DIY ATX charger step by step. Converting a computer power supply to a charger in detail. Charging a car battery from an old PC

A diagram of a simple modification of an ATX power supply so that it can be used as a car battery charger. After the modification, we will get a powerful power supply with voltage regulation within 0-22 V and current 0-10 A. We will need a regular ATX computer power supply made on a TL494 chip. To start an ATX type power supply that is not connected anywhere, you need to short-circuit the green and black wires for a second.

We solder out the entire rectifier part and everything that is connected to legs 1, 2 and 3 of the TL494 microcircuit. In addition, you need to disconnect pins 15 and 16 from the circuit - this is the second error amplifier that we use for the current stabilization channel. You also need to unsolder the power circuit connecting the output winding of the power transformer from the + power supply of the TL494, it will be powered only by a small “standby” converter, so as not to depend on the output voltage of the power supply (it has 5 V and 12 V outputs). It is better to reconfigure the duty room a little by selecting a voltage divider in the feedback and obtaining a voltage of 20 V for powering the PWM and 9 V for powering the measuring and control circuit. Here is a schematic diagram of the modification:

We connect the rectifier diodes to the 12-volt taps of the secondary winding of the power transformer. It is better to install more powerful diodes than those that are usually found in a 12-volt circuit. We make choke L1 from a ring from a group stabilization filter. They are different in size in some power supplies, so the winding may differ. I got 12 turns of wire with a diameter of 2 mm. We take choke L2 from the 12 Volt circuit. An output voltage and current measuring amplifier is assembled on the LM358 op-amp chip (LM2904, or any other dual low-voltage op-amp that can operate in single-pole switching and with input voltages from almost 0 V), which will provide control signals to the TL494 PWM. Resistors VR1 and VR2 set the reference voltages. Variable resistor VR1 regulates the output voltage, VR2 regulates the current. Current measuring resistor R7 is 0.05 ohm. We take power for the op-amp from the output of the “standby” 9V power supply of the computer. The load is connected to OUT+ and OUT-. Pointer instruments can be used as a voltmeter and ammeter. If current adjustment is not needed at some point, then simply turn VR2 to maximum. The operation of the stabilizer in the power supply will be like this: if, for example, 12 V 1 A is set, then if the load current is less than 1 A, the voltage will stabilize, if more, then the current. In principle, you can also rewind the output power transformer, the extra windings will be thrown out and you can install a more powerful one. At the same time, I also recommend setting the output transistors to a higher current.

At the output there is a load resistor somewhere around 250 ohm 2 W in parallel with C5. It is needed so that the power supply does not remain without load. The current through it is not taken into account; it is connected before the measuring resistor R7 (shunt). Theoretically, you can get up to 25 volts at a current of 10 A. The device can be charged by both regular 12 V batteries from a car and small lead batteries that are in a UPS.

Unlike other chargers, this advanced charger automatically maintains the battery in working condition, preventing it from discharging below a set level. The described operating cycle of the device allows it to be used for automatic training of rechargeable batteries with “charge-discharge” cycles when a discharge resistor is connected to it in parallel with the battery.

Melnichuk Vasily Vasilyevich (UR5YW), Grigoryak Sergey Anatolievich, Chernivtsi, Ukraine. When converting computer switching power supplies (hereinafter referred to as UPS) with a TL494 control chip into power supplies for powering transceivers, radio equipment and chargers for car batteries, part of the UPS accumulated , which were faulty and could not be repaired, were unstable, or had a different type of control chip. They also got around to the remaining power supplies, and after some experimentation they developed the technology for converting them into chargers (hereinafter referred to as chargers) for car batteries.

Also, after the publication of my article “PC UPS for amateur radio purposes on TL494 with voltage and current stabilization,” emails began to arrive with various questions, like what and how, where to start.

Before you begin the rework, you should carefully read the book, it provides a detailed description of the operation of the UPS with the TL494 control chip. It would also be a good idea to visit the sites and, where the issues of redesigning computer UPSs are discussed in detail. For those radio amateurs who could not find the specified book, we will try to explain “on the fingers” how to “tame” the UPS. And so about everything in order. The UPS circuit can be divided into the following main parts: - input noise suppression filter (not always installed by the manufacturer); - network rectifier; - smoothing capacitive filter; - key voltage converter with pulse power transformer (power inverter); - matching cascade; - control circuit; - circuits for generating output voltages and transmitting a feedback signal to the control circuit; - output rectifier with filter; - auxiliary converter (absent in AT type power supply units). Input circuits (Fig. 1) include: input noise suppression filter (circled in dotted line in the diagram), mains rectifier, smoothing capacitive filter. Thermistor TR1 with a negative TKS serves to limit the surge of charging current through capacitors C5 and C6. In a cold state, the resistance of the thermistor is several Ohms; the charging current through the rectifying diodes of the VDS1 bridge is limited to a level that is safe for them. As a result of current flowing through the thermistor, it heats up and its resistance decreases to fractions of an Ohm and subsequently has virtually no effect on the operation of the UPS circuit. Mains fuse FU1 is designed to protect the supply network from overload in the event of possible short circuits in the primary circuit of the UPS, but does not actually prevent the rectifier diodes and key transistors from breaking down when the output is overloaded.

