A fairly simple diagram of a laboratory power supply or charger, for example, for a battery. It is implemented quite simply, as can be seen from the diagram. A unique feature of the circuit is the fact that it is possible to adjust not only the voltage, but also the current, which even many commercial chargers do not have.
The circuit is built on 4 transistors, the main role is played by power transistor V4 (see diagram) in this case, 2N3055 is taken, which can easily be replaced with the domestic analogue of KT803. In general, the output power of the device and the possible maximum current will ultimately depend on this transistor, so if you need higher currents, just replace V4 with a more powerful transistor. It is clear that the power transistor must be installed on the heat sink.
Another feature of such a charger is its cost-effectiveness; all the elements will cost you 100-200 rubles. When using the 2N3055 transistor shown in the diagram or its domestic analogue KT803, the current can be accelerated to 6 A. Although the transistor itself, according to its characteristics, can handle 15 A, we do not recommend loading it to such an extent. Limiting resistor R2 with a nominal value of 1 Ohm is taken with a power of at least 5 W, for the remaining resistors 0.25 W is enough.
So far we have considered only the part of the circuit responsible for regulating voltage and current. However, it is clear that the device must be powered with something, especially with a constant voltage, so a power source is needed capable of delivering sufficient output power, with a constant voltage of up to 16 V, and a current of up to 10 A. In principle, for power supply from a 220V, 50 Hz network it was It would be enough to wind up a step-down transformer and put a bridge at its output. However, even a superficial calculation shows that a transformer is needed with a power of up to 200 W.
The core for it can be obtained from old tube TVs, but not everyone has this opportunity, and if you buy it, it will be quite expensive. Plus, using such a circuit will greatly increase the dimensions of the device itself. Therefore, to reduce the dimensions of the transformer, we will use the presented circuit of a switching power supply increasing the frequency to 50 kHz, which ultimately leads to a reduction in the dimensions of the output transformer.
The only thing is that the transformer was taken from a computer power supply designed for bipolar voltage; we understand that one polarity is enough. The ratings and types of elements are indicated in the diagram.
The circuit has short circuit protection; when it is triggered, the LED lights up, which is also very useful when working with a source. When winding an output transformer, the primary winding consists of 37 turns with a wire with a cross-section of at least 0.5 mm?, the secondary winding consists of 6 turns with a cross-section of at least 2.5 mm?, which can be wound with three cores with a wire of 0.8 mm?. The core can be taken from any computer power supply. The diodes of the rectifier bridge at the output must be high-frequency, we recommend taking KD213.
To adjust the limiting current (protection operation), it is enough to change the value of resistor R10; the lower its value, the greater the protection operation current will be and vice versa. All transistors involved in the circuit must be installed on separate heat sinks or isolated from each other.
After the first rectifier bridge, filter capacitors should be rated from 100 to 470 µF with permissible voltage values up to 400 V.
A good and interesting circuit for a high-quality charger based on the IR2153 microcircuit, a self-clocked half-bridge driver, which is often used in electronic ballasts for energy-saving lamps.
The circuit operates from an alternating voltage network of 220 Volts, its output power is about 250 watts, which is about 20 Amperes at 14 Volts of output voltage, which is quite enough to charge car batteries.
There is a surge filter at the input and protection against voltage surges and overload of the power supply. The thermistor protects the keys during the initial moment of turning on the circuit to a 220 Volt network. Then the mains voltage is rectified by a diode bridge.
The voltage passes through a limiting resistance of 47 kOhm to the generator microcircuit. Pulses of a certain frequency follow to the gates of high-voltage switches, which, when triggered, pass voltage into the network winding of the transformer. On the secondary winding we have the voltage required to charge the batteries.
The output voltage of the charger depends on the number of turns in the secondary winding and the operating frequency of the generator. But the frequency should not be raised above 80 kHz, optimally 50-60 kHz.
High voltage switches IRF740 or IRF840. By changing the capacitance of the capacitors in the input circuit, you can increase or decrease the output power of the charger; if necessary, you can reach 600 watt power. But you need 680 uF capacitors and a powerful diode bridge.
The transformer can be taken ready-made from a computer power supply. Or you can do it yourself. The primary winding contains 40 turns of wire with a diameter of 0.8 mm, then we apply a layer of insulation and wind the secondary winding - about 3.5-4 turns of fairly thick wire or use stranded wire.
After the rectifier, a filter capacitor with a capacity of no more than 2000 μF is installed in the circuit.
At the output it is necessary to install pulsed diodes with a current of at least 10-30A, ordinary ones will immediately burn out.
Attention, the charger circuit does not have short circuit protection and will immediately fail if this happens.
Another version of the charger circuit on the IR2153 chip |
The diode bridge consists of any rectifier diodes with a current of at least 2A, or more, and with a reverse voltage of 400 Volts; you can use a ready-made diode bridge from an old computer power supply; it has a reverse voltage of 600 Volts at a current of 6 A.
To ensure the required power parameters of the microcircuit, you need to take a resistance of 45-55 kOhm with a power of 2 watts; if you cannot find such, connect several low-power resistors in series.
At least once in his life, every motorist is faced with the problem of a dead battery. To prevent such a malfunction, it is necessary to properly maintain the battery and charge it on time using a charger. What is a pulse charger for a car battery, what is its operating principle and how to build the device with your own hands - read on.
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Devices designed for batteries are divided into several types - transformer and pulse. Transformer chargers for car batteries are large in weight and size, while their efficiency is significantly lower than that of other devices. As a result, the demand for such chargers has gradually decreased. Today, the pulse charger is the most popular type.
