29.06.2020
Devices with very high circuit efficiency. News and analytical portal "electronics time". Beijing crashes Wall Street
Today we will look at several circuits of simple, one might even say simple, pulse DC-DC voltage converters (DC voltage converters of the same magnitude, in constant pressure different size)
What are the benefits of pulse converters? Firstly, they have high efficiency, and secondly, they can operate at an input voltage lower than the output voltage. Pulse converters are divided into groups:
- - bucking, boosting, inverting;
- - stabilized, unstabilized;
- - galvanically isolated, non-insulated;
- - with a narrow and wide range of input voltages.
To make homemade pulse converters, it is best to use specialized integrated circuits- they are easier to assemble and not capricious when setting up. So, here are 14 schemes for every taste:
This converter operates at a frequency of 50 kHz, galvanic isolation is provided by transformer T1, which is wound on a K10x6x4.5 ring made of 2000NM ferrite and contains: primary winding - 2x10 turns, secondary winding - 2x70 turns of PEV-0.2 wire. Transistors can be replaced with KT501B. Almost no current is consumed from the battery when there is no load.
Transformer T1 is wound on a ferrite ring with a diameter of 7 mm, and contains two windings of 25 turns of wire PEV = 0.3.
Push-pull unstabilized converter based on a multivibrator (VT1 and VT2) and a power amplifier (VT3 and VT4). The output voltage is selected by the number of turns of the secondary winding of the pulse transformer T1.
Stabilizing type converter based on the MAX631 microcircuit from MAXIM. Generation frequency 40…50 kHz, storage element - inductor L1.
You can use one of the two chips separately, for example the second one, to multiply the voltage from two batteries.
Typical circuit for connecting a pulse boost stabilizer on the MAX1674 microcircuit from MAXIM. Operation is maintained at an input voltage of 1.1 volts. Efficiency - 94%, load current - up to 200 mA.
Allows you to obtain two different stabilized voltages with an efficiency of 50...60% and a load current of up to 150 mA in each channel. Capacitors C2 and C3 are energy storage devices.
8. Switching boost stabilizer on the MAX1724EZK33 chip from MAXIM
Typical connection diagram specialized chip from MAXIM. It remains operational at an input voltage of 0.91 volts, has a small-sized SMD housing and provides a load current of up to 150 mA with an efficiency of 90%.
A typical circuit for connecting a pulsed step-down stabilizer on a widely available TEXAS microcircuit. Resistor R3 is regulated output voltage within +2.8…+5 volts. Resistor R1 sets the current short circuit, which is calculated by the formula: Ikz(A)= 0.5/R1(Ohm)
Integrated voltage inverter, efficiency - 98%.
Two isolated voltage converters DA1 and DA2, connected in a “non-isolated” circuit with a common ground.
The inductance of the primary winding of transformer T1 is 22 μH, the ratio of turns of the primary winding to each secondary is 1: 2.5.
Typical circuit of a stabilized boost converter on a MAXIM microcircuit.
Single-ended converters with high efficiency, 12/220 volts
Some familiar household electrical appliances such as lamp daylight, photo flash and a number of others, sometimes it is convenient to use in a car.
Since most devices are designed to be powered from a network with an operating voltage of 220 V, a step-up converter is needed. An electric razor or a small fluorescent lamp consumes no more than 6...25 W of power. Moreover, such a converter is often not required AC voltage at the exit. The above household electrical appliances operate normally when powered by direct or unipolar pulsating current.
The first version of a single-cycle (flyback) pulse DC voltage converter 12 V/220 V is made on an imported UC3845N PWM controller chip and a powerful N-channel field-effect transistor BUZ11 (Fig. 4.10). These elements are more affordable than their domestic counterparts, and make it possible to achieve high efficiency from the device, including due to the low source-drain voltage drop across an open field-effect transistor (the efficiency of the converter also depends on the ratio of the width of the pulses transmitting energy to the transformer to the pause).
The specified microcircuit is specially designed for single-cycle converters and has all the necessary components inside, which allows reducing the number of external elements. It has a high-current quasi-complementary output stage specifically designed for direct power control. M-channel field-effect transistor with insulated gate. The operating pulse frequency at the output of the microcircuit can reach 500 kHz. The frequency is determined by the ratings of elements R4-C4 and in the above circuit is about 33 kHz (T = 50 μs).