The input noise suppression filter prevents the penetration of high-frequency impulse noise from the network into the UPS and from the UPS into the network, but in practice it is very common that manufacturers (aka the Chinese) do not install a filter in order to save money, although there is a place for it, and the windings Dr1 are replaced with jumpers, thereby worsening the EMC around. Thanks to Chinese savings on power filter parts, now the noise level in the city on the 160 and 80 m bands reaches 57 - 59 on the receiver's S-meter scale, this excludes the possibility of normal reception in urban conditions on these bands.

A key voltage converter with a pulse power transformer (power inverter) is built using a push-pull half-bridge circuit; the main difference lies in the circuit design solutions for constructing the basic circuits of power key transistors. The configuration of the base circuits is determined by the type of UPS starting circuit.

The output rectifier with filter is built according to approximately the same circuit (Fig. 4) with minor variations. The rectifiers are built according to a full-wave circuit with a midpoint, this ensures a symmetrical mode of magnetization reversal of the core of the pulse power transformer Tr. To reduce dynamic switching losses in the high-current channels of the + 12 and + 5 V rectifiers, diode assemblies of two Schottky diodes VD3 and VD4 are used as rectifier elements, since they have a very short switching time, and the forward voltage drop across the Schottky diode is 0.3 - 0.4 V, which, in contrast to a conventional silicon diode (the forward voltage drop across which is 0.8 - 1.2 V) at a load current of 10 - 20 A, gives a gain in UPS efficiency. All rectified voltages are smoothed by LC filters, which starts with inductance. The inductor windings for rectifiers + 5, – 5, + 12 and – 12 V are usually wound on one magnetic core.

The UPS produces the main voltages +5 V, -5 V, +12 V, -12 V, in new ATX units there is also + 3.3 V, the Power good (PG) signal, etc. We are primarily interested in the +12 voltage generation channel B, we will mainly work with him. The output voltages of the UPS are supplied to the nodes and computer unit using multi-colored wires assembled into bundles.

The six-pin connectors (not available in the ATX series UPS) are color coded as follows:

