List of elements of the regulated power supply circuit on LM317. List of circuit elements for an adjustable power supply on LM317 Switching voltage stabilizer 12 volt 10a circuit
A stabilizer is a device that, regardless of fluctuations in input characteristics, always produces a stable rated voltage at the output. And it may be needed not only for use in 220V networks, but also in 12V systems. For example, in a car, or where there is a need to use low-voltage equipment (lighting in wet areas, etc.).
For example, connecting LED backlighting in a car without a 12V voltage stabilizer chip is fraught with rapid failure of the diodes, since the car’s generator cannot provide a stable voltage in the on-board network. However, it is not necessary to buy a ready-made device - you can assemble such a circuit yourself.
Types of 12V stabilizers
There are several variations of such device circuits for 12 Volts, but the most common are linear and pulsed. How are they essentially different?
- A linear stabilizer is, in its properties, a conventional voltage divider that receives the incoming voltage on one of the arms, and changes the resistance on the other so that the desired voltage is obtained at the output. If the input/output delta is too large, the efficiency of such a device drops sharply, since a significant part of the energy is dissipated as heat - this leads to the need for cooling.
- In the pulsed version, the current enters the storage device (capacitor or inductor) in short pulses generated by a switch. When the electronic switch is closed, the accumulated energy is supplied to the load, while the voltage value remains stable. The stabilization process itself occurs by controlling the pulse duration using PWM. This version of the device has high efficiency, but produces impulse noise at the output, which is not always acceptable.
There are also autotransformer and ferroresonant devices used primarily for alternating current, but they are relatively complex.
Thanks to the availability of many electronic components and radio parts on the free market, anyone, even a novice radio amateur, can, if necessary, assemble a 12-volt voltage stabilizer at home for their needs - if only there was a circuit.
How to make a 12V stabilizer
Stabilizer on LM317
The easiest way to get a working 12-volt stabilizer at home is to purchase a ready-made microcircuit, for example, and by adding a resistor, get a ready-made voltage equalizer. This option is perfect for starting LEDs in conditions of constantly jumping voltage.
A 120-130 Ohm resistor is soldered to the finished LM317 microcircuit, namely to the middle contact, the left contact is soldered to the load output immediately behind the resistance, and voltage from the source is applied to the right contact. For a better understanding, everything is shown in the picture below.
Circuit on the LD1084 chip
The 12-volt voltage stabilizer on the LD1084 chip is also very simple. Thanks to smooth stabilization, such a device will help not only when using LEDs, but also, for example, to get rid of changes in the brightness of light in a car, which is always present due to the peculiarities of the on-board electrical system. The diagram of such a device is shown below.
Stabilizer on diodes and L7812 board
Another option for making the device at home can be a simple circuit using L7812 and Schottky diodes. In addition to these parts, you will need a couple of capacitors and soldering wires. So, a diode and capacitors are soldered to the regulatory microcircuit according to the diagram. The diode must be between the + input power and the left pin of the microcircuit. The right contact of the scarf is soldered to + load. Medium – to the minuses of the capacitors and the minus of the power source. Thus, a simple and reliable voltage stabilization circuit is obtained.
The simplest stabilizer is the KREN board
Perhaps the simplest option for making a device at home is the KREN microcircuit, more precisely KR142EN8B (this is its full name). In addition to the scarf itself, you will need a 1n4007 rectifying diode. By soldering these elements according to the diagram below, you can get the most basic, but very reliable device.
By using any of these stabilization schemes, you can quickly and inexpensively assemble a device that can provide the necessary output characteristics in 12V electrical networks.
If your knowledge of electronics does not allow you to solder and tinker, then the best option would be to purchase a factory device that is assembled in a factory, has a suitable housing, a cooling system, and is assembled from a well-selected and matched element base.
The main points regarding the manufacture of a 12 Volt stabilizer are given in this video:
Circuits of homemade pulse DC-DC voltage converters using transistors, seven examples.
