The topic of car chargers is interesting to a lot of people. From the article you will learn how to convert a computer power supply into a full-fledged charger for car batteries. It will be a pulse charger for batteries with a capacity of up to 120 Ah, that is, charging will be quite powerful.

You don’t need to assemble anything - just the power supply is being redone. Only one component will be added to it.

A computer power supply has multiple output voltages. The main power buses are 3.3, 5 and 12 V. Thus, the device will need a 12-volt bus (yellow wire) to operate the device.

To charge car batteries, the output voltage should be in the region of 14.5-15 V, therefore, 12 V from a computer power supply is clearly not enough. Therefore, the first step is to raise the voltage on the 12-volt bus to a level of 14.5-15 V.

Then, you need to assemble an adjustable current stabilizer or limiter so that you can set the required charge current.

The charger can be said to be automatic. The battery will be charged to the set voltage with a stable current. As the charge increases, the current will decrease, and at the very end of the process it will equal zero.

Starting to manufacture the device, you need to find a suitable power supply. For these purposes, suitable blocks in which there is a TL494 PWM controller or its full-fledged analogue K7500.

When the correct power supply is found, you need to check it. To start the unit, you need to connect the green wire to any of the black wires.

If the unit starts, you need to check the voltage on all tires. If everything is in order, then you need to remove the board from the tin case.

After removing the board, it is necessary to remove all wires, except for two black ones, two green ones and goes to start the unit. It is recommended to unsolder the remaining wires with a powerful soldering iron, for example, 100 watts.

This step will require all of your attention, as this is the most important point in the whole rework. You need to find the first pin of the microcircuit (in the example, the microcircuit is 7500), and find the first resistor that is applied from this pin to the 12 V bus.

There are many resistors on the first output, but finding the right one is not difficult if you ring everything with a multimeter.

After finding the resistor (in the example it is 27 kOhm), it is necessary to unsolder only one output. In order not to get confused in the future, the resistor will be called Rx.

Now you need to find a variable resistor, say, 10 kOhm. Its power is not important. You need to connect 2 wires about 10 cm long each in this way:

One of the wires must be connected to the soldered output of the Rx resistor, and the second one must be soldered to the board in the place where the output of the Rx resistor was soldered from. Thanks to this adjustable resistor, it will be possible to set the required output voltage.

A stabilizer or charge current limiter is a very important addition that every charger should have. This node is made on the basis of an operational amplifier. Almost any "opamp" will do here. The example uses the budget LM358. There are two elements in the case of this microcircuit, but only one of them is needed.

A few words about the operation of the current limiter. This circuit uses an op amp as a comparator that compares the voltage across a low resistance resistor to a reference voltage. The latter is set using a zener diode. And the adjustable resistor now changes this voltage.

When the voltage value changes, the operational amplifier will try to smooth the voltage at the inputs and will do this by reducing or increasing the output voltage. Thus, the "opamp" will control the field effect transistor. The latter regulates the output load.

The field-effect transistor needs a powerful one, since all the charge current will pass through it. The example uses IRFZ44, although any other appropriate parameter can be used.

The transistor must be installed on a heat sink, because at high currents it will heat up well. In this example, the transistor is simply attached to the power supply case.

The printed circuit board was bred in haste but it worked out pretty well.

Now it remains to connect everything according to the picture and proceed with the installation.

The voltage is set in the region of 14.5 V. The voltage regulator can not be brought out. For control on the front panel, there is only a charge current regulator, and a voltmeter is also not needed, since the ammeter will show everything that needs to be seen when charging.

The ammeter can be taken Soviet analog or digital.

Also, a toggle switch for starting the device and output terminals was displayed on the front panel. Now the project can be considered completed.

It turned out to be an easy-to-make and inexpensive charger that you can safely repeat yourself.

Attached files:

To establish various electronic devices, a power source is required, which provides for the adjustment of not only the output voltage, but also the threshold for operating the protection against current overload. In many simple devices of a similar purpose, protection only limits the maximum load current, and the possibility of its regulation is absent or difficult. Such protection is more for the power supply itself than for its load. For the safe operation of both the source and the device connected to it, it is necessary to be able to regulate the level of operation of the current protection over a wide range. When it is triggered, the load should be automatically disconnected. The proposed device meets all of the above requirements.

