Electrical diagrams for free. Regulation of charging current on the primary winding

The device (see diagram) is based on a triac regulator, with an additionally introduced low-power diode bridge VD1 - VD4 and resistors R3 and R5.

After connecting the device to the network at its positive half-cycle (plus on the top wire in the diagram), capacitor C2 begins to charge through resistor R3, diode VD1 and series-connected resistors R1 and R2. With a negative half-cycle of the network, this capacitor is charged through the same resistors R2 and R1, diode VD2 and resistor R5. In both cases, the capacitor is charged to the same voltage, only the charging polarity changes.

As soon as the voltage on the capacitor reaches the ignition threshold of the neon lamp HL1, it lights up and the capacitor is quickly discharged through the lamp and the control electrode of the smistor VS1. In this case, the triac opens. At the end of the half-cycle, the triac closes. The described process is repeated in each half-cycle of the network.

It is well known, for example, that controlling a thyristor using a short pulse has the disadvantage that with an inductive or high-resistance active load, the anode current of the device may not have time to reach the holding current value during the action of the control pulse. One of the measures to eliminate this drawback is to connect a resistor in parallel with the load.

In the described charger, after turning on the triac VS1, its main current flows not only through the primary winding of transformer T1, but also through one of the resistors - R3 or R5, which, depending on the polarity of the half-cycle of the mains voltage, are alternately connected parallel to the primary winding of the transformer with diodes VD4 and VD3, respectively .

The main unit of the device is transformer T1. It can be made on the basis of a laboratory transformer LATR-2M by insulating its winding (it will be the primary) with three layers of varnish and winding a secondary winding consisting of 80 turns of insulated copper wire with a cross-section of at least 3 mm2, with a tap from the middle. The transformer and rectifier can also be borrowed from a power source of suitable power. When making a transformer yourself, you can use the following calculation method; in this case, they are set by a voltage on the secondary winding of 20 V at a current of 10 A.

Capacitors C1 and C2 - MBM or others for a voltage of at least 400 and 160 V, respectively. Resistors R1 and R2 are SP 1-1 and SPZ-45, respectively. Diodes VD1-VD4 -D226, D226B or KD105B. Neon lamp HL1 – IN-3, IN-ZA; It is very desirable to use a lamp with electrodes of the same design and size - this will ensure symmetry of the current pulses through the primary winding of the transformer.

KD202A diodes can be replaced with any of this series, as well as with D242, D242A or others with an average direct tone of at least 5 A. The diode is placed on a duralumin heat-sinking plate with a useful dissipation surface area of ​​at least 120 cm2. The triac should also be mounted on a heat sink plate with approximately half the surface area. Resistor R6 – PEV-10; it can be replaced with five MLT-2 resistors connected in parallel with a resistance of 110 Ohms.

One of the main tools at hand in a radio amateur's laboratory is, of course, a power supply, and as you know, the basis of most power supplies is a power voltage transformer. Sometimes we come across excellent transformers, but after checking the windings it becomes clear that the voltage we need is missing due to a burnout of the primary or secondary. There is only one way out of this situation - to rewind the transformer and wind the secondary winding with your own hands. In amateur radio equipment, you usually need a voltage from 0 to 24 volts to power a variety of devices.

Since the power supply will operate from a household network of 220 volts, when carrying out small calculations it becomes clear that on average every 4-5 turns in the secondary winding of the transformer produce a voltage of 1 volt.

How to make a charger for a car battery with your own hands?

This means that for a power supply with a maximum voltage of 24 volts, the secondary winding should contain 5 * 24, resulting in 115-120 turns. For a powerful power supply, you also need to select a wire of the required cross-section for rewinding; on average, the diameter of the wire chosen for a medium-power power supply is 1 millimeter (from 0.7 to 1.5 mm).

To create a powerful power supply, you need to have a powerful transformer on hand; a transformer from a black-and-white TV made in the Soviet Union is perfect. The transformer needs to be disassembled, the cores (pieces) taken out and all secondary windings unwinded, leaving only the network winding, the whole process takes no more than 30 minutes.

Next, we take the indicated wire and wind it onto the transformer frame with the calculation of 5 turns of 1 volt. Thus, you can assemble, for example, a charger for a car battery with your own hands; to charge a car battery, the secondary winding must contain 60-70 turns (charging voltage must be at least 14 volts, current 3-10 amperes), then you need a powerful diode bridge for rectification AC and you're done.

