power converter can benefit from improved efficiency because it transfers battery power to the engine and can be used in the battery charger circuit and any needed auxiliary power (Figure 1). Figure 1. SiC power devices have many uses in electric vehicles The SiC power supply that converts 750V to 27V for low-voltage electric vehicles is a good example of using SiC power devices to improve the efficiency of electric vehicles. This architecture increases efficiency from 88% to a staggering 96%, reduces size and weight by 25%, and does not require fans to cool excess heat compared to Si solutions. Table 1 shows some important applications of SiC power devices for electric vehicles. The reference information mentioned in the table can be found by referring to Reference 1 at the end of this article. Table 1. Some SiC applications in the electric vehicle electronics architecture III GaN power supply for electric vehicles Gallium nitride (GaN) also contributed to the improvement of the power supply of electric vehicles. IGBTs widely used in motor drive and DC/DC control have been silicon-based products. These designs typically have switching times on the order of 10kHz to 100kHz, while GaN devices can switch nanoseconds and can easily operate in a 200°C automotive environment. Like SiC, GaN devices can also reduce the size of inductors, capacitors, and transformers in power supply architectures due to their higher switching speeds. They can also reduce the overall size and weight due to the shrinking size of passive components. We will analyze their efficacy based on the chemical composition of electric vehicle batteries, such as lithium-based chemistry and NiMH with high energy density. As described in the previous SiC device section, the efficiency of the power conversion architecture also needs to be improved in order to enable longer distances for a single charge. The switching speed and minimum on-resistance of silicon devices have reached their maximum limit, and GaN seems to be a viable solution that exceeds these limits. Experiments show that if the switching frequency can be increased by 5 times, the inductor and capacitor can be reduced to one-fifth the size. Today's GaN technology can support very high speeds. GaN power devices perform quite well in four key areas: high temperature operation, higher breakdown voltage, low on-resistance, and nanoscale switching speeds for higher operating frequencies. GaN is similar to SiC in terms of these advantages. There are two differences between them: LEDs and RF transistors always use GaN; many silicon manufacturing processes are compatible with GaN processes, which reduces wafer costs and processes compared to the higher substrate costs of SiC. cost. Since the reliability problem was solved as early as 2003, today's technology has achieved the first batch of GaN high electron mobility transistor (HEMT) devices already in production. These are normal conduction devices, so the gate voltage of 0V will become conductive, and any voltage less than 0V will turn the device off. The SiC substrate was used early. Once the Si substrate is perfectly integrated with GaN, the production cost can be significantly reduced. The new cascaded architecture implemented in 2014 changed the ever-changing devices into normally-off devices. Since then, the drive technology has made great progress, the integration is getting higher and higher, and the power inverter has also made significant progress. GaN devices also perform well in battery chargers for electric vehicles, which consist of AC/DC converters plus DC/DC converters. This combination is a power factor controller (PFC) (Figure 2). Figure 2: A typical electric vehicle power architecture With GaN, coupled with higher switching speed GaN HEMTs, smaller passive devices can be realized. At higher frequency conditions, using a smaller inductor can make the ripple current of the power supply architecture lower, improve the power factor, and get a capacitor with a smaller size and lower cost. Lower ripple currents also have less stress on the capacitors, increasing their reliability and lifetime. Over the past few years, the reliability of GaN has been raised to a very high standard, which is the key to the use of GaN in automobiles. IV Utilizing hybrid vehicle transmission system to reduce greenhouse gas emissions At present about 72% of traffic emissions are generated by cars driving on the road. Improving the design of the hybrid powertrain drive system to increase its efficiency is the primary means of reducing emissions. One approach is to increase the efficiency of the DC-link voltage control architecture, which means that first it is necessary to increase the power converter efficiency of the series hybrid electric vehicle drive system. The DC-link is usually connected to three drive systems: a primary power supply consisting of a three-phase rectifier; a secondary power supply consisting of a dual active bridge (DAB) DC/DC converter; and a propulsion load consisting of a three-phase inverter ( Figure 3). They relate to tandem hybrid cars. Figure 3: Block diagram of the drive train of a hybrid vehicle In a design topology where the DC-link and battery voltages are not equal, an intermediate DC/DC converter solution is required. The paper "Voltage Control Methods for Improving