Powerful pulse stabilized power supply. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

 Comments on the article

The article brought to the attention of readers describes a powerful switching source for powering various electronic equipment. It is assembled according to the scheme of a half-bridge inverter controlled by a TL494 SHI controller.

The emergence of high-power high-voltage field-effect transistors was a prerequisite for the development of high-frequency network power supplies with pulse-width (PW) control [1,2, 3]. The main advantages of such sources over traditional linear ones are obtaining more power at the load with smaller dimensions and, accordingly, greater efficiency [XNUMX].

The scheme of the proposed switching power supply is shown in fig. 1. The basis of the device is a converter assembled according to a half-bridge circuit. The power supply has a complete galvanic isolation between the input high-voltage and output circuits. The control unit is assembled on the basis of the TL494 SHI controller.

(click to enlarge)

Main technical specifications of the power supply

• Output voltage, V ...... 28
• Maximum load current, A ...... 10
• Rated conversion frequency, kHz......100

Transistor optocoupler U2 provides galvanic isolation in the negative voltage feedback circuit. The voltage drop across the resistor R7 is approximately 2,5 V. The resistance of this resistor is calculated by setting the current through the resistive divider R6R7. The resistance of the resistor R6 is calculated by the formula

where Uvyx - output voltage of the power supply; I1 - current through the resistive divider R6R7.

The resistance of the resistor R9 determines the current through the emitting diode of the optocoupler U2.1, as well as the minimum operating current of the stabilizer DA1. With the selected current in this circuit I2 (the current value must be within the acceptable limits for the stabilizer DA1), the resistance of the resistor R9 is calculated by the formula

where UF is the voltage drop across the emitting diode of the optocoupler U2.1.

The DA5 chip stabilizes the voltage of 8 V to power the divider, which consists of the U2.2 optocoupler phototransistor and the R17 resistor. The voltage from the middle point of the divider is fed to the non-inverting input of the first error signal amplifier of the DA6 SHI controller.

The voltage for powering the control unit and drivers (DA7 chip) of field-effect transistors provides an auxiliary source on the network transformer T2 and analog voltage regulators DA2 and DA3.

The current protection node is assembled on the DA4 comparator and the DD1.1 trigger. The function of the current sensor is performed by the resistor R5, included in the diagonal of the half-bridge. A triangular-shaped voltage is supplied to the non-inverting input of the comparator DA4 from the capacitor (C26) of the frequency-setting circuit of the clock generator of the SHI controller (Fig. 2). At the output of the comparator, clock pulses are generated, which are fed to the input C of the trigger DD1.1.

(click to enlarge)

If the voltage drop across the resistor R5 reaches 1,1V, the emitting diodes turn on and the phototransistor of the optocoupler U1 opens. The input S trigger DD1.1 will go low. At the direct output of the trigger DD1.1 and, therefore, at the non-inverting input of the second error signal amplifier of the SHI controller DA6, a high level will be set. In this case, both transistors VT1 and VT2 will be closed.

To control powerful switching field-effect transistors, a specialized microcircuit is used - a two-channel driver DA7. On fig. 3 shows the internal structure of one channel. Numbers of outputs of the second channel are indicated in brackets. Each channel contains an optocoupler and an amplifier with a high current output. Such microcircuits are widely used to control both asynchronous and DC motors.

The driver parameters allow you to directly control the field-effect transistors with an insulated gate, switching current up to 50 A at a voltage not exceeding 1200 V.

Main parameters of the HCPL315J chip

• Maximum peak output current, A......0,6
• Maximum output voltage, V......1
• Maximum current consumption, mA......5
• Supply voltage interval, V.......15...30
• Operating temperature range, °С......-40...+100

The resistance of resistors R3 and R4 in the gate circuits of switching transistors is calculated by the formula

where UC2o (C22) is the driver supply voltage (voltage across capacitor C20 or C22); UL - driver output voltage; lL is the maximum peak output current.