And so let’s consider the case when the battery is not yet connected. The AC mains voltage is supplied through the thermistor TR1, mains fuse FU1, and noise suppression filter to the rectifier on the diode assembly VDS1. The rectified voltage is smoothed by a filter on capacitors C6, C7, and the output of the rectifier produces a voltage of + 310 V. This voltage is supplied to a voltage converter using powerful key transistors VT3, VT4 with a pulse power transformer Tr2. Let’s immediately make a reservation that for our charger there are no resistors R26, R27, intended for slightly opening transistors VT3, VT4. The base-emitter junctions of transistors VT3, VT4 are shunted by circuits R21R22 and R24R25, respectively, as a result of which the transistors are closed, the converter does not work, and there is no output voltage. When the battery is connected to the output terminals Cl1 and Cl2, the VD12 LED lights up, voltage is supplied through the chain VD6R16 to pin No. 12 for powering the MC1 microcircuit and through the VD5R12 chain to the middle winding of the driver matching transformer Tr1 on transistors VT1, VT2. Control pulses from pins 8 and 11 of the MC1 chip are supplied to the driver VT1, VT2, and through the matching transformer Tr1 to the base circuits of the power key transistors VT3, VT4, opening them one by one. The alternating voltage from the secondary winding of the power transformer Tr2 of the voltage generation channel + 12 V is supplied to a full-wave rectifier based on an assembly of two VD11 Schottky diodes. The rectified voltage is smoothed out by the LC filter L1C16 and goes to the output terminals Cl1 and Cl2. The output of the rectifier also powers the standard fan M1, intended for cooling UPS parts, connected through a damping resistor R33 to reduce the rotation speed of the blades and fan noise. The battery is connected through terminal Cl2 to the negative output of the UPS rectifier through resistor R17. When the charging current flows from the rectifier to the battery, a voltage drop is formed across resistor R17, which is supplied to pin No. 16 of one of the comparators of the MC1 chip. When the charging current exceeds the set level (by the slider of the charging current setting resistor R4), the MC1 microcircuit increases the pause between output pulses, reducing the current to the load and thereby stabilizing the battery charging current. The R14R15 output voltage stabilization circuit is connected to pin No. 1 of the second comparator of the microcircuit MC1 is designed to limit its value (at + 14.2 – + 16 V) in the event of battery disconnection. When the output voltage increases above the set level, the MC1 microcircuit will increase the pause between the output pulses, thereby stabilizing the output voltage. Microammeter PA1, using switch SA1, is connected to different points of the UPS rectifier, used to measure the charge current and voltage on the battery. As a PWM -control regulator MC1 uses a microcircuit of type TL494 or its analogues: IR3M02 (SHARP, Japan), µA494 (FAIRCHILD, USA), KA7500 (SAMSUNG, Korea), MV3759 (FUJITSU, Japan, KR1114EU4 (Russia). We unsolder all the wires from the output connectors , leave five yellow wires (+12 V voltage generation channel) and five black wires (GND, case, ground), twist four wires of each color together and solder them, these ends will subsequently be soldered to the output terminals of the charger. Remove the switch. 115/230V and sockets for connecting cords. In place of the upper socket we install a microammeter PA1 for 150 - 200 μA from cassette recorders, for example M68501, M476/1. The original scale has been removed and a homemade scale made using the FrontDesigner_3.0 program has been installed instead; scale files can be downloaded from the magazine’s website. We cover the place of the lower socket with tin measuring 45×25 mm and drill holes for the resistor R4 and the switch for the type of measurement SA1. On the rear panel of the case we install terminals Cl 1 and Cl 2. Also, you need to pay attention to the size of the power transformer (on the board - the larger one), in our diagram (Fig. 5) this is Tr 2. The maximum power of the power supply depends on it . Its height should be at least 3 cm. There are power supplies with a transformer less than 2 cm high. The power of these is 75 W, even if it is written 200 W. In the case of converting an AT-type UPS, remove resistors R26, R27 that slightly open the transistors of the key voltage converter VT3, VT4. In case of alteration of an ATX type UPS, we remove the parts of the duty converter from the board. We solder all the parts except: noise suppression filter circuits, high-voltage rectifier VDS1, C6, C7, R18, R19, inverter on transistors VT3, VT4, their base circuits, diodes VD9, VD10, power transformer circuits Tr2, C8, C11, R28, driver on transistors VT3 or VT4, matching transformer Tr1, parts C12, R29, VD11, L1, output rectifier, according to the diagram (Fig. 5). We should end up with a board that looks something like this (Fig. 6). Even if a microcircuit like DR-B2002, DR-B2003, DR-B2005, WT7514 or SG6105D is used as a control PWM regulator, it is easier to remove them and make them from scratch on TL494. We manufacture the A1 control unit in the form of a separate board (Fig. 7). The standard diode assembly in the +12 V rectifier is designed for too low a current (6 - 12 A) - it is not advisable to use it, although it is quite acceptable for a charger. In its place, you can install a diode assembly from a 5-volt rectifier (there it is designed for a higher current, but has a reverse voltage of only 40 V). Since in some cases the reverse voltage on the diodes in the +12 V rectifier reaches a value of 60 V! , it is better to install the assembly on Schottky diodes with a current of 2×30 A and a reverse voltage of at least 100 V, for example, 63CPQ100, 60CPQ150. We replace the rectifier capacitors of a 12-volt circuit with an operating voltage of 25 V (16-volt ones often swelled). The inductance of inductor L1 should be in the range of 60 - 80 µH, we must unsolder it and measure the inductance, we often came across specimens at 35 - 38 µH, with them the UPS operates unstable, buzzes when the load current increases more than 2 A. If the inductance is too high, more 100 μH, reverse voltage breakdown of the Schottky diode assembly may occur if it was taken from a 5-volt rectifier. To improve cooling of the +12 V rectifier winding and the ring core, remove unused windings for the -5 V, -12 V and +3.3 V rectifiers. You may have to wind several turns of wire to the remaining winding until the required inductance is obtained (Fig. 8). If the key transistors VT3, VT4 were faulty, and the original ones cannot be purchased, then you can install more common transistors like MJE13009. Transistors VT3, VT4 are screwed to the radiator, usually through an insulating gasket. It is necessary to remove the transistors and, to increase thermal contact, coat the gasket on both sides with thermal conductive paste. Diodes VD1 - VD6 designed for a forward current of at least 0.1 A and a reverse voltage of at least 50 V, for example KD522, KD521, KD510. We replace all electrolytic capacitors on the +12 V bus with a voltage of 25 V. During installation, it is also necessary to take into account that resistors R17 and R32 heat up during operation of the unit, they should be placed closer to the fan and away from the wires. The VD12 LED can be glued to the PA1 microammeter from above to illuminate its scale. When setting up the charger, it is advisable to use an oscilloscope, it will allow you to see the pulses at the control points and will help save us a lot of time. We check the installation for errors. We connect the rechargeable battery (hereinafter referred to as the battery) to the output terminals. First of all, we check the presence of generation at pin No. 5 of the MS sawtooth voltage generator (Fig. 9). We check the presence of the indicated voltages according to the diagram (Fig. 5) at pins No. 2, No. 13 and No. 14 of the MC1 microcircuit. We set the resistor R14 slider to the position of maximum resistance, and check for the presence of pulses at the output of the MC1 microcircuit, at pins No. 8 and No. 11 (Fig. 10). We also check the shape of the signal between pins No. 8 and No. 11 of MS1 (Fig. 11), on the oscillogram we see a pause between pulses, the lack of symmetry of the pulses may indicate a malfunction of the basic driver circuits on transistors VT1, VT2. We check the shape of the pulses on the collectors of transistors VT1, VT2 (Fig. 12), as well as the shape of the pulses between the collectors of these transistors (Fig. 13). The lack of symmetry of the pulses may indicate a malfunction of the transistors themselves VT1, VT2, diodes VD1, VD2, the base-emitter junction of transistors VT3, VT4 or their base circuits . Sometimes a breakdown of the base-emitter junction of transistor VT3 or VT4 leads to the failure of resistors R22, R25, the diode bridge VDS1, and only then to the blowing of fuse FU1. According to the diagram, the left terminal of resistor R14 is connected to a reference voltage source of 16 V (why exactly 16 V - to compensate for losses in the wires and internal resistance of a heavily sulfated battery, although 14.2 V is also possible). By reducing the resistance of resistor R14 until the pulses disappear at pins No. 8 and No. 11 of the MS, more precisely at this moment the pause becomes equal to the half-cycle of pulse repetition. A correctly assembled, error-free device starts immediately, but for safety reasons, instead of the mains fuse, we turn on an incandescent lamp with a voltage of 220 With a power of 100 W, it will serve as a ballast resistor and in an emergency will save the UPS circuit parts from damage. We set the resistor R4 to the position of minimum resistance, turn on the charger (charger) to the network, and the incandescent lamp should flash briefly and go out. When the charger operates at a minimum load current, the radiators of transistors VT3, VT4 and the diode assembly VD11 practically do not heat up. As the resistance of resistor R4 increases, the charging current begins to increase; at a certain level, the incandescent lamp will flash. Well, that's all, you can remove the llama and put fuse FU1 in place. If you still decide to install a diode assembly from a 5-volt rectifier (we repeat that it is calculated, but the reverse voltage is only 40 V!), turn on the UPS to the network for one minute, and use resistor R4 to set the current to load 2 – 3 A, turn off the UPS. The radiator with the diode assembly should be warm, but under no circumstances hot. If it is hot, it means that this diode assembly in this UPS will not work for a long time and will definitely fail. We check the charger at the maximum current into the load; for this it is convenient to use a device connected in parallel with the battery, which will prevent the battery from being damaged by long-term charges during the setup of the charger. To increase the maximum charging current, you can slightly increase the resistance of resistor R4, but you should not exceed the maximum power for which the UPS is designed. By selecting the resistances of resistors R34 and R35, we set the measurement limits for the voltmeter and ammeter, respectively. Installation of the assembled device is shown in (Fig. 14 ). Now you can close the lid. The appearance of the charger is shown in (Fig. 15). RA1 scales for UPS charger: ▼ Shkaly-dlya-ampermetra-8-12-16-20A.7z | The 7.3 Kb file has been downloaded 194 times.