Main technical characteristics
Input voltage, V......26...29
Output voltage, V......1...20
Protection actuation current, А......................0.03...2

Device diagramshown in the figure. The adjustable voltage regulator is assembled on the op amp DA1.1. An exemplary voltage is supplied to its non-inverting input (pin 3) from the engine of the variable resistor R2, the stability of which is ensured by the zener diode VD1, and to the inverting input (pin 2) - the negative feedback voltage (NFB) from the emitter of the transistor VT2 through the voltage divider R11R7 OOS maintains equality voltage at the inputs of the op-amp, compensating for the influence of destabilizing factors. By moving the slider of the variable resistor R2, you can adjust the output voltage.

The current overload protection unit is assembled on the op-amp DA1.2, which is included as a comparator that compares the voltages at the inverting and non-inverting inputs. The voltage from the load current sensor - resistor R13 is supplied to the non-inverting input through the resistor R14, the exemplary voltage is supplied to the inverting input, the stability of which is ensured by the VD2 diode, which acts as a stabistor with a stabilization voltage of about 0.6 V. While the voltage drop created by the load current across the resistor R13 , less than the exemplary one, the output voltage (pin 7) of the op amp DA1.2 is close to zero.

If the load current exceeds the allowable voltage at the output of the op-amp DA1.2 will increase almost to the supply voltage. A current will flow through the resistor R9, which will turn on the HL1 LED and open the transistor VT1. Diode VD3 opens and through the resistor R8 closes the positive feedback circuit (PIC). The open transistor VT1 connects a low-resistance resistor R12 in parallel to the zener diode VD1, as a result of which the output voltage will decrease to almost zero, since the regulating transistor VT2 will close and turn off the load. Despite the fact that the voltage at the load current sensor drops to zero, due to the action of the PIC, the load will remain disconnected, which is indicated by the luminous indicator HL1. You can turn on the load again by briefly turning off the power or by pressing the SB1 button. Diode VD4 protects the emitter junction of the transistor VT2 from reverse voltage from the capacitor C5 when the load is turned off, and also ensures the discharge of this capacitor through the resistor R10 and the output of the op-amp DA1.1.

Details.Transistor KT315A (VT1) can be replaced with KT315B-KT315E. Transistor VT2 - any of the KT827, KT829 series. The zener diode (VD1) can be any with a stabilization voltage of 3 V at a current of 3 ... 8 mA. Diodes KD521V (VD2-VD4) may be different from this series or KD522B Capacitors SZ, S4 - any film or ceramic. Oxide capacitors: C1 - K50-18 or similar imported, the rest - from the K50-35 series. The rated voltage of the capacitors must not be less than that indicated in the diagram. Fixed resistors - MLT, variables - SPZ-9a. Resistor R13 can be made up of three MLT-1 connected in parallel with a resistance of 1 ohm. Button (SB1) - P2K without fixation or similar.

Setting up the device begins with measuring the supply voltage at the terminals of the capacitor C1, which, taking into account the ripples, should be within the limits indicated in the diagram. After that, the slider of the variable resistor R2 is moved to the upper position according to the diagram and, by measuring the maximum output voltage, set it to 20 V, selecting the resistor R11. Then a load equivalent is connected to the output, for example, such as is described in the article by I. Nechaev "Universal load equivalent" in Radio, 2005, No. 1, p. 35. Measure the minimum and maximum protection operation current. To reduce the minimum level of protection operation, it is necessary to reduce the resistance of the resistor R6. To increase the maximum level of protection operation, it is necessary to reduce the resistance of the resistor R13 - the load current sensor.


P. VYSOCHANSKII, Rybnitsa, Transnistria, Moldova
"Radio" №9 2006

Chip LM358 in one package contains two independent low-power operational amplifiers with high gain and frequency compensation. Features low current consumption. A feature of this amplifier is the ability to work in circuits with a single supply from 3 to 32 volts. The output is short circuit protected.

