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Transformerless step-down converter 220 volts. Step-up voltage converter without transformer. Transformer input impedance

Inverters from 220 to 12 volts are produced different shapes and sizes. There are transformer and pulse types. Transformer converter 220 to 12 volts The design, as the name suggests, is based on a step-down transformer.

Types of converters and their design

A transformer is a product consisting of two main parts:

  • a core assembled from electrical steel;
  • windings made in the form of turns of conductor material.

Its work is based on the appearance of electromotive force in a closed conductive circuit. When alternating current flows through the primary winding, alternating lines of magnetic flux are formed. These lines penetrate the core and all windings on which electromotive force appears. When the secondary winding is under load, current begins to flow under the influence of this force.

The value of the potential difference will be determined by the ratio of the number of turns of the primary winding and the secondary. Thus, by changing this ratio, you can get any value.

To reduce the voltage value, the number of turns in the secondary winding is made smaller. It is worth noting that the above only works when AC is applied to the primary winding. When using direct current, a constant magnetic flux is created, which does not induce an EMF and energy will not be transferred.

Transformerless converter from 220 to 12 volts

Such power devices are called switching power devices. The main part of such a device is usually a specialized microcircuit (pulse width modulator).

Inverting 220 to 12 volts occurs in the following way. The mains voltage is supplied to the rectifier circuit, and then smoothed out by a capacitance with a nominal value of 300-400 volts. Then the rectified signal is converted using transistors into high-frequency rectangular pulses with the required duty cycle. Converter pulse type Due to the use of an inverting circuit, it produces a stable output voltage. In this case, the conversion occurs both with galvanic isolation from the output circuits and without it.

In the first case it is used pulse transformer, which receives a high-frequency signal up to 110 kHz.

Ferromagnets are used in the manufacture of the core, which leads to a reduction in weight and size. The second uses a low-pass filter instead of a transformer.

Advantages pulse sources are as follows:

  1. light weight;
  2. improved efficiency;
  3. cheapness;
  4. presence of built-in protection.

The disadvantages include the fact that using in work high frequency pulses, the device itself creates interference. This requires elimination and brings complications to electrical circuits.

How to make 12 volts from 220 volts yourself

The easiest way is to make an analog device based on a torus transformer. This device is easy to make yourself. To do this, you will need any transformer with a primary winding rated for 220 volts. The secondary winding is calculated according to simple formulas or selected practically.

For selection you may need:

  • voltage measuring device;
  • insulating tape;
  • keeper tape;
  • copper wire;
  • soldering iron;
  • disassembly tool (nippers, screwdrivers, pliers, knife, etc.).

First of all, it is necessary to determine on which side of the transformer being converted the secondary winding is located. Carefully remove the protective layer to gain access. Using a tester, measure the voltage at the terminals.

In case of lower voltage, solder a wire to either end of the winding, carefully insulating the connection point. Using this wire make ten turns and measure the voltage again. Depending on how much the voltage has increased, calculate the additional number of turns.

If the voltage exceeds the required, reverse actions are taken. Ten turns are unwound, the voltage is measured and it is calculated how many of them need to be removed. After this, the excess wire is cut off and soldered to the terminal.

It should be noted that when using a diode bridge, the output potential difference will rise by an amount equal to the product AC voltage and magnitude 1.41.

The main advantage of transformer conversion is simplicity and high reliability. The downside is the size and weight.

Self-assembly pulse inverters is possible only with a good level of training and knowledge of electronics. Although you can buy ready-made kits WHALE. This set contains printed circuit board and electronic components. The set also includes electrical diagram And drawing with detailed arrangement of elements. All that remains is to carefully unsolder everything.

Using pulse technology, you can also make a converter from 12 to 220 volts. Which is very useful when used in cars. A striking example is an uninterruptible power supply made from stationary equipment.

Many radio amateurs do not consider power supplies without transformers. But despite this, they are used quite actively. In particular, in security devices, in radio control circuits for chandeliers, loads and in many other devices. In this video tutorial we will look at simple design such a rectifier is 5 volts, 40-50 mA. However, you can change the circuit and get almost any voltage.

Transformerless sources are also used as chargers and used in power supply LED lamps and in Chinese lanterns.

This Chinese store has everything for radio amateurs.

Scheme analysis.

Let's consider simple diagram transformerless. The voltage from the 220 volt network goes through a limiting resistor, which also acts as a fuse, to a quenching capacitor. The output also has mains voltage, but the current is greatly reduced.

