Switching voltage converter dc. Review of adjustable voltage converters (stabilizers, DC-DC converters)
Pulse DC-DC converters are designed for both increasing and decreasing voltage. With their help, you can convert 5 volts, for example, into 12, or 24, or vice versa, with minimal losses. There are also high-voltage DC-DC converters; they are capable of obtaining a very significant potential difference of hundreds of volts from a relatively low voltage (5-12 volts). In this article we will consider the assembly of just such a converter, the output voltage of which can be adjusted within 60-250 volts.
It is based on the common NE555 integrated timer. Q1 in the diagram is a field-effect transistor; you can use IRF630, IRF730, IRF740 or any others designed to operate with voltages above 300 volts. Q2 is a low-power bipolar transistor, you can safely install BC547, BC337, KT315, 2SC828. Choke L1 should have an inductance of 100 μH, however, if this is not at hand, you can install chokes in the range of 50-150 μH, this will not affect the operation of the circuit. It’s easy to make a choke yourself - wind 50-100 turns of copper wire on a ferrite ring. Diode D1 according to the FR105 circuit; instead, you can install UF4007 or any other high-speed diode with a voltage of at least 300 volts. Capacitor C4 must be high-voltage, at least 250 volts, more possible. The larger its capacity, the better. It is also advisable to install a small-capacity film capacitor in parallel with it for high-quality filtering of high-frequency interference at the output of the converter. VR1 is a tuning resistor with which the output voltage is regulated. The minimum supply voltage for the circuit is 5 volts, the most optimal is 9-12 volts.
Converter manufacturing
The circuit is assembled on printed circuit board dimensions 65x25 mm, a file with a drawing of the board is attached to the article. You can take a textolite larger than the drawing itself, so that there is space at the edges for attaching the board to the case. A few photos of the manufacturing process:
After etching, the board must be tinned and checked for short circuits. Because present on the board high voltage, there should be no metal burrs between the tracks, otherwise a breakdown is possible. First of all, small parts are soldered onto the board - resistors, diode, capacitors. Then the microcircuit (it is better to install it in the socket), transistors, trimming resistor, inductor. To make it easier to connect wires to the board, I recommend installing screw terminal blocks; places for them are provided on the board.
Download the board:
(downloads: 240)
First launch and setup
Before starting, be sure to check the correct installation and ring the tracks. Set the trimming resistor to the minimum position (the slider should be on the side of resistor R4). After this, you can apply voltage to the board by connecting an ammeter in series with it. At idle, the current consumption of the circuit should not exceed 50 mA. If it fits within the norm, you can carefully turn the trimming resistor, controlling the output voltage. If everything is fine, connect a load, for example, a 10-20 kOhm resistor to the high-voltage output and test the operation of the circuit again, this time under load.The maximum current that such a converter can produce is approximately 10-15 mA. It can be used, for example, as part of lamp technology to power lamp anodes, or to light gas-discharge or luminescent indicators. The main application is a miniature stun gun, because the output voltage of 250 volts is noticeable to a person. Happy building!
LM2596 - buck converter direct current, it is often produced in the form of ready-made modules, costing about $1 (search for LM2596S DC-DC 1.25-30 V 3A). By paying $1.5, you can buy a similar module on Ali with LED indication of input and output voltage, turning off the output voltage and fine-tuning buttons with displaying values on digital indicators. Agree - the offer is more than tempting!
Below is circuit diagram of this converter board (key components are marked in the picture at the end). At the input there is protection against polarity reversal - diode D2. This will prevent the regulator from being damaged by incorrectly connected input voltage. Despite the fact that the lm2596 chip can process input voltages up to 45 V according to the datasheet, in practice the input voltage should not exceed 35 V for long-term use.
For lm2596, output voltage is determined by the equation below. Using resistor R2, the output voltage can be adjusted from 1.23 to 25 V.
Although the lm2596 chip is designed for a maximum current of 3 A of continuous operation, the small surface of the foil mass is not sufficient to dissipate the generated heat over the entire operating range of the circuit. Also note that the efficiency of this converter varies greatly depending on the input voltage, output voltage and load current. Efficiency can range from 60% to 90% depending on operating conditions. Therefore, heat removal is mandatory if continuous operation occurs at currents of more than 1 A.
