A 5-12 volt DC-DC boost converter is easiest to assemble using the LM2577, which provides 12V output using a 5V input signal and a maximum load current of 800 mA. M\C LM2577 is a boost forward pulse converter. It is available in three different output voltage versions: 12V, 15V and adjustable. Here is the detailed documentation.
The circuitry on it requires a minimum number of external components, and such regulators are cost-effective and easy to use. Other features include a built-in oscillator at a fixed frequency of 52 kHz that does not require any external components, a soft start mode to reduce inrush current, and a current control mode to improve input voltage tolerance and output variable load.
An adjustable chip is used here LM2577-adj. To obtain other output voltages, you need to change the value of the feedback resistor R2 and R3. The output voltage is calculated using the formula:
V Out = 1.23V (1+R2/R3)
In general, LM2577 is inexpensive, the inductor in this circuit is unified - 100 μH and the maximum current is 1 A. Thanks to the pulsed operation, no large radiators are required for cooling - so this converter circuit can be safely recommended for repetition. It is especially useful in cases where you need to get 12 volts from the USB output.
How to lower the voltage from 24 volts to 12 volts in the easiest way.
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We recently looked at a device that reduces voltage from 24 to 12 volts, and now we will study a step-up converter 12-24 V. This DC-DC converter is assembled on the basis of a specialized LM2585 microcircuit manufactured by Texas Instruments. The circuit was needed for use in a car (in particular, for charging a laptop at 20 V) and was chosen for its extreme simplicity, requiring a minimum number of external components. The switching element is a transistor, integrated inside the regulator, and is capable of withstanding a maximum current of 3A and a voltage of 60V. The switching frequency is determined by the parameters of the internal oscillator and is fixed at 100 kHz. Additional features include a soft start circuit to eliminate current surges during starting and internal current limiting. Maintaining output voltage accuracy is 4% depending on the load.
In general, the microcircuit itself has a wider range of voltages and currents. Input voltage is 4-40 V, output up to 60 volts, and the maximum current is 3 amperes. Study in more detail in the datasheet on LM2585.
The input capacitor and diode should be located close enough to the regulator to minimize inductance. The elements IC1, L1, D1, C1, C2, C5, C6 are the main parts used in the voltage converter. When installed, capacitor C3 should be located as close as possible to IC1. Choose low ESR capacitors with low DC resistance.
At maximum output power, significant heat generation is noticeable, for this reason the chip is mounted directly on the common ground of the board.
The last graph shows the ripple of the output voltage and inductive current. We see that the output voltage ripple is about 0.6 Vpp and the peak current is 2.4 A. The inductor in the design is used at 5 A DC, so it can easily handle this current and without heating the coil too much.
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3 years ago from Ales Volkov
3 answers
11 months ago by MichaelSloks
2 answers
2 years ago by Alexey Rassolov
engangs.ru
Friend, electrician...why are you toiling around with crap....asking bad questions...if you were able to reduce the voltage from 220 volts to 24x...then you will think of reducing the number of turns in the secondary winding of the transformer...before you get 12 volts output...
if you know the current in the load, you can extinguish it with additional resistance R = 12 volts/current, just don’t go wrong with the power of the resistor
Install a resistance (resistor), or better yet, a diode bridge, a filter (capacitor) and a zener diode
only alternating current comes out of the transformer, and with a bridge you will straighten it and change the frequency, and if there is nothing, rewind the transformer.
You need a 220/12 transformer, not 220/24. If it is not possible to change it, but you need to invent it from what you have, then you need to unwind the turns from the secondary winding. The secondary winding is wound with a thicker wire. You need to unwind 10 turns and measure the voltage on the secondary winding (output). Let's say it became 22 volts instead of 24 volts. This means that you have 5 turns per 1 volt. So you need to rewind 60 turns. Good luck, colleague!
Predlagaju esche odnu ideju: stavish diod. Odin. V lubom vkluchenii.
Itogo: esli u teb"a bylo 24V peremenki- poluchish slegka sglazhennyh 12V.
Simply winding back half of the secondary winding will lower not only the voltage but also the permissible current. It’s better to wind up the entire secondary and rewind it with a thicker wire with half as many turns.