Drawing. Transformerless rectifier circuit

Next to the full-wave diode rectifier, at its output we get a direct current, which is stabilized by the VD5 stabilizer and smoothed by a capacitor. In our case, the capacitor is 25 V, 100 µF, electrolytic. Another small capacitor is installed in parallel with the power supply.

Then it goes to a linear voltage stabilizer. IN in this case A 7808 linear stabilizer is used. There is a small typo in the circuit; the output voltage is actually approximately 8 V. Why is there a linear stabilizer, a zener diode, in the circuit? In most cases, linear voltage stabilizers are not allowed to supply voltages higher than 30 V to the input. Therefore, a zener diode is needed in the circuit. The output current rating is determined in to a greater extent capacity of the quenching capacitor. In this version, it has a capacitance of 0.33 μF, with a rated voltage of 400 V. A discharge resistor with a resistance of 1 MOhm is installed in parallel with the capacitor. The value of all resistors can be 0.25 or 0.5 W. This resistor is so that after turning off the circuit from the network, the capacitor does not hold residual voltage, that is, it is discharged.

A diode bridge can be assembled from four 1 A rectifiers. The reverse voltage of the diodes must be at least 400 V. You can also use ready-made diode assemblies of the KTs405 type. In the reference book you need to look at the permissible reverse voltage through the diode bridge. Zener diode is preferably 1 W. The stabilization voltage of this zener diode should be from 6 to 30 V, no more. The current at the output of the circuit depends on the value of this capacitor. With a capacitance of 1 µF the current will be around 70 mA. You should not increase the capacitance of the capacitor more than 0.5 μF, since a fairly large current, of course, will burn the zener diode. This scheme The good thing is that it is small in size and can be assembled from available materials. But the disadvantage is that it does not have galvanic isolation from the network. If you are going to use it, be sure to use it in a closed case so as not to touch the high-voltage parts of the circuit. And, of course, you should not associate with this scheme big hopes, since the output current of the circuit is small. That is, it is enough to power low-power devices with a current of up to 50 mA. In particular, powering LEDs and building LED lamps and night lights. The first start must be done with a light bulb connected in series.

This version contains a 300 Ohm resistor, which will fail if something happens. We no longer have this resistor on the board, so we added a light bulb that will light up slightly while our circuit is operating. In order to check the output voltage, we will use the most ordinary multimeter, a constant 20 V meter. We connect the circuit to a 220 V network. Since we have a safety light, it will save the situation if there are any problems in the circuit. Use extreme caution when working with high voltage, since after all, 220 V is supplied to the circuit.

Conclusion.

The output is 4.94, that is, almost 5 V. At a current of no more than 40-50 mA. An excellent option for low-power LEDs. You can power LED strips from this circuit, but only replace the stabilizer with a 12-volt one, for example, 7812. In principle, you can get any output voltage within reason. That's all. Don't forget to subscribe to the channel and leave your feedback on future videos.

Attention! When the power supply is assembled, it is important to place the assembly in a plastic case or carefully insulate all contacts and wires to prevent accidental touching of them, since the circuit is connected to a 220-volt network and this increases the likelihood of electric shock! Be careful and TB!

Voltage 12 Volts is used for power supply large quantity electrical appliances: receivers and radios, amplifiers, laptops, screwdrivers, LED strips, etc. They often run on batteries or power supplies, but when one or the other fails, the user is faced with the question: “How to get 12 Volts AC”? We will talk about this further, providing an overview of the most rational methods.

We get 12 Volts from 220

The most common task is to obtain 12 volts from a 220V household power supply. This can be done in several ways:

  1. Reduce voltage without a transformer.
  2. Use a 50 Hz mains transformer.
  3. Use pulse block power supply, possibly paired with a pulse or linear converter.

Voltage reduction without transformer

You can convert the voltage from 220 Volts to 12 without a transformer in 3 ways:

  1. Reduce the voltage using a ballast capacitor. The universal method is used to power low-power electronics, such as LED lamps, and to charge small batteries, such as flashlights. The disadvantage is the low cosine Phi of the circuit and low reliability, but this does not prevent it from being widely used in cheap electrical appliances.
  2. Reduce the voltage (limit the current) using a resistor. The method is not very good, but it has a right to exist; it is suitable for powering some very weak load, such as an LED. Its main disadvantage is the release of a large amount active power as heat across the resistor.
  3. Use an autotransformer or inductor with similar winding logic.