Efficiency of Power Circuits in Series Hybrid Electric Vehicles" (Reference 3) describes many methods for studying different architectures and solutions for various DC-link voltage and DC/DC converter control. . The following will discuss the proportional control law that controls the dynamic DC-link voltage to achieve the phase shift between the waveforms of the gate switching of the DAB DC/DC converter bridge. This converter is located between the DC-link and the battery of a series hybrid vehicle drivetrain, as shown in Figure 4. In this case, the controller lowers the power consumption of the DC/DC converter and the entire drive system. Figure 4: Hybrid driveline interconnection diagram in the control schematic In this model, the diesel engine is the main power source of the hybrid vehicle, and the DC battery is the secondary power source. The supervisory control system (SCS) controls the ratio of power provided by the two power sources based on battery state of charge (SOC) and motor load. In fact, in this series hybrid vehicle, the DC-link voltage imposes restraint conditions on the ideal working area of PMSM and PMSG corresponding to the unit modulation index, so that the system can avoid signal distortion and reduce system efficiency. Overshoot state. Keeping the modulation index close to 1 can increase the total efficiency of the power circuit in the drive system, thereby maximizing the efficiency of the inverter and the rectifier, and the switching process is the main factor of its efficiency loss. Therefore, reducing the switching voltage can improve efficiency. This permanent zero pressure switch (PZVS) mechanism that minimizes power loss is best suited for cars with high mixing factors, especially in urban environments. The mixing factor (HF) is the ratio of the installed power from the power source to the total installed power. This mixing factor affects the fuel consumption in hybrid vehicles. V Automotive inverter The main power inverter controls the electric motor in the electric drive system and is an important component in the hybrid/electric vehicle. Power inverters, like engine management systems (EMS) in internal combustion engine cars, determine driving behavior. This inverter is suitable for any motor, such as synchronous, asynchronous or brushless motor, controlled by an integrated electronic PCB board. This PCB is specifically designed by automotive manufacturers to minimize switching losses and maximize thermal efficiency. The other function of the inverter is to capture the energy released by the regenerative brake and feedback to charge the battery. The distance traveled by hybrid/electric vehicles is directly related to the efficiency of the main inverter (Figure 5). Figure 5: Infineon main inverter block diagram in a hybrid/electric vehicle VI Dual-voltage battery system Managing batteries in hybrid and electric vehicles requires high-voltage technology. Dual-voltage systems incorporating 12V and 48V batteries require bi-directional DC/DC conversion, as shown in Figure 6, with the goal of protecting the circuit and supporting architectural functions. Figure 6: Bidirectional DC/DC converters from 48V to 12V In addition, automotive architecture designs typically have a single-phase 3.5kW or 7kW on-board charger module (OBCM) for charging an electric vehicle or plug-in hybrid electric vehicle (PHEV) from the grid. In contrast, electric vehicles and plug-in hybrid vehicles can be used as energy sources, and can also be used as energy storage devices in smart grids that integrate renewable energy. Smart grid work takes into account the smart charging and discharging of electric vehicles and plug-in hybrid vehicles. This is why OBCM must be a bi-directional DC/DC charger. The best architecture for this design is a boost series of resonant bi-directional topologies, as shown in Figure 7. It operates above the resonant frequency, has a zero-voltage switching function, and has maximum power transfer performance at the minimum switching frequency point. Compared to unidirectional power converters, this technology replaces diode rectifiers with MOSFET rectifiers. This solution also has higher efficiency and wider battery capacity. One of the major drawbacks of this architecture shown in Figure 7 is that the rectifier bridge has large losses when it is turned off. This problem must be addressed in future designs. Figure 7: Designers sometimes use a modulated DAB converter to control simple high-frequency isolation VII Delphi integration and wiring It is amazing that Delphi integrates all of the components discussed in this article and some of the other hybrid electric vehicle power electronics (Figure 8). Figure 8. Delphi achieves high integration in hybrid/electric vehicles It is also important to use suitable internal connectors in hybrid/electric vehicles (Figure 9). Figure 9. The key element of a hybrid/electric car is to minimize the quality     VIII Electric wheel drive system “Design and implementation of electric drive systems for in-vehicle electric vehicle applications” (Reference 8) proposes a hub drive system for hybrid and electric vehicles, and a hub-drive hybrid vehicle that provides computing performance. The SIMULINK model has been successfully developed. Two 14kW DC brushless DC (BLDC) motors are manufactured according to