According to the datasheet, the feedforward capacitor must be installed in parallel with resistor R2, especially when the output voltage exceeds 10 V - this is necessary to ensure stability. But this capacitor is often not present on Chinese inexpensive inverter boards. During the experiments, several copies of DC converters were tested under various operating conditions. As a result, we came to the conclusion that the LM2596 stabilizer is well suited for low and medium supply currents digital circuits, but for higher power outputs a heat sink is required.
Today we are reviewing the famous DC-DC boost voltage converter based on the MT3608 chip. The board is popular among those who like to create something with their own hands. It is used in particular for building homemade external chargers (power banks).
Today we will conduct a very detailed review, study all the advantages and find out the disadvantages
Such a board costs only $0.5, knowing that during the review there would be tough tests that could result in failure of the boards, I bought several of them at once.
The board is of very good quality, double-sided installation, to be more precise, almost all of it back side- mass, at the same time plays the role of a heat sink. Overall dimensions 36 mm * 17 mm * 14 mm
The manufacturer specifies the following parameters
1). Maximum output current - 2A
2). Input voltage: 2V~24V
3). Maximum output voltage: 28V
4). Efficiency: ≤93%
Product size: 36mm * 17mm * 14mm
And the diagram is presented below.
The board has a tuning multi-turn resistor with a resistance of 100 kOhm, designed to regulate the output voltage. Initially, for the converter to work, you need to rotate the variable 10 steps counterclockwise, only after this the circuit will begin to increase the voltage, in other words, the variable turns idle until halfway.
The input and output are marked on the board, so there will be no connection problems.
Let's move directly to the tests.
1) The declared maximum voltage is 28 Volts, which corresponds to the real value
2) The minimum voltage at which the board starts working is 2 Volts, I will say that this is not entirely true, the board remains operational at this voltage, but starts working at 2.3-2.5 Volts
3) The maximum value of the input voltage is 24 Volts, I will say that one of the 8 boards I purchased could not withstand such an input voltage, the rest passed the exam perfectly.
4) Output short circuit mode. The laboratory power supply from which the source is powered is equipped with a current limiting system; in case of a short circuit at the output, the consumption from the laboratory power supply is 5 A (this is the maximum that the LPS can provide). Based on this, we conclude that if you connect an inverter, for example, to a battery, then in the event of a short circuit, the latter will instantly burn out - it has no protection against short circuits. There is also no overload protection.
6) What happens if the connection polarity is reversed. This test is clearly visible in the video, the board simply burns up with smoke, and it’s the microcircuit that burns out.
7) Current idle move only 6mA, a very good result.
8) Now the output current. The input voltage is 12 Volts, the output is 14 Volts, i.e. the input-output difference is only 2 Volts, guaranteed best conditions work and if with this situation the circuit does not produce 2 Amperes, then with other input-output values it cannot provide this.
Temperature tests
P.S. During the tests, the throttle began to smell of varnish and therefore it was replaced with a better one, at least the diameter of the wire of the new throttle is 2 times thicker than that of the original one.
In the case of these tests, a voltage of 12 Volts is applied to the input of the board, and 14 Volts is set at the output
Heat generation on the throttle, the throttle has already been replaced
Heat dissipation on the diode
Heat dissipation on the chip
As you can see, the temperature in some cases is above 100 degrees, but is stable.
It should also be pointed out that under such operating conditions the output parameters deteriorate significantly, which is to be expected.
As we can see, with an output current of 2A, the voltage drops, so I recommend using the board at currents of 1-1.2 Amps maximum, at large values The stability of the output voltage is lost, and the microcircuit, inductor and output rectifier diode overheat.
9) Oscillogram of the output voltage, where we observe ripples.
The situation can be improved if an electrolyte (35-50 Volts) is soldered parallel to the output, the capacity is from 47 to 220 μF (up to 470 is possible, there is no point anymore)
Generator operating frequency is about 1.5 MHz
Test error is no more than 5%
!
In this homemade product, AKA KASYAN will make a universal step-down and step-up voltage converter.
Recently the author collected lithium battery. And today he will reveal the secret for what purpose he made it.
Here is a new voltage converter, its operating mode is single-cycle.
The converter has small dimensions and quite high power.
Conventional converters do one of two things. They only increase or only decrease the voltage supplied to the input.
The version made by the author can both increase,
and lower the input voltage to the required value.
The author has various regulated power sources with which he tests assembled homemade products.
Charges batteries and uses them for various other tasks.
Not long ago, the idea of creating a portable power source appeared.