09/23/2014 Sergey (Chugunov) sent his signet. The signet has not yet been tested by assembly. ▼ TL494-Sergey-Kuznecov.7z | File 13.63 Kb downloaded 261 times.

Thank you, Sergey!

09/25/2014 PCB drawing for smd from Andrey (UR5YFE).

▼ tl494board4atx-Andrey-UR5YFE.7z | File 21.35 Kb downloaded 216 times. Thank you, Andrey! 1. V. Melnichuk. Remaking a computer power supply // Radiomir. – 2012. - No. 5, p. 181. V. Melnichuk. Computer power supply with adjustable output voltage // Electrician. – 2012. - No. 12, p. 662. A. Golovkov, V. Lyubitsky. Power supplies for system modules of the IBM PC-XT/AT type // M.: LAD i N, 1995. – 90 pp.: ill.

3. Once again about converting the power supply from PC-ATX. Forum cqham.ru

4. Source from the power supply from the PC 5. Laboratory power supply from the AT power supply 6. //www.chirio.com7. V. Melnichuk. Car battery simulator // Electric.

Vasily Melnichuk (korjavy)

Ukraine, Chernivtsi

I was once a signalman.

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datagor.ru

Car charger from computer power supply

Since the topic of charging car batteries is always relevant, I want to tell you how to make a charger from a computer power supply. The manufacturing technology is not particularly complicated, but you can always recharge the battery if necessary. Yes, and you can make the device yourself at home.

Almost any PC power supply will suit you, the power of which will be even one hundred and fifty watts. When you take this block out of the system unit, you will see a bundle of wires. You won't need all of them. Cut off all excess, leaving only the output of the positive wire with a voltage of twelve volts. Then you need to unsolder the resistor, the function of which is to lower the voltage to twelve volts. It is quite easy to detect. It passes through the circuit of the wire we need to the microcircuit through two resistors. I’m not sure exactly, but most likely this picture is observed in every power supply.

Instead of the removed resistor, solder a potentiometer; its value should be lower than the removed part. This is necessary so that the charger from the computer power supply allows you to regulate the current. Our goal is to achieve an output voltage of fifteen volts, and that the current range can vary from zero to six amperes per hour. As you understand, such indicators are simply ideal for any battery, and our simple charger can also provide them.

Go ahead. There is only one green wire on the power supply, which is used to turn it on. We must solder it to the case at minus. As for the fan, it will need to be rotated so that air is forced inward. You will also need to purchase some kind of ammeter and add it to the circuit. It will be possible to obtain information about the current strength of the current supplied to the battery.

I'll tell you exactly how I made a charger from a computer power supply. I had a new potentiometer, which was soldered instead of a resistor, mounted on the case. I attached the ammeter to the opposite side. For the clips that attach to the terminals, I used metal clothespins. They are excellent conductors and have good adhesive strength to stay on the terminals. You can also purchase special so-called crocodiles. Some people have successfully used special curtain clips for this purpose.

So, I propose to summarize the results of this undertaking, namely: what are the pros and cons of our charger from the computer power supply. The advantages are that you do not have to spend any financial resources for this purpose. I hope you can find some old computer power supply. Since these devices use pulse transformers, the entire structure will not be as bulky and heavy as in traditional standard ones. As for the shortcomings, there is only one. You will hear noise from the fan running.

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Make a charger using a computer power supply.

Turn on the power supply and make sure it is working.