But to charge a car battery, the wire of the secondary winding of the transformer must be selected with a diameter of at least 1.5 millimeters (from 1.5 to 3 millimeters in order to have a charging current of 3 to 10 amperes). In the same way, you can design a welding machine and other power devices.

DIY 12V battery charger

I made this charger to charge car batteries, the output voltage is 14.5 volts, the maximum charge current is 6 A. But it can also charge other batteries, for example lithium-ion ones, since the output voltage and output current can be adjusted within a wide range. The main components of the charger were purchased on the AliExpress website.

These are the components:

You will also need an electrolytic capacitor 2200 uF at 50 V, a transformer for the TS-180-2 charger (see this article for how to solder the TS-180-2 transformer), wires, a power plug, fuses, a radiator for the diode bridge, crocodiles. You can use another transformer with a power of at least 150 W (for a charging current of 6 A), the secondary winding must be designed for a current of 10 A and produce a voltage of 15 - 20 volts. The diode bridge can be assembled from individual diodes designed for a current of at least 10A, for example D242A.

The wires in the charger should be thick and short.

How to charge a car battery

The diode bridge must be mounted on a large radiator. It is necessary to increase the radiators of the DC-DC converter, or use a fan for cooling.

Circuit diagram of a charger for a car battery

Charger assembly

Connect a cord with a power plug and a fuse to the primary winding of the TS-180-2 transformer, install the diode bridge on the radiator, connect the diode bridge and the secondary winding of the transformer. Solder the capacitor to the positive and negative terminals of the diode bridge.

Connect the transformer to a 220 volt network and measure the voltages with a multimeter. I got the following results:

1. The alternating voltage at the terminals of the secondary winding is 14.3 volts (mains voltage 228 volts).
2. The constant voltage after the diode bridge and capacitor is 18.4 volts (no load).

Using the diagram as a guide, connect a step-down converter and a voltammeter to the DC-DC diode bridge.

Setting the output voltage and charging current

There are two trimming resistors installed on the DC-DC converter board, one allows you to set the maximum output voltage, the other allows you to set the maximum charging current.

Plug in the charger (nothing is connected to the output wires), the indicator will show the voltage at the device output and the current is zero. Use the voltage potentiometer to set the output to 5 volts. Close the output wires together, use the current potentiometer to set the short circuit current to 6 A. Then eliminate the short circuit by disconnecting the output wires and use the voltage potentiometer to set the output to 14.5 volts.

Reverse polarity protection

This charger is not afraid of a short circuit at the output, but if the polarity is reversed, it may fail. To protect against polarity reversal, a powerful Schottky diode can be installed in the gap in the positive wire going to the battery. Such diodes have a low voltage drop when connected directly. With such protection, if the polarity is reversed when connecting the battery, no current will flow. True, this diode will need to be installed on a radiator, since a large current will flow through it during charging.

Suitable diode assemblies are used in computer power supplies. This assembly contains two Schottky diodes with a common cathode; they will need to be paralleled. For our charger, diodes with a current of at least 15 A are suitable.

It must be taken into account that in such assemblies the cathode is connected to the housing, so these diodes must be installed on the radiator through an insulating gasket.

It is necessary to adjust the upper voltage limit again, taking into account the voltage drop across the protection diodes. To do this, use the voltage potentiometer on the DC-DC converter board to set 14.5 volts measured with a multimeter directly at the output terminals of the charger.

How to charge the battery

Wipe the battery with a cloth soaked in soda solution, then dry. Remove the plugs and check the electrolyte level; if necessary, add distilled water. The plugs must be turned out during charging. No debris or dirt should get inside the battery. The room in which the battery is charged must be well ventilated.

Connect the battery to the charger and plug in the device. During charging, the voltage will gradually increase to 14.5 volts, the current will decrease over time. The battery can be conditionally considered charged when the charging current drops to 0.6 - 0.7 A.

DC-DC buck converter TC43200 - product link.

Review of DC-DC CC CV TC43200 Buck Converter.

The device can be used to recharge car batteries with a capacity of up to 100 Ah, to charge motorcycle batteries in a mode close to optimal, and also (with simple modifications) as a laboratory power supply.