Due to their high efficiency, switching voltage stabilizers have recently become increasingly widespread, although they are usually more complex and contain a larger number of elements.
Since only a small fraction of the energy supplied to the switching stabilizer is converted into thermal energy, its output transistors heat up less, therefore, by reducing the area of heat sinks, the weight and size of the device are reduced.
A noticeable disadvantage of switching stabilizers is the presence of high-frequency ripples at the output, which significantly narrows the scope of their practical use - most often switching stabilizers are used to power devices on digital microcircuits.
Step-down switching voltage stabilizer
A stabilizer with an output voltage lower than the input voltage can be assembled using three transistors (Fig. 1), two of which (VT1, VT2) form a key regulatory element, and the third (VT3) is an amplifier of the mismatch signal.
Rice. 1. Circuit of a pulse voltage stabilizer with an efficiency of 84%.
The device operates in self-oscillating mode. The positive feedback voltage from the collector of the composite transistor VT1 through capacitor C2 enters the base circuit of transistor VT2.
The comparison element and mismatch signal amplifier is a cascade based on the VTZ transistor. Its emitter is connected to the reference voltage source - zener diode VD2, and the base - to the output voltage divider R5 - R7.
In pulse stabilizers, the regulating element operates in switch mode, so the output voltage is regulated by changing the duty cycle of the switch.
Turning on/off transistor VT1 based on the signal from transistor VTZ is controlled by transistor VT2. At the moments when transistor VT1 is open, electromagnetic energy is stored in inductor L1, due to the flow of load current.
After the transistor closes, the stored energy is transferred to the load through the diode VD1. The ripples in the output voltage of the stabilizer are smoothed out by filter L1, SZ.
The characteristics of the stabilizer are entirely determined by the properties of the transistor VT1 and diode VD1, the speed of which should be maximum. With an input voltage of 24 V, output voltage of 15 V and a load current of 1 A, the measured efficiency value was 84%.
Choke L1 has 100 turns of wire with a diameter of 0.63 mm on a K26x16x12 ferrite ring with a magnetic permeability of 100. Its inductance at a bias current of 1 A is about 1 mH.
Step-down DC-DC voltage converter to +5V
The circuit of a simple switching stabilizer is shown in Fig. 2. Chokes L1 and L2 are wound on plastic frames placed in armored magnetic cores B22 made of M2000NM ferrite.
Choke L1 contains 18 turns of a harness of 7 wires PEV-1 0.35. A 0.8 mm thick gasket is inserted between the cups of its magnetic circuit.
The active resistance of the inductor winding L1 is 27 mOhm. Choke L2 has 9 turns of a harness of 10 wires PEV-1 0.35. The gap between its cups is 0.2 mm, the active resistance of the winding is 13 mOhm.
Gaskets can be made of rigid heat-resistant material - textolite, mica, electrical cardboard. The screw holding the magnetic circuit cups together must be made of non-magnetic material.
Rice. 2. Circuit of a simple key voltage stabilizer with an efficiency of 60%.
To set up the stabilizer, a load with a resistance of 5...7 Ohms and a power of 10 W is connected to its output. By selecting resistor R7, the rated output voltage is set, then the load current is increased to 3 A and, by selecting the size of capacitor C4, the generation frequency is set (approximately 18...20 kHz) at which high-frequency voltage surges on capacitor SZ are minimal.
The output voltage of the stabilizer can be increased to 8...10V by increasing the value of resistor R7 and setting a new operating frequency. In this case, the power dissipated by the VTZ transistor will also increase.
In switching stabilizer circuits, it is advisable to use electrolytic capacitors K52-1. The required capacitance value is obtained by connecting capacitors in parallel.
Main technical characteristics:
- Input voltage, V - 15...25.
- Output voltage, V - 5.
- Maximum load current, A - 4.
- Output voltage ripple at a load current of 4 A over the entire range of input voltages, mV, no more than 50.
- Efficiency, %, not lower than 60.