Printed circuit board and layout of current limiter elements

In the factory version, the +12V inductor winding is wound with a single-core wire with a diameter of 1.3 mm. The PWM frequency is 42 kHz, with which the current penetration depth into copper is about 0.33 mm. Due to the skin effect at this frequency, the effective cross-section of the wire is no longer 1.32 mm2, but only 1 mm2, which is not enough for a current of 16A. In other words, simply increasing the diameter of the wire to obtain a larger cross-section, and therefore reducing the current density in the conductor, is ineffective for this frequency range. For example, for a wire with a diameter of 2 mm, the effective cross-section at a frequency of 40 kHz is only 1.73 mm2, and not 3.14 mm2, as expected. To effectively use copper, we wind the inductor winding with Litz wire. We will make Litz wire from 11 pieces of enameled wire 1.2 m long and 0.5 mm in diameter. The diameter of the wire can be different, the main thing is that it is less than twice the depth of current penetration into the copper - in this case, the cross-section of the wire will be used 100%. The wires are folded into a “bundle” and twisted using a drill or screwdriver, after which the bundle is threaded into a heat-shrink tube with a diameter of 2 mm and crimped using a gas torch.

If you find an error, please select a piece of text and press Ctrl+Enter.

avtomag329km.ru

Charger based on ATX power supply

A computer power supply, along with such advantages as small size and weight with a power of 250 W and above, has one significant drawback - shutdown in case of overcurrent. This drawback does not allow the power supply unit to be used as a charger for a car battery, since the charging current of the latter reaches several tens of amperes at the initial moment of time. Adding a current limiting circuit to the power supply will prevent it from shutting down even if there is a short circuit in the load circuits.

Charging a car battery occurs at a constant voltage. With this method, the charger voltage remains constant throughout the charging time. Charging the battery using this method is in some cases preferable, since it provides a faster way to bring the battery to a state that allows the engine to start. The energy reported at the initial charging stage is spent primarily on the main charging process, that is, on the restoration of the active mass of the electrodes. The strength of the charging current at the initial moment can reach 1.5C, however, for serviceable but discharged car batteries such currents will not bring harmful consequences, and the most common ATX power supplies with a power of 300 - 350 W are not able to deliver a current of more than 16 - 20A without consequences. .

The maximum (initial) charging current depends on the model of the power supply used, the minimum limit current is 0.5A. The idle voltage is regulated and can be 14...14.5V to charge the starter battery.

First, you need to modify the power supply itself by turning off its overvoltage protections +3.3V, +5V, +12V, -12V, and also removing components not used for the charger.

For the manufacture of the charger, a power supply unit of the FSP ATX-300PAF model was selected. The diagram of the secondary circuits of the power supply was drawn from the board, and despite careful checking, minor errors, unfortunately, cannot be excluded.

The figure below shows a diagram of the already modified power supply.

For convenient work with the power supply board, the latter is removed from the case, all wires of the power circuits +3.3V, +5V, +12V, -12V, GND, +5Vsb, feedback wire +3.3Vs, signal circuit PG, circuit turning on the PSON power supply, fan power +12V. Instead of a passive power factor correction choke (installed on the power supply cover), a jumper is temporarily soldered in, the ~220V power wires coming from the switch on the rear wall of the power supply are desoldered from the board, and the voltage will be supplied by the power cord.

First of all, we deactivate the PSON circuit to turn on the power supply immediately after applying mains voltage. To do this, instead of elements R49, C28, we install jumpers. We remove all elements of the switch that supplies power to the galvanic isolation transformer T2, which controls power transistors Q1, Q2 (not shown in the diagram), namely R41, R51, R58, R60, Q6, Q7, D18. On the power supply board, the collector and emitter contact pads of transistor Q6 are connected by a jumper.

After this, we supply ~220V to the power supply, make sure it is turned on and is operating normally.

Next, turn off the control of the -12V power circuit. We remove elements R22, R23, C50, D12 from the board. Diode D12 is located under the group stabilization choke L1, and its removal without dismantling the latter (altering the choke will be written below) is impossible, but this is not necessary.

We remove elements R69, R70, C27 of the PG signal circuit.

Turn on the power supply and make sure it is working.

Then the +5V overvoltage protection is turned off. To do this, pin 14 of the FSP3528 (pad R69) is connected by a jumper to the +5Vsb circuit.

A conductor is cut out on the printed circuit board connecting pin 14 to the +5V circuit (elements L2, C18, R20).

Elements L2, C17, C18, R20 are soldered.

Turn on the power supply and make sure it is working.

Disable overvoltage protection +3.3V. To do this, we cut out a conductor on the printed circuit board connecting pin 13 of the FSP3528 to the +3.3V circuit (R29, R33, C24, L5).

We remove from the power supply board the elements of the rectifier and magnetic stabilizer L9, L6, L5, BD2, D15, D25, U5, Q5, R27, R31, R28, R29, R33, VR2, C22, C25, C23, C24, as well as elements of the OOS circuit R35, R77, C26. After this, we add a divider from resistors 910 Ohm and 1.8 kOhm, which generates a voltage of 3.3V from a +5Vsb source. The midpoint of the divider is connected to pin 13 of the FSP3528, the output of the 931 Ohm resistor (a 910 Ohm resistor is suitable) is connected to the +5Vsb circuit, and the output of the 1.8 kOhm resistor is connected to ground (pin 17 of the FSP3528).

Next, without checking the functionality of the power supply, we turn off the protection along the +12V circuit. Unsolder the chip resistor R12. In the contact pad R12 connected to the pin. 15 FSP3528 drills a 0.8 mm hole. Instead of resistor R12, a resistance is added, consisting of series-connected resistors of 100 Ohm and 1.8 kOhm. One resistance pin is connected to the +5Vsb circuit, the other to the R67 circuit, pin. 15 FSP3528.