Rice. 4.10. Circuit of a single-cycle pulse converter that increases voltage
The chip also contains a protection circuit to shut down the converter when the supply voltage drops below 7.6 V, which is useful when powering devices from a battery.
Let's take a closer look at the operation of the converter. In Fig. Figure 4.11 shows voltage diagrams that explain the ongoing processes. When positive pulses appear at the gate of the field-effect transistor (Fig. 4.11, a), it opens and resistors R7-R8 will receive the pulses shown in Fig. 4.11, c.
The slope of the top of the pulse depends on the inductance of the transformer winding, and if at the top there is a sharp increase in the voltage amplitude, as shown by the dotted line, this indicates saturation of the magnetic circuit. At the same time, conversion losses increase sharply, which leads to heating of the elements and deteriorates the operation of the device. To eliminate saturation, you will need to reduce the pulse width or increase the gap in the center of the magnetic circuit. Usually a gap of 0.1...0.5 mm is sufficient.
When the power transistor is turned off, the inductance of the transformer windings causes voltage surges to appear, as shown in the figures.
Rice. 4.11. Voltage diagrams at circuit control points
With proper manufacturing of transformer T1 (sectioning of the secondary winding) and low-voltage power supply, the surge amplitude does not reach a value dangerous for the transistor and therefore, in this circuit, special measures in the form of damping circuits in the primary winding of T1 are not used. And in order to suppress surges in the current signal feedback, coming to the input of the DA1.3 chip, a simple RC filter is installed from elements R6-C5.
The voltage at the converter input, depending on the condition of the battery, can vary from 9 to 15 V (which is 40%). To limit the change in output voltage, input feedback is removed from the divider of resistors R1-R2. In this case, the output voltage at the load will be maintained in the range of 210...230 V (Rload = 2200 Ohm), see table. 4.2, i.e. it changes by no more than 10%, which is quite acceptable.
Table 4.2. Circuit parameters when changing supply voltage
Stabilization of the output voltage is carried out by automatically changing the width of the pulse that opens transistor VT1 from 20 μs at Upit = 9 V to 15 μs (Upit = 15 V).
All elements of the circuit, except for capacitor C6, are placed on a single-sided printed circuit board made of fiberglass with dimensions of 90x55 mm (Fig. 4.12).
Rice. 4.12. Topology printed circuit board and arrangement of elements
Transformer T1 is mounted on the board using an M4x30 screw through a rubber gasket, as shown in Fig. 4.13.
Rice. 4.13 Mounting type of transformer T1
Transistor VT1 is installed on the radiator. Plug design. XP1 must prevent erroneous supply of voltage to the circuit.
The T1 pulse transformer is made using the widely used BZO armor cups from the M2000NM1 magnetic core. At the same time, in the central part they should have a gap of 0.1...0.5 mm.
The magnetic core can be purchased with an existing gap or it can be made using coarse sandpaper. It is better to select the gap size experimentally when tuning so that the magnetic circuit does not enter the saturation mode - this is convenient to control by the shape of the voltage at the source VT1 (see Fig. 4.11, c).
For transformer T1, winding 1-2 contains 9 turns of wire with a diameter of 0.5-0.6 mm, windings 3-4 and 5-6 each contain 180 turns of wire with a diameter of 0.15...0.23 mm (wire type PEL or PEV). In this case, the primary winding (1-2) is located between two secondary windings, i.e. First, winding 3-4 is wound, and then 1-2 and 5-6.
When connecting the transformer windings, it is important to observe the phasing shown in the diagram. Incorrect phasing will not damage the circuit, but it will not work as intended.
The following parts were used during assembly: adjusted resistor R2 - SPZ-19a, fixed resistors R7 and R8 type S5-16M for 1 W, the rest can be of any type; electrolytic capacitors C1 - K50-35 for 25 V, C2 - K53-1A for 16 V, C6 - K50-29V for 450 V, and the rest are of the K10-17 type. Transistor VT1 is installed on a small (by the size of the board) radiator made of duralumin profile. Setting up the circuit consists of checking the correct phrasing of connecting the secondary winding using an oscilloscope, as well as setting resistor R4 to the desired frequency. Resistor R2 sets the output voltage at the XS1 sockets when the load is on.
The given converter circuit is designed to work with a previously known load power (6...30 W - permanently connected). At idle, the voltage at the circuit output can reach 400 V, which is not acceptable for all devices, as it can lead to damage due to insulation breakdown.