Quenching capacitor

Before you begin to consider this scheme, it is first worth mentioning the conditions that you must comply with:

  • The power supply is not universal, so it is designed and used only to work with one known device.
  • All external elements power supplies, such as regulators, if you use additional components for the circuit, must be insulated, and plastic caps are put on the metal potentiometer knobs. Do not touch the power supply board or output wires unless there is a load connected to them or unless a Zener diode or low DC voltage regulator is installed in the circuit.

However, such a scheme is unlikely to kill you, but the blow electric shock you can get it.

The diagram is shown in the figure below:

R1 - needed to discharge the quenching capacitor, C1 - the main element, the quenching capacitor, R2 - limits the currents when the circuit is turned on, VD1 - diode bridge, VD2 - zener diode for the required voltage, for 12 volts the following are suitable: D814D, KS207V, 1N4742A. A linear converter can also be used.

Or an enhanced version of the first scheme:

The rating of the quenching capacitor is calculated using the formula:

C(uF) = 3200*I(load)/√(Uinput²-Uoutput²)

C(uF) = 3200*I(load)/√Uinput

But you can also use calculators, they are available online or in the form of a PC program, for example, as an option from Vadim Goncharuk, you can search on the Internet.

Capacitors should be like this - film:

Or these:

It makes no sense to consider the remaining listed methods, because Reducing the voltage from 220 to 12 Volts using a resistor is not effective due to the large heat generation (the dimensions and power of the resistor will be appropriate), and winding the inductor with a tap from a certain turn to get 12 volts is impractical due to labor costs and dimensions.

Power supply on mains transformer

A classic and reliable circuit, ideal for powering audio amplifiers, such as speakers and radios. Provided that a normal filter capacitor is installed, which will provide the required level of ripple.

In addition, you can install a 12 volt stabilizer, such as KREN or L7812 or any other for the desired voltage. Without it, the output voltage will change according to voltage surges in the network and will be equal to:

Uout=Uin*Ktr

Ktr – transformation coefficient.

It is worth noting here that the output voltage after the diode bridge should be 2-3 volts greater than the output voltage of the power supply - 12V, but not more than 30V, it is limited technical characteristics stabilizer, and the efficiency depends on the voltage difference between the input and output.

The transformer should produce 12-15V AC. It is worth noting that the rectified and smoothed voltage will be 1.41 times the input voltage. It will be close to the amplitude value of the input sinusoid.

I would also like to add an adjustable power supply circuit on LM317. With it, you can get any voltage from 1.1 V to the rectified voltage from the transformer.

12 Volts from 24 Volts or other higher DC voltage

To reduce the DC voltage from 24 Volts to 12 Volts, you can use a linear or switching stabilizer. Such a need may arise if you need to power a 12 V load from the on-board network of a bus or truck with a voltage of 24 V. In addition, you will receive a stabilized voltage in the vehicle network, which often changes. Even in cars and motorcycles with on-board network at 12V it reaches 14.7V with the engine running. Therefore, this circuit can also be used for power supply LED strips and LEDs on vehicles.

The circuit with a linear stabilizer was mentioned in the previous paragraph.

You can connect a load with a current of up to 1-1.5A to it. To amplify the current, you can use a pass transistor, but the output voltage may decrease slightly - by 0.5V.

LDO stabilizers can be used in a similar way; these are the same linear voltage stabilizers, but with a low voltage drop, such as AMS-1117-12v.

Or pulse analogues such as AMSR-7812Z, AMSR1-7812-NZ.

Connection diagrams are similar to L7812 and KRENK. These options are also suitable for reducing the voltage from the laptop power supply.

It is more effective to use pulsed step-down voltage converters, for example, based on the LM2596 IC. The board is marked with contact pads In (input +) and (- Out output), respectively. On sale you can find a version with a fixed output voltage and with an adjustable one, as in the photo above on the right side you see a blue multi-turn potentiometer.

12 Volts from 5 Volts or other reduced voltage

You can get 12V from 5V, for example from a USB port or charger For mobile phone, can also be used with currently popular lithium batteries with a voltage of 3.7-4.2V.