- Operating frequency at an input voltage of 20 b and a load current of 3A, kHz - 20.
An improved version of the +5V switching stabilizer
In comparison with the previous version of the pulse stabilizer, the new design of A. A. Mironov (Fig. 3) has improved and improved such characteristics as efficiency, stability of the output voltage, duration and nature of the transient process when exposed to a pulse load.
Rice. 3. Circuit of a pulse voltage stabilizer.
It turned out that when the prototype operates (Fig. 2), a so-called through current occurs through the composite switch transistor. This current appears at those moments when, based on a signal from the comparison node, the key transistor opens, but the switching diode has not yet had time to close. The presence of such a current causes additional heating losses of the transistor and diode and reduces the efficiency of the device.
Another drawback is the significant ripple of the output voltage at a load current close to the limit. To combat ripples, an additional output LC filter (L2, C5) was introduced into the stabilizer (Fig. 2).
The instability of the output voltage from changes in load current can only be reduced by reducing the active resistance of inductor L2.
Improving the dynamics of the transient process (in particular, reducing its duration) is associated with the need to reduce the inductance of the inductor, but this will inevitably increase the output voltage ripple.
Therefore, it turned out to be advisable to eliminate this output filter, and increase the capacitance of capacitor C2 by 5... 10 times (by parallel connecting several capacitors into a battery).
Circuit R2, C2 in the original stabilizer (Fig. 6.2) practically does not change the duration of the output current decline, so it can be removed (short circuit resistor R2), and the resistance of resistor R3 can be increased to 820 Ohms.
But then, when the input voltage increases from 15 6 to 25 6, the current flowing through resistor R3 (in the original device) will increase by 1.7 times, and the power dissipation will increase by 3 times (up to 0.7 W).
By connecting the lower output of resistor R3 (in the diagram of the modified stabilizer this is resistor R2) to the positive terminal of capacitor C2, this effect can be weakened, but at the same time the resistance of R2 (Fig. 3) should be reduced to 620 Ohms.
One of the effective ways to combat through current is to increase the rise time of the current through the opened key transistor.
Then, when the transistor is fully opened, the current through the diode VD1 will decrease to almost zero. This can be achieved if the shape of the current through the key transistor is close to triangular.
As calculations show, to obtain such a current shape, the inductance of storage choke L1 should not exceed 30 μH.
Another way is to use a faster switching diode VD1, for example, KD219B (with a Schottky barrier). Such diodes have higher operating speed and lower voltage drop at the same value of forward current compared to conventional silicon high-frequency diodes. Capacitor C2 type K52-1.
Improved device parameters can also be obtained by changing the operating mode of the key transistor. The peculiarity of the operation of the powerful transistor VTZ in the original and improved stabilizers is that it operates in the active mode, and not in the saturated mode, and therefore has a high current transfer coefficient and closes quickly.
However, due to the increased voltage across it in the open state, the power dissipation is 1.5...2 times higher than the minimum achievable value.
You can reduce the voltage on the key transistor by applying a positive (relative to the positive power wire) bias voltage to the emitter of transistor VT2 (see Fig. 3).
The required value of the bias voltage is selected when setting up the stabilizer. If it is powered by a rectifier connected to a mains transformer, then a separate winding on the transformer can be provided to obtain the bias voltage. However, the bias voltage will change along with the network voltage.
Converter circuit with stable bias voltage
To obtain a stable bias voltage, the stabilizer must be modified (Fig. 4), and the inductor must be turned into transformer T1 by winding an additional winding II. When the key transistor is closed and the diode VD1 is open, the voltage on winding I is determined from the expression: U1=UBыx + U VD1.
Since the voltage at the output and at the diode changes slightly at this time, regardless of the value of the input voltage on winding II, the voltage is almost stable. After rectification, it is supplied to the emitter of transistor VT2 (and VT1).
Rice. 4. Scheme of a modified pulse voltage stabilizer.