The charger is made on the basis of a push-pull transistor voltage converter with autotransformer coupling and can operate in two modes - a current source and a voltage source. When the output current is less than a certain limit value, it operates as usual - in voltage source mode. If you try to increase the load current above this value, the output voltage will decrease sharply - the device will switch to current source mode.

DIY car battery chargers

The current source mode (which has a high internal resistance) is ensured by including a ballast capacitor in the primary circuit of the converter.

The schematic diagram of the charger is shown in Fig. 2.94.

Rice. 2.94.Schematic diagram of a charger with a quenching capacitor in the primary circuit.

The mains voltage is supplied through the ballast capacitor C1 to the rectifier bridge VD1. Capacitor C2 smoothes out ripples, and zener diode VD2 stabilizes the rectified voltage. Zener diode VD2 simultaneously protects the transistors of the converter from overvoltage at idle, as well as when the device output is shorted, when the voltage at the output of bridge VD1 increases. The latter is due to the fact that when the output circuit is closed, the generation of the converter may be disrupted, while the load current of the rectifier decreases and its output voltage increases. In such cases, the zener diode VD2 limits the voltage at the output of bridge VD1.

The voltage converter is assembled using transistors VT1, VT2 and transformer T1. The converter operates at a frequency of 5 ÷ 10 kHz.

The VD3 diode bridge rectifies the voltage removed from the secondary winding of the transformer. Capacitor C3 is a smoothing capacitor.

The experimentally measured load characteristic of the charger is shown in Fig. 2.95. When the load current increases to 0.35 ÷ 0.4 A, the output voltage changes slightly, and with a further increase in current it decreases sharply. If an undercharged battery is connected to the output of the device, the voltage at the output of bridge VD1 decreases, the zener diode VD2 leaves the stabilization mode and, since capacitor C1 with a high reactance is included in the input circuit, the device operates in current source mode.

If the charging current decreases, the device smoothly switches to voltage source mode. This makes it possible to use the charger as a low-power laboratory power supply. When the load current is less than 0.3 A, the ripple level at the operating frequency of the converter does not exceed 16 mV, and the output resistance of the source decreases to several Ohms. The dependence of the output resistance on the load current is shown in Fig. 2.95.

Rice. 2.95. Load characteristics of a charger with a quenching capacitor in the primary circuit.

Setting up a charger with a quenching capacitor in the primary circuit

Installation begins with checking the correct installation. Then they make sure that the device is working when the output circuit is closed. The circuit current must be at least 0.45-0.46 A. Otherwise, resistors R1, R2 should be selected in order to ensure reliable saturation of transistors VT1, VT2. A higher fault current corresponds to a lower resistance of the resistors.

If it is necessary to use a device for charging small-sized batteries with a capacity of up to several ampere-hours and regenerating galvanic cells, it is advisable to regulate the charging current. To do this, instead of one capacitor C1, a set of smaller capacitors should be provided, switched by a switch. With sufficient accuracy for practice, the maximum charging current - the closing current of the output circuit - is proportional to the capacity of the ballast capacitor (at 4 μF the current is 0.46 A).

If you need to reduce the output voltage of a laboratory power supply, it is enough to replace the VD2 zener diode with another one with a lower stabilization voltage.

Transformer T1 is wound on a ring magnetic core of standard size K40x25x11 made of 1500NM1 ferrite. The primary winding contains 2×160 turns of PEV-2 0.49 wire, the secondary winding contains 72 turns of PEV-2 0.8 wire. The windings are insulated with each other by two layers of varnished fabric.

Install the VD2 zener diode on a heat sink with a useful area of ​​25 cm 2

The transistors of the converter do not need additional heat sinks, since they operate in switching mode.

Capacitor C1 is paper, designed for a rated voltage of at least 400 V.

A simple charger circuit for a car battery

As is known from the laws of transformer operation, the current in the primary winding, if the transformer is step-down, is less than the current in the secondary winding in relation to the voltage or number of turns of the transformer. I consider a good charger if it is capable of delivering 10A output. At the transformer input there will be 10/(220/15)= 0.7A. Agree, it is easier to control the current if it is smaller. Charger with current control on the primary winding is given below:

The circuit is very simple and does not require adjustment. The bridge diodes in the low-voltage network must be installed on the radiator. Since the KU202N thyristor will be loaded less than 10% on the radiator, there is no point in installing it; it can be installed directly on the printed circuit board. An example of an assembled circuit on a printed circuit board is shown below.

