Switching power supply with half-bridge converter. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

This circuit of a switching power supply with a half-bridge converter with an adjustable output voltage without stabilization is used to power a soldering station. The construction and adjustment of this power source does not cause difficulties, which is its main advantage. The control unit is made on the KR1156EU2 chip, which is a high-frequency one. PWM controller optimized for building push-pull high-frequency switching power supplies.

The scheme of the device is shown in fig. 5.23. The mains voltage is supplied to the filter C1, L1, C2, rectified by the diode bridge VD1 and charges the capacitors through the current-limiting resistor R6. SP and C12, forming one shoulder of the bridge. The other shoulder is formed by transistors VT1, VT2. The primary winding of the transformer T2 is connected to the diagonal of the bridge. Field-effect transistors VT1, VT2 are alternately opened by pulses from the output of the DA1 microcircuit, and VT2 is controlled directly from the microcircuit, and VT1 through the transformer T1, which serves for galvanic isolation. Resistors R8 and R9 are included in the gate circuit, which, together with the gate capacitances, form. Low-pass filters that reduce switching noise.

Chip. The KR1156EU2 PWM controller has two output stages (pins 11, 14), designed for a significant output current (both incoming and outgoing): constant - 0,5 A, pulse - up to 2 A. The microcircuit is controlled by an internal generator, the frequency of which is set connecting a resistor to terminal 5 and a capacitor to terminal 6 (R5, C7 in Fig. 5.23). The transducer frequency in this case is chosen to be 50 kHz.

(click to enlarge)

For pulse-width modulation of the output signals, a device consisting of flip-flops and an error signal amplifier is used. With the help of an error signal amplifier, it is possible to stabilize the output voltage by comparing part of the output voltage with the reference voltage by connecting the negative feedback to the input of the amplifier in an appropriate way. However, in this design, this possibility is not used, so the connections are made as follows. The non-inverting input of the microcircuit (pin 2) is supplied with a voltage of +5,1 V from the reference voltage source (pin 16). A sawtooth voltage is applied to pin 7 from pin 6. The inverting input of the amplifier (pin 1) is connected to a common wire through resistor R4.

With this inclusion, the error signal amplifier is set to the maximum duration of the output pulses. To control the duration of the pulses, another controller feature was used - a "soft start" node with pin 8. If a voltage varying from approximately 2,25 to 4,5 V is applied to this pin, then the duration of the output pulses will be regulated within 0 ... 100% from maximum. The maximum duration of the pulses is, respectively, 80% of the duration of the half-cycle.

The current at pin 8 is very small (on the order of 10 µA); by connecting a capacitor to this output (you can carry out the so-called "soft start", when the operation of the converter starts with a minimum pulse duration, and gradually, due to the charge of the capacitor, increases to a stationary value. In this device, the pulse duration, and hence the output voltage, regulated by a variable resistor R2.The resistor is connected to the divider circuit R1.R3, connected to the reference voltage +5,1 V.

The purpose of pin 9 of the microcircuit is current protection. If the current through the transistor VT2 exceeds 1 A, then the voltage at pin 9 will be more than 1 V and the outputs of the microcircuit will switch to the "off" state until the end of the current cycle. The supply voltage of the microcircuit is supplied to pin 15. Separate power supply pins (pin 13) and a common wire (pin 12) allow, if necessary, to decouple the powerful output stage, which is a source of interference, from the rest of the converter.

The supply voltage to the microcircuit comes from a rectifier on diodes VD12, VD13 and capacitor C10. When the device is connected to the network, this voltage is absent, so it is necessary to solve the problem of initial start-up. For this, the following feature of the microcircuit is used. If the supply voltage of the microcircuits is less than 9 V, the controller is in the off state, the signals are at the outputs. A and. In the absence, the microcircuit consumes a current of the order of 1 mA and does not bypass the capacitor C6, which is charged through the resistor R7.

When the voltage reaches approximately 9,8 V, the microcircuit turns on. The converter starts up, a voltage appears on the winding III of the transformer, which is rectified and provides power to the microcircuit during operation (about 15 V in this device). Pin 15 of the microcircuit has a hysteresis of about 0,8 V, so the microcircuit will turn off only when the supply voltage drops below 9 V, as a result, a short-term decrease in voltage at pin 15 when starting the microcircuit does not turn it off.

As already mentioned, the waveform at outputs A and B (pins 11 and 14, respectively) is an alternately appearing pulses with a maximum duration of 80% of the half-cycle, so there is a fairly large interval between closing one transistor and opening another. As a result, the moment when both transistors are open is excluded, and there are no through currents.