Heating losses decreased in the first version of the modified stabilizer by 14.7%, and in the second - by 24.2%, which allows them to operate at a load current of up to 4 A without installing a key transistor on the heat sink.
In the stabilizer of option 1 (Fig. 3), the inductor L1 contains 11 turns, wound with a bundle of eight PEV-1 0.35 wires. The winding is placed in an armored magnetic core B22 made of 2000NM ferrite.
Between the cups you need to lay a 0.25 mm thick textolite gasket. In the stabilizer of option 2 (Fig. 4), transformer T1 is formed by winding two turns of PEV-1 0.35 wire over the inductor coil L1.
Instead of a germanium diode D310, you can use a silicon diode, for example, KD212A or KD212B, and the number of turns of winding II must be increased to three.
DC voltage stabilizer with PWM
A stabilizer with pulse-width control (Fig. 5) is close in principle to the stabilizer described in, but, unlike it, it has two feedback circuits connected in such a way that the key element closes when the load voltage exceeds or the current increases , consumed by the load.
When power is applied to the input of the device, the current flowing through resistor R3 opens the key element formed by transistors VT.1, VT2, as a result of which a current appears in the circuit transistor VT1 - inductor L1 - load - resistor R9. Capacitor C4 is charged and energy is accumulated in inductor L1.
If the load resistance is large enough, then the voltage across it reaches 12 B, and the zener diode VD4 opens. This leads to the opening of transistors VT5, VTZ and the closing of the key element, and thanks to the presence of the diode VD3, inductor L1 transfers the accumulated energy to the load.
Rice. 5. Stabilizer circuit with pulse-width control with efficiency up to 89%.
Stabilizer technical characteristics:
- Input voltage - 15...25 V.
- Output voltage - 12 V.
- Rated loading current is 1 A.
- Output voltage ripple at a load current of 1 A is 0.2 V. Efficiency (at UBX = 18 6, IN = 1 A) is 89%.
- Current consumption at UBX=18 V in load circuit closure mode is 0.4 A.
- Output short circuit current (at UBX =18 6) - 2.5 A.
As the current through the inductor decreases and capacitor C4 discharges, the voltage across the load will also decrease, which will lead to the closing of transistors VT5, VTZ and the opening of the key element. Next, the stabilizer operation process is repeated.
Capacitor C3, which reduces the frequency of the oscillatory process, increases the efficiency of the stabilizer.
With low load resistance, the oscillatory process in the stabilizer occurs differently. An increase in load current leads to an increase in the voltage drop across resistor R9, opening of transistor VT4 and closing of the key element.
In all operating modes of the stabilizer, the current it consumes is less than the load current. Transistor VT1 should be installed on a heat sink measuring 40x25 mm.
Choke L1 consists of 20 turns of a bundle of three PEV-2 0.47 wires, placed in a cup magnetic core B22 made of 1500NMZ ferrite. The magnetic core has a gap 0.5 mm thick made of non-magnetic material.
The stabilizer can be easily adjusted to a different output voltage and load current. The output voltage is set by choosing the type of zener diode VD4, and the maximum load current is set by a proportional change in the resistance of resistor R9 or by supplying a small current to the base of transistor VT4 from a separate parametric stabilizer through a variable resistor.
To reduce the level of output voltage ripple, it is advisable to use an LC filter similar to that used in the circuit in Fig. 2.
Switching voltage stabilizer with conversion efficiency 69...72%
The switching voltage stabilizer (Fig. 6) consists of a trigger unit (R3, VD1, VT1, VD2), a reference voltage source and a comparison device (DD1.1, R1), a direct current amplifier (VT2, DD1.2, VT5), a transistor switch (VTZ, VT4), an inductive energy storage device with a switching diode (VD3, L2) and filters - input (L1, C1, C2) and output (C4, C5, L3, C6). The switching frequency of the inductive energy storage device, depending on the load current, is in the range of 1.3...48 kHz.
Rice. 6. Circuit of a pulse voltage stabilizer with a conversion efficiency of 69...72%.