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Install a step-down transformer
This power supply is not suitable for a car amplifier, because it is too weak 24W, I think your amplifier will be more powerful
Probably install the stabilizer from the lm317 theme (you can, of course, disassemble and change the resistance near the OS optocoupler, but this depends on the circuit design and is more complex than the stub)
Voltage divider across resistances. Remember Kirchoff's or Ohm's laws
Through a light bulb. By selection method.
If the current is alternating, use a transformer (wind it yourself). If it is constant, the best option is a stabilizer (Kren8b, 7812, etc.); if you need a low current, a voltage divider with 2 resistors.
the easiest way is to hook up a 12 volt consumer
you can take a 12 volt light bulb and connect the circuits in series. That is, connect + to the plus of the amplifier to - of the amplifier, connect 1 contact of the light bulb and throw the second contact to the minus of the power supply
science.ques.ru
Assemble a 20 volt stabilizer. Or a 24x220 converter and a native power supply.
increasing it to 220 and using a native charger is the most competent approach, because the native one has good stabilization within 150-240 volts, that is, you can “miss” with a voltage within almost 100 volts - and nothing will happen to the laptop, the charger will output exactly 20 volts! If you lower it to 20 volts yourself and miss by at least two volts, the consequences can be disastrous
only pulse stabilizer!! ! no more. I think it's easier to buy. There is 12-18 volts, I think yours should be too. if not, then assemble one like this. If anything, you can power it from one battery<12 v>
While you're charging the laptop, measure the voltage under load on the laptop, it can be more than 20 volts, look at the voltage on the laptop's battery. Even if the laptop battery has 20 volts, charging this battery requires 23-24 volts
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There is a standard voltage of 24 or 48 V. How to get 5 V per 3 A output current from such an input voltage? With a special DC-DC converter BD9G341AEFJ from ROHM. This chip is ideal for taking high input voltage and reducing it to 5 volt low voltage with a current of 3 A. The BD9G341AEFJ chip is a buck switching regulator with a built-in MOSFET transistor with a channel resistance of 150 milliohms. The architecture provides quick start and easy configuration of phase compensation. The operating frequency is programmable from 50 kHz to 750 kHz.
A huge plus of the board is that the 3-pin configuration is similar to the LM7805 ldo regulator, so the inverter is intended as a replacement for the old series PSU chip, which can also provide much more current and accept a higher input voltage.
If necessary, you can obtain a different output voltage by replacing several radio components in the circuit according to the datasheet.
Additionally, there are protection functions such as over-current, over-temperature and under-voltage blocking protection. Blocking and hysteresis can be set by an external resistor. PCB drawing here.
4 answers
7 months ago by kayane
2 answers
2 years ago by polkovnik_s_yuga
2 answers
8 months ago by Artem Krotov
Please name the brand of printer. It would be better to remake the power supply itself. You wave a soldering iron - we’ll figure out what needs to be done. True, this is no longer the simplest method. The simplest one is to install a KR142en8v stabilizer (15 V, 1.5 A) into the positive wire gap: 1 pin to the power supply, 2 pins to the negative wire, 3 pins. - to the amplifier. Don't forget to install the MC on the radiator. Judging by the supply voltages, you have an amplifier with an output power of no more than 8 W (not Chinese, but electric)
Install a step-down transformer
This power supply is not suitable for a car amplifier, because it is too weak 24W, I think your amplifier will be more powerful
Probably install the stabilizer from the lm317 theme (you can, of course, disassemble and change the resistance near the OS optocoupler, but this depends on the circuit design and is more complex than the stub)
Voltage divider across resistances. Remember Kirchoff's or Ohm's laws
One option is to connect it in series through a non-polar powerful capacitor to the network and select the capacitance. Another option is on the stabilizer board, next to the zener diode there should be a control resistor, perhaps it is variable. For permanent residents, the first option is not suitable. I didn't read it right away.
Through a light bulb. By selection method.
