Damping circuits in a push-pull power converter. DC-DC converters. Voltage converter with PWM control
A push-pull inverter, built on the basis of an emitter power follower, is a push-pull pulse source current, with low weight and small dimensions. Used to charge batteries at a stable voltage. The maximum current set at the beginning of the charge decreases towards the end to the state of a buffer charge - this is close in characteristics to charging batteries in cars.
The current source uses radio components from outdated power supplies for computers and monitors.
The main functional parts of the charger circuit:
1. Input circuits for protection against overloads and short circuits.
2. Network noise suppression two-section filter.
3. Network rectifier.
3. Anti-aliasing filter high voltage.
4. Power inverter based on an emitter follower based on bipolar transistors.
5. Circuits for transmitting and generating a voltage stabilization feedback signal.
6. Rectangular pulse generator.
7. Output current regulator.
8. Secondary voltage rectifier.
9. Protection and load indication circuits.
In the push-pull inverter circuit, a triple voltage conversion occurs: the alternating voltage of the network is rectified and smoothed to direct current, then converted into a pulsed one, with a frequency of up to several tens of kilohertz, transformed into a low-voltage circuit and rectified. The secondary circuit voltage is used to charge the batteries.
The negative feedback circuit allows you to charge batteries or power the load with a stabilized voltage.
The push-pull inverter circuit contains transistors with reduced power and voltage compared to the flyback circuit.
The feedback circuits on the optocoupler and the pulse transformer galvanically separate the high mains voltage of the inverter from the low-voltage circuits.
The low-voltage unit is equipped with powerful avalanche diodes in the assembly, low voltage and load current indication.
The output voltage is stabilized by introducing negative voltage feedback into the circuit circuit, and the increase in the temperature of the transistors due to overheating is controlled by a thermistor.
Basic specifications:
Supply voltage. V - 165...240
Output voltage. B - 12...16
Output load current. A - 10
Conversion frequency, kHz - 22...47
Scheme
The input noise suppression filter consists of a two-winding inductor T2 (Fig. 1) and capacitors C13, C14, which reduce the interference of the converter into the network and eliminate the possibility of impulse noise from the power supply network.
The mains voltage from the filter is supplied to the rectifier VD7 through fuse FU1 and mains switch SA1.
The mains rectifier is supplemented with a smoothing filter made of large capacitors C8, C9, shunted by resistors R12, R13 for voltage equalization. Thermistor RK2 limits the charging current of the capacitors when applying mains voltage.
The high-frequency transformer L of the inverter is connected with one terminal to the middle connection point of capacitors C8, C9, and the second - to the connection point of the transistors of the push-pull converter, through the separating capacitor C7.
Introducing resistor R15 into the oscillatory circuit reduces the quality factor of the transformer winding and accelerates the attenuation of the oscillatory process.
Transistors VT2, VT3 are shunted by high-speed diodes VD4, VD5 from breakdown by reverse currents.
Separating capacitor C7 eliminates magnetization of the magnetic circuit of the inverter transformer T1, when the parameters of capacitors C7, C8 vary and half of the supply voltage is incorrectly set at the middle point of connection of transistors VT2, VT3.
Due to the low transmission coefficient of the inverter's powerful transistors, a bipolar transistor VT1 was added to the circuit.
Setting half the power supply voltage at the connection point of transistors VT2, VT3 is done by selecting the resistance value of resistor R8.
Diode VD3 speeds up the switching of the emitter follower on transistors VT1, VT2.
The load of the emitter follower is transistor VT3, operating in static mode with a grounded, alternating current, base. For direct current, a small bias is applied to the base of transistor VT3, through resistor R8, to create a voltage at the collector close to half the supply voltage.
The master oscillator is based on an analog timer DA1.
The microcircuit contains: two operational amplifiers operating as comparators; RC trigger; output amplifier and key transistor for discharging the external time-charging capacitor C1.