the literature and are installed in the rim of the hybrid vehicle wheels. In addition, two independently driven rear wheels are also mounted on Fiat's Linea. By detecting the angle of the steering wheel, electronic control technology replaces the mechanical differential device. The electric drive control system of the car and the electronic control unit (ECU) communicate via the CAN bus. A successful cascade is achieved between the electrically driven rear wheel and the ICE-driven front axle. Figure 10. A rear-wheel brushless DC motor image This design chose a brushless DC motor with a concentrated coil because it has a very low power-to-weight ratio and high efficiency, and it is easy to control. Figure 11. Exploded view of a direct-drive brushless DC motor in wheel rims and motor-generator units The brushless DC motor power drive consists of an integrated power module (IPM), an 8-bit microcontroller and an electronic control system. Driver software development for IGBT converter control and motor pulse width modulation (PWM) voltage control. The system has optocoupler isolation, current and temperature protection, and the system is also embedded with speed, current and voltage sensors. In summary, this article describes some recent developments in the power management of electric vehicles and hybrid vehicles. In the future, there will certainly be more development results that will be further improved to benefit our planet. IX Conclusion Electric propulsion technology requires the integration of a completely new architecture of the powertrain in the vehicle. This newly added component requires a multidisciplinary and in-depth study of the corresponding system components. Electric vehicle systems consist of electric motors, power converters, and energy storage devices such as lithium-ion batteries. This new architecture system must be optimized to maximize system efficiency, enabling the car to achieve maximum travel distance on a single charge. These developments in electronic technology have created conditions for reducing the emissions from transportation.   FAQ   1. What is energy management system in electric vehicles? Energy management strategies are the algorithms that decide the power split between engine and motor in order to improve the fuel economy and optimize the performance of HEVs. ... A lot of research work has been conducted for energy optimization and the same is extended for Plug-in Hybrid Electric Vehicles (PHEVs).   2. What is EV technology? EVs (also known as plug-in electric vehicles) derive all or part of their power from electricity supplied by the electric grid. They include AEVs and PHEVs. AEVs (all-electric vehicles) are powered by one or more electric motors. They receive electricity by plugging into the grid and store it in batteries.   3. What is the biggest challenge with electric vehicles? The major challenge is costs. Battery technology is expensive, and because batteries in electric cars need to be able to hold massive amounts of charge to make the cars practical for most drivers, they have to be built using expensive materials, most of which are tough to procure.   4. Why electric cars are bad for the environment? Nevertheless, at the end of the manufacturing process, electric cars are the ones generating more carbon emissions, according to the Union of Concerned Scientists. Why is this? Because electric cars store energy in large batteries (the larger they are, the bigger their range is) that have high environmental costs.   5. What are the main problems with electric cars? The biggest problem with EVs is range. While a plug-in hybrid can count on gasoline as a backup, EVs can't. An EV like the Tesla Model S can travel nearly 400 miles on a single charge, but not all EVs can make it quite that far. EVs like the Model S tend to be pretty expensive too.   6. What is meant by electric vehicle? An EV is a shortened acronym for an electric vehicle. EVs are vehicles that are either partially or fully powered on electric power. Electric vehicles have low running costs as they have less moving parts for maintaining and also very environmentally friendly as they use little or no fossil fuels (petrol or diesel).   7. How do electric vehicles work? Electric cars function by plugging into a charge point and taking electricity from the grid. They store the electricity in rechargeable batteries that power an electric motor, which turns the wheels. Electric cars accelerate faster than vehicles with traditional fuel engines – so they feel lighter to drive.   8. What are the types of electric vehicles? There are two basic types of EVs: all-electric vehicles (AEVs) and plug-in hybrid electric vehicles (PHEVs). AEVs include Battery Electric Vehicles (BEVs) and Fuel Cell Electric Vehicles (FCEVs).   9. Do electric cars run on AC or DC? Electric cars can use AC or DC motors: If the motor is a DC motor, then it may run on anything from 96 to 192 volts. Many of the DC motors used in electric cars come from the electric forklift industry.   10. Are there any benefits of owning an electric car? They can reduce emissions and even save you money. Fueling with electricity offers some advantages not available in conventional internal combustion engine vehicles. Because electric motors react quickly, EVs are very responsive and have very good torque.  