The half-bridge diagonal includes the primary winding of the transformer T1 and the inductor L2 (the inductance of the inductor may include the leakage inductance of the transformer) [4]. The transformer is made on the magnetic circuit E-E, size F-43515 from Magnetics Inc. The primary has 38 turns of #19AWG wire and the secondary has 5+5 turns of #12AWG wire. The L2 inductor is wound on an F-41808EC magnetic circuit from Magnetics Inc. The L2 inductor winding consists of 8 turns of #19AWG wire.

The inductor L3 is made on a toroidal magnetic circuit MPP 55930A2 from Magnetics Inc. The L3 inductor winding contains 20 turns of #12AWG wire. The input filter inductor L1 is E3993 from Coilcraft, its inductance is 900 μH.

When the transistor VT1 (or VT2) is turned on, a linearly increasing current begins to flow through the primary winding of the transformer T1 during the control pulse t1 (Fig. 4). When the transistor VT1 (or VT2) closes, due to the energy accumulated in the primary winding of the transformer and inductor L2, a linearly decreasing current continues to flow in the circuit during the time t2 in the same direction. It closes through the VD7 diode if the VT1 transistor is turned off (or through the VD6 diode if the VT2 transistor is turned off).

Without taking into account the active power losses in the primary circuit of the transformer, we write the equations for the time intervals t1 and t2:

where E0 \u2d Upit / 0 - half the supply voltage; U'1 - output voltage of the source, reduced to the primary winding of the transformer; L1 is the total inductance of the primary winding of the transformer T2 and inductor LXNUMX.

From here we obtain expressions for the time t1 and t2 (see Fig. 4):

where lm is the maximum current of the primary winding of the transformer.

The time of current flow through the primary winding of the transformer in one direction tn = t1 + t2 can be expressed as follows:

If we accept that

then the current flow time is

From this equality, we obtain an equation for the external characteristic of the power source. For example, for the duty cycle of control pulses

should

whence

If we denote

then the equation of the external characteristic of the power supply has the form

The external characteristic of the power supply is shown in fig. 5. The output voltage of the source depends on the resistance of the resistor R17 - the lower the resistance, the lower the output voltage. The protection trip current is determined by the resistance of the sensor - resistor R5.

Literature

1. Hexfet designer's manual, vol. I. - Published by International Rectifier, 1993.
2. Carmelo L. A New Driving Circuit for IGBT Devices. - IEEE Transaction On Power electronics, vol. 10, No. 3, May 1995, pp. 373-378.
3. Brown M. Practical Switching Power Supply Design. - San Diego, 1990.
4. Ivensky G. Reducing IGBT Losses in ZCS Series Resonant Converters. - IEEE Transactions on industrial electronics, vol. 46, No. 1, February 1999.

Authors: R.Karov, S.Ivanov, Sofia, Bulgaria

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 Action camera Amkov AMK100S 18.04.2016 The Amkov AMK100S action camera has entered the market, which can be purchased at an estimated price of $130. The novelty is equipped with a lens with a fixed focal length and 8-megapixel CMOS sensor. Supports video recording with a resolution of 1920 x 1440 and 1440 x 1080 pixels at 30 frames per second. The device allows you to take panoramic photographs with a coverage angle of 360 degrees. The maximum image resolution is 3840 x 2160 pixels. Recorded footage is stored on a microSD card (supports media up to 32 GB). The action camera is endowed with a 0,96-inch display and a Micro-USB 2.0 port. There is a Wi-Fi wireless adapter for interacting with a smartphone or tablet. Power is provided by a 1000 mAh rechargeable battery. The device measures 51 x 42 x 34,6 mm and weighs 84 grams. Various accessories will be available for the novelty, including all kinds of mounts, as well as a sealed case that allows you to use the camera underwater at a depth of up to 30 meters.

Other interesting news:

▪ Algae fuel

▪ The updated line of Wireless Plus from Seagate

▪ smart fuse

▪ The robot performed before the British House of Lords

▪ Sony SmartWatch 2

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Intercoms. Article selection

▪ Humpbacked Grave's article will fix it. The art of audio

▪ article Which writer got the stone that lay on Gogol's first grave? Detailed answer

▪ article Crusher. Job description

▪ article Digital phosphor oscilloscopes. Encyclopedia of radio electronics and electrical engineering

▪ article Broadband power amplifier. Encyclopedia of radio electronics and electrical engineering

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