If the current is alternating, use a transformer (wind it yourself). If it is constant, the best option is a stabilizer (Kren8b, 7812, etc.); if you need a low current, a voltage divider with 2 resistors.
the easiest way is to hook up a 12 volt consumer
you can take a 12 volt light bulb and connect the circuits in series. That is, connect + to the plus of the amplifier to - of the amplifier, connect 1 contact of the light bulb and throw the second contact to the minus of the power supply
KR142EN8B is the best option. on leg No. 1 (if you look at the “face” of the rollers) - you supply 24 Volts, leg No. 2 is a general minus, leg No. 3 is the output of 12 Volts. And also, the crank must be on the radiator!
It’s easier, of course, with a crank. But you need to take into account that the bank has a current limit of 1A; if you want a reserve, it is better to use the AMS or PWM series; examples of regulators and switching circuits: [link blocked by decision of the project administration]
unwind some of the turns from the secondary winding to 12 volts, make a tap and wind the wire back. I did this because I needed all the winding
I did this. 
According to the PUE, a voltage of no higher than 50 Volts should be used to power portable lighting, and when working in particularly dangerous and confined spaces - 12 Volts (PUE 6.1.16-18). In this case, power must be supplied through transformers. This is necessary in order to prevent electric shock. And the output parameters of power supplies or batteries do not always allow you to connect gadgets or other electronics. In connection with all this, we will talk about how to reduce the DC and AC voltage to the value you need.
Let's consider typical situations when you need to lower the voltage in order to connect a device that runs on alternating current, but its supply voltage does not correspond to the usual 220 Volts. This could be various household appliances, tools, or the lamps mentioned above.
Perhaps the most common situation arises when a person buys some kind of device from foreign online stores, and upon receiving it determines that it is designed for power from 110 Volts. The first option is to rewind the transformer powering the device, but most devices operate from a switching power source, and to connect a power tool it is better to do without rewinding at all. To do this you need to use a step-down transformer. In addition, you can reduce the voltage in the network using an autotransformer or a regular transformer with taps from the primary winding at 110-127V - these were often found in Soviet televisions and other electrical appliances.
However, when using such a switch on the transformer, if a part of the winding breaks after the 110 Volt is removed (see figure below), all 220V will go to the device, and it will fail.
If we talk about ready-made devices, then you can pay attention to the STIHL autotransformers.
Important! When purchasing transformers or autotransformers, consider the rated current of its windings and the power it can withstand.
A more reliable solution to the problem would be to lower the voltage from 220 to 110V or from 220 to 127V using a transformer. There are many companies on the market that sell such products, mainly toroidal transformers. They come in metal boxes or smaller cases with a built-in socket, as well as in the form of adapters in plastic cases.
Let's summarize by listing the basic requirements for a transformer for powering 110V devices:
At the beginning of the article, we mentioned that the portable lamp should be powered from a reduced voltage. In everyday life, this issue will be especially relevant for car enthusiasts when repairing a car in the garage. The same lamps are also used as a local light source on machines (drilling, turning, sharpening and others).
In order to lower the voltage from 220 to 36V, you can use transformers of the following brand:
To reduce the voltage from 220 to 12V, you can use transformers of the following brand:
Along with the problem with high and low voltage, there is often a problem. This leads to premature failure of heating devices, lamps and other consumer devices. Let's say you need to reduce the voltage from 260 to 220V, then your choice is to use a voltage stabilizer. They come in different types, the cheapest of them is relay, essentially an autotransformer in which relays automatically switch taps from the winding.
If you need to protect a specific device, for example, a computer, use low-power models with a power of about 1000 VA (1 kVA), such as SVEN VR-L1000, its cost is 17-20 dollars. But keep in mind that their active output power is less than the indicated total power in Volt-Amps. For example, a 1 kVA model can power a load of up to 0.3-0.4 kW. Also look at the characteristics. This model can withstand up to 285 Volts, but most models are limited to 260 V.
To protect the entire house, in most cases, the RUCELF SRWII-12000-L model is sufficient; its total power is 12,000 VA, and the active power load capacity is 10,000 W. It can withstand input voltages up to 270V.