Warm hints: The word in this article is about 1000 and the  reading time is about 6 minutes. MIT researchers found a way to triple the efficiency by using "topological" materials with special electronic properties. Although previous research has indicated that topological materials could be used to create efficient thermoelectric systems, little is known about how electrons in such topological materials can move in response to temperature differences to produce a thermoelectric effect. Researchers not only found that they can push the boundaries of this nanostructured material in a way that makes topological materials a good thermoelectric material,more so than conventional semiconductors like silicon,but also this could be a clean-energy way to help us use a heat source to generate electricity, which will lessen our release of carbon dioxide. NewsToday, thermoelectric devices are used for relatively low-power applications, such as powering small sensors along oil pipelines, backing up batteries on space probes, and cooling minifridges. Scientists hope to develop more efficient thermoelectric devices that will harvest heat produced as a byproduct of industrial processes and combustion engines and convert it into electricity. However, thermoelectric devices' power, or the amount of energy they can generate, is currently limited. "We discovered that we can push the limits of this nanostructured material in a way that makes topological materials a better thermoelectric material than traditional semiconductors like silicon," says Te-Huan Liu, a postdoctoral researcher in MIT's Department of Mechanical Engineering. "In the end, this could be a clean-energy way to help us use a heat source to generate electricity, which will lessen our release of carbon dioxide," Liu added. Liu is first author of the PNAS paper, which includes graduate students Jiawei Zhou, Zhiwei Ding, and Qichen Song; Mingda Li, assistant professor in the Department of Nuclear Science and Engineering; former graduate student Bolin Liao, now an assistant professor at the University of California at Santa Barbara; Liang Fu, the Biedenharn Associate Professor of Physics; and Gang Chen, the Soderberg Professor and head of the Department of Mechanical Engineering.A Path Travel Freely When a thermoelectric material is exposed to a temperature gradient — for example, one end is heated while the other is cooled — electrons begin to flow from the hot end to the cold end, resulting in an electric current. The greater the temperature difference, the more electric current and power are made. The amount of energy that can be produced is determined by the electron transport properties of a given material. Scientists have discovered that certain topological materials can be converted into efficient thermoelectric devices using nanostructuring, a technique used by scientists to create a material by patterning its features at the nanometer scale. Scientists believe that the thermoelectric benefit of topological materials stems from decreased thermal conductivity in their nanostructures. However, it is uncertain how this increase in efficiency relates to the material's inherent, topological properties.     Liu and his colleagues investigated the thermoelectric efficiency of tin telluride, a topological material considered to be a strong thermoelectric material, to try to address this issue. Tin telluride electrons also have unusual properties that resemble a class of topological materials known as Dirac materials. The researchers wanted to understand the effect of nanostructuring on the thermoelectric efficiency of tin telluride by simulating electron movement through the material. Scientists often use a calculation known as the "mean free path" to characterize electron transport. This is the average distance an electron with a given energy can freely travel within a material before being dispersed by different objects or defects in that material. Nanostructured materials resemble a patchwork of tiny crystals, each with its own boundary, known as grain boundaries, that separates one crystal from the next. As electrons come into contact with these limits, they scatter in a variety of ways. Electrons with long mean free paths scatter violently, similar to bullets ricocheting off a wall, whereas electrons with shorter mean free paths are much less affected. The researchers discovered that the electron properties of tin telluride have an important effect on their mean free paths in their simulations. They plotted the spectrum of electron energies in tin telluride against the related mean free paths and discovered that the resulting graph looked very different from that of most traditional semiconductors. In particular, for tin telluride and probably other topological materials, the findings indicate that higher-energy electrons have a shorter mean free path, while lower-energy electrons have a longer mean free path. The researchers then investigated how these electron properties influence the thermoelectric efficiency of tin telluride by essentially summing up the thermoelectric contributions from electrons with different energies and mean free paths. It turns out that the ability of a substance to conduct electricity, or produce a flow of electrons, under a temperature gradient is largely determined by the electron energy. They discovered that lower-energy electrons have a negative effect on the production of a voltage difference, and hence electric current. Since low-energy electrons have longer mean free paths, they can be dispersed more intensely by grain boundaries than high-energy electrons.Size DownGoing a step further in their simulations, the team experimented with the size of individual grains of tin telluride to see whether this had some impact on the movement of electrons under a temperature gradient. They discovered that raising the diameter of an average grain to around 10 nanometers, putting its boundaries closer together, increased the contribution of higher-energy electrons. Higher-energy electrons contribute much more to the material's electrical conduction with smaller grain sizes