If we are talking about power supplies, you can intervene in internal circuit, edit source reference voltage, but for this you need to have some knowledge in electronics. But you can make it simpler and get 12V using a boost converter, for example based on the XL6009 IC. There are options on sale with a fixed 12V output or adjustable ones with adjustment in the range from 3.2 to 30V. Output current – ​​3A.

It is sold on a finished board, and there are marks on it with the purpose of the pins - input and output. Another option is to use MT3608 LM2977, it increases to 24V and can withstand output current up to 2A. Also in the photo you can clearly see the signatures for the contact pads.

How to get 12V from improvised means

The easiest way to get 12V voltage is to connect 8 in series AA batteries 1.5 V each.

Or use a ready-made 12V battery marked 23AE or 27A, the kind used in remote controls remote control. Inside it is a selection of small “tablets” that you see in the photo.

We looked at a set of options for getting 12V at home. Each of them has its pros and cons, varying degrees efficiency, reliability and efficiency. Which option is better to use, you must choose yourself based on your capabilities and needs.

It is also worth noting that we did not consider one of the options. You can also get 12 volts from an ATX computer power supply. To start it without a PC, you need to short-circuit the green wire to any of the black ones. 12 volts are on the yellow wire. Typically, the power of a 12V line is several hundred watts and the current is tens of amperes.

Now you know how to get 12 Volts from 220 or other available values. Finally, we recommend watching this useful video

Transformer is a device for transferring energy from one circuit to another through electrical induction. It is intended for converting current and voltage values, for galvanic separation of electrical circuits, for converting resistance in magnitude and for other purposes.

A transformer can consist of two or more windings. We will consider a transformer made of two separated windings without a ferromagnetic core (air transformer), the diagram of which is shown in Fig. 5.12.

The winding with terminals 1-1’ connected to the power source is the primary winding, the winding to which the load resistance is connected is the secondary. Primary winding resistance , secondary resistance – .

The transformer equations with the accepted polarity of the coils and the direction of the currents have the form:

- for the primary winding

For secondary winding

Transformer input impedance

Let us denote the active resistance of the secondary circuit

then the equations can be rewritten

(5.22)

Transformer input impedance. Considering that and substituting into the first equation (5.21), we obtain that

Thus, the input resistance of the transformer from the side of the primary terminals consists of two terms: – the resistance of the primary winding without taking into account mutual induction, which appears due to the phenomenon of mutual induction. Resistance is, as it were, added (introduced) from the secondary coil and is therefore called introduced resistance.


Input impedance of an ideal transformer.

An ideal transformer ( theoretical concept) is a transformer in which the conditions are met

(5.24)

Moreover, with a certain error, such conditions can be met in a transformer with a core with high magnetic permeability, on which wires with low active resistance are wound.

The input impedance of this transformer is

(5.25)

Consequently, an ideal transformer connected between the load and the energy source changes the load resistance in proportion to the square of the transformation ratio n.

The property of a transformer to convert resistance values ​​is widely used in various fields of electrical engineering, communications, radio engineering, automation and, above all, for the purpose of matching the resistance of the source and load.


Transformer equivalent circuit

The circuit of a two-winding transformer without a ferromagnetic core can be depicted as shown in Fig. 5.14. The current distribution in it is the same as in the circuit in Fig. 5.12 without a common point between the windings.

Let's do it in the diagram in Fig. 5.14 decoupling of inductive couplings. In this case, we obtain a transformer equivalent circuit (Fig. 5.15), in which there are no magnetic connections.

Energy processes in inductively coupled coils

Differential equations of an air transformer (Fig. 5.15):

(5.25)

Let's multiply the first equation by and the second by :

(5.26)

Adding these equations, we obtain the total instantaneous power that is consumed from the source and consumed in the primary and secondary transformer windings and under load

(5.27)

where is the instantaneous power at the load, ;

– instantaneous power spent on heat in the windings of the transformer, ;

– energy magnetic field transformer windings, .


Three-phase generators.

A three-phase circuit (system) is understood as a combination of a three-phase source (generator), load and connecting wires.

It is known that when a conductor rotates in a uniform magnetic field, an emf is induced in it

. (1.1)

Let's fix three identical coils (windings) rigidly on one axis, displaced relative to each other in space by (120°) and begin to rotate them in a uniform magnetic field with angular velocity w (Fig. 1.1).

In this case, coil A will be induced

The same EMF values ​​will appear in coils B and C, but respectively 120° and 240° after the start of rotation, i.e.

