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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 

    This article shows how to use the buck converter for inverting or non-inverting voltage rails, and use it as an inverting buck-boost converter.     Catalog I. Brief Introduction II. Buck Converter III. Three DC/DC Converter Topologies 3.1 Isolated Buck Topology 3.2 Inverting Buck-boost (step-up and step-down)   Topology4 3.3 Isolated   Buck-boost Topology: +/- output5 FAQ   I. Brief Introduction   As we all known,power supply circuits come in the form of voltage step-up or step-down DC/DC converter. Nowadays,more and more applications require multiple voltage rails to drive ICs.The rails may be inverting,or non-inverting,with or without isolation.   While designers typically use multiple buck converters with single filter inductors, they add cost, footprint, and height. A simpler alternative is to use a single buck converter with coupled inductors or transformers configured in isolated converter topologies. Designers can use the buck converter for inverting or non-inverting voltage rails, and they can configure it for use as an inverting buck-boost converter.   Coupled inductors or transformers can also be used with a buck-boost converter to generate multiple inverting or non-inverting outputs with voltage step-up/down function. However, do you know what is isolated non-isolate DC/DC converter topologies? How they can be implemented using a single synchronous buck converter?   II. Buck Converter   A step-down transformer is a transformer that converts the higher voltage of the input end to the ideal voltage with relatively low output to achieve the purpose of reducing the pressure. A step-down transformer is a very important piece of equipment in the power transmission and transformation system.   Its normal operation is related to not only its own safety, but also the reliable power supply of users, and directly affects the stability of the power system. The protection configuration of the step-down transformer should satisfy in any case, the transformer can not be burned, the accident is enlarged, and the stability of the power system is affected. The principle of its work, the principle of relay protection, operation conditions, operation and requirements, and the abnormal operation and processing methods are introduced in detail. III. Three DC/DC Converter Topologies   The beauty of generating various converter topologies based on a single buck converter is that an optocoupler and its related circuitry are not required. This provides the benefit of a smaller footprint, lower component count, reduced complexity, and cost savings. Besides generating multiple outputs, the buck converter is configurable to operate as an inverting buck-boost converter, essentially providing a voltage step-up function. In addition, designers can create an isolated buck-boost converter using a similar concept.   3.1 Isolated Buck Topology A. +/- Step-down output: circuit operation1 An inverting and non-inverting step-down output can be generated with an isolated buck topology. Fig1 shows how it delivers a +/- output rail to any application that requires a positive and a negative supply. Fig1 Synchronous buck regulator uses isolated buck topology to generate ± Vout rail1   With reference to Fig1, the primary and secondary outputs are given by the following equations, assuming the leakage inductance of the coupled inductor or transformer and the DC resistance of the windings is negligible: where VIN is the input voltage, VO1 and VO2 are the primary and secondary outputs, respectively, D is the duty cycle, N is the turns ratio of the transformer, and Vdiode is the forward voltage drop across the diode.   During the cycle when the high side switch is on (current flow indicated by the green arrow in Fig1), the primary current ramps up and stores the energy in the magnetizing inductance of the transformer and the primary output capacitor. The diode on the secondary side is reverse biased and the load current on the secondary side is supplied by the output capacitor.   During the cycle when the low side switch is on (current flow indicated by the red arrow in Fig1), the primary current ramps down and releases the stored energy in the magnetizing inductance of the transformer, and the load current on the primary side is supplied by the output capacitor.   The diode on the secondary side is forward biased and the current flows from the transformer to supply current to the load, and charges up the secondary output capacitor. At steady state, the voltage at the secondary output is proportionally inverted compared to the voltage at the primary output, assuming the diode voltage drop, transformer winding resistance, and leakage inductances are negligible. Fig2 shows the operating waveforms for this architecture.   Fig2 Operating waveforms for a +/- step-down design1   B. +/+ step-down output2 Employing the same concept of generating secondary outputs using a coupled inductor or transformer, the secondary side can be configured differently to generate positive or negative secondary voltages. To generate a positive secondary output, the polarities of the transformer/coupled inductor as well as the secondary side diode are reversed. Fig3 shows an isolated buck topology to generate a dual +VOUT rail. Fig3 Isolated buck topology to generate a dual + VOUT rail2 C. +/+/- step-down output3 Fig4 shows an isolated buck topology to generate three outputs (dual +VOUT and single –VOUT rail). For a multiple output configuration, the total current of the various outputs reflected to the primary side must accounted for to make sure the IC is able to handle the resultant current. Fig4 Isolated buck topology to generate three outputs, dual +VOUT and single –VOUT rail3 The equations for the above circuit are as given below: Where VO1 is the primary output and VO2 and VO3 are the positive and negative secondary outputs, respectively, D is the duty cycle, N1 and N2 are the turns ratio of the transformer for VO2 and VO3, respectively. Vdiode is the forward voltage drop across the diode. IOUT1, IOUT2, and IOUT3 are the output current drawn from VO1, VO2, and VO3, respectively, IDS_pk is the peak current through the top switch and Δi is the triangular portion of the primary inductor ripple current.   