If the converter is intended to be used in operation with a load of different power, which is also turned on during operation of the converter, then it is necessary to remove the voltage feedback signal from the output. A variant of such a scheme is shown in Fig. 4.14. This not only allows you to limit the output voltage of the circuit in idle mode to 245 V, but also reduces the power consumption in this mode by about 10 times (Ipot=0.19 A; P=2.28 W; Uh=245 V).
Rice. 4.14. Single-cycle converter circuit with maximum no-load voltage limitation
Transformer T1 has the same magnetic circuit and winding data as in the circuit (Fig. 4.10), but contains an additional winding (7-4) - 14 turns of PELSHO wire with a diameter of 0.12.0.18 mm (it is wound last). The remaining windings are made in the same way as in the transformer described above.
To manufacture a pulse transformer, you can also use square cores of the series. KV12 made of M2500NM ferrite - the number of turns in the windings in this case will not change. To replace armor magnetic cores (B) with more modern square ones (KB), you can use the table. 4.3.
The voltage feedback signal from winding 7-8 is supplied through a diode to the input (2) of the microcircuit, which makes it possible to more accurately maintain the output voltage in a given range, as well as provide galvanic isolation between the primary and output circuits. The parameters of such a converter, depending on the supply voltage, are given in table. 4.4.
Table 4.4. Circuit parameters when changing supply voltage
The efficiency of the described converters can be increased a little more if the pulse transformers are secured to the board with a dielectric screw or heat-resistant glue. A variant of the printed circuit board topology for assembling the circuit is shown in Fig. 4.15.
Rice. 4.15. PCB topology and arrangement of elements
Using such a converter, you can power electric shavers "Agidel", "Kharkov" and a number of other devices from the vehicle's on-board network.
This article will talk about the familiar, but not clear to many, term efficiency factor (efficiency). What is it? Let's figure it out. Efficiency factor, hereinafter referred to as efficiency, is a characteristic of the efficiency of the system of any device in relation to the conversion or transmission of energy. It is determined by the ratio of the useful energy used to the total amount of energy received by the system. Is it usually indicated? (" this"). ? = Wpol/Wcym. Efficiency is a dimensionless quantity and is often measured as a percentage. Mathematically, the definition of efficiency can be written as: n=(A:Q) x100%, where A is useful work, and Q is expended work. Due to the law of conservation of energy, efficiency is always less than or equal to unity, that is, it is impossible to obtain more useful work than the energy expended! Looking through different sites, I am often surprised how radio amateurs report, or rather, praise their designs for high efficiency, without having any idea what it is! For clarity, let’s look at a simplified converter circuit using an example and find out how to find the efficiency of the device. A simplified diagram is shown in Fig. 1Let's say we took as a basis a step-up DC/DC voltage converter (hereinafter referred to as PN), from unipolar to increased unipolar. We connect the ammeter RA1 into the power supply circuit break, and the voltmeter RA2 parallel to the power supply input PN, the readings of which are needed to calculate the power consumption (P1) of the device and the load together from the power source. At the output of the PN in the load supply break we also connect an ammeter RAZ and a voltmeter RA4, which are required to calculate the power consumed by the load (P2) from the PN. So, everything is ready to calculate the efficiency, then let's get started. We turn on our device, take measurements of instrument readings and calculate the powers P1 and P2. Hence P1=I1 x U1, and P2=I2 x U2. Now we calculate the efficiency using the formula: efficiency (%) = P2: P1 x100. Now you have found out approximately the real efficiency of your device. Using a similar formula, you can calculate PN with a two-polar output using the formula: Efficiency (%) = (P2+P3) : P1 x100, as well as a step-down converter. It should be noted that the value (P1) also includes current consumption, for example: PWM controller and (or) control driver field effect transistors, and other structural elements.
For reference: car amplifier manufacturers often indicate output power The amplifier is much larger than in reality! But you can find out the approximate real power of a car amplifier using a simple formula. Let’s say there is a +12v fuse on the car amplifier in the power supply circuit, there is a 50 A fuse. We calculate, P = 12V x 50A, and in total we get a power consumption of 600 W. Even in high-quality and expensive models, the efficiency of the entire device is unlikely to exceed 95%. After all, part of the efficiency is dissipated in the form of heat on powerful transistors, transformer windings, rectifiers. So let's go back to the calculation, we get 600 W: 100% x92=570W. Consequently, this car amplifier will not produce any 1000 W or even 800 W, as the manufacturers write! I hope this article will help you understand such a relative value as efficiency! Good luck to everyone in developing and repeating designs. The invertor was with you.