We unsolder the elements of the OOS circuit +5V R36, C47.

After removing the OOS in the +3.3V and +5V circuits, it is necessary to recalculate the value of the OOS resistor in the +12V R34 circuit. The reference voltage of the FSP3528 error amplifier is 1.25V, with the variable resistor VR1 regulator in the middle position, its resistance is 250 Ohms. When the voltage at the power supply output is +14V, we get: R34 = (Uout/Uop - 1)*(VR1+R40) = 17.85 kOhm, where Uout, V is the output voltage of the power supply, Uop, V is the reference voltage of the FSP3528 error amplifier (1.25V), VR1 – resistance of the trimming resistor, Ohm, R40 – resistance of the resistor, Ohm. We round the rating of R34 to 18 kOhm. We install it on the board.

It is advisable to replace capacitor C13 3300x16V with a capacitor 3300x25V and add the same one to the place vacated by C24 in order to divide the ripple currents between them. The positive terminal of C24 is connected through a choke (or jumper) to the +12V1 circuit, the +14V voltage is removed from the +3.3V contact pads.

Turn on the power supply, adjust VR1 and set the output voltage to +14V.

After all the changes made to the power supply unit, we move on to the limiter. The current limiter circuit is shown below.

Resistors R1, R2, R4…R6, connected in parallel, form a current-measuring shunt with a resistance of 0.01 Ohm. The current flowing in the load causes a voltage drop across it, which op-amp DA1.1 compares with the reference voltage set by trimming resistor R8. The DA2 stabilizer with an output voltage of 1.25V is used as a reference voltage source. Resistor R10 limits the maximum voltage supplied to the error amplifier to 150 mV, which means the maximum load current to 15A. The limiting current can be calculated using the formula I = Ur/0.01, where Ur, V is the voltage on the R8 engine, 0.01 Ohm is the shunt resistance. The current limiting circuit works as follows.

The output of the error amplifier DA1.1 is connected to the output of resistor R40 on the power supply board. As long as the permissible load current is less than that set by resistor R8, the voltage at the output of op-amp DA1.1 is zero. The power supply operates in normal mode, and its output voltage is determined by the expression: Uout=((R34/(VR1+R40))+1)*Uop. However, as the voltage on the measuring shunt increases due to an increase in the load current, the voltage on pin 3 of DA1.1 tends to the voltage on pin 2, which leads to an increase in the voltage at the op-amp output. The output voltage of the power supply begins to be determined by another expression: Uout=((R34/(VR1+R40))+1)*(Uop-Uosh), where Uosh, V is the voltage at the output of the error amplifier DA1.1. In other words, the output voltage of the power supply begins to decrease until the current flowing in the load becomes slightly less than the set limiting current. The equilibrium state (current limitation) can be written as follows: Ush/Rsh=(((R34/(VR1+R40))+1)*(Uop-Uosh))/Rн, where Rsh, Ohm – shunt resistance, Ush, V – drop voltage across the shunt, Rн, Ohm – load resistance.

Op-amp DA1.2 is used as a comparator, signaling using the HL1 LED that the current limiting mode is turned on.

The printed circuit board (under the “iron”) and the layout of the current limiter elements are shown in the figures below.

A few words about parts and their replacement. It makes sense to replace the electrolytic capacitors installed on the FSP power supply board with new ones. First of all, in the rectifier circuits of the standby power supply +5Vsb, these are C41 2200x10V and C45 1000x10V. Do not forget about the forcing capacitors in the base circuits of power transistors Q1 and Q2 - 2.2x50V (not shown in the diagram). If possible, it is better to replace the 220V (560x200V) rectifier capacitors with new ones of larger capacity. The output rectifier capacitors 3300x25V must be low ESR - WL or WG series, otherwise they will quickly fail. As a last resort, you can supply used capacitors of these series with a lower voltage - 16V.

The precision op-amp DA1 AD823AN “rail-to-rail” is perfect for this scheme. However, it can be replaced by an order of magnitude cheaper op-amp LM358N. In this case, the stability of the output voltage of the power supply will be somewhat worse; you will also have to select the value of resistor R34 downward, since this op-amp has a minimum output voltage instead of zero (0.04V, to be precise) 0.65V.

The maximum total power dissipation of current measuring resistors R1, R2, R4…R6 KNP-100 is 10 W. In practice, it is better to limit yourself to 5 watts - even at 50% of the maximum power, their heating exceeds 100 degrees.

Diode assemblies BD4, BD5 U20C20, if they really cost 2 pieces, there is no point in replacing them with something more powerful; they hold up well as promised by the manufacturer of the 16A power supply. But it happens that in reality only one is installed, in which case it is necessary either to limit the maximum current to 7A, or to add a second assembly.

Testing the power supply with a current of 14A showed that after only 3 minutes the temperature of the winding of inductor L1 exceeds 100 degrees. Long-term trouble-free operation in this mode is seriously questionable. Therefore, if you intend to load the power supply with a current of more than 6-7A, it is better to remake the inductor.

The finished wire is completely wound around the ring, and the manufactured inductor is installed on the board. There is no point in winding a -12V winding; the HL1 “Power” indicator does not require any stabilization.

All that remains is to install the current limiter board in the power supply housing. The easiest way is to screw it to the end of the radiator.