This charger is highly reliable and easy to assemble. The only thing you need to have is a transformer of 200 W or more, although this condition applies to almost all chargers.
This circuit can be used not only for car charging but also for any one that has a transformer...
Also, this circuit can be used for a high-power laboratory source...
Again, if you find a powerful 220/220 transformer, you can get LATR

THINK FOR YOURSELF FOR ITS FURTHER APPLICATION......

Under normal operating conditions, the vehicle's electrical system is self-sufficient. We are talking about energy supply - a combination of a generator, a voltage regulator, and a battery works synchronously and ensures uninterrupted power supply to all systems.

This is in theory. In practice, car owners make amendments to this harmonious system. Or the equipment refuses to work in accordance with the established parameters.

For example:

1. Operating a battery that has exhausted its service life. The battery does not hold a charge
2. Irregular trips. Prolonged downtime of the car (especially during hibernation) leads to self-discharge of the battery
3. The car is used for short trips, with frequent stopping and starting of the engine. The battery simply does not have time to recharge
4. Connecting additional equipment increases the load on the battery. Often leads to increased self-discharge current when the engine is turned off
5. Extremely low temperature accelerates self-discharge
6. A faulty fuel system leads to increased load: the car does not start immediately, you have to turn the starter for a long time
7. A faulty generator or voltage regulator prevents the battery from charging properly. This problem includes worn power wires and poor contact in the charging circuit.
8. And finally, you forgot to turn off the headlights, lights or music in the car. To completely discharge the battery overnight in the garage, sometimes it is enough to close the door loosely. Interior lighting consumes quite a lot of energy.

Any of the following reasons leads to an unpleasant situation: you need to drive, but the battery is unable to crank the starter. The problem is solved by external recharge: that is, a charger.

It is absolutely easy to assemble it with your own hands. An example of a charger made from an uninterruptible power supply.

Any car charger circuit consists of the following components:

• Power unit.
• Current stabilizer.
• Charge current regulator. Can be manual or automatic.
• Indicator of current level and (or) charge voltage.
• Optional - charge control with automatic shutdown.

Any charger, from the simplest to an intelligent machine, consists of the listed elements or a combination thereof.

Simple diagram for a car battery

Normal charge formula as simple as 5 kopecks - the basic battery capacity divided by 10. The charging voltage should be a little more than 14 volts (we are talking about a standard 12 volt starter battery).

Simple principle electrical The car charger circuit consists of three components: power supply, regulator, indicator.

Classic - resistor charger

The power supply is made of two winding “trans” and a diode assembly. The output voltage is selected by the secondary winding. The rectifier is a diode bridge; a stabilizer is not used in this circuit.
The charging current is controlled by a rheostat.

Important! No variable resistors, even those with a ceramic core, will withstand such a load.

Wire rheostat is necessary to counter the main problem with such a scheme - excess power is released in the form of heat. And this happens very intensively.

Of course, the efficiency of such a device tends to zero, and the service life of its components is very low (especially the rheostat). Nevertheless, the scheme exists, and it is quite workable. For emergency charging, if you don’t have ready-made equipment at hand, you can literally assemble it “on your knees.” There are also limitations - a current of more than 5 amperes is the limit for such a circuit. Therefore, you can charge a battery with a capacity of no more than 45 Ah.

DIY charger, details, diagrams - video

Quenching capacitor

The operating principle is shown in the diagram.

Thanks to the reactance of the capacitor included in the primary winding circuit, the charging current can be adjusted. The implementation consists of the same three components - power supply, regulator, indicator (if necessary). The circuit can be configured to charge one type of battery, and then the indicator will not be needed.

If we add one more element - automatic charge control, and also assemble a switch from a whole bank of capacitors - you get a professional charger that remains easy to manufacture.

The charge control and automatic shutdown circuit does not need any comments. The technology has been proven, you can see one of the options in the general diagram. The response threshold is set by variable resistor R4. When the own voltage at the battery terminals reaches the configured level, relay K2 turns off the load. An ammeter acts as an indicator, which stops showing the charge current.