Modern automotive industry has reached a level of development at which, without fundamental scientific research It is almost impossible to achieve fundamental improvements in the design of traditional internal combustion engines. This situation forces designers to pay attention to alternative power plant designs. Some engineering centers have focused their efforts on creating and adapting hybrid and electric models for serial production, while other automakers are investing in the development of engines using fuel from renewable sources (for example, biodiesel using rapeseed oil). There are other power unit projects that in the future could become a new standard propulsion system for Vehicle.
Possible sources of mechanical energy for future cars include the external combustion engine, which was invented in the mid-19th century by Scotsman Robert Stirling as a thermal expansion engine.
Scheme of work
The Stirling engine converts thermal energy supplied from outside into useful mechanical work by changes in working fluid temperature(gas or liquid) circulating in a closed volume.
IN general view The operating diagram of the device is as follows: in the lower part of the engine, the working substance (for example, air) heats up and, increasing in volume, pushes the piston upward. Hot air enters the upper part of the engine, where it is cooled by a radiator. The pressure of the working fluid decreases, the piston is lowered for the next cycle. In this case, the system is sealed and the working substance is not consumed, but only moves inside the cylinder.
There are several design options for power units using the Stirling principle.
Stirling modification "Alpha"
The engine consists of two separate power pistons (hot and cold), each of which is located in its own cylinder. Heat is supplied to the cylinder with the hot piston, and the cold cylinder is located in a cooling heat exchanger.
Stirling modification "Beta"
The cylinder containing the piston is heated at one end and cooled at the opposite end. A power piston and a displacer move in the cylinder, designed to change the volume of the working gas. The regenerator carries out the return movement of the cooled working substance into the hot cavity of the engine.
Stirling modification "Gamma"
The design consists of two cylinders. The first is completely cold, in which the power piston moves, and the second, hot on one side and cold on the other, serves to move the displacer. A regenerator for circulating cold gas can be common to both cylinders or be part of the displacer design.
Advantages of the Stirling engine
Like most external combustion engines, Stirling is characterized multi-fuel: the engine operates due to temperature changes, regardless of the reasons that caused it.
Interesting fact! An installation was once demonstrated that operated on twenty fuel options. Without stopping the engine, gasoline, diesel fuel, methane, crude oil and vegetable oil- the power unit continued to operate steadily.
The engine has simplicity of design and does not require additional systems and attachments (timing belt, starter, gearbox).
The features of the device guarantee a long service life: more than one hundred thousand hours of continuous operation.
The Stirling engine is silent, since detonation does not occur in the cylinders and there is no need to remove exhaust gases. The “Beta” modification, equipped with a rhombic crank mechanism, is a perfectly balanced system that has no vibrations during operation.
No processes occur in the engine cylinders that could have a negative impact on environment. By choosing a suitable heat source (eg solar energy), Stirling can be absolutely environmentally friendly power unit.
Disadvantages of the Stirling design
Despite all the positive properties, immediate mass use of Stirling engines is impossible for the following reasons:
The main problem is the material consumption of the structure. Cooling the working fluid requires large-volume radiators, which significantly increases the size and metal consumption of the installation.
The current technological level will allow the Stirling engine to compare in performance with modern gasoline engines only through the use of complex types of working fluid (helium or hydrogen) under pressure of more than one hundred atmospheres. This fact raises serious questions both in the field of materials science and in ensuring user safety.
An important operational problem is related to issues of thermal conductivity and temperature resistance of metals. Heat is supplied to the working volume through heat exchangers, which leads to inevitable losses. In addition, the heat exchanger must be made of heat-resistant metals that are resistant to high blood pressure. Suitable materials are very expensive and difficult to process.
The principles of changing the modes of the Stirling engine are also fundamentally different from traditional ones, which requires the development of special control devices. Thus, to change power it is necessary to change the pressure in the cylinders, the phase angle between the displacer and the power piston, or influence the capacity of the cavity with the working fluid.
One way to control the shaft speed on a Stirling engine model can be seen in next video:
Efficiency
In theoretical calculations, the efficiency of the Stirling engine depends on the temperature difference of the working fluid and can reach 70% or more in accordance with the Carnot cycle.