All inductors L1 - L3 are identical and are wound in B20 armored magnetic cores made of 2000NM ferrite with a gap between the cups of about 0.2 mm.
The rated output voltage is 5 V when the input voltage changes from 8 to 60 b and the conversion efficiency is 69...72%. Stabilization coefficient - 500.
The amplitude of the output voltage ripple at a load current of 0.7 A is no more than 5 mV. Output impedance - 20 mOhm. The maximum load current (without heat sinks for transistor VT4 and diode VD3) is 2 A.
Switching voltage stabilizer 12V
The switching voltage stabilizer (Fig. 6.7) with an input voltage of 20...25 V provides a stable output voltage of 12 V at a load current of 1.2 A.
Output ripple up to 2 mV. Due to its high efficiency, the device does not use heat sinks. The inductance of the inductor L1 is 470 μH.
Rice. 7. Circuit of a pulse voltage stabilizer with low ripple.
Transistor analogues: VS547 - KT3102A] VS548V - KT3102V. Approximate analogues of transistors BC807 - KT3107; BD244 - KT816.
Powerful power supply 14 volts 20 amperes on KT819 transistors | RadioDom - Website for radio amateurs. DIY voltage stabilizer 12 volt 10 ampere
Stabilized power supply 12V/30A - Automotive DIY
We present a powerful stabilized 12 V power supply. It is built on an LM7812 stabilizer chip and TIP2955 transistors, which provides a current of up to 30 A. Each transistor can provide a current of up to 5 A, respectively, 6 transistors will provide a current of up to 30 A. You can change the number of transistors and get desired current value. The microcircuit produces a current of about 800 mA.
A 1 A fuse is installed at its output to protect against large transient currents. It is necessary to ensure good heat dissipation from transistors and the microcircuit. When the current through the load is large, the power dissipated by each transistor also increases, so that excess heat can cause the transistor to fail.
In this case, a very large radiator or fan will be required for cooling. 100 ohm resistors are used for stability and to prevent saturation as... the gain factors have some scatter for the same type of transistors. The bridge diodes are designed for at least 100 A.
Notes
The most expensive element of the entire design is perhaps the input transformer. Instead, it is possible to use two series-connected car batteries. The voltage at the input of the stabilizer must be a few volts higher than the required output (12V) so that it can maintain a stable output. If a transformer is used, the diodes must be able to withstand a fairly large peak forward current, typically 100A or more.
No more than 1 A will pass through LM 7812, the rest is provided by transistors. Since the circuit is designed for a load of up to 30 A, six transistors are connected in parallel. The power dissipated by each of them is 1/6 of the total load, but it is still necessary to ensure sufficient heat dissipation. Maximum load current will result in maximum dissipation and will require a large heatsink.
To effectively remove heat from the radiator, it may be a good idea to use a fan or water-cooled radiator. If the power supply is loaded to its maximum load, and the power transistors fail, then all the current will pass through the chip, which will lead to a catastrophic result. To prevent breakdown of the microcircuit, there is a 1 A fuse at its output. The 400 MOhm load is for testing only and is not included in the final circuit.
Computations
This diagram is an excellent demonstration of Kirchhoff's laws. The sum of currents entering a node must be equal to the sum of currents leaving this node, and the sum of the voltage drops on all branches of any closed circuit circuit must be equal to zero. In our circuit, the input voltage is 24 volts, of which 4V drops across R7 and 20 V at the input of LM 7812, i.e. 24 -4 -20 = 0. At the output, the total load current is 30A, the regulator supplies 0.866A and 4.855A each 6 transistors: 30 = 6 * 4.855 + 0.866.
The base current is about 138 mA per transistor, to get a collector current of about 4.86A, the DC gain for each transistor must be at least 35.
TIP2955 meets these requirements. The voltage drop across R7 = 100 Ohm at maximum load will be 4V. The power dissipated on it is calculated by the formula P= (4 * 4) / 100, i.e. 0.16 W. It is desirable that this resistor be 0.5 W.