We talked in more detail about how to choose a voltage stabilizer and what types of stabilizers there are in the articles:
To power low-power devices, you can do without a transformer - with one capacitor. This circuit is called a transformerless power supply with a ballast capacitor. The principle of its operation is based on limiting the current using the reactance of the capacitance. Below you see options for its implementation.
Calculation of the capacitance of the ballast capacitor for transformerless power supply is made based on the current consumption of the load and its supply voltage.
Or according to this formula, they give approximately the same result:
By the way, the expression under the root result when calculating capacitors for powering devices from 5-20V gives approximately 220, or a value equal to Uinput.
This power source is suitable for connecting receivers, LEDs, night lights, charging small batteries and other low-power consumers.
When designing electronics, it is often necessary to reduce the voltage of the existing power supply. We will also look at several typical situations.
If you work with microcontrollers, you may have noticed that some of them operate on 3 Volts. Finding the right power supplies can be difficult, so you can use a phone charger. Then you need to lower its output from 5 to 3 Volts (3.3V). This can be done by lowering the output voltage of the power supply by replacing the zener diode in the feedback circuit. You can achieve any voltage, both high and low, by installing a zener diode of the desired rating. It can be determined by selection; in the diagram below it is highlighted with a red ellipse.
And on the board it looks like this:
On chargers of a more advanced design, an adjustable zener diode TL431 is used, then adjustment is possible by replacing the resistor or the ratio of a pair of resistors, depending on the circuit design. They are marked in red in the diagram below.
In addition to replacing the zener diode on the charger board, you can lower the voltage using a resistor and a zener diode - this is called a parametric stabilizer.
Another option is to install a chain of diodes in the open circuit. Each silicon diode will drop about 0.6-0.7 Volts. So you can lower the voltage to the desired level by dialing the required number of diodes.
It often becomes necessary to connect the device to the vehicle’s on-board network; it ranges from 12 to 14.3-14.7 Volts. To lower the DC voltage from 12 to 9 Volts, you can use a linear stabilizer like L7809, and to lower it from 12 to 5 Volts, use L7805. Or their analogues ams1117-5.0 or ams1117-9.0 or amsr-7805-nz and similar for any desired voltage. The connection diagram for such stabilizers is shown below.
To power more powerful consumers, it is convenient to use pulse converters to reduce and regulate the voltage from the power source. An example of such devices are boards based on LM2596, and in English-language online stores they can be found by searching for “DC-DC step down” or “DC-DC buck converter”.
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DC-DC converter 12>3 Volt, was created to power low-power players powered by two AA batteries. Since the players were designed to work in a car, and the car’s on-board network supplies 12 Volts, it was somehow necessary to lower the voltage to a nominal value of 3-4 Volts.
When the car engine is running, the on-board voltage rises to 14 Volts; this also needs to be taken into account.
Without thinking twice, I decided to make the simplest step-down converter, if the presented device can even be called a converter. The design of a DC-DC converter is quite simple and is based on the phenomenon of voltage decay that passes through the semiconductor diode crystal. As is known, when passing through a semiconductor diode, the DC voltage rating drops around 0.7 Volts. Therefore, to obtain the desired voltage drop, 12 cheap IN4007 series semiconductor diodes were used. These are ordinary rectifier diodes with a current of 1 Ampere and a reverse voltage of about 1000 Volts; it is advisable to use these diodes, since they are the most accessible and cheapest option. Under no circumstances should you use diodes with a Schottky barrier., the voltage drop on them is too small, therefore, they are not suitable for our purposes.
After the diodes, it is advisable to install a capacitor (electrolyte 100-470 μF) to smooth out ripples and interference.
The output voltage of our “DC-DC converter” is 3.3-3.7 Volts, the output current (maximum) is up to 1 Ampere. During operation, the diodes should overheat a little, but this is quite normal.
The entire installation can be done on a regular breadboard or in a hinged manner, but do not forget that vibrations can destroy the solder joints, so if you use a hinged version, it is advisable to glue the diodes to each other using hot-melt adhesive.
In a similar way, you can lower the voltage of the car's on-board network to 5 Volts to charge portable digital electronics - tablet computers, navigators, GPS receivers and mobile phones.