Rectangular pulses are removed from pin 3 of the DA1 microcircuit generator. At high level at output 3 DA1, the pulse through the integrated RC circuit R5, C4 is supplied to the base of the transistor VT1 of the composite emitter follower, the transistor opens and opens the powerful bipolar transistor VT2. Capacitor C7 is charged from the positive bus of the power source. A current pulse will occur in the primary circuit of transformer T1. At the end of the positive pulse from pin 3 of the DA1 microcircuit, with an internal trigger, pin 7 of DA1 switches to a conducting state relative to the negative power supply of the DA1 microcircuit, the base of the transistor VT1 closes to the negative power supply of the microcircuit, capacitor C4 is also rapidly discharged. The emitter follower transistors close and capacitor C7 is discharged through the open transistor VT3.
To properly match the generator pulses to the base-emitter junction of the VT1, VT2 inverter follower, the generator is powered from the positive bus of the high-voltage power source through the voltage-limiting resistor R10, with stabilization by the Zener diode VD2. The minus power supply of the microcircuit is taken from the middle point of connection of transistors VT2, VT3. With the arrival of a subsequent pulse from the generator to the input of the emitter follower, transistors VT1, VT2 open and the process repeats.
A continuous sequence of pulses in the primary winding of the high-frequency transformer T1 activates the appearance of high-frequency voltage in the secondary winding of the transformer and current on the load KhTZ, KhT4.
Pins 2 and 6 of the input comparators of the DA1 microcircuit switch the internal trigger depending on the voltage level on the capacitor C1, the charging time of which depends on the ratings of the RC circuit R1, R2, C1.
Pin 5 of DA1 allows direct access to the divider point with a level of 2/3 of the supply voltage, which is the reference point for the operation of the upper comparator. Usage this conclusion allows you to change this level to obtain modifications to the circuit.
The constructive use of this pin in the negative feedback circuit allows for stabilization of the output voltage.
The voltage from the load through the thermistor RK1 is supplied to the installation variable resistor R14, which regulates the voltage at the load. When the voltage at the HTZ, HT4 terminals increases, the amplifier on the parallel stabilizer DA2 increases the brightness of the optocoupler LED U1, the optocoupler transistor opens and reduces the voltage at pin 5 of DA1. The generator frequency increases. The duration of the output pulses is reduced, which leads to a decrease in voltage across the load.
The DA2 parallel stabilizer serves as an amplifier for the load voltage level mismatch signal and operates in linear mode. Installation in this circuit transistor amplifier undesirable due to variation in parameters and significant influence of external temperature.
Temperature increase key transistors VT2, VT3 of the inverter will lead to a decrease in the resistance of thermistor RK1 and a decrease in the duty cycle of pulses and power in the load.
The DA1 microcircuit is powered from the high voltage of the inverter through a voltage limiter on resistor R10 and stabilized by diode VD2.
The secondary circuit rectifier is made of a powerful pair of VD6 avalanche diodes assembled into an assembly; the polarity of the presence of secondary voltage is indicated by the HL1 LED. The capacitor SY smoothes out voltage ripples in low-voltage circuits.
Printed circuit board, parts
Printed circuit board electronic circuit consists of two parts (Fig. 2 and Fig. 3), connected by conductors.
We will replace the DA1 timer with reduced power consumption of the 7555 series with the 555 series with micro-power consumption.
Network diode bridge VD7 for voltage not lower than 400 V and current more than 3 A, low-voltage rectifier
VD6 for a voltage of at least 50 V and a current of at least 20 A will be replaced with the S40D45C assembly from computer power supplies.
Transistors VT2.VT3 are suitable for a voltage of at least 300 V and a current of more than 3 A - type 2SC2555, 2625, 3036, 3306, 13009 when installed on a radiator with insulating gaskets.
Aluminum oxide capacitors from Nicon or REC.
Optocouplers are from the LTV817, RS816 series.
Transformer T1 is used without rewinding from the AT/TX power supply of the computer. The 1T1 winding consists of 38 turns of wire with a diameter of 0.8 mm, the secondary has two windings of 7.5 turns each, with a cross-section of 4 * 0.31 mm in the bundle.