The highlight of the charger– capacitor battery. The peculiarity of circuits with a quenching capacitor is that by adding or decreasing capacitance (simply connecting or removing additional elements) you can regulate the output current. By selecting 4 capacitors for currents of 1A, 2A, 4A and 8A, and switching them with ordinary switches in various combinations, you can adjust the charge current from 1 to 15 A in 1 A steps.

If you are not afraid to hold a soldering iron in your hands, you can assemble a car accessory with continuously adjustable charge current, but without the disadvantages inherent in the resistor classics.

By adjusting the degree of opening of the junction on transistor VT1 with resistor R5, you ensure smooth and very precise control of the trinistor VS1.

The circuit is reliable, easy to assemble and configure. But there is one condition that prevents such a charger from being included in the list of successful designs. The power of the transformer must provide a threefold reserve of charging current.

That is, for the upper limit of 10 A, the transformer must withstand a continuous load of 450-500 W. A practically implemented scheme will be bulky and heavy. However, if the charger is permanently installed indoors, this is not a problem.

Circuit diagram of a pulse charger for a car battery

All the shortcomings The solutions listed above can be changed to one - the complexity of the assembly. This is the essence of pulse chargers. These circuits have enviable power, heat up little, and have high efficiency. In addition, their compact size and light weight allow you to simply carry them with you in the glove compartment of your car.

The circuit design is understandable to any radio amateur who has an idea of ​​what a PWM generator is. It is assembled on the popular (and completely inexpensive) IR2153 controller. This circuit implements a classic semi-bridge inverter.

With the existing capacitors, the output power is 200 W. This is a lot, but the load can be doubled by replacing the capacitors with 470 µF capacitors. Then it will be possible to charge with a capacity of up to 200 Ah.

The assembled board turned out to be compact and fits into a box 150*40*50 mm. No forced cooling required, but ventilation holes must be provided. If you increase the power to 400 W, power switches VT1 and VT2 should be installed on radiators. They must be taken outside the building.

The power supply from the PC system unit can act as a donor.

Important! When using an AT or ATX power supply, there is a desire to convert the finished circuit into a charger. To implement such an idea, you need a factory power supply circuit.

Therefore, we will simply use the element base. A transformer, inductor and diode assembly (Schottky) as a rectifier are ideal. Everything else: transistors, capacitors and other little things are usually available to the radio amateur in all sorts of boxes. So the charger turns out to be conditionally free.

The video shows and explains how to assemble a pulse charger for a car yourself.

The cost of a factory 300-500 W pulse generator is at least $50 (in equivalent).

Conclusion:

Collect and use. Although it is wiser to keep your battery in good shape.

Compliance with the operating mode of rechargeable batteries, and in particular the charging mode, guarantees their trouble-free operation throughout their entire service life. Batteries are charged with a current, the value of which can be determined by the formula

where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.

A classic charger for a car battery consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats (see Fig. 1) and transistor current stabilizers are used as current regulators.

In both cases, these elements generate significant thermal power, which reduces the efficiency of the charger and increases the likelihood of its failure.

To regulate the charging current, you can use a store of capacitors connected in series with the primary (mains) winding of the transformer and acting as reactances that dampen excess network voltage. A simplified version of such a device is shown in Fig. 2.

In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is insignificant.

The disadvantage in Fig. 2 is the need to provide a voltage on the secondary winding of the transformer one and a half times greater than the load (~ 18÷20V).

The charger circuit, which provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.

It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.

Switches Q1 - Q4 can be used to connect various combinations of capacitors and thereby regulate the charging current.

The variable resistor R4 sets the response threshold of K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.

In Fig. Figure 4 shows another charger in which the charging current is smoothly regulated from zero to the maximum value.

The change in current in the load is achieved by adjusting the opening angle of the thyristor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5. The maximum battery charging current is 10A, set with an ammeter. The device is provided on the mains and load side with fuses F1 and F2.

A version of the charger printed circuit board (see Fig. 4), 60x75 mm in size, is shown in the following figure:

In the diagram in Fig. 4, the secondary winding of the transformer must be designed for a current three times greater than the charging current, and accordingly, the power of the transformer must also be three times greater than the power consumed by the battery.

This circumstance is a significant drawback of chargers with a current regulator thyristor (thyristor).

Note:

The rectifier bridge diodes VD1-VD4 and the thyristor VS1 must be installed on radiators.