Let's connect the "OOS" circuit of the current regulator to resistor R40 on the power supply board. To do this, we will cut out part of the track on the printed circuit board of the power supply unit, which connects the output of resistor R40 to the “case”, and next to the contact pad R40 we will drill a 0.8 mm hole into which the wire from the regulator will be inserted.

Let's connect the power supply to the +5V current regulator, for which we solder the corresponding wire to the +5Vsb circuit on the power supply board.

The “body” of the current limiter is connected to the “GND” contact pads on the power supply board, the -14V circuit of the limiter and the +14V circuit of the power supply board go to external “crocodiles” for connection to the battery.

Indicators HL1 “Power” and HL2 “Limitation” are fixed in place of the plug installed instead of the “110V-230V” switch.

Most likely, your outlet does not have a protective ground contact. Or rather, there may be a contact, but the wire does not go to it. There is nothing to say about the garage... It is strongly recommended that at least in the garage (basement, shed) organize protective grounding. Don't ignore safety precautions. This sometimes ends extremely badly. For those who have a 220V socket that does not have a grounding contact, equip the power supply with an external screw terminal to connect it.

After all the modifications, turn on the power supply and adjust the required output voltage with trimming resistor VR1, and adjust the maximum current in the load with resistor R8 on the current limiter board.

We connect a 12V fan to the -14V, +14V circuits of the charger on the power supply board. For normal operation of the fan, two series-connected diodes are connected to the +12V or -12V wire, which will reduce the fan supply voltage by 1.5V.

We connect the passive power factor correction choke, 220V power from the switch, screw the board into the case. We fix the output cable of the charger with a nylon tie.

Screw on the lid. The charger is ready for use.

In conclusion, it is worth noting that the current limiter will work with an ATX (or AT) power supply from any manufacturer using PWM controllers TL494, KA7500, KA3511, SG6105 or the like. The difference between them will only be in the methods of bypassing the protections.

Below you can download the limiter PCB in PDF and DWG format (Autocad)

List of radioelements

Download list of elements (PDF)

Attached files:

cxem.net

Charging from the computer power supply

This review is devoted to how to make a battery charger from a power supply. The maximum voltage that a car battery charger must provide should not exceed 14.4 V. The maximum current is determined only by the capabilities of the charger itself. In normal operation of the vehicle's electrical system, this is exactly the method used.

In this article, the charging manufacturing process is simplified as much as possible. It does not require the use of transistors, homemade printed circuit boards and other additional elements.

For the modification, we use the power supply of a regular personal computer, the power of which is 230 W. The 12 V channel can consume a current not exceeding 8 A. Having opened the power supply, we found a UC 3843 microcircuit inside. This microcircuit is not connected according to the standard circuit. It simply serves as a pulse generator. The functions of the output voltage regulator are assigned to another microcircuit - TL431, which is installed on an additional board. There is also a trimming resistor on the additional board, which allows you to regulate the output voltage in a narrow range of values.

First of all, to convert the power supply into a charger, you need to remove all unnecessary things, namely:

All output wires except the yellow wire bundle (+) and the black wire bundle (0V). - 220/110 V switch with wires. Simply unsolder the wires from the board. The power supply will operate from a 220V mains voltage. This eliminates the possibility of burning out the power supply if accidentally switched to the 110V position.

Next, you need to make sure that the power supply works constantly when connected to the network. By default, the power supply only works if certain wires in the output bundle are short-circuited. It is also necessary to remove the overvoltage protection. It turns off the power supply when the output voltage rises above a certain limit. This must be done because instead of 12 V, we need to get 14.4 at the output. The built-in protective blocks perceive this as overvoltage, and the power supply automatically turns off.

It turns out that the protection action and “on-off” signals pass through one optocoupler. There are three optocouplers in the device - they are needed to connect the input and output parts of the power supply. In order for the unit to operate continuously and not be sensitive to output overvoltage, you need to close the contacts of a certain optocoupler using a jumper. Now this optocoupler will always be on. Thus, the power supply will now work constantly when connected to the network, regardless of the input voltage.

Now let’s set the voltage at the output of the power supply to 14.4V. If it is not possible to replace the output voltage using the trimming resistor located on the additional board, then you need to replace the resistor that is connected in series with the 2.7 kOhm trimmer. The setting range will thus shift upward.

Now we need to remove the transistor, which is located next to TL 431. Its purpose is unknown to us, but it can interfere with the operation of the microcircuit itself. To make the output voltage stable in idle mode, you need to add a small load at the output of the unit along the 12 V channel and the 5 V channel. For additional load on the +12V channel, a 200 Ohm resistor is suitable, and for the +5V channel - 68 Ohms. The no-load output voltage should be adjusted only after installing these resistors.

How to make a full-fledged power supply yourself with an adjustable voltage range of 2.5-24 volts is very simple; anyone can repeat it without any amateur radio experience.

We will make it from an old computer power supply, TX or ATX, it doesn’t matter, fortunately, over the years of the PC Era, every home has already accumulated a sufficient amount of old computer hardware and a power supply unit is probably also there, so the cost of homemade products will be insignificant, and for some masters it will be zero rubles .

I got this AT block for modification.

The more powerful you use the power supply, the better the result, my donor is only 250W with 10 amperes on the +12v bus, but in fact, with a load of only 4 A, it can no longer cope, the output voltage drops completely.

Look what is written on the case.

Therefore, see for yourself what kind of current you plan to receive from your regulated power supply, this potential of the donor and lay it in right away.