than lower-energy electrons because they have shorter mean free paths and are less likely to scatter against grain boundaries. As a result, a greater voltage difference can be produced. Furthermore, the researchers discovered that shrinking the average grain size of tin telluride to around 10 nanometers yielded three times the amount of electricity that the material would have produced with larger grains. Although the findings are based on simulations, Liu claims that researchers can achieve comparable results by synthesizing tin telluride and other topological materials and changing their grain size using a nanostructuring technique. Other researchers have proposed that shrinking the grain size of a material can improve its thermoelectric efficiency, but Liu claims that they have mostly assumed that the ideal size is much larger than 10 nanometers. "In our simulations, we discovered that we can shrink the grain size of a topological material far more than previously thought, and based on this principle, we can increase its performance," Liu says. Tin telluride is one of the topological materials that have yet to be discovered. If researchers can determine the optimal grain size for each of these materials, topological materials, according to Liu, can soon be a viable, more effective alternative to producing renewable energy. ConclusionLiu believes that topological materials are excellent for thermoelectric materials, and our findings indicate that this is a very promising material for potential applications. The Solid-State Solar Thermal Energy Conversion Center, an Energy Frontier Research Center of the United States Department of Energy, and the Defense Advanced Research Projects Agency contributed to this research (DARPA). Article From Proceedings of the National Academy of SciencesArticle Edited by kynix 

Warm hints: The word in this article is about 1000 and the  reading time is about 6 minutes.SummaryFujitsu,a company that provide innovative IT services and digital technologies like mobile,AI,cloud or etc,announced the development of a gallium-nitride(GaN) high-electron mobility transistor(HEMT) power amplifier for use in W-band(75-110 GHz)transmissions in July 2017 at the 12th international Conference. To realize long-distance,high-capacity wireless communications,a promising approach is to utilize the W-band and other high frequency bands that encompass a broad range of usable frequencies, and increase output with a transmission power amplifier. At the same time, demand exists for improved efficiency in power amplifiers in order to mitigate the increased power consumption of communication systems. Fujitsu has now succeeded in developing a power amplifier for use in W-band transmissions that offers both high output power and high efficiency, improving transistor performance through the reduction of electrical current leakage and internal GaN-HEMT resistance. Fujitsu has achieved 4.5 watts per millimeter of gate width, the world's highest output density in the W-band, and has confirmed a 26% reduction in energy consumption compared to conventional technology. Fujitsu anticipates that setting this power amplifier between wireless communication systems in two locations will achieve high-bandwidth communications at 10 gigabits per second (Gbit/s) over a distance of 10km. Part of this research was carried out with support from Innovative Science and Technology Initiative for Security, established by the Acquisition, Technology & Logistics Agency (ATLA), Japan Ministry of Defense. Development Background Wireless data traffic from mobile communications has increased dramatically over the last few years, and with the spread of 5G and IoT devices it is predicted to increase at an annual growth rate of 1.5 times until the year 2020. In order to build this sort of high capacity next-generation wireless communications network, attention has been focused on wireless communication technology using the high frequency W-band. The range of frequencies that can be used in the W-band is very broad, and because communication speed can be rapidly increased in this band, it is well-suited for this kind of high bandwidth wireless communication. Conventional wireless communications technology, has allowed for performance of several Gbit/s over distances of several kilometers, but achieving an even greater increase in wireless communication distance and capacity utilizing the W-band demands further increases to the output of power amplifiers to boost signals during transmission. Issues To increase distance and capacity, it will be necessary to expand the frequency bandwidth that can be amplified while simultaneously supporting modulation methods that can transmit more information within the same frequency bandwidth, and a strong requirement is to have less distortion when the signal is amplified. Another pursuit is keeping in check the energy consumption of communication systems that accompanies greater distances and capacities, and the improved energy efficiency in power amplifiers.In order to both increase the distance and capacity of wireless communications and decrease energy consumption with indium-aluminum-gallium-nitride (InAlGaN) HEMTs, Fujitsu has developed two technologies that effectively reduce internal resistance and current leakage. Features of the newly developed technologies are as follows: Technology to reduce internal resistance Fujitsu has developed device technology that can reliably reduce resistance to one tenth that of previous technology when current flows between the source or drain electrodes and the GaN-HEMT device. The technology utilizes a manufacturing process that embeds GaN plugs directly below the source and drain electrodes, which generate electrons at high densities (fig. 1). It is necessary to transport the electrons that come from the source electrode to the two dimensional electron gas field as smoothly as possible. The structure of the previous technology causes the electron supply layer to become a barrier, however, and internal resistance increases between the source electrode and the two dimensional electron gas. By