It is possible to significantly reduce power losses in the SCR, and therefore increase the efficiency of the charger, by moving the control element from the circuit of the secondary winding of the transformer to the circuit of the primary winding. such a device is shown in Fig. 5.

In the diagram in Fig. 5 control unit is similar to that used in the previous version of the device. SCR VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is approximately 10 times less than the charging current, relatively little thermal power is released on the diodes VD1-VD4 and the thyristor VS1 and they do not require installation on radiators. In addition, the use of an SCR in the primary winding circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the current curve shape coefficient (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing a design (for example, use a variable resistor with a plastic axis).

A version of the printed circuit board of the charger in Figure 5, measuring 60x75 mm, is shown in the figure below:

Note:

The rectifier bridge diodes VD5-VD8 must be installed on radiators.

In the charger in Figure 5 there is a diode bridge VD1-VD4 type KTs402 or KTs405 with the letters A, B, C. Zener diode VD3 type KS518, KS522, KS524, or made up of two identical zener diodes with a total stabilization voltage of 16÷24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is unijunction, type KT117A, B, V, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247, etc.). The diodes are installed on radiators with an area of ​​at least 200 sq.cm, and the radiators will become very hot; a fan can be installed in the charger case for ventilation.

Thyristor regulator in the charger.

For a more complete overview of the following material, review the previous articles: And.

♣ These articles say that there are 2 half-wave rectification circuits with two secondary windings, each of which is designed for the full output voltage. The windings operate alternately: one on the positive half-wave, the other on the negative.
Two semiconductor rectifier diodes are used.

♣ Preference for this scheme:

• - the current load on each winding and each diode is two times less than on a circuit with one winding;
• - the cross-section of the wire of the two secondary windings can be half as large;
• - rectifier diodes can be selected for a lower maximum permissible current;
• - the wires of the windings best cover the magnetic circuit, the magnetic stray field is minimal;
• - complete symmetry - identity of the secondary windings;

♣ We use such a rectification circuit on a U-shaped core to make an adjustable charger using thyristors.
The two-frame design of the transformer allows this to be done in the best possible way.
In addition, the two half-windings turn out to be exactly the same.

♣ And so, ours exercise: build a device to charge a battery with voltage 6 – 12 volts and smooth regulation of charging current 0 to 5 amperes .
I have already proposed it for production, but the charging current in it is adjusted in stages.
Look in this article at how the transformer was calculated on the Ш - shaped core. These calculated data are also suitable for U-shaped transformer of the same power.

The calculated data from the article is as follows:

• - transformer power – 100 watt ;
• - core section – 12 cm square;
• - rectified voltage - 18 volts;
• - current - up to 5 amps;
• - number of turns per 1 volt – 4,2 .

Primary winding:

• - number of turns – 924 ;
• - current – 0,45 ampere;
• - wire diameter – 0,54 mm.

Secondary winding:

• - number of turns – 72 ;
• - current – 5 ampere;
• - wire diameter – 1,8 mm.

♣ We will take these calculated data as the basis for constructing a transformer based on P- shaped core.
Taking into account the recommendations of the above mentioned articles on the manufacture of a transformer using P- shaped core, we will build a rectifier for charging the battery with smoothly adjustable charging current .

The rectifier circuit is shown in the figure. It consists of a transformer TR, thyristors T1 and T2, charging current control circuits, ammeter on 5 - 8 ampere, diode bridge D4 - D7.
Thyristors T1 and T2 simultaneously act as rectifier diodes and as regulators of the charging current.

♣ Transformer Tr consists of a magnetic core and two frames with windings.
The magnetic core can be assembled from either steel P– shaped plates, and from cut ABOUT– a shaped core made of wound steel tape.
Primary winding (220 volt network - 924 turns) divided in half - 462 turns (a – a1) on one frame, 462 turns (b – b1) on another frame.
Secondary winding (at 17 volts) consists of two half-windings (72 turns each) dangles on the first (A - B) and on the second (A1 – B1) frame 72 turns each. Total 144 turn.