(1.3)

A set of three coils (windings) rotating on the same axis with an angular velocity w, in which EMFs are induced, equal in magnitude and shifted from each other by an angle of 120°, is called a symmetrical three-phase generator. Each generator coil is a generator phase. In the generator in Fig. 1.1 phase B “follows” phase A, phase C follows phase B. This sequence of phase alternation is called direct sequence. When changing the direction of rotation of the generator, a reverse phase sequence will occur. The direct sequence based on relations (1.2, 1.3) corresponds to the EMF vector diagram shown in Fig. 1.2, a, for the reverse – vector diagram of the EMF in Fig. 1.2, b.

In the future, all discussions on the calculation of three-phase circuits will concern only three-phase systems with a direct sequence of generator EMFs.


The graph of changes in instantaneous EMF values ​​at y = 90° is shown in Fig. 1.3. At every instant, the algebraic sum of the emf is zero.

The extreme points of the coils (windings) are called end and beginning. The beginnings of the coils are designated A, B, C, the ends are X, Y, Z, respectively (Fig. 1.4, a).

The phase windings of a three-phase generator can be depicted as EMF sources (Fig. 1.4, b).

This article is further development ideas for transformerless power supply.

In all the diagrams below, the numbering of elements that perform the same purpose is preserved from diagram to diagram. Additional new circuit elements are continuously numbered. If there is no next element number, this means that it was in the previous circuit (and in this one this number simply is not present). 1.Low frequency amplifier

The ULF circuit (Fig. 1) is known as a transformer circuit. Its peculiarity is the absence of a power transformer. The lamp anodes are powered from a 220 V network using a voltage doubling circuit and Ua-k = 620 V. The lamps are heated from a 220 V network through a current-limiting capacitor C6. As Tr1, Tr2, you can use power transformers from old tube radios with a midpoint in the secondary winding (as a rule, kenotrons of the 5Ts4S, 5TsZS type, etc. were installed in them). The network winding of these transformers is used as a high output when operating in line for subscribers, the filament winding is used as a low-impedance output.


Fig.1

In amateur conditions, a power transformer from tube radios can be used as an output transformer without midpoint on the secondary winding (for example from "Records"), but for this you need to connect the mains and boost windings in series, and the connection point will be the middle one.

As an input transformer, in amateur conditions, an output transformer from tube amplifiers of old radios with a push-pull output stage (two 6P14P, two 6P6S, etc.) tubes can be used.

This amplifier provides at Pin = 20...30 W at the output Pout = 120... 130 W. Capacitors C4, C5 limit the anode current of the lamps, proportional to their capacity, for example, if C4 = C5 = 20 μF each, then the anode current of the lamps is limited at 400 mA.

There is no point in using C4, C5 of larger capacity, because... the anode current of two lamps does not exceed 350 mA. In addition, the larger the capacitance of these capacitors, the greater the current surge when first connected to a 220 V network and breakdown of the diodes is possible. D226 or the like, connected in pairs in parallel, can be used as diodes. 2. KB wideband power amplifier

The amplifier circuitry (Fig. 2) is practically no different from the ULF, only the transformers are made on ferrite rings. Moreover, up to frequencies of 7 MHz, 2000NN rings can be successfully used, but 400...600NN rings are better; when operating up to 28 MHz - 50 HF, while ensuring minimal frequency response in the HF ranges. There must be good insulation between the primary and secondary windings. The windings contain 12...15 turns each.


Fig.2 (click to enlarge)

The output transformer is of standard size K40x25x25 or close to it. Input transformer - K16x8x6 or close to it. Standard sizes can be achieved through a set of several rings. At Рвх=30 W, the lamp anode current was 250 mA at Uа-к=620V. 3. Common cathode KB power amplifier

As is known, the switching circuit for lamps with a common cathode requires a full set of supply voltages: anode, screen grid, control grid, filament (Fig. 3).

The usual network doubling circuit (220V) provides a source for powering the anode-screen circuits of lamps (+620V +310V). To power the lamp filaments, capacitor C6 is used, which limits the filament current.


Fig.3 (click to enlarge)

The negative voltage source is assembled at Tp1, V9...V12, C20. A small-sized transformer is used as Tr1, because consumption on control grids is very small.