Transformer T2 is a two-winding mains filter choke.
Coil L1 is a filter choke, 10 turns of wire with a diameter of 1 mm on a 20 mm ferrite ring.
Setup
Adjusting the circuit involves checking the power supply modes. Using resistor R8, set a voltage on the emitter of VT3 equal to half the voltage of the power source - about 150 V.
During testing, the inverter circuit must be powered through a 220/220 V * 100 W transition transformer to eliminate possible electrical injuries.
Before starting, a 220 V * 100 W light bulb is connected to the mains power circuit instead of fuse FU1, and a 12-24 V * 50 candles car light bulb is connected instead of the load.
Increased brightness of the mains light and absence of light from the light bulb in the load indicate a malfunction in the circuit.
When the mains light is dimly lit and the load light is bright, with brightness adjustment available, the operating state of the circuit is confirmed.
After a short period of operation, disconnect the circuit from the network and check the radio components for heating.
When setting up and testing the device, the Safety Regulations must be observed.
You can download printed circuit board drawings in lay6 format (file The-push-pull-inverter.zip) from our website: You do not have access to download files from our server
Vladimir Konovalov, Alexander Vanteev
Irkutsk-43, PO Box 380
Literature
1. Ilya Lipavsky. Hybrid power amplifier based on Andrea Ciuffoli repeater. - Radio Hobby, No. 2, 2009, p. 49.
2. . - Solon-Press, Moscow, 2003, p. 108-142.
3. V. Konovalov. Methodological developments and articles. - Irkutsk, 2009.
Download: Push-pull inverter based on emitter power follower
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Perhaps one of the most simple circuits Voltage converters are a simple push-pull converter based on field-effect transistors, which are connected according to a multivibrator circuit. Zener diodes can be excluded from the circuit, unless of course the circuit is designed to be powered from a voltage of no more than 12 volts. Resistors in the circuit are not critical; their value can be in the range from 220 ohm to 1 kiloohm; they limit the gate current field effect transistors, therefore, by selecting their nominal value, you can adjust the frequency of the converter. It is advisable to use resistors with a power of 0.5-1 watt; overheating of these resistors is possible, but this is not a big deal.
The operation of a push-pull converter is quite simple; the transistors, alternately opening and closing, create an alternating voltage in the primary winding of the transformer high frequency. The transformer is wound on a yellow ferrite ring made of computer unit power supply, although you can also use 2000NM brand rings.
To power the LDS, the transformer in the primary winding contains 6 turns with a tap from the middle, a wire of 0.6-1 mm, the secondary winding contains 90 turns and is stretched across the entire ring, a wire of 0.2-0.4 mm, insulation can be omitted if For primary use stranded wire in rubber insulation.
The converter is capable of developing power up to 20 watts when using field-effect transistors of the IRF344 series and up to 30 watts when using transistors of the IRF3205 type. The scope of application of this kind of push-pull converters is quite wide, since the converter is capable of developing good output power and has a very compact size, it is advisable to use it to charge capacitors or to power LDS in field conditions, where there is no household 220 volt network, to power active devices with such a converter - receivers, low power charging device This is not possible, since the frequency of the converter is quite high.
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Essentially, the soldering iron tip is hardened due to Push-pull converters use the magnetic core of a pulse transformer more efficiently. In such circuits there is no need to combat the magnetization of the core, which makes it possible to reduce its dimensions. The output voltage is symmetrical. In addition, the transistors of the converter operate in a lighter mode.
Sometimes, for low power (up to 15 W), the simplest converter is used, made according to the circuit of a self-oscillator (Fig. 4.16, a). This circuit is not critical to the parts used, but selecting the operating point of the transistor operating mode using resistor R2 can improve the characteristics of the device (sometimes a capacitor is installed in parallel with R2). A divider of resistors R1-R2 provides the necessary initial current to start the autogenerator.