Third winding (c - c1 = 36 turns) + (d - d1 = 36 turns) in total 8.5 V +8.5 V = 17 volts serves to power the control circuit and consists of 72 turns of wire. There are 36 turns on one frame (c - c1) and 36 turns on the other frame (d - d1).
The primary winding is wound with a wire with a diameter of - 0.54 mm.
Each secondary half-winding is wound with a wire with a diameter 1.3 mm. rated for current 2,5 ampere
The third winding is wound with a wire diameter 0.1 - 0.3 mm, whatever happens, the current consumption here is small.

♣ Smooth regulation of the rectifier charging current is based on the property of the thyristor to go into the open state according to a pulse arriving at the control electrode. By adjusting the arrival time of the control pulse, it is possible to control the average power passing through the thyristor for each period of alternating electric current.

♣ The given thyristor control circuit works on the principle phase-pulse method.
The control circuit consists of an analogue of a thyristor assembled using transistors Tr1 and Tr2, a temporary chain consisting of a capacitor WITH and resistors R2 and Ry, zener diode D 7 and isolation diodes D1 and D2. The charging current is adjusted using a variable resistor Ry.

AC voltage 17 volts removed from the third winding, straightened by a diode bridge D3 – D6 and has the shape (point No. 1) (in circle No. 1). This is a pulsating voltage of positive polarity with a frequency 100 hertz, changing its value from 0 to 17 volts. Through a resistor R5 voltage is supplied to the zener diode D7 (D814A, D814B or any other on 8 – 12 volts). At the zener diode the voltage is limited to 10 volts and has the form ( point No. 2). Next comes the charge-discharge chain (Ry, R2, C). As the voltage increases from 0, the capacitor begins to charge WITH, through resistors Ry, and R2.
♣ Resistor resistance and capacitor capacity (Ry, R2, C) selected in such a way that the capacitor is charged during one half-cycle of the pulsating voltage. When the voltage across the capacitor reaches its maximum value (point No. 3), from resistors R3 and R4 to the control electrode of a thyristor analogue (transistors Tr1 and Tr2) voltage to open will be supplied. The thyristor analogue will open and the charge of electricity accumulated in the capacitor will be released on the resistor R1. Pulse shape across a resistor R1 shown in circle №4 .
Via isolation diodes D1 and D2 the trigger pulse is applied simultaneously to both control electrodes of the thyristors T1 and T2. The thyristor that is currently receiving a positive half-wave of alternating voltage from the secondary windings of the rectifier opens. (point No. 5).
Changing the resistance of the resistor Ry, we change the time during which the capacitor is fully charged WITH, that is, we change the turn-on time of the thyristors during the action of a half-voltage wave. IN point No. 6 shows the voltage waveform at the rectifier output.
The resistance Ry changes, the time at which the thyristors begin to open changes, and the shape of filling the half-cycle with the current changes (Figure No. 6). The half-cycle fill can be adjusted from 0 to maximum. The entire process of voltage regulation over time is shown in the figure.
♣ All voltage waveform measurements shown in points No. 1 - No. 6 carried out relative to the positive terminal of the rectifier.

Rectifier parts:
- thyristors T1 and T2 - KU 202I-N for 10 amperes. Install each thyristor on a radiator with an area 35 – 40 cm2;
- diodes D1 – D6 D226 or any on current 0.3 ampere and the voltage is higher 50 volts;
- zener diode D7 - D814A - D814G or any other on 8 – 12 volts;
- transistors Tr1 and Tr2 any low-power voltages above 50 volts.
It is necessary to select a pair of transistors with the same power, different conductivities and with equal gain factors (at least 35 - 50 ).
I tested different pairs of transistors: KT814 – KT815, KT816 – KT817; MP26 – KT308, MP113 – MP114.
All options worked well.
- Capacitor 0.15 microfarads;
- Resistor R5 set the power to 1 watt. Other power resistors 0.5 watt.
- The ammeter is designed for current 5 – 8 amperes

♣ Care must be taken when installing the transformer. I advise you to re-read the article. Especially the place where recommendations are given on the phasing of the primary and secondary windings.

You can use the primary winding phasing diagram shown below, as in the figure.

♣ An electric light bulb is connected in series to the primary winding circuit for voltage 220 volt and power 60 watt. this light bulb will serve instead of a fuse.
If the windings are phased wrong, bulb will light up.
If connections are made Right, when the transformer is connected to the network 220 volt the light bulb should flare up and go out.
There must be two voltages at the terminals of the secondary windings 17 volts, together (between A and B) 34 volts.
All installation work must be carried out in compliance with ELECTRICAL SAFETY RULES!

