Simple switching power supply 5 volts 4 amps. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

The article describes a simple and inexpensive network power supply with an output voltage of 5 V and a load current of up to 4 A.

The power supply is a self-excited single-ended flyback voltage converter. A distinctive feature of the proposed device is the absence of specialized microcircuits, simplicity and low cost in manufacturing.

The diagram of the device is shown in Figure 1. The power supply contains a mains rectifier VD1-VD4, an interference suppression filter L1C1-C3, a converter based on a switching transistor VT1 and a pulse transformer T1, an output rectifier VD8 with a filter C9C10L2 and a stabilization unit made on the stabilizer DA1 and optocoupler U1.

Rice. 1. Schematic diagram of the device (click to enlarge)

The device works as follows. After turning on the power source, the switching transistor VT1 opens slightly and current begins to flow through the primary winding of the pulse transformer T1. In the feedback winding II of the transformer, an EMF is induced, which is fed through the positive feedback circuit - resistor R9, diode VD5, capacitor C5 to the gate of the field-effect transistor VT1. As a result, an avalanche-like process develops, leading to the complete opening of the switching transistor. The accumulation of energy in the transformer T1 begins. The current through the switching transistor VT1 increases linearly, and the voltage from the current sensor - resistor R10 through the diode VD6 and capacitor C7 acts on the base of the phototransistor of the optocoupler U1.1, opening it slightly, due to which the voltage at the gate of the field effect transistor decreases. The reverse process begins, leading to the closing of the switching transistor VT1. At this moment, the diode VD8 opens and the energy stored in the transformer T1 is transferred to the output filter capacitor C9.

When the output voltage for some reason exceeds the nominal value, the DA1 stabilizer opens and current begins to flow through it and the series-connected emitting diode of the optocoupler U1.2. The radiation of the diode leads to an earlier opening of the optocoupler transistor, as a result of which the on-time of the switching transistor decreases, less energy is stored in the transformer, and, consequently, the output voltage decreases.

If the output voltage drops, the current through the emitting diode of the optocoupler decreases, and the optocoupler transistor closes. As a result, the on-time of the switching transistor increases, more energy is stored in the transformer and the output voltage is restored.

Resistor R3 is necessary to reduce the effect of the dark current of the optocoupler transistor and improve the thermal stability of the entire device. Capacitor C7 increases the stability of the power supply. The C6R8 circuit forces the switching processes of the transistor VT1 and increases the efficiency of the device.

According to the above scheme, several dozen power supplies with an output power of 15 ... 25 W were manufactured.

In place of the switching transistor VT1, both field-effect and bipolar transistors can be used, for example, the 2T828, 2T839, KT872, KP707, BUZ90 series, etc. We can replace the 4N35 transistor optocoupler with any of the AOT110, AOT126, AOT128 series, and the KR142EN19A stabilizer - TL431 . However, the best results were obtained with imported elements (BUZ90, 4N35, TL431).

All resistors in the power supply are for surface mounting of size 1206 with a power of 0,25 W, capacitors C1-C3, C8 - K10-47v for a voltage of 500 V, C5-C7 are for surface mounting of size 0805, the rest are any oxide.

Transformer T1 is wound on two K19x11x6,7 ring magnetic circuits stacked together from MP 140 permalloy. The primary winding contains 180 turns of PEV-2 0,35 wire, winding II - 8 turns of PEV-2 0,2 wire, winding III for output voltage 5V - 7 turns of five PEV-2 conductors 0,56. The winding order corresponds to their numbering, and the turns of each winding must be evenly distributed around the entire perimeter of the magnetic circuit.

Inductors L1 and L2 are made on ring magnetic cores K15x7x6,7 made of MP140 permalloy. The first one contains two windings of 30 turns each, wound with PEV-2 0,2 wire on different halves of the magnetic circuit, the second one is wound with PEV-2 0,8 wire in one layer along the entire length of the magnetic circuit as much as it will fit.

To reduce the output voltage ripple, the common point of the capacitors C2 and C3 must first be connected to the negative terminal of the capacitor C10, and then to the remaining parts - winding III of the transformer T1, the negative terminal of the capacitor C9, resistor R12 and terminal 2 of the stabilizer DA1.

The device is assembled on a printed circuit board measuring 80x60 mm. On one side of the board there are printed conductors and elements for surface mounting, as well as a switching transistor VT1 and a diode VD8, which are pressed against an aluminum heat sink plate of the same size, and on the other - all the rest.

It is better to turn on the device for the first time from a current-limiting power source, for example, B5-50, and the operating voltage should be applied immediately, and not gradually increased. Establishing the device consists in adjusting the output voltage by the divider R11R12 and, if necessary, setting the threshold for limiting the output power with the current sensor R10 (the beginning of a sharp drop in the output voltage with increasing load current).

To obtain a different output voltage, you need to proportionally change the number of turns of the winding III of the transformer T1 and the division ratio of the divider R11R12.

When operating the device, it should be remembered that its negative output is galvanically connected to the network.

Author: M.Dytskov, Zhukov; Publication: cxem.net

See other articles Section Power Supplies.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Motherboard Gigabyte G1.Sniper Z87 15.11.2013 Gigabyte has introduced the G1.Sniper Z87 ATX motherboard designed for building gaming and high-performance computers. Like the previous models of the Sniper series, the novelty is made in black and green colors. G1.Sniper Z87, as the name suggests, is based on the Intel Z87 Express chipset and is designed for Intel LGA 1150 processors. Gigabyte G1.Sniper Z87 is endowed with four slots for RAM modules, DDR3 strips with a frequency of up to 3000 MHz are supported (in overclocking mode). There are two PCI Express x16 slots, they are accompanied by three PCI Express x1 ports. When using two 3D cards in the system, each of them operates in x8 mode. The design of the board provides six SATA 6 Gb / s ports, the manufacturer reports support for RAID modes 0, 1, 5 and 10. The motherboard interface panel has three video outputs, four USB 3.0 ports and two USB 2.0 ports, an RJ-45 connector, a PS/2 port, an S/PDIF output, and standard jacks for connecting audio devices. The Gigabyte G1.Sniper Z87 uses high-quality Ultra Durable 4 Plus components, voltage test points, two BIOS chips, and a debug LED. The features of the product, which the potential audience will surely pay attention to, are the Qualcomm Atheros Killer E2200 gigabit network adapter, the Creative Sound Core3D quad-core audio processor, and the OP-AMP detachable operational amplifier.

Other interesting news:

▪ Genes responsible for photosynthesis can increase crop yields

▪ Artificial mother of pearl

▪ Biomaterial will replace plastic

▪ Computer mouse controls biometric parameters

▪ Qualitative growth of semiconductor lasers on silicon

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Digital technology. Article selection

▪ article Kunkator. Popular expression

▪ article What did the philosopher Auguste Comte consider the most striking example of such knowledge that will forever remain hidden from man, and why was he wrong? Detailed answer

▪ article Fundamentals of the adoption and application of state regulatory requirements for labor protection

▪ article Low-frequency amplifier on the TDA1514 chip. Encyclopedia of radio electronics and electrical engineering

▪ article Amphibian Man. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024