Rice. 4.16. Schemes of push-pull self-generators
The 2N3055 universal transistors used are replaced by similar domestic ones KT818GM, KT8150A, and if you change the polarity of the supplied power, you can also use pnp transistors. The supply voltage of the circuit can be from 12 to 24 V. For long-term operation of the device, transistors must be installed on radiators.
The transformer can be made on a ferrite M2000NM1 ring magic conductor, its working cross-section depends. on the power in the load. For a simplified choice, you can use the recommendations, see table. 4.5.
Table 4.5. Permissible maximum power for ring ferrite magnetic cores of the M2000NM1 brand
When manufacturing transformer T1, windings 1 and 2 are wound simultaneously, but the phasing of their connection must correspond to that shown in the diagram. For a cross-section of a ring magnetic core of standard size K32x20x6, windings 1 and 2 each contain 8 turns (PEL wire with a diameter of 1.2...0.81 mm); 3 and 4, 2 turns each (0.23 mm); 5 - the number of turns of the secondary winding depends on the required voltage (0.1...0.23 mm).
Using this circuit, you can obtain voltages of up to 30 kV if you use a magnetic circuit from transformers used in modern TVs.
A similar circuit of a self-oscillator, made using field-effect transistors, is shown in Fig. 4.16, b. It allows the use of a simpler transformer that does not require feedback windings. Zener diodes VD1, VD2 prevent the appearance of dangerous voltages on the gates of transistors.
The operating frequency of such circuits is set by the parameters of the transformer magnetic circuit and the inductance of the windings, since the delay of the feedback signal depends on this (it is better if the frequency is in the range of 20...50 kHz).
The disadvantage of these circuits is their low efficiency, which makes it difficult to use them at high power, as well as the unstabilized output voltage, which can vary greatly depending on changes in the supply voltage. A more successful push-pull converter circuit, made using a specialized microcircuit (Fig. 4.17), is characterized by high efficiency and can maintain a stable voltage across the load.
Rice. 4.17. Push-pull pulse converter circuit
The converter is made on the widely used T114EU4 PWM controller chip (a complete imported analogue of the TL494), which makes the circuit quite simple. IN in good condition(at zero gate voltage) transistors VT1, VT2 are closed and open by pulses from the corresponding outputs of the microcircuit. Resistors R7-R9 and R8-R10 limit the output current of the microcircuit, as well as the voltage at the gate of the switches. The circuit of elements C1-R2 ensures a smooth transition to operating mode when the power is turned on (a gradual increase in the pulse width at the outputs of the microcircuit). Diode VD1 prevents damage to circuit elements when the power polarity is incorrectly connected.
Stress diagrams explaining the operation are shown in Fig. 4.18. As can be seen in Figure (a), the trailing edge of the pulse has a longer duration than the leading edge. This is explained by the presence of a gate capacitance of the field-effect transistor, the charge of which is absorbed through resistor R9 (R10) during the time when the output transistor of the microcircuit is closed. This increases the time it takes to close the key. Since in the open state the voltage drops on the field-effect transistor is no more than 0.1 V, power losses in the form of slight heating of VT1 and VT2 occur mainly due to the slow closing of the transistors (this is what limits the maximum permissible load power).
Rice. 4.18. Stress diagrams
The parameters of this circuit when operating on a 100 W lamp are given in Table. 4.6. At idle, the current consumption is 0.11 A (9 V) and 0.07 A (15 V). The operating frequency of the converter is about 20 kHz.
Table 4.6. Basic parameters of the scheme
Transformer T1 is made on two ring cores made of ferrite grade M2000NM1, size K32x20x6, folded together. The parameters of the windings are indicated in the table. 4.7.
Table 4.7. Parameters of windings of transformer T1
Before winding, the sharp edges of the core must be rounded off with a file or coarse sandpaper. When making a transformer, the secondary winding is first wound. Winding is carried out turn to turn, in one layer, followed by insulation with varnished cloth or fluoroplastic tape. Primary windings 1 and 2 are wound with two wires simultaneously, as shown in Fig. 4.19 (evenly distributing the turns on the magnetic circuit). This winding can significantly reduce voltage surges at the fronts when closing the field switches. The transistors are installed on a heat sink, which is made from a duralumin profile (Fig. 4.20).