Description of the operational amplifier LM358

The scope is as an amplifying converter, in DC voltage conversion circuits, and in all standard circuits where operational amplifiers are used, both with unipolar supply voltage and bipolar.

Specifications LM358

• Single supply: 3V to 32V.
• Dual supply: ± 1.5 to ± 16 V.
• Consumption current: 0.7 mA.
• Common mode input voltage: 3 mV.
• Differential input voltage: 32V.
• Common mode input current: 20 nA.
• Differential input current: 2nA.
• Differential voltage gain: 100 dB.
• Output voltage swing: 0 V to VCC - 1.5 V.
• Harmonic distortion factor: 0.02%.
• Maximum output slew rate: 0.6 V/µs.
• Unity gain frequency (temperature compensated): 1.0 MHz.
• Maximum power dissipation: 830 mW.
• Operating temperature range: 0…70 gr.С.

Dimensions and pin assignments LM358 (LM358N)

Analogs LM358

Below is a list of foreign and domestic analogues of the LM358 operational amplifier:

• GL358
• NE532
• OP221
• OP290
• OP295
• TA75358P
• UPC358C
• AN6561
• CA358E
• HA17904
• KR1040UD1 (domestic analogue)
• KR1053UD2 (domestic analogue)
• KR1401UD5 (domestic analogue)

Application examples (switching circuits) of the LM358 amplifier

A simple non-inverting amplifier

Comparator with hysteresis

Assume that the potential at the inverting input increases smoothly. When it reaches a level slightly above the reference (Vh -Vref), the output will go high. If the input potential then begins to slowly decrease, then the comparator output will switch to a low logic level at a value slightly below the reference (Vref - Vl). In this example, the difference between (Vh -Vref) and (Vref - Vl) will be the hysteresis value.

Wien Bridge Sine Wave Generator

The Wien bridge oscillator is a type of electronic oscillator that generates sinusoidal waves. It can generate a wide range of frequencies. The generator is based on the bridge circuit originally developed by Max Wien in 1891. The classic Wien oscillator consists of four resistors and two capacitors. The oscillator can also be thought of as a direct amplifier combined with a bandpass filter that provides positive feedback.

Differential amplifier on LM358

The purpose of this circuit is to amplify the difference between two input signals, each of which is multiplied by a certain constant value.

A differential amplifier is a well-known electrical circuit used to amplify the voltage difference of 2 signals at its inputs. In the theoretical model of a differential amplifier, the magnitude of the output signal does not depend on the magnitude of each individual input signal, but depends strictly on their difference.

The most popular two-channel operational amplifier LM358, LM358N. The operating unit belongs to the LM158, LM158A, LM258, LM258A, LM2904, LM2904V series. It has many switching circuits, analogues and datasheet.

Chips LM358 and LM358N are identical in parameters and differ only in housing.

You will be interested in datasheets and characteristics of other ICs,. They are used in conjunction with switching regulators and power supplies.

• 1. Characteristics, description
• 2. Table of characteristics.
• 3. Pinout, pinout
• 4. Analog
• 5. Typical switching circuits
• 6. Datasheet LM358 LM358N

Characteristics, description

The IC power supply can be unipolar from 3 to 32V. The operational amplifier works stably at standard 3.3V. Bipolar power supply from 1.5 to 16 Volts. At the specified temperature of 0° to 70°, the characteristics remain within the normal range. If the number of degrees goes beyond these limits, then a deviation of the parameters will appear.

Many are interested in the description in Russian of LM328N, but the datasheet is large, the main part is understandable without translation. So that you do not look for the LM358 datasheet in Russian, I compiled a table of the main parameters.

A few popular datasheets for download:

Table of characteristics.

Chips from different manufacturers may have different parameters, but everything is within the normal range. The only thing that can differ greatly is the maximum frequency for some it is 0.7 MHz, for others it is up to 1.1 MHz. There are a lot of options for using ICs, only there are about 20 of them in the documentation. Radio amateurs have expanded this number to over 70 circuits.