The input current of the microcircuit comes through a resistor in the emitter circuit and the B-E junction of the transistors. Let's apply Kirchhoff's laws once again. The input current of the regulator consists of a current of 871 mA flowing through the base circuit and 40.3 mA through R = 100 Ohm. 871.18 = 40.3 + 830. 88. The input current of the stabilizer must always be greater than the output current. We can see that it only consumes about 5 mA and should barely get warm.
Testing and Bugs
During the first test, there is no need to connect the load. First, we measure the output voltage with a voltmeter; it should be 12 volts, or a value not very different. Then we connect a resistance of about 100 Ohms, 3 W as a load. The voltmeter readings should not change. If you do not see 12 V, then, after turning off the power, you should check the correctness of installation and the quality of soldering.
One of the readers received 35 V at the output, instead of the stabilized 12 V. This was caused by a short circuit in the power transistor. If there is a short circuit in any of the transistors, you will have to unsolder all 6 to check the collector-emitter transitions with a multimeter.
A charger for car batteries is an irreplaceable thing that every car enthusiast should have, no matter how good the battery is, since it can fail at the most inconvenient moment.
We have repeatedly reviewed the designs of numerous chargers on the pages of the site. The charger, in theory, is nothing more than a power supply with current and voltage stabilization. It works simply - we know that the voltage of a charged car battery is about 14-14.4 Volts, you need to set exactly this voltage on the charger, then set the desired charging current, in the case of acid starter batteries this is a tenth of the battery capacity, for example - a 60 A battery /h, we charge it with a current of 6 Amps.
As a result, as the battery charges, the current will drop and eventually reach zero - as soon as the battery is charged. This system is used in all chargers; the charging process does not need to be constantly monitored, since all output parameters of the charger are stable and do not depend on changes in mains voltage.
Based on this, it becomes clear that to build a charger you need to have three nodes.
1) Step-down transformer or switching power supply plus rectifier2) Current stabilizer3) Voltage stabilizer
With the help of the latter, the voltage threshold is set to which the battery will be charged, and today we will talk specifically about the voltage stabilizer.
The system is incredibly simple, only 2 active components, minimal costs, and assembly will take no more than 10 minutes if all components are available.
What we have. a field-effect transistor as a power element, an adjustable zener diode that sets the stabilization voltage, this voltage can be set manually using a variable (or better yet, a tuning, multi-turn) 3.3 kOhm resistor. A voltage of up to 50 Volts can be supplied to the input of the stabilizer, and at the output we already obtain a stable voltage of the required rating.
The minimum possible voltage is 3 Volts (depending on the field-effect transistor), the fact is that in order for the field-effect transistor to open at its gate, you need to have a voltage above 3 volts (in some cases more) except for field-effect transistors that are designed to operate in circuits with a logical control level.
The stabilizer can switch currents up to 10 Amps depending on conditions, in particular on the type of field-effect transistor, the presence of a radiator and active cooling.
The TL431 adjustable zener diode is a popular item and can be found in any computer power supply; it is used to control the output voltage and is located next to the optocoupler.
I disassembled one of my chargers to show what the stabilizer looks like, there is no need to judge strictly the quality of installation, a friend’s charger has been working for 2 years without any complaints, I made it in a hurry and didn’t bother too much.
And I also want to note one point: if you decide to change the oil in your car, I would like to recommend the excellent trading house “Maslyonka”, which deals specifically in this direction. Come in and choose industrial oil, there are no fakes here...