Rice. 4.19 Type of design of a pulse transformer
Rice. 4.20. Radiator design
Heatsinks are fixed to the edges of the printed circuit board. One-sided printed circuit board made of fiberglass laminate with a thickness of 1.5...2 mm and has dimensions of 110x90 mm (see Fig. 4.21 and 4.22).
Rice. 4.21. PCB topology
Rice. 4.22. Arrangement of elements
This circuit can be used to power a load that constantly consumes power up to 100 W. For more power, it is necessary to reduce the switching time of the field switches. This can be done by specially designed microcircuits that have a complementary output stage designed to control powerful field-effect transistors, for example, K1156EU2, UC3825.
In the above circuit, N-type transistors with static induction KP958A (BCIT-Bipolar Static Induction Transistor) can also be used as power switches for power up to 60 W. They are designed specifically to operate in high frequency power supplies. The physics of operation of such a transistor is close to the operation of a conventional bipolar one, but due to design features it has a number of advantages:
1) low source-drain voltage drop in the open state;
2) increased gain;
3) high speed when switching;
4) increased resistance to thermal breakdown.
In this case, it is better to select transistors with the same parameters, and reduce resistors R9 and R10 to 100...150 Ohms.
Push-pull converter is a voltage converter that uses a pulse transformer. The transformation ratio of the transformer can be arbitrary. Although fixed, in many cases the pulse width can be varied, expanding the available voltage regulation range. The advantage of push-pull converters is their simplicity and the ability to increase power.
In a properly designed push-pull converter, there is no direct current through the winding and no core bias. This allows you to use a full magnetization reversal cycle and get maximum power.
The following simplified technique allows you to calculate the main parameters of a pulse transformer made on a ring magnetic core.
- Calculation of overall transformer power
where Sc is the area cross section magnetic circuit, cm2; Sw—core window area, cm2; f - f - oscillation frequency, Hz; Bmax is the permissible induction value for domestic nickel-manganese and nickel-zinc ferrites at frequencies up to 100 kHz.
Limit frequencies and induction values of widespread ferrites
Manganese-zinc ferrites.
| Parameter | Ferrite grade | |||||
| 6000NM | 4000NM | 3000NM | 2000NM | 1500NM | 1000NM | |
| 0,005 | 0,1 | 0,2 | 0,45 | 0,6 | 1,0 | |
| 0,35 | 0,36 | 0,38 | 0,39 | 0,35 | 0,35 | |
Nickel-zinc ferrites.
| Parameter | Ferrite grade | |||||
| 200NN | 1000NN | 600NN | 400NN | 200NN | 100NN | |
| Cutoff frequency at tg δ ≤ 0.1, MHz | 0,02 | 0,4 | 1,2 | 2,0 | 3,0 | 30 |
| Magnetic induction B at Hm = 800 A/m, T | 0,25 | 0,32 | 0,31 | 0,23 | 0,17 | 0,44 |
To calculate the cross-sectional area of the magnetic core and the window area of the magnetic core, the following formulas are used:
Sc = (D - d) ⋅ h / 2
Sw=(d / 2)2 π
where D is the outer diameter of the ferrite ring, cm; d—inner diameter; h is the height of the ring;
2. Calculation of the maximum power of the transformer
We select the maximum power of the transformer as 80% of the overall power:
Pmax = 0.8 Pgab
3. Calculation of the minimum number of turns of the primary winding W1
The minimum number of turns of the primary winding W1 is determined by the maximum voltage on the winding U1 and the permissible core induction Bmax:
4. Calculation of the effective value of the current in the primary winding:
Effective value The primary winding current is calculated by the formula:
I1 = Pmax / Ueff
It should be taken into account that Ueff = U1 / 1.41 = 0.707U1, since Ueff is the effective voltage value, and U1 is the maximum voltage value.