I would like to draw attention to the fact that such circuits have two “common wires”. One - for the circuit according to DC, this is the negative plate of capacitor C5, designated 0V. Direct current measurements must be taken relative to this point. Moreover, during these measurements it is necessary to observe safety precautions, because such targets do not have galvanic isolation from the network. For example, to measure the anode and screen voltages, you need to connect the “-” of the voltmeter to the 0V point, and the “+” of the voltmeter to leg 3 V5 or V6. This is the voltage on the screen grids. If there are 6 V5 or V6 per leg, this will be the anode voltage.

To measure “-” on the control grid, you need to change the polarity of the voltmeter, i.e. apply “+” of the voltmeter to the 0V point, and “-” to leg 2 V5 or V6 and use resistor R1 to set the quiescent current of the lamps in TX mode - transmission (no input signal). In the receive mode (RX) on the control grids there is a maximum “-” and the lamps are closed, the current through them is zero. The lamp mode is set by resistor R1 in carrier mode using the PA1 device. By moving R1 towards the relay contact P2, reduce the “-” on the control grids until there is a linear increase in the readings of PA1. As soon as the linear growth has stopped, R1 is slightly returned back and fixed with varnish.

The second common wire is the amplifier housing - this is the common wire for the RF signal. And all RF voltage measurements; if necessary, they are made relative to the body. Most amplifier elements are non-critical and can vary significantly in ratings. For example, capacitances C1, C2, C7, C8, C19, C1b can fluctuate within 1000 PF...10000 pF. The main thing is that they can withstand the voltage of the circuit, i.e. C1, C2 - at least 250 V, C8 - at least 1000 V (it can be assembled from two at 500 V), C7 - at least 500 V, C19 - at least 250 V, C16 - any. From 14 - 80...200 pF.

Only one element is critical - C9. It must have a significant voltage reserve - at least 1000 V, and most importantly, its capacitance should not be more than 3000 pF. C9 is the “highlight” of the circuit that ensures safety with transformerless power supply. In the event of a break in the common grounding, the current between the housing and the common grounding does not reach a value that affects the human body, because limited to C9 capacity< 3000 пФ на уровне 250...300 мкА в самом неблагоприятном случае. Еще одна особенность- вместо дросселя в управляющей сетке используется резистор R5. Как показал опыт, использование резистора значительно попытает устойчивость каскада к самовозбуждению.

The issue of using circuits L7, L8, L9, L10, L11, L12 was also quite successfully resolved. They are used reversely, i.e. when receiving (RX) they are narrowband inputs with input adjustment C18, and when transmitting (TX) they match the low output impedance of the transceiver (usually 50...75 Ohms) with a high input impedance tube amplifier according to the scheme with a common cathode.

During transmission (TX), C 17 is connected in parallel with C18, but since The capacitance of C17 is small (2pF), it almost does not affect the configuration of circuits L7, L8, L9, L10, L11, L12, similarly, CSV is connected in parallel with C12 and also does not affect the configuration of the circuit. The SSV is made in the form of one or two turns around the mounting wire connecting C10 to C12. This piece of mounting wire is made of high-voltage wire or coaxial cable, from which the outer braid has been removed, and the turns are wound over a thick nylon filler. Such a coupling capacitor can withstand high reactive voltages and currents and can be used in more powerful amplifiers. After low capacitance (Csv) - and low voltages, so P1 is not very critical to the gap between the contacts.

This circuit for switching the antenna from RX to TX with the reverse use of elements of the P-circuit and the input “narrowband” circuit allows for “cold” tuning to the correspondent - at maximum volume, with knobs C12, C13, C18, without emitting a “carrier” into the air, which Significantly reduces mutual interference and tuning on the DC frequency. Instead of L7, L8, L9, L10, L11, L12, you can get by with just two coils: one is adjusted in the HF ranges - at 28 MHz minimum C18, the other at 7.0 MHz with a minimum C18, but the maximum capacity of C18 should be up to 500 pF (to cover the remaining ranges).

The taps for the coils L7, L8, L9, L10, L11, L12 are made from approximately 1/3 turns (from the grounded end), but it is better to select for each range according to the maximum RF voltage on the control grids of the lamps.

Coils are made on any frame with cores (and even without them). The main thing is that they need to be adjusted according to the maximum volume of received stations (if there are no devices), you may have to slightly change the containers connected in parallel to them.

Tubes V5, V6 are switched on for power addition in the 28 MHz range; L5 and L6 are tuned to maximum output power at 28 MHz by shifting and spreading the turns. It must be remembered that L5, L6, L4 are under anode voltage and all precautions must be observed.