3.2 Inverting Buck-boost (step-up and step-down) Topology4 An inverting buck-boost converter can be derived from the synchronous buck converter by connecting its GND terminal as the negative output of the buck-boost converter and the VOUT terminal of the buck converter as the GND of the buck-boost converter. Fig5 shows the circuit diagram of configuring the ISL85415 buck switcher as an inverting buck-boost converter. FigConfiguring a buck converter into an inverting buck-boost converter4 The equation for output voltage and output current are as follows: where VIN is the input voltage, VO1 is the output voltage, D is the duty cycle, IOUT is the output current, and IL is the inductor current.   During the cycle when the high side switch is on (current flow indicated by the green arrow in Fig5), the inductor current ramps up and stores energy in the inductor, and the output capacitor provides current to the load.    During the cycle when the low side switch is on (current flow indicated by the red arrow in Fig5), the inductor current ramps down and provides current to the load as well as charges the output capacitor. Operating waveforms for the inverting buck-boost design are shown in Fig6.     Fig6 Operating waveforms for an inverting buck-boost design4   3.3 Isolated Buck-boost Topology: +/- output5 A ± step-up/down output voltage can be realized using the isolated buck-boost topology. The filter inductor can be replaced with a transformer (or coupled inductor) to obtain a positive secondary output. Fig7 shows an isolated buck-boost topology to generate a ± step-up/down VOUT rail. Fig8 shows the operating waveforms for the isolated buck-boost design.   Fig7 Isolated buck-boost topology to generate a ± VOUT rail5 The voltage and current equations for the above circuit are given below: where VIN is the input voltage, VO2 is the secondary output voltage, Vdiode is the forward voltage drop across the diode, D is the duty cycle, N is the turns ratio of the transformer, IDS_pk is the peak current through the top switch, Δi is the triangular portion of the primary inductor ripple current, and IOUT1 and IOUT2 are the output current drawn from VO1 and VO2, respectively. Fig8 Operating waveforms for an Isolated buck-boost Topology: +/- output5 FAQ   1. What does a buck converter do? The buck converter is a very simple type of DC-DC converter that produces an output voltage that is less than its input. The buck converter is so named because the inductor always “bucks” or acts against the input voltage. The output voltage of an ideal buck converter is equal to the product of the switching duty cycle and the supply voltage. Like many power supply topologies, the buck converter operates on the principal of storing energy in an inductor. The voltage drop across an inductor is proportional to changes in electric current flowing through the device. 2. What is principle of Buck-boost converter? A Buck-Boost converter transforms a positive DC voltage at the input to a negative DC voltage at the output. The circuit operation depends on the conduction state of the MOSFET: On-state: The current through the inductor increases and the diode is in blocking state. 3. Are buck converters safe? A buck converter is probably no less reliable than most other topologies. It usually comes down to the reliability of the solder joints. The thing to remember about buck regulators is; if the series switch transistor fails SC - it dumps the full unregulated voltage into the load. 4. Are buck converters efficient? Buck converters can be highly efficient (often higher than 90%), making them useful for tasks such as converting a computer's main (bulk) supply voltage (often 12 V) down to lower voltages needed by USB, DRAM and the CPU (5V, 3.3V or 1.8V, see PSU). 5. How do buck converters work? The buck Converter circuit consists of the switching transistor, together with the flywheel circuit (Dl, L1 and C1). While the transistor is on, current is flowing through the load via the inductor L1. The action of any inductor opposes changes in current flow and also acts as a store of energy. 6. Do buck converters waste power? In a buck or boost converter, some energy is transferred directly from the source to the load as well, but the same principle applies. You can also look at a buck converter as an L-C filter on a square wave from the source. Again, all components are lossless, so there's no waste. 7. Does a buck converter limit current? The buck converter must operate at a very small duty cycle to keep the inductor current below the peak current limit threshold. ... Valley Current Limiting: Provides an additional level of protection. You can implement valley current limiting by sensing the inductor current when the low-side switch is on. 8. How do you adjust the current in a buck converter? You don't "adjust" output current. Loads draw whatever amount of current they need, provided the power supply can deliver it. If your total load exceeds the buck converter's rating of 3A, then you will be overloading it. If your total load is less than 3A, then you need not adjust anything. 9. How do you control a buck converter? A Buck converter consists of a transistor and diode that applies the supply voltage on an inductor capacitor, LC, circuit. The output voltage is the voltage across the capacitor. The input voltage u on the LC circuit is controlled by pulse width modulation, PWM. 10. What is the difference between buck and boost converter? In PV applications, generally, a Buck converter is used to charge the battery (since the output from a Buck converter is supposed to be less than its input), while a Boost converter is used to "match the load voltage" from the (supposedly) low voltage PV input.  