applying this new technology, Fujitsu succeeded in running high currents through the transistor with significantly less resistance (fig. 2). Technology to control current leakageA current leakage occurs when the two dimensional electron gas, which moves at high speed on the boundary at the top of the channel layer, takes a detour below the gate when the transistor is in its off-state. This leakage causes deterioration in the operational performance of the power amplifier. Normally, it is possible to reduce current leakage by placing a barrier layer beneath the channel layer, but in that case the amount of two dimensional electron gas also decreases, and leads to a reduction of the drain current. This new technology maintains high drain currents by effectively distributing indium-gallium-nitride (InGaN) to create a barrier layer below the channel layer. This reduces electron detours during operation, successfully providing significant reductions in current leakage(just see the fist and second picture).Effects The previous world record for power amplifier output density in the W-band for transmitters was 3.6 watts per millimeter of gate width with technology developed by Fujitsu Laboratories. This has improved significantly with the newly developed technology, which delivers power output of 4.5 watts per millimeter of gate width for a power amplifier designed to operate at 94GHz. In addition, this new technology achieved a reduction in energy consumption of 26% compared to the previous technology through a reduction in current leakage. It is anticipated that the use of this power amplifier will allow the achievement of high capacity, long distance wireless communications between two connected systems at different locations at over 10Gbit/s and at distances greater than 10km.Fujitsu aims to apply this technology broadly to the development of power amplifiers for purposes that call for wireless communications that offer long range and higher capacity, while offering easier installation than fiber optics. The goal is to commercialize this technology in high speed wireless communication systems by 2020, with an aim to employ it in such situations as a method of restoring communications when fiber optic cables have been severed by natural disasters or as a way of setting up temporary communications infrastructure when holding events.  Article provide by FujitsuArticle edited by kynix

SummaryThere is an article named "Working principle and Development of Solar Cell" in the Kynix Semiconductor Electronic Blog, it detailed shows that the development of new energy sources mainly concentrates on renewable energies such as solar energy,hydrogen energy, wind energy and geothermal energy, among which solar energy resources are abundant and widely distributed, and are the most promising renewable energy sources. In 1839,French scientist E.Becquerel discovered the photovoltaic effect of the liquid,the solar cell has undergone a long development history of more than 160 years. In terms of the overall development, both basic research and technological advancement have played a positive role in promoting them. Now,researchers at Osaka University, in an international collaboration with Max Planck Institute for Polymer Research, have redesigned one of their previously reported polymers to make a new kind of solar cell that needs no extra special treatments. They also managed to keep excellent power conversion efficiency of solar power to electricity, as recently reported in Advanced Energy Materials.  DiscussionIt's truely that energy industry  is not only the basic industry of national economy, but also a technology-intensive industry.Due to the continuous demand of mankind for renewable energy, people are devoted to developing new sources. The energy that the sun shines on the Earth's surface in 40 minutes can be used for one year at a speed of the current global energy consumption. Reasonable utilization of solar energy will be a long-term development strategy for mankind to solve energy problems and it is also one of the most studied research hot spots.Humankind is in the midst of a massive drive to harness solar energy to power our homes, gadgets, and industry. Plastic solar cells, based on blends of conducting organic polymers, are of interest for making lightweight and cheap solar cells. The problem with these kinds of solar cells is that their solar power efficiencies are very closely related to the way the different types of materials mix and crystalize in thin films. This means complex and careful processing is usually needed to make efficient polymer solar cells. According to lead author Yutaka le,Conventional organic solar cells have now achieved good efficiencies but the polymer films in these devices typically require special processing to ensure correct crystallization.(Organic solar cells, as its name implies, are solar cells that form of organic materials. We are not familiar with organic solar cells, which is a reasonable thing. More than 95% of today's solar cells are silicon-based, while less than 5% of the remaining solar cells are made from other inorganic materials.) Instead, we have been focusing on amorphous polymer blends to avoid these issues. Organic solar cells work based on light energy exciting electrons in a polymer. The excited electrons can then transfer to a soccer ball-shaped fullerene and move to the positive side of the solar cell. The space left by an electron is known as a hole. It too must move through the polymer to the other side of the device to complete the circuit. The Osaka researchers knew that one of their polymers could not transport holes so effectively. They redesigned the structure by adding an extra component, which improved its hole conductivity, and in turn enhanced the solar power conversion performance. Coauthor Yoshio Aso says, "Being able to make these cells without having to pay such close attention to the crystal structure of the polymer films could allow us to mass produce these devices by simple printing methods, which should considerably lower costs of the devices and lead to much wider uptake." 