Any pulse charger for a car battery is a device designed to restore charge.
Structurally, the pulse memory consists of the following elements:
It should be noted that all the elements that make up the pulse charger are small in size when compared with transformer chargers. In principle, building such a device for charging a car battery with your own hands is not so difficult - all you need is a board that will control the transistor. Due to the fact that the design of this type of device is quite simple, and the components for manufacturing are easily accessible, pulse chargers are popular among our car enthusiasts.
As for the principle of operation, the charging procedure itself can be carried out using one of several methods:
In principle, the method of stressing constant values is the most correct from a theoretical point of view. This is because pulse chargers for car batteries can automatically control current parameters only if the voltage is constant. If you want to ensure that the charging level is as high as possible, you must also take into account the discharge parameter.
As for the DC voltage method, this option is not the most optimal. This is because when the battery is quickly charged as a result of exposure to direct current, the plates of the device can simply crumble. And it will be impossible to restore them.
The combined battery charging option is one of the most gentle. When using this method, a direct current first passes, and at the very end of the procedure it begins to change to alternating current. Further, this parameter gradually decreases to zero, thus stabilizing the voltage level. According to experts, this operating scheme allows you to prevent or minimize the likelihood of a car battery boiling. In addition, this approach also reduces the likelihood of gas release.
If you want to ensure that your car battery works properly, you need to think in advance about purchasing the necessary charger for charging.
There are certain nuances of this issue that it is advisable to take into account:
When operating a charger with your own hands, you need to consider several points. First of all, this is a sequence of actions. To begin with, it is recommended to dismantle the cover of the device and unscrew the plugs. If it is necessary to add electrolyte to the system, use distilled water to do this; this must be done before the charging procedure is carried out.
Consider several parameters:
Never charge the device for more than 24 hours, this will cause the electrolyte to simply boil and a short circuit to occur inside the circuit.
To build a charger for a car battery with your own hands, use the IR2153 circuit. This circuit differs from the production circuit of a conventional charger in that instead of two capacitors connected to the midpoint, only one electrolyte is used. It should be noted that this do-it-yourself manufacturing scheme allows you to make a charger for a car battery, designed for low power. But this problem can also be solved by using more powerful elements.
In the diagram above, 8N50 type keys are used, equipped with an insulated housing. As for diode bridges, it is better to use those that are installed in computer power supplies. If you don’t have such circuit elements, then you can try to assemble a diode bridge from four rectifier diodes (the author of the video about creating a charger for a car battery is Blaze Electronics).
Now let's move on to the power circuit of the circuit device. To build this component with your own hands, use a resistor to dampen the current; use an 18 kOhm device. After the resistor in the circuit there is a regular rectifier component installed on one diode, while the power itself will in any case be supplied to the board. Directly on the power supply there is an electrolyte, which is connected in parallel to a capacitor (this element can be either film or ceramic). The use of a capacitor is necessary in order to ensure the most optimal smoothing of pulses and noise.
As for the transformer, it can also be removed from the PC power supply. It should be noted that such a transformer is excellent for creating a battery charger, since it allows for a good output current. In addition, a transformer of this type can simultaneously provide several output voltage parameters. The diodes themselves should only be pulsed, since standard elements will not be able to function as a result of too high a frequency.
The filter does not need to be added to the circuit, but instead it is advisable to install several containers and the inductor itself. To reduce the surge level at the input to the filter element, it is advisable to add a 5 Ohm thermistor to the circuit. You can also remove this element with your own hands from the PC power supply. An important point will be the installation of an electrolytic capacitor. It must be selected based on a special ratio of 1 Watt - 1 µF, the voltage level should be 400 volts.
In general, this scheme is quite simple in design. In practice, if you approach this issue correctly, it will not be so difficult to build, even if you have no experience. And considering that you will have the material with all the necessary diagrams and symbols at hand, coping with such a task will be as easy as shelling pears. Of course, if you cannot distinguish a transformer from a resistor, then it is better to just go to the store and buy the necessary charger.
All the nuances that need to be taken into account, as well as detailed step-by-step instructions for making a pulse charger for a car battery, are given below (the author of the video is Soldering Iron TV).
Every car enthusiast has for 12 V batteries. All these old chargers work and perform their functions with varying degrees of success, but they have a common drawback - they are too large in size and weight. This is not surprising, because a 200-watt power transformer alone can weigh up to 5 kg. That’s why I decided to assemble a pulse charger for a car battery. On the Internet, or rather on the Kazus forum, I found a diagram of this charger.
Schematic diagram of the charger - click to increase size
Assembled, works great! I charged a car battery, set the charger to 14.8 V and a current of about 6 A, there is no overcharging or undercharging, when the voltage at the battery terminals reaches 14.8 V, the charging current drops automatically. I also charged the gel lead battery from the PC's uninterruptible power supply - it was fine. This charger is not afraid of short circuits at the output. But you need to make protection against polarity reversal, I did it myself on the relay.
The printed circuit board, datasheets for some radio elements and other files can be found on the forum.
In general, I advise everyone to do it, since this charger has many advantages: small size, the base of radio elements is not in short supply, you can buy a lot of things, including a ready-made pulse transformer. I bought it myself in an online store - they sent it quickly and cheaply. I’ll make a reservation right away, instead of a VD6 Schottky diode (thermal stabilization), I just put a 100 Ohm resistance, a charger, and it works great with it! I assembled and tested the circuit:Demo.