The output voltage from winding II is rectified by diodes VD14 ... VD17 and fed through the inductor L2 to capacitor C13 and then to the output of the converter. The purpose of the inductor L2 is the selection of a constant component from a rectified sequence of rectangular pulses. In the pauses between the rectified voltage pulses, all rectifier diodes are open, and through them the energy accumulated in the inductor enters the load.

The block uses parts of imported and domestic production: VD1 - W06M diode bridge with a reverse voltage of 600 V and a maximum current of 1,5 A; SP, C12 - two parallel-connected capacitors 47 uF 160 V from Jamicon; VD14...VD17 - imported SF22 diodes with a reverse voltage of 100 V and a maximum current of 2 A; recovery time 35 ns. It should be noted that the efficiency and noise level of the device strongly depend on the speed of these diodes.

Transformer T1 is wound on a K10x6x4,5 ring made of M2000NM1 ferrite, the number of turns of windings I is 50, II is 40, wire diameter is 0,15 mm, transformer T2 is wound on a K31x18,5x7 ring made of M1000NM1 ferrite, winding I contains 160 turns of PEV-wire 1 with a diameter of 0,3 mm, II - 40 turns of the same wire with a diameter of 0,6 mm, III - 2x15 turns of wire with a diameter of 0,15 mm. The inductor L2 is wound on a K20x10x5 ring made of ferrite M2000NM1 with a gap in the ring of 1,5 mm; number of turns - software, wire with a diameter of 0,5 mm. The gap is made with a hacksaw for metal or a "grinder" with a diamond wheel, a textolite gasket is glued into the gap for strength.

The transistors are mounted on small heatsinks. VD7, VD8 - two zener diodes connected in series for a total stabilization voltage of 18 V. The rest of the details are typical for pulsed sources.

When setting up the device, an external +15 V power supply is connected to pins 10 and 1 of the DA12 microcircuit and the presence of signals at outputs A and B is checked, their shape and change in pulse duration when regulated by resistor R2. If necessary, resistors R1 and R3 are selected for the required control range.

Further, instead of 220 V, a voltage of the order of 30 ... 40 V is connected, without turning off the +12 V source, and the signal at the junction point of the transistors is checked, as well as the formation of voltages at the output of the device and on the capacitor C10. The voltages should be proportionally reduced compared to the steady state.

After that, the +12 V source is removed and the device can be connected to the 220 V network. Lastly, the number of turns of the windings I and III of the T2 transformer is specified: III - to provide + 15 V power, as well as winding II - for the required maximum source voltage.

Author: Semyan A.P.

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 Artificial intelligence will predict magnetic storms 21.05.2023 Scientists have developed an algorithm that can track and predict magnetic storms every minute. Thanks to artificial intelligence, experts will have about 30 minutes before a deadly magnetic storm will cover the Earth. The NASA team is reportedly actively applying artificial intelligence models to solar storm data to develop an early warning system. In their opinion, AI can report the planet about 30 minutes before a potentially destructive magnetic storm will cover the Earth. This time is due to the fact that light travels faster than the material ejected from the Sun. In some cases, such as in Quebec about 35 years ago, solar storms can cut off electricity for several hours. More extreme events, such as the Carrington solar storm more than 150 years ago, could lead to widespread destruction of electrical and communications infrastructure if they occur in modern times. Researchers have long recognized this problem and have not sat idly by. They combined data from satellites and ground stations. The created algorithm was called DAGGER - it has quite impressive characteristics compared to analogues. Most notable is the increase in forecasting speed. AI can predict the severity and direction of a solar storm in less than a second, and is capable of making a prediction every minute, scientists say. The development of such AI is critical as the sun approaches the peak of its 11-year cycle in 2025. According to preliminary calculations, two more magnetic storms are expected on Earth by the end of May. The first will be no higher than 4 points, but will last for three days - from May 23 to May 25. Then on May 25, a powerful one-day magnetic storm is expected, the strength of which will reach 5 points.

Other interesting news:

▪ Insect Camera

▪ Warmer in Europe

▪ Display for creating 3D holograms in the air

▪ Seafood packaging material

▪ Coradia iLint hydrogen trains

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site for those who like to travel - tips for tourists. Article selection

▪ article Admiralty anchors. Tips for a modeler

▪ article How big is the largest mosque in the world? Detailed answer

▪ article Malabar spinach. Legends, cultivation, methods of application

▪ article Generators of harmonic signals LF. Encyclopedia of radio electronics and electrical engineering

▪ Article Gelatin. Chemical experience

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