Summary As is listed in the market,there is a little of small,inexpensive switch for latching power to a load unless you buy low-current,momentary action pushbotton switches like PCB-mount‘tactile types'. However, we can get a suitable latching power switch passing by converting a pushbutton's momentary action into a latching function.   New Design Idea Previous Design Ideas have proposed solutions based on discrete components  and IC-based circuits . The circuit outlined below, however, requires just two transistors and a handful of passive components to achieve the same result.   Circuit One The circuit in Figu1(a) is configured to latch power to a low-side (ground-referred) load. It works in 'toggle' mode; that is, the first switch closure applies power to the load, the second removes power, and so on. fig1  Circuit converts momentary action push switch into latching power switch     To understand how the circuit operates, assume that the DC power supply, +VS, has just been applied, capacitor C1 is initially uncharged, and Q1 is off. The P-channel MOSFET, Q2, is held in its off state by R1 and R3, which work in series to pull the gate up to +VS, such that VGS is zero. The circuit is now in its 'unlatched' state, where the load voltage, VL, at the OUT (+) terminal is zero.   If the normally-open push switch is momentarily closed, C1 – being uncharged – pulls Q2's gate to 0V, thus turning on the MOSFET. The load voltage at OUT (+) now rises immediately toward +VS , and Q1 receives base bias via R4 and turns on. Under these conditions, Q1 saturates and pulls Q2's gate low via R3, thus holding the MOSFET on when the switch has opened. The circuit is now in its 'latched' state, where both transistors are on, the load is energized, and C1 charges up to +VS via R2.   When the switch is momentarily closed for a second time, the voltage on C1 (by now approximately equal to +VS) is transferred to Q2's gate. Since Q2's gate-source voltage is now roughly zero, the MOSFET turns off and the load voltage falls to zero. Q1's base-emitter voltage also falls to zero and the transistor turns off. Therefore, when the switch is released, there is nothing to hold Q2 on, and the circuit reverts to its 'unlatched' state, where both transistors are off, the load is de-energized, and C1 discharges via R2. Resistor R5 across the output terminals is an optional component that acts as a pull-down. When the switch is released, C1 discharges via R2 into the load. If the load impedance is very high (i.e., similar in magnitude to R2), or if it contains active devices such as LEDs, the load voltage at the instant Q2 turns off may be large enough to bias Q1 on via R4, thereby preventing the circuit from turning off properly. The presence of R5 pulls the OUT (+) terminal down to 0V when Q2 turns off, thus ensuring that Q1 turns off rapidly, and allowing the circuit to revert to its unlatched state in a proper manner.   Provided the transistors are correctly rated, the circuit will work over a wide voltage range and is well suited to driving loads such as relays, solenoids, LEDs, and so on. However, beware that certain DC fans and motors continue to rotate when their drive power is removed. This rotation can generate an EMF large enough to bias Q1 on, thereby preventing the circuit from switching off. You can eliminate this problem by inserting a blocking diode in series with the output, as shown in Fig1(b). You must also include R5 to ensure Q1 turns off properly.   Ciruit Two The complementary circuit outlined in Fig2 is intended for 'high-side' loads connected to the positive supply rail such as the relay shown in this example. fig2 Complementary circuit intended for high-side loads   Note that Q1 has been replaced with a PNP transistor, and Q2 is now an N-channel MOSFET. The circuit operates in a similar way to the one described above. Here, R5 acts as a pull-up resistor which pulls the OUT (-) terminal up to +VS when Q2 turns off, thus ensuring that Q1 turns off quickly. As in the previous circuit, R5 is optional and only necessary for the types of load mentioned previously.   Note that in both circuits, the time constant produced by C1-R2 provides for debouncing of the push switch contacts. Normally, a value of 0.25s to 0.5s should be adequate. Smaller time constants may lead to erratic behaviour, whereas a larger time constant increases the waiting time between switch closures necessary to ensure that C1 charges and discharges properly. With C1 = 330nF and R2 = 1MΩ as shown, the time constant is nominally 0.33s. This is usually sufficient to debounce the contacts and to allow the load power to be toggled after a couple of seconds or so.   Both circuits are intended to latch and unlatch in response to brief, momentary switch closures. However, they have each been designed to ensure correct operation even if the push switch is held closed for any length of time. Consider the circuit in Fig2 when Q2 is on. When the switch is pressed to unlatch the circuit, the gate is pulled down toward 0V (since C1 is uncharged) and the MOSFET switches off, allowing  the junction of R1-R2 to rise toward +VS via R5 and the load impedance. At the same time, Q1 also switches off, such that Q2's gate is pulled to 0V via the series combination of R3 & R4. If the switch is released immediately, C1 will simply charge up toward +VS via R2. However, if the switch is kept closed, Q2's gate voltage will be defined by the potential divider formed mainly by R2 and R3+R4. If we assume that the OUT (-) terminal is roughly equal to +VS when the circuit is unlatched, Q2's gate-source voltage is given by: VGS = (+VS) × (R3 + R4)/(R2 + R3 + R4) = 0.02(+VS). Even if +VS is as high as 30V, the resulting gate-source voltage of around 0.6V will be too low to switch the MOSFET on again. Consequently, both transistors remain off until the switch contacts open.   The circuit in Fig2 is latched on by momentarily closing the push switch when C1 has charged up to +VS , which causes OUT (-) to drop to 0V as Q2 immediately turns on, rapidly followed by Q1. A momentary switch closure would allow C1 to discharge to zero via R2 after the contacts open. However, if the switch is held closed, Q2's gate voltage will be defined by the potential divider formed by R2 and R3. Since Q1 is saturated, the junction of R3-R4 at Q1's collector will be pulled up to +VS, and the junction of R1-R2 will be pulled down to 0V via Q2. Therefore, with the switch held closed, Q2's gate-source voltage is given by: VGS = (+VS) × R2/(R2 + R3) = 0.99(+VS). Consequently, provided the supply voltage is at least equal to Q2's gate-source threshold voltage, both Q2 and Q1 will remain on until the switch contacts open.   Both circuits provide an inexpensive way of deriving a latching function from a momentary switch and, just like a mechanical latching switch, the quiescent (unlatched) power dissipation is zero.