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The circuit of a small but powerful power supply of 14 volts and up to 10 ampere load is described; it can be used as a charger, or as a simple laboratory power supply for a novice radio amateur. To do this, you will have to equip it with a digital voltmeter and ammeter for convenience, since they are now easy to get at any amateur radio store. Capacitor C1 is of very large capacity - from 200,000 μF, for smoothing pulses. Resistor R1 and Zener diode VD5 form a 10-volt parametric DC voltage stabilizer. This voltage, the ripples of which are additionally smoothed out by capacitor C2, is supplied to pin 8 of the KR142EN5A stabilizer with a fixed output voltage of 5 volts. From the output (pin 2) of the stabilizer, a voltage of about 15 volts is supplied to the base of the emitter follower, composed of three powerful silicon transistors VT1 - VT3 connected in parallel.  By selecting a VD5 zener diode with a lower stabilization voltage, you can set the voltage at the source output from 8 to 12 volts. Using the VD6 diode and the SZ capacitor, a single semi-periodic AC voltage rectifier winding with terminals 14 - 16 of the network transformer is assembled, which powers the HL1 LED - an indicator that the device is connected to the network. Resistor R2 limits the current flowing through the LED. Network transformer T1 - unified, brand TN61. It can be replaced with a transformer with two secondary windings, each of which provides an alternating voltage of 14...16 volts with a load current of up to 20 amperes. All radio components are domestic and may have foreign analogues: FU1 - fuse designed to operate from 5 amperes SA1 - switch for 220 volts 10 amperes T1 - Mains transformer with a secondary winding of 15 -15 volts DA1 - KR142EN5AVT1 - KT819BVT2 - KT819BVT3 - KT819BVD1 - D305VD2 - D305VD3 - D305VD4 - D305VD5 - KS210B - zener diodeVD 6 - KD103AS1 - 200000 uF x 20 volts C2 - 1000 uF x 15 volts C3 - 10 uF x 15 voltHL1 - AL307BR1 - 300 OhmR2 - 680 Ohm - selectable Similar articles: |
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The source produces an adjustable DC voltage from 5 to 14 volts, with a current of up to 15 amperes. Designed for power supply both in the laboratory and at home for developing your own homemade devices, setting up voltage converters, tape recorders, radios, powerful automobile UZMCHs, and simply an indispensable thing for starting an amateur radio business.  It is quite possible to use a domestic transformer from TS-180 TVs. We remove all the factory secondary windings except the mains winding, and on top of each frame we wind 57 turns of copper wire with a diameter no thinner than 1.2 mm, thereby obtaining the voltage we need 17-19 volts. Stabilizer voltage is assembled on a domestic microcircuit KR142EN5A, designed for 5 volts. Resistor R2 varies in the range of 0...9 volts, and thereby regulates the voltage at output D1 in the range of 5...14 volts. The power supply is equipped in a small case with dimensions of 28x16x21 cm. The rear part is an aluminum finned heat sink for VT1 and VT2. For reliability during long-term operation at full power, the total heat sink area should be more than 380 sq.cm. Microcircuit D1 is installed on a sheet copper heat sink. Technical data of the device: Input - 220 volts Output - adjustable from 5 to 14 volts Maximum load current - no more than 15 amperes Efficiency - 85% Radio components of the device are domestic and can be replaced with similar foreign ones: D1 - KR142EN5A - foreign analogue LM7805T1 - TS-180VD1 - D243 - there is a typo on the diagram (written KD243) VD2 - D243VD3 - D243VD4 - D243VD5 - zener diode KS210B - foreign analogue - 1N1985AC1 - 4000 uF x 25 volts...more is possible if case dimensions allow C2 - 4000 uF x 25 volts C3 - 1000 uF x 15 volts VT1 - KT819B - silicon transistor VT2 - KT819BR1 - 300 Ohm - 0.5 W - constant resistor R2 - 2 kOhm - variable resistor. |
At 1-2 amperes, but it is already problematic to obtain a higher current. Here we will describe a high-power power supply with a standard voltage of 13.8 (12) volts. The circuit is 10 amperes, but this value can be increased further. There is nothing special in the circuit of the proposed power supply, except that, as tests have shown, it is capable of delivering a current of up to 20 Amps for a short time or 10A continuously. To further increase power, use a larger transformer, diode bridge rectifier, higher capacitor capacity and number of transistors. For convenience, the power supply circuit is shown in several figures. The transistors do not have to be exactly the ones in the circuit. We used 2N3771 (50V, 20A, 200W) because there are many of them in stock.