However, the first samples realized in metal had extremely low efficiency for the following reasons:
- ineffective coolant (working fluid) options that limit the maximum heating temperature;
- energy losses due to friction of parts and thermal conductivity of the engine housing;
- absence construction materials resistant to high pressure.
Engineering solutions constantly improved the design of the power unit. Thus, in the second half of the 20th century, a four-cylinder automobile The Stirling engine with a rhombic drive showed an efficiency of 35% in tests on a water coolant with a temperature of 55 ° C. Careful design development, the use of new materials and fine-tuning of working units ensured the efficiency of the experimental samples was 39%.
Note! Modern gasoline engines of similar power have an efficiency of 28-30%, and turbocharged diesel engines within 32-35%.
Modern examples of the Stirling engine, such as that created by the American company Mechanical Technology Inc, demonstrate efficiency of up to 43.5%. And with the development of the production of heat-resistant ceramics and similar innovative materials, it will be possible to significantly increase the temperature of the working environment and achieve an efficiency of 60%.
Examples of successful implementation of automobile Stirlings
Despite all the difficulties, there are many known efficient Stirling engine models that are applicable to the automotive industry.
Interest in Stirling, suitable for installation in a car, appeared in the 50s of the 20th century. Work in this direction was carried out by such concerns as Ford Motor Company, Volkswagen Group and others.
The UNITED STIRLING company (Sweden) developed Stirling, which made maximum use of serial components and assemblies produced by automakers (crankshaft, connecting rods). The resulting four-cylinder V-engine had a specific weight of 2.4 kg/kW, which is comparable to the characteristics of a compact diesel engine. This unit was successfully tested as a power plant for a seven-ton cargo van.
One of the successful samples is the four-cylinder Stirling engine made in the Netherlands, model “Philips 4-125DA”, intended for installation on a car. The engine had a working power of 173 hp. With. in dimensions similar to a classic gasoline unit.
General Motors engineers achieved significant results by building an eight-cylinder (4 working and 4 compression cylinders) V-shaped Stirling engine with a standard crank mechanism in the 70s.
A similar power plant in 1972 equipped with a limited series of Ford Torino cars, whose fuel consumption has decreased by 25% compared to the classic gasoline V-shaped eight.
Currently, more than fifty foreign companies are working to improve the design of the Stirling engine in order to adapt it to mass production for the needs of the automotive industry. And if we can eliminate the shortcomings of this type engines, while at the same time maintaining its advantages, then it is Stirling, and not turbines and electric motors, that will replace gasoline internal combustion engines.
65 nanometers is the next goal of the Zelenograd plant Angstrem-T, which will cost 300-350 million euros. The company has already submitted an application for a preferential loan for the modernization of production technologies to Vnesheconombank (VEB), Vedomosti reported this week with reference to the chairman of the board of directors of the plant, Leonid Reiman. Now Angstrem-T is preparing to launch a production line for microcircuits with a 90nm topology. Payments on the previous VEB loan, for which it was purchased, will begin in mid-2017.
Beijing crashes Wall Street
Key American indices marked the first days of the New Year with a record drop; billionaire George Soros has already warned that the world is facing a repeat of the 2008 crisis.
The first Russian consumer processor Baikal-T1, priced at $60, is being launched into mass production
The Baikal Electronics company promises to launch in early 2016 industrial production Russian Baikal-T1 processor costs about $60. The devices will be in demand if the government creates this demand, market participants say.
MTS and Ericsson will jointly develop and implement 5G in Russia
Mobile TeleSystems PJSC and Ericsson have entered into cooperation agreements in the development and implementation of 5G technology in Russia. In pilot projects, including during the 2018 World Cup, MTS intends to test the developments of the Swedish vendor. At the beginning of next year, the operator will begin a dialogue with the Ministry of Telecom and Mass Communications on the formation of technical requirements for the fifth generation of mobile communications.
Sergey Chemezov: Rostec is already one of the ten largest engineering corporations in the world
The head of Rostec, Sergei Chemezov, answered pressing questions in an interview with RBC: about the Platon system, the problems and prospects of AVTOVAZ, the interests of the State Corporation in the pharmaceutical business, and spoke about international cooperation in conditions of sanctions pressure, import substitution, reorganization, development strategy and new opportunities in difficult times.
Rostec is “fencing itself” and encroaching on the laurels of Samsung and General Electric
The Supervisory Board of Rostec approved the “Development Strategy until 2025”. The main objectives are to increase the share of high-tech civilian products and catch up with General Electric and Samsung in key financial indicators.