L4, to reduce the dimensions of the P-circuit and ease of mechanical fastening, is made on a toroidal ring made of textolite, getinax, fluoroplastic, etc., and is attached directly to the biscuit. The taps on L4 are selected experimentally, depending on the input impedance of the antenna.

L5, L6 - frameless, they are wound on a frame with a diameter of 15 mm and contain 6 turns of PEV-1 wire 1.5 mm, winding length - 25 mm.

L4 - 60 turns, winding - turn to turn, taps - approximately from 4, 18, 32 turns, the first 4 turns - with 1 mm wire, the rest - 0.6 mm.

Choke L3 is wound on any insulating material and contains approximately 160 turns of wire 0.25...0.27 mm, some of the turns are wound turn to turn, the rest are in bulk. The winding turn to turn is connected to cL4 (the “hot” end of L3).

Coils L7, L8, L9, L10, L11, L12 - on a frame of at least 6 mm with an SCR-1 core.
L7 - 10 turns of PEL 0.51, tap from the 3rd from the bottom;
L8 - 12 turns PEL 0.51, tap from the 4th from the bottom;
L9 - 16 turns of PEL 0.25, tap from the 5th from the bottom;
L10 - 25 turns of PEL 0.25, tap from the 8th from the bottom;
L11 - 35 turns of PEL 0.25, tap from the 10th from the bottom;
L12 - 45 turns of PEL 0.25, tap from the 12th from the bottom;

C21 -10pF; S22-15pF; C23-- 68 pF; C24 - 120 pF; C25 - 200 pF; S26-430pF.

P1, P2 can be connected either according to the diagram in Fig. 3 or in parallel; one relay with several groups of contacts can be used, for example RES-9, RES-22, etc. The type of relay also depends on Ucontrol. coming from the transceiver. 4. Hybrid power amplifier

Hybrid amplifiers are known to many radio amateurs. In Fig.4. Some details of coupling these amplifiers with a transformerless power supply are presented.

The voltage regulator for the lamp screen grids is assembled on transistor VI 4 and resistor R7. Resistors R4 and R6 are current-limiting (a kind of protection) at the extreme positions of R7, as well as in emergency situations. R5 creates leakage current from the base-emitter junction for normal operation voltage regulator. Resistor R1 sets negative voltage on the control grids of the lamps, when receiving (RX), the lamps are locked at maximum voltage (negative). R2 is protection against “pumping” of the amplifier and creates a partial automatic bias on the control grids of the lamps.

R8, R9, R10, R11 - load for the transceiver. These same resistors determine the input impedance of the amplifier.

The circuit in Fig. 4 has a common DC wire, isolated from the housing. This is the negative plate of capacitor C5 (indicated by point 0V). All DC measurements in the circuit must be made relative to this point.


Fig.4 (click to enlarge)

Setting methods and techniques come down to the right choice initial current through V 13, which must be no less than the initial current (at the beginning of the straight section of characteristic V13). The same current through the lamps must be set by resistors R1, R7. Good results are obtained when using 6P45S lamps.

C14 should be high voltage, like C9.

I would like to warn radio amateurs against the mistake that many make when repeating such schemes. Many people, by controlling the anode current of the lamps, try to obtain the maximum possible current. This is incorrect, because such circuits are capable of providing large anode currents, but output power however, it does not correspond to them (currents). So, through one GU-50 (according to this scheme) I was able to obtain a current of up to 450 mA (Uac = 620 V), but there was no output power of 200 W, which significantly reduced the service life (cathode emission was quickly lost), causing TVI, those. the circuit worked as a DC amplifier.

Taking into account the above, it is necessary to “squeeze” not the maximum possible anode currents (they are only indirectly related to the output power), but the maximum RF voltage at the equivalent, or at the antenna according to the output indicator. When the RF voltage increases, you also need to use only a straight section and not lead it into the “saturation” zone. The lamps are turned on for power addition, the parameters of the P-circuit are standard (described in the previous section). You can use bipolar KT907 instead of KP904. The emitter is turned on instead of the source, the collector - instead of the drain. The required bias is supplied to the base through a powerful 500m resistor shifting a 3.3 k potentiometer connected between the "-" rectifier and the lower terminal of R7, which is accordingly disconnected from the "-" rectifier. This potentiometer sets the initial current of the cascade. Between the potentiometer slider and the “-” rectifier, a small blocking capacitor is connected (<100В) напряжение, 5. Усилитель на ГУ74Б

The diagram in Fig. 5 shows a power amplifier using a GU74B lamp, which needs 1200V at the anode. This voltage is obtained by adding the voltages of two sources. The first is assembled using a voltage doubling circuit without a transformer from a 220 V network and produces two voltages (relative to the 0V point): +310 V and +620 V. These voltages are quite sufficient to power the screen grids of most lamps with high anode voltage.