5. Calculation of the wire diameter in the primary winding:
where I1 is the effective value of the current in the primary winding, A; j—current density, A/mm2;
The current density depends on the power of the transformer, the dissipated amount of heat is proportional to the area of the winding and the temperature difference between it and the environment. As the size of the transformer increases, the volume grows faster than the area, and for the same overheating, the specific losses and current density must be reduced. For transformers with a power of 4..5 kVA, the current density does not exceed 1..2 A/mm².
For reference, the table shows current density data depending on the power of the transformer
| Pn, Tue | 1 .. 7 | 8 .. 15 | 16 .. 40 | 41 .. 100 | 101 .. 200 |
| j, A/mm 2 | 7 .. 12 | 6 .. 8 | 5 .. 6 | 4 .. 5 | 4 .. 4,5 |
6. The effective value of the secondary winding current (I2), the number of turns in the secondary winding (W2) and the diameter of the wire in the secondary winding (d2) are calculated using the following formulas:
I2 = Pmax / U2eff
where Uout is the output voltage of the secondary winding, Pmax is the maximum output power transformer, it should also be taken into account that the Pmax value can be replaced by the load power, provided that the load power is less than the maximum output power of the transformer.
W2 = (U2eff*W1) / Ueff
Based on all the above formulas (taking into account the current density, which depends on the power of the transformer), you can approximately calculate the main parameters of the pulse transformer; for the convenience of calculations, you can use an online calculator.
This article is a simplified method for calculating a pulse transformer for a push-pull converter; all formulas and an online calculator allow you to calculate approximate Pulse transformer winding data, since the transformer has many interdependent parameters.
If you find errors in the formulas, methods of their application and other comments, please leave them in the comments.
After determining the diameter of the wire, it should be taken into account that the diameter of the wire is calculated without insulation, use the winding wire data table to determine the diameter of the wire with insulation.
Winding wire data table.
|
Diameter without insulation, mm |
Copper cross section, mm² |
Diameter with insulation, mm |
| 0,03 | 0,0007 | 0,045 |
| 0,04 | 0,0013 | 0,055 |
| 0,05 | 0,002 | 0,065 |
| 0,06 | 0,0028 | 0,075 |
| 0,07 | 0,0039 | 0,085 |
| 0,08 | 0,005 | 0,095 |
| 0,09 | 0,0064 | 0,105 |
| 0,1 | 0,0079 | 0,12 |
| 0,11 | 0,0095 | 0,13 |
| 0,12 | 0,0113 | 0,14 |
| 0,13 | 0,0133 | 0,15 |
| 0,14 | 0,0154 | 0,16 |
| 0,15 | 0,0177 | 0,17 |
| 0,16 | 0,0201 | 0,18 |
| 0,17 | 0,0227 | 0,19 |
| 0,18 | 0,0255 | 0,2 |
| 0,19 | 0,0284 | 0,21 |
| 0,2 | 0,0314 | 0,225 |
| 0,21 | 0,0346 | 0,235 |
| 0,23 | 0,0416 | 0,255 |
| 0,25 | 0,0491 | 0,275 |
| 0,27 | 0,0573 | 0,31 |
| 0,29 | 0,0661 | 0,33 |
| 0,31 | 0,0755 | 0,35 |
| 0,33 | 0,0855 | 0,37 |
| 0,35 | 0,0962 | 0,39 |
| 0,38 | 0,1134 | 0,42 |
| 0,41 | 0,132 | 0,45 |
| 0,44 | 0,1521 | 0,49 |
| 0,47 | 0,1735 | 0,52 |
| 0,49 | 0,1885 | 0,54 |
| 0,51 | 0,2043 | 0,56 |
| 0,53 | 0,2206 | 0,58 |
| 0,55 | 0,2376 | 0,6 |
| 0,57 | 0,2552 | 0,62 |
| 0,59 | 0,2734 | 0,64 |
| 0,62 | 0,3019 | 0,67 |
| 0,64 | 0,3217 | 0,69 |
| 0,67 | 0,3526 | 0,72 |
| 0,69 | 0,3739 | 0,74 |
| 0,72 | 0,4072 | 0,78 |