There are many options for modifying a standard computer power supply, but they are all based on a change in the wiring of the IC chip - TL494CN (its analogues DBL494, KA7500, IR3M02, A494, MV3759, M1114EU, MPC494C, etc.).

Fig No. 0 Pinout of the TL494CN microcircuit and analogues.

Let's look at several options execution of computer power supply circuits, perhaps one of them will be yours and dealing with the wiring will become much easier.

Scheme No. 1.

Let's get to work.
First you need to disassemble the power supply housing, unscrew the four bolts, remove the cover and look inside.

We are looking for a chip on the board from the list above, if there is none, then you can look for a modification option on the Internet for your IC.

In my case, a KA7500 chip was found on the board, which means we can begin to study the wiring and the location of unnecessary parts that need to be removed.

For ease of operation, first completely unscrew the entire board and remove it from the case.

In the photo the power connector is 220v.

Let's disconnect the power and fan, solder or cut out the output wires so that they don't interfere with our understanding of the circuit, leave only the necessary ones, one yellow (+12v), black (common) and green* (start ON) if there is one.

My AT unit does not have a green wire, so it starts immediately when plugged into the outlet. If the unit is ATX, then it must have a green wire, it must be soldered to the “common” one, and if you want to make a separate power button on the case, then just put a switch in the gap of this wire.

Now you need to look at how many volts the output large capacitors cost, if they say less than 30v, then you need to replace them with similar ones, only with an operating voltage of at least 30 volts.

In the photo there are black capacitors as a replacement option for the blue one.

This is done because our modified unit will produce not +12 volts, but up to +24 volts, and without replacement, the capacitors will simply explode during the first test at 24v, after a few minutes of operation. When selecting a new electrolyte, it is not advisable to reduce the capacity; increasing it is always recommended.

The most important part of the job.
We will remove all unnecessary parts in the IC494 harness and solder other nominal parts so that the result is a harness like this (Fig. No. 1).

Rice. No. 1 Change in the wiring of the IC 494 microcircuit (revision scheme).

We will only need these legs of the microcircuit No. 1, 2, 3, 4, 15 and 16, do not pay attention to the rest.

Rice. No. 2 Option for improvement based on the example of scheme No. 1

Explanation of symbols.

You should do something like this, we find leg No. 1 (where the dot is on the body) of the microcircuit and study what is connected to it, all circuits must be removed and disconnected. Depending on how the tracks will be located and the parts soldered in your specific modification of the board, the optimal modification option is selected; this may be desoldering and lifting one leg of the part (breaking the chain) or it will be easier to cut the track with a knife. Having decided on the action plan, we begin the remodeling process according to the revision scheme.

The photo shows replacing resistors with the required value.

In the photo - by lifting the legs of unnecessary parts, we break the chains.

Some resistors that are already soldered into the wiring diagram can be suitable without replacing them, for example, we need to put a resistor at R=2.7k connected to the “common”, but there is already R=3k connected to the “common”, this suits us quite well and we leave it there unchanged (example in Fig. No. 2, green resistors do not change).

On the picture- cut tracks and added new jumpers, write down the old values with a marker, you may need to restore everything back.

Thus, we review and redo all the circuits on the six legs of the microcircuit.

This was the most difficult point in the rework.

We make voltage and current regulators.

We take variable resistors of 22k (voltage regulator) and 330Ohm (current regulator), solder two 15cm wires to them, solder the other ends to the board according to the diagram (Fig. No. 1). Install on the front panel.

Voltage and current control.
To control we need a voltmeter (0-30v) and an ammeter (0-6A).

These devices can be purchased in Chinese online stores at the best price; my voltmeter cost me only 60 rubles with delivery. (Voltmeter: )

I used my own ammeter, from old USSR stocks.

IMPORTANT- inside the device there is a Current resistor (Current sensor), which we need according to the diagram (Fig. No. 1), therefore, if you use an ammeter, then you do not need to install an additional Current resistor; you need to install it without an ammeter. Usually a homemade RC is made, a wire D = 0.5-0.6 mm is wound around a 2-watt MLT resistance, turn to turn for the entire length, solder the ends to the resistance terminals, that's all.

Everyone will make the body of the device for themselves.
You can leave it completely metal by cutting holes for regulators and control devices. I used laminate scraps, they are easier to drill and cut.

Hi all! This device will also be very useful for charging gel batteries used, for example, in UPS (uninterruptible power supplies).

There are many schemes for such a device on the Internet, but this one caught my attention.

Briefly: The device is built according to the AT topology and, according to the operating principle, is a current stabilizer with a maximum voltage limit at 14.4 V. The charging current is 10-12 A with the appropriate T21 transformer, which is more than enough for a car battery...

The main advantage of this circuit, in my opinion, is that when the charging current exceeds the set level, the circuit acts as a current stabilizer, reducing the output voltage and charging the battery with constant current.

Upon reaching the set voltage level, the circuit goes into voltage stabilization mode, when the voltage remains constant and the current gradually drops to almost zero. Thus, the battery is not allowed to be “overcharged”...

Fig. 1 Automatic memory circuit

I also really wanted to see the charging voltage and current, despite the fact that the author of the charger circuit abandoned the indicator. Several options for a voltammeter were selected, but the choice fell on a voltammeter with an LCD indicator. The device “can” measure voltage up to 32 V and current up to 12 A.