Fig.5 (click to enlarge)

The second source (it can be conventionally called a “voltage booster”) is assembled on a transformer (TS-270). In order to obtain a total voltage of 1200 V, there must be approximately 400 V AC voltage on the secondary winding of the transformer. After rectification by diodes V10...V17 and filtering by capacitors C27, C28, the DC voltage is about 1/3 higher - in sum with the first (+620 V) the voltage required for lamp operation is achieved. Since these sources work by adding voltages and powers, the power consumption is distributed approximately in proportion to their voltages, which means that you can safely use a transformer with an overall power of at least half that of a conventional transformer circuit. The negative voltage source is assembled on diode V9 and capacitor C20. Since the circuit is half-wave, the capacitance C20 should be quite large - 200 μF.

Instead of a choke, a resistor R5 is used in the control grid, which makes the cascade more resistant to self-excitation.

Serial power supply of the lamp is applied through the elements of the P-circuit. This has its disadvantages - the elements of the P-circuit are under high voltage, and its advantages - when powered in series, the efficiency in the HF ranges is somewhat higher, and the requirements for the L3 inductor for electrical strength are somewhat lower, because it stands after the P-circuit elements (L5, L4).

The P-circuit can also be made according to a standard parallel power supply circuit.

Slightly increased requirements for capacitors C12, C13 - they must have a sufficient gap between the plates. C12, when the rotor plates are wound up, must have a gap of at least 1.5 mm. C10, C11 must withstand high reactive powers at a voltage of at least 2.5 kV. Capacitor C9 ensures safety precautions, and its capacity should not be more than 3000 pF. C4, C5, C27, C28 - 180 µF x 350 V each.

The power amplifier is put into operation in the following sequence.

1. S1 turns on (all others must be turned off). The lamp blowing motor starts working, the entire circuit is switched to a reduced voltage through capacitors C, C. They prevent the current from rushing to charge capacitors C4, C5, C27, C28.

2. After a few seconds, S1 turns on - it supplies full voltage to the circuit, while a maximum negative voltage appears on the control grid of the lamp and full filament voltage - the lamp is warming up.

3. After a few minutes, when the heat has warmed up the lamp, the VK2 toggle switch turns on. If there are no emergency modes in the circuit, VK1 is turned on. When working on the air, switching from reception to transmission is carried out by relay P1.

Turning off the amplifier is carried out in the reverse order.

The mode is set by resistor R1. The linear increase in power is controlled by the output indicator PA1. If the power increase has stopped or is too slow (saturation zone), you need to move R1 back a little and fix it.

S2, S1, S1", VK1, VK2 must have switch levers made of insulating material. In addition, it is advisable to install them on an insulating decorative lining (isolate from the body) made of thick plexiglass, PCB, etc.

L4 is mounted directly on S2 in order to reduce its size and ease of fastening. It is advisable to perform it on a toroidal ring made of fluoroplastic, getinax, etc.

Circuits L7, L8, L9, L10, L11, L12 - the same as in section 3.

If your transceiver does not “swing” this amplifier, do not be upset - you can install another amplification stage in it according to the diagram in Fig. 6. These are lamps of the 6P15P, 6P18P, 6P9 type (or any other triode lamp of sufficient power), connected by a triode.


Fig.6

The heat is taken from the TS-270 (-6.3 V). The common wire is connected to point 0V - this is the “-” of capacitor C5. The anode voltage is taken from “+” C4 (+620 V). Negative voltage is taken from R1 (Fig. 5a) in parallel connection. The input-output of the cascade is connected to the breaking point (marked “x” in Fig. 5) of capacitor C14. The contour data is the same as in section 3.

L1, L2 are wound on ferrite with a thicker wire - 0.37...0.4 mm, 25...30 turns.

Using this circuitry, you can get small-sized amplifiers (desktop with a source) with good energy.

Literature

1. V. Kulagin. HF power amplifier "Retro". RL, 8/95, p.26.

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