| 0,74 | 0,4301 | 0,8 |
| 0,77 | 0,4657 | 0,83 |
| 0,8 | 0,5027 | 0,86 |
| 0,83 | 0,5411 | 0,89 |
| 0.86 | 0,5809 | 0,92 |
| 0,9 | 0,6362 | 0,96 |
| 0,93 | 0,6793 | 0,99 |
| 0,96 | 0,7238 | 1,02 |
| 1 | 0,7854 | 1,07 |
| 1,04 | 0,8495 | 1,12 |
| 1,08 | 0,9161 | 1,16 |
| 1,12 | 0,9852 | 1,2 |
| 1,16 | 1,057 | 1,24 |
| 1,2 | 1,131 | 1,28 |
| 1,25 | 1,227 | 1,33 |
| 1,3 | 1,327 | 1,38 |
| 1,35 | 1,431 | 1,43 |
| 1,4 | 1,539 | 1,48 |
| 1,45 | 1,651 | 1,53 |
| 1,5 | 1,767 | 1,58 |
| 1,56 | 1,911 | 1,64 |
| 1,62 | 2,061 | 1,71 |
| 1,68 | 2,217 | 1,77 |
| 1,74 | 2,378 | 1,83 |
| 1,81 | 2,573 | 1,9 |
| 1,88 | 2,777 | 1,97 |
| 1,95 | 2,987 | 2,04 |
| 2,02 | 3,205 | 2,12 |
| 2,1 | 3,464 | 2,2 |
| 2,26 | 4,012 | 2,36 |
A fairly powerful and simple push-pull voltage converter can be built using just two powerful field-effect transistors. I have repeatedly used such an inverter in a variety of designs. The circuit uses two powerful N-channel transistors; it is advisable to take them with an operating voltage of 100 Volts, a permissible current of 40 Amps or more.
The scheme is quite popular on the Internet.
In addition to transistors in the circuit, we have ultra-fast diodes; you can use diodes such as UF4007, HER207, HER307, HER308, MUR460 and others. Two 12-volt zener diodes to limit the voltage on the gates of field switches; it is advisable to take zener diodes with a power of 1 or 1.5 watts; if 12-volt zener diodes are not available, then you can use them with a stabilization voltage of 9-15 volts, not critical.
It is advisable to take limiting resistors with a power of 0.5 or 1 watt; slight overheating of these resistors is possible. The transformer can be wound on the core from a computer power supply, you can even not wind anything, and use the transformer in the opposite way - as a step-up one. Just in case, I’ll say that the primary or power winding consists of 2x5 turns, wound with a bus of 5 individual cores 0.7mm (each bus) wire is not critical.
The secondary, step-up winding is wound on top of the primary and consists of 45 turns - this is quite enough to produce 220 Volts, taking into account the operating frequency of the generator.
The circuit does not contain critical components, the spread of the element base is quite wide. The transistors must be installed on the heat sink; do not forget to separate them from the heat sink with mica spacers, but this is in the case of one solid heat sink.
The choke can be wound on a ring from the output chokes of a computer power supply; the winding is wound with a busbar of 3 strands of 1 mm wire (each), the number of turns is from 6 to 12.
A little about power and safety measures. The output voltage depends on the connected load; this inverter is designed to work with passive loads (lamp, soldering iron, etc.) since the output frequency is hundreds of times higher than the network frequency.
To connect active loads to the inverter, the voltage from the output of the transformer must first be rectified, then smoothed with an electrolytic capacitor; do not forget that in the rectifier it is necessary to use fast diodes with reverse voltage not less than 600 volts and with a current of 2 Amperes or more. Electrolytic capacitor for voltage 400 Volts, capacity 47-330 µF. The inverter power is 300 watts!
Be extremely careful— the output voltage after the rectifier with a capacitor is deadly!