The voltage regulator operates within small limits, from 11 V to 13.8 at full load. With an open circuit voltage value of 13.8V (nominal battery voltage is 12V), the output will drop to 13.5 for about 1.5A, and 12.8V for about 13A.
The output transistors are connected in parallel, with 0.1 ohm 5 watt wirewound resistors in the emitter circuits. The more transistors you use, the higher the peak current that can be drawn from the circuit.
The LEDs will show incorrect polarity, and the relay will block the power supply stabilizer from the rectifiers. High power thyristor BT152-400 opens when overvoltage occurs and takes on the current, causing the fuse to blow. Don't think that the triac will burn out first, the BT152-400R can withstand up to 200A for 10ms. This power source can also serve as a charger for car batteries, but to avoid incidents, no need to leave the battery connected for a long time unattended.
Voltage stabilizers are an essential part of all electronic circuits; they provide continuous, stable power to system components, ensuring the stability of its parameters and protection in case of faults in the circuit or in the primary voltage source. 12 volts DC voltage is the most popular, used to power many devices used separately or built into various structures.
Classic stabilizer
Most power systems are built using a 12-volt linear voltage regulator circuit, which can have several options:
- Parallel – adjustment using a parallel control element;
- Sequential – activation of the adjustment element in series with the load.
The simplest voltage stabilizer is a zener diode, also called a Zener diode - this is a diode that operates constantly in breakdown mode. The voltage at which breakdown occurs is the stabilization voltage, the main parameter of the zener diode. When the load is connected in parallel, an elementary voltage stabilizer is obtained, approximately equal to the stabilization voltage.
The ballast resistance R determines the zener diode current specified in the specification. This solution is characterized by a low stabilization coefficient, temperature dependence and is used at low load currents to power individual components of the main circuit. It is possible to significantly increase the output current if a powerful transistor is installed in series with the load.
In this circuit, the transistor is connected in series with the load as an emitter follower, all the current flows through its junction. The level on the base is controlled by a zener diode: as the current at the output increases, more voltage is applied to the base, the conductivity of the transistor increases, and the output voltage is restored. The power of such a stabilizer is determined by the type of transistor and can reach tens of watts.
It is important to note! In this form, the stabilizer is not protected from overload and short circuit, in which it instantly fails. For practical use, the circuit becomes significantly more complicated: current limiting elements and various protective functions are introduced.
Integral stabilizer
A 12 volt voltage stabilizer can easily be implemented by using a specialized integrated linear stabilizer from the 78XX series with a fixed output voltage. For an output voltage of 12 volts, 7812 microcircuits are produced; from different manufacturers they are called LM7812, L7812, K7812, etc.
The domestic analogue is KR142EN8B. Manufactured in TO – 220, TO – 3, D2PAK packages with three terminals. These microcircuits can be found in power supplies of any equipment; they have practically replaced stabilizers based on discrete elements.
Main characteristics of the stabilizer in a widely used housingTO – 220:
- Output stabilized voltage – from 11.5 to 12.5 V;
- Input voltage – up to 30 V;
- Output current – up to 1A;
- Built-in overload and short circuit protection.
The input voltage must exceed the output voltage (12 volts) by at least 3 volts over the entire output current range. For an output current of up to 100 mA, a variant of the –78L12 microcircuit is available. A typical connection circuit allows you to assemble a reliable 12-volt voltage stabilizer with your own hands with characteristics suitable for many tasks.
The circuit has stabilization parameters similar to the used microcircuit.
In some cases, it is advisable to use 1083/84/85 series microcircuits. These are integrated stabilizers with an output current of 3.5 and 7.5 amperes. The devices are of the Low Dropout type - for them the difference between the input and output voltage can be 1 volt. The connection circuit is fully consistent with 7812 type microcircuits.
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