Typical functionality from the datasheet in Russian:

1. comparators;
2. active RC filters;
3. LED driver;
4. DC summing amplifier;
5. pulse and pulsation generator;
6. low voltage peak voltage detector;
7. bandpass active filter;
8. for amplification with a photodiode;
9. inverting and non-inverting amplifier;
10. symmetrical amplifier;
11. current stabilizer;
12. AC inverting amplifier;
13. DC differential amplifier;
14. bridge current amplifier.

Plinth, pinout

Analog

Great popularity determines the large number of analogues LM358 LM358N. Depending on the manufacturer, the characteristics may vary slightly, but everything is within tolerance. Before replacing, check the electrical specifications with the manufacturer, in case it does not suit you. The switching schemes are similar. There are more than 30 analogues, I will show the first dozen completely similar: by parameters:

1. KR1040UD1
2. KR1053UD2
3. KR1401UD5
4. GL358
5. NE532
6. OP295
7. OP290
8. OP221
9. OPA2237
10. TA75358P
11. UPC1251C
12. UPC358C

Typical switching circuits

I had to look through several specifications from different factories to find the most complete one. Most are short and uninformative. To make it as clear as possible how the LM358 and LM358N switching circuits work, familiarize yourself with the typical switching.

Datasheet LM358 LM358N

Scope of application specified by manufacturers:

1. Blu-ray players and home theaters;
2. chemical and gas sensors;
3. DVD recorders and players;
4. digital multimeters;
5. temperature sensor;
6. engine control systems;
7. oscilloscopes;
8. generators;
9. mass determination systems.

The LM358 operational amplifier has become one of the most popular types of analog electronics components. This small component can be used in a wide variety of signal amplification circuits, various oscillators, ADCs and other useful devices.

All electronic components should be divided by power, operating frequency range, supply voltage and other parameters. And the LM358 operational amplifier belongs to the middle class of devices that have received the widest scope for designing various devices: temperature control devices, analog converters, intermediate amplifiers and other useful circuits.

Description of the LM358 chip

Confirmation of the high popularity of the microcircuit are its performance, allowing you to create many different devices. The main indicative characteristics of the component should include the following.

Acceptable operating parameters: the microcircuit provides single and double-pole power supply, a wide range of supply voltages from 3 to 32 V, an acceptable output signal slew rate equal to only 0.6 V / μs. Also, the microcircuit consumes only 0.7 mA, and the bias voltage will be only 0.2 mV.

Pin Description

Chip implemented in standard DIP, SO packages and has 8 pins for connecting to power circuits and signal generation. Two of them (4, 8) are used as bipolar and unipolar power outputs, depending on the type of source or the design of the finished device. Chip inputs 2, 3 and 5, 6. Outputs 1 and 7.

The op-amp circuit has 2 cells with a standard pin topology and no correction circuits. Therefore, to implement more complex and technological devices, it will be necessary to provide additional signal conversion circuits.

The chip is popular and used in household appliances operating under normal conditions, and in special conditions with high or low ambient temperatures, high humidity and other adverse factors. For this, the integral element is available in various housings.

Microcircuit analogues

Being average in parameters, the operational amplifier LM358 has analogues according to technical characteristics. Component without letter can be replaced by OP295, OPA2237, TA75358P, UPC358C, NE532, OP04, OP221, OP290. And to replace the LM358D, you will need to use KIA358F, NE532D, TA75358CF, UPC358G. The integrated circuit is produced in a series with other components that differ only in the temperature range, designed to work in harsh environments.

There are operational amplifiers with a maximum temperature of up to 125 degrees and a minimum temperature of up to 55. Because of this, the cost of the device in various stores varies greatly.

Chip series include LM138, LM258, LM458. When selecting alternative analog elements for use in devices, it is important to consider operating temperature range. For example, if the 0 to 70 degree LM358 is not enough, the more rugged LM2409 can be used. Also, quite often, for the manufacture of various devices, not 2 cells, but 1 are required, especially if the space in the case of the finished product is limited. Some of the most suitable for use in the design of small devices are the LM321, LMV321 op amps, which also have analogues AD8541, OP191, OPA337.