Compliance with the operating mode of rechargeable batteries, and in particular the charging mode, guarantees their trouble-free operation throughout their entire service life. Batteries are charged with a current, the value of which can be determined by the formula

where I is the average charging current, A., and Q is the nameplate electric capacity of the battery, Ah.

A classic charger for a car battery consists of a step-down transformer, a rectifier and a charging current regulator. Wire rheostats (see Fig. 1) and transistor current stabilizers are used as current regulators.

In both cases, these elements generate significant thermal power, which reduces the efficiency of the charger and increases the likelihood of its failure.

To regulate the charging current, you can use a store of capacitors connected in series with the primary (mains) winding of the transformer and acting as reactances that dampen excess network voltage. A simplified version of such a device is shown in Fig. 2.

In this circuit, thermal (active) power is released only on the diodes VD1-VD4 of the rectifier bridge and the transformer, so the heating of the device is insignificant.

The disadvantage in Fig. 2 is the need to provide a voltage on the secondary winding of the transformer one and a half times greater than the rated load voltage (~ 18÷20V).

The charger circuit, which provides charging of 12-volt batteries with a current of up to 15 A, and the charging current can be changed from 1 to 15 A in steps of 1 A, is shown in Fig. 3.

It is possible to automatically turn off the device when the battery is fully charged. It is not afraid of short-term short circuits in the load circuit and breaks in it.

Switches Q1 - Q4 can be used to connect various combinations of capacitors and thereby regulate the charging current.

The variable resistor R4 sets the response threshold of K2, which should operate when the voltage at the battery terminals is equal to the voltage of a fully charged battery.

In Fig. Figure 4 shows another charger in which the charging current is smoothly regulated from zero to the maximum value.

The change in current in the load is achieved by adjusting the opening angle of the thyristor VS1. The control unit is made on a unijunction transistor VT1. The value of this current is determined by the position of the variable resistor R5. The maximum battery charging current is 10A, set with an ammeter. The device is provided on the mains and load side with fuses F1 and F2.

A version of the charger printed circuit board (see Fig. 4), 60x75 mm in size, is shown in the following figure:

In the diagram in Fig. 4, the secondary winding of the transformer must be designed for a current three times greater than the charging current, and accordingly, the power of the transformer must also be three times greater than the power consumed by the battery.

This circumstance is a significant drawback of chargers with a current regulator thyristor (thyristor).

Note:

The rectifier bridge diodes VD1-VD4 and the thyristor VS1 must be installed on radiators.

It is possible to significantly reduce power losses in the SCR, and therefore increase the efficiency of the charger, by moving the control element from the circuit of the secondary winding of the transformer to the circuit of the primary winding. such a device is shown in Fig. 5.

In the diagram in Fig. 5 control unit is similar to that used in the previous version of the device. SCR VS1 is included in the diagonal of the rectifier bridge VD1 - VD4. Since the current of the primary winding of the transformer is approximately 10 times less than the charging current, relatively little thermal power is released on the diodes VD1-VD4 and the thyristor VS1 and they do not require installation on radiators. In addition, the use of an SCR in the primary winding circuit of the transformer made it possible to slightly improve the shape of the charging current curve and reduce the value of the current curve shape coefficient (which also leads to an increase in the efficiency of the charger). The disadvantage of this charger is the galvanic connection with the network of elements of the control unit, which must be taken into account when developing a design (for example, use a variable resistor with a plastic axis).

A version of the printed circuit board of the charger in Figure 5, measuring 60x75 mm, is shown in the figure below:

Note:

The rectifier bridge diodes VD5-VD8 must be installed on radiators.

In the charger in Figure 5 there is a diode bridge VD1-VD4 type KTs402 or KTs405 with the letters A, B, C. Zener diode VD3 type KS518, KS522, KS524, or made up of two identical zener diodes with a total stabilization voltage of 16÷24 volts (KS482, D808 , KS510, etc.). Transistor VT1 is unijunction, type KT117A, B, V, G. The diode bridge VD5-VD8 is made up of diodes, with a working current not less than 10 amperes(D242÷D247, etc.). The diodes are installed on radiators with an area of ​​at least 200 sq.cm, and the radiators will become very hot; a fan can be installed in the charger case for ventilation.