SummaryFor years,people had treated the poor conductivity of organics as an unavoidable fact,and this shows that that is no always the case. Said Stephen Forrest,the Peter A. Franken Distinguished University Professor of Engineering and Paul G. Goebel Professor of Engineering at U-M, who led the research,which is  a way to coax electrons to travel much further than was previously thought possible in the materials often used for organic solar cells and other organic semiconductors under the condition of pushing cheap,ubiquitous solar power closer to reality. The fatal weakness of organic material may adjust its conductivityUnlike the inorganic solar cells widely used today, organics can be made of inexpensive, flexible carbon-based materials like plastic. Manufacturers could churn out rolls of them in a variety of colors and configurations, to be laminated unobtrusively into almost any surface. Organics’ notoriously poor conductivity, however, has slowed research. Forrest believes this discovery could change the game.  The team showed that a thin layer of fullerene molecules—the curious round carbon molecules also called Buckyballs—can enable electrons to travel up to several centimeters from the point where theyre knocked loose by a photon. That’s a dramatic increase; in today's organic cells, electrons can travel only a few hundred nanometers or less. But organic materials have much looser bonds between individual molecules, which can trap electrons. This has long been an Achilles’ heel of organics, but the new discovery shows that it may be possible to tweak their conductive properties for specific applications. The ability to make electrons move more freely in organic semiconductors The ability to make electrons move more freely in organic semiconductors could have far-reaching implications. For example, the surface of today's organic solar cells must be covered with a conductive electrode that collects electrons at the point where they’re initially generated. But freely moving electrons can be collected far away from their point of origination. This could enable manufacturers to shrink the conductive electrode into an invisible grid, paving the way for transparent cells that could be used on windows and other surfaces. “This discovery essentially gives us a new knob to turn as we design organic solar cells and other organic semiconductor devices,” said Quinn Burlingame, a U-M electrical engineering and computer science graduate researcher and author on the study. “The possibility of long-range electron transport opens up a lot of new possibilities in device architecture.” Burlingame says that the initial discovery of the phenomenon came as something of an accident as the team was experimenting with organic solar cell architecture in hopes of boosting efficiency. Using a common technique called vacuum thermal evaporation, they layered in a thin film of C60 fullerenes—each made of 60 carbon atoms—on top of an organic cell's power-producing layer, where the photons from sunlight knock electrons loose from their associated molecules. On top of the fullerenes, they put another layer to prevent the electrons from escaping. They discovered something they’d never seen before in an organic—electrons were skittering unfettered through the material, even outside the power-generating area of the cell. Through months of experimentation, they determined that the fullerene layer formed what's known as an energy well—a low-energy area that prevents the negatively charged electrons from recombining with the positive charges left behind in the power-producing layer.“You can imagine an energy well as sort of a canyon—electrons fall into it and can’t get back out,” said Caleb Cobourn, a graduate researcher in the U-M Department of Physics and an author on the study. “So they continue to move freely in the fullerene layer instead of recombining in the power-producing layer, as they normally would. It's like a massive antenna that can collect an electron charge from anywhere in the device.”Forrest cautions that widespread use of the discovery in applications like solar cells is theoretical at this point. But, he is excited by the discovery’s larger implications for understanding and exploiting the properties of organic semiconductors. “I believe that ubiquitous solar power is the key to powering our constantly warming and increasingly crowded planet, and that means putting solar cells on everyday objects like building facades and windows,” Forrest said. “Technology like this could help us produce power in a way that’s inexpensive and nearly invisible.” The study is titled “Centimeter-Scale Electron Diffusion in Photoactive Organic Heterostructures.” The research was supported by the U.S. Department of Energy SunShot Program and by the Air Force Office of Scientific Research.    Article from University of MichiganArticle edited by kynix