Features of inclusion

Exists many wiring diagrams operational amplifier LM358, depending on the necessary requirements and the functions performed, which will be presented to them during operation:

• non-inverting amplifier;
• current-voltage converter;
• voltage-current converter;
• differential amplifier with proportional gain without adjustment;
• differential amplifier with an integrated gain control circuit;
• current control circuit;
• voltage-frequency converter.

Popular circuits on lm358

There are various devices assembled on the LM358 N that perform certain functions. At the same time, these can be all kinds of amplifiers, both UMZCH and in intermediate circuits for measuring various signals, an LM358 thermocouple amplifier, comparing circuits, analog-to-digital converters, and so on.

Non-inverting amplifier and voltage reference

These are the most popular types of connection schemes used in many devices to perform various functions. In a non-inverting amplifier circuit the output voltage will be equal to the product of the input and the proportional gain formed by the ratio of the two resistances included in the inverting circuit.

The reference voltage source circuit is very popular due to its high practical characteristics and stability in various modes. The circuit perfectly maintains the required output voltage level. It has been used to build reliable and high-quality power supplies, analog signal converters, in devices for measuring various physical quantities.

One of the highest quality sinusoidal generator circuits is device on the bridge of Wien. With the correct selection of components, the generator generates pulses in a wide frequency range with high stability. Also, the LM 358 chip is often used to implement a rectangular pulse generator of various duty cycles and durations. The signal is stable and of high quality.

Amplifier

The main application of the LM358 chip is amplifiers and various amplifying equipment. What is provided due to the features of the inclusion, the choice of other components. Such a scheme is used, for example, to implement a thermocouple amplifier.

Thermocouple amplifier on LM358

Very often in the life of a radio amateur it is required to control the temperature of any devices. For example, on the tip of the soldering iron. You can’t do this with an ordinary thermometer, especially when it is necessary to make an automatic control circuit. To do this, you can use the op amp LM 358. This microcircuit has a small thermal drift of zero, therefore it belongs to high-precision ones. Therefore, it is actively used by many developers for the manufacture of soldering stations and other devices.

The circuit allows measuring temperature in a wide range from 0 to 1000 o C with a sufficiently high accuracy up to 0.02 o C. The thermocouple is made of nickel-based alloy: chromal, alumel. The second type of metal has a lighter color and is less susceptible to magnetization, the chrome is darker, it magnetizes better. The features of the circuit include the presence of a silicon diode, which should be placed as close as possible to the thermocouple. The thermoelectric pair chromal-alumel, when heated, becomes an additional source of EMF, which can make significant adjustments to the main measurements.

A simple current regulator circuit

The circuit includes a silicon diode. The transition voltage from it is used as a source of a reference signal, which is fed through a limiting resistor to the non-inverting input of the microcircuit. To adjust the stabilization current of the circuit, an additional resistor was used, connected to the negative output of the power source, to the non-inverting input of the MS.

The circuit consists of several components:

• A resistor supporting the op-amp with a negative terminal and a resistance of 0.8 ohms.
• Resistive voltage divider, consisting of 3 resistances with a diode acting as a reference voltage source.

A resistor with a nominal value of 82 kΩ is connected to the minus of the source and the positive input of the MS. The reference voltage is formed by a divider consisting of a 2.4 kΩ resistor and a forward-connected diode. After that, the current is limited by a 380 kΩ resistor. The op-amp drives a bipolar transistor whose emitter is connected directly to the inverting input of the MS, forming a negative deep connection. Resistor R 1 acts as a measuring shunt. The reference voltage is formed using a divider consisting of a diode VD 1 and a resistor R 4.

In the presented circuit, subject to the use of a resistor R 2 with a resistance of 82 kOhm, the stabilization current in the load is 74 mA at an input voltage of 5V. And with an increase in the input voltage to 15V, the current increases to 81mA. Thus, when the voltage changes 3 times, the current changes by no more than 10%.

Charger for LM 358

Using the op amp LM 358 is often made charging device with high stabilization and output voltage control. As an example, consider a USB powered Li - ion charger. This circuit is an automatic current regulator. That is, when the voltage on the battery increases, the charging current decreases. And when the battery is fully charged, the circuit stops working, completely closing the transistor.