SummarySeveral days ago, I was facing a challenge in my lab is--what is the perfect way to power breadboard projects?Situation and SolutionActually,I used breadboards to prototype almost all of my designs and I have always had less than ideal setups.Between my bench power supply, which has banana plugs, and the many wall transformer power supplies I have around the house with 2.1 mm plugs, I just do not have any options that are breadboard friendly.Here,just see the following photos,you will know that I end up with solutions in the past,well,it's not the easiest or prettiest of ways to connect to the breadboard.It does not take more than a casual glance at the pictures above to recognize that while functional, these are not ideal solutions. In both cases, the connections are too easy to accidentally dislodge and there is a risk of a short with the second one.  There had to be a better way.Before a design could be had, it needed some requirements.  As I pondered the requirements, I came up with the following technical specifications for this little device. I wanted to be able to optionally use my bench power supply or wall transformer and that each would have a secure connection to the breadboard.  I also wanted the ability to switch it on or off and have the option to power either both rails or just one with the external supply.As I worked through the design, it became a simple but effective solution.( I am excited)At first,I created a project in Eagle CAD around the connectors I needede,and designed the board shape to match up to the standard 830 point breadboards that I use in my lab. There were a handful of other features I wanted to include such as an optional filter cap, an on/off switch, and a power status LED.   As I got designing, I decided to refine a few of the features.  Many of my projects have more than one input voltage.  To facilitate this, I added a jumper block to connect or disconnect the second power rail for projects that need a dual voltage. Electronic partsHere just let me list the material we need in this project firstly: Deltron 571-0100 : Test Sockets SINGLE PCB SOCK BLKDeltron 571-0500 : Test Sockets SINGLE PCB SOCK REDKobiconn 163-7620E-E : DC Power Connectors PCB 2.1MMFCI / Amphenol 67997-472HLF : Headers & Wire Housings 72P HDRHarwin M7581-08 : Headers & Wire Housings JUMPER SOCKET OPEN TOP REDKOA Speer MF1/2DC1501F : Metal Film Resistors – Through Hole 1.5K 1% 100PPM Kingbright WP710A10SGD : Standard LEDs – Through Hole Grn 40mcd 568nm 40 deg DiffusedPanasonic ECA-1HM100I : Aluminum Electrolytic Capacitors – Leaded 10UF 50V ELECT M RADIAL If you would like to build one following me , these parts you can find from: https://www.kynix.com Schematic and ComponentsWith the basic design framework laid out, I started researching the components needed.  I personally tend to use the online Mouser catalog to help me sort through the vast quantities of components available.  I stuck with all through-hole components to make this project easier to assemble at home.  With all the parts identified, I returned to my project in Eagle CAD and found each of the components in my component libraries.  I connected them electrically as shown in the schematic below, and double-checked the design (an often under rated step in the design process). Board LayoutWith the schematic complete, it was time to move on to the board layout. Breadboards use a standard 0.1 inch pin spacing, but when I measured the spacing between the power busses, I noticed that they were slightly different.  After some trial and error, I realized that the actual spacing between the power bus pins was 1.85 inches O.C.  With the header pins placed at this location, the board outline was adjusted to create a proper fit.  After arranging the components, I added a ground pour to the top layer to simplify routing.  The Eagle autorouter made quick work of the rest of trace routing and the resulting board design looks like this:Board Assembly and TestingI ordered a batch of these boards from my favorite purple PCB vendor (OSHPark) online and assembled them.  I couldn’t be happier with the finished product.  The fit is perfect and they snap into the power bus tightly and stay put.  This little device has gone through extensive testing as I have been using these on all of my breadboard projects ever since I got the first one assembled.  They really work wonderfully!     Article edited by: kynix