The problem statement was as follows: the device should be able to charge all kinds of portable gadgets.
From ordinary smartphones and tablets to laptops and video cameras, and even coped with powering the author’s favorite soldering iron TS-100.
Naturally, you can simply use universal chargers with power adapters.
But they are all powered by 220V
In the author’s case, what was needed was a portable source of various output voltages.
But the author did not find any of these for sale.
The supply voltages for these gadgets have a very wide range.
For example, smartphones need only 5 V, laptops 18, some even 24 V.
The battery manufactured by the author is designed for an output voltage of 14.8 V.
Therefore, a converter capable of both increasing and decreasing the initial voltage is required.
Please note that some of the values of the components indicated on the diagram differ from those installed on the board.
These are capacitors.
The diagram shows the reference values, and the author made the board to solve his own problems.
Firstly, I was interested in compactness.
Secondly, the author's power converter allows you to easily create an output current of 3 Amps.
AKA KASYAN nothing more is needed.
This is due to the fact that the capacity of the storage capacitors used is small, but the circuit is capable of delivering an output current of up to 5 A.
Therefore, the scheme is universal. The parameters depend on the capacitance of the capacitors, the parameters of the inductor, the diode rectifier and the characteristics of the field switch.
Let's say a few words about the scheme. It is a single-cycle converter based on the UC3843 PWM controller.
Since the voltage from the battery is slightly higher than the standard power supply of the microcircuit, a 12V 7812 stabilizer was added to the circuit to power the PWM controller.
This stabilizer was not indicated in the diagram above.
Assembly. About jumpers installed on the mounting side of the board.
There are four of these jumpers, and two of them are power ones. Their diameter must be at least a millimeter!
The transformer, or rather the choke, is wound on a yellow ring made of powdered iron.
Such rings can be found in the output filters of computer power supplies.
Dimensions of the core used.
External diameter 23.29mm.
Inner diameter 13.59mm.
Thickness 10.33mm.
Most likely, the thickness of the insulation winding is 0.3mm.
The choke consists of two equal windings.
Both windings are wound with copper wire with a diameter of 1.2 mm.
The author recommends using wire with a slightly larger diameter, 1.5-2.0 mm.
There are ten turns in the winding, both wires are wound at once, in the same direction.
Before installing the throttle, seal the jumpers with nylon tape.
The efficiency of the scheme lies in correct installation throttle.
It is necessary to solder the winding terminals correctly.
Simply install the throttle as shown in the photo.
Power N-channel field-effect transistor, almost any low-voltage one will do.
The transistor current is not lower than 30A.
The author used an IRFZ44N transistor.
The output rectifier is a YG805C dual diode in a TO220 package.
It is important to use Schottky diodes, as they give a minimal voltage drop (0.3V versus 0.7) at the junction, which affects losses and heating. They are also easy to find in notorious computer power supplies.
In blocks they are located in the output rectifier.
In one case there are two diodes, which in the author’s circuit are paralleled to increase the passing current.
The converter is stabilized and there is feedback.
The output voltage is set by resistor R3
It can be replaced with an external variable resistor for ease of operation.
The converter is also equipped with short circuit protection. Resistor R10 is used as a current sensor.
This is a low-resistance shunt, and the higher its resistance, the lower the protection response current. An SMD option is installed on the side of the tracks.
If short circuit protection is not needed, then we simply exclude this unit.
More protection. There is a 10A fuse at the input of the circuit.
By the way, the battery control board already has short circuit protection installed.
It is highly desirable to take capacitors used in the circuit with low internal resistance.
The stabilizer, field-effect transistor and diode rectifier are attached to an aluminum radiator in the form of a bent plate.
Be sure to isolate the transistor and stabilizer substrates from the radiator using plastic bushings and heat-conducting insulating pads. Don't forget about thermal paste. And the diode installed in the circuit already has an insulated housing.
Today we will look at several circuits of simple, one might even say simple, pulsed DC-DC voltage converters (converters of direct voltage of one value to constant voltage of another value)
Why are they good? pulse converters. Firstly, they have high efficiency, and secondly, they can operate at an input voltage lower than the output voltage. Pulse converters are divided into groups:
- - bucking, boosting, inverting;
- - stabilized, unstabilized;
- - galvanically isolated, non-insulated;
- - with a narrow and wide range of input voltages.
To make homemade pulse converters, it is best to use specialized integrated circuits - they are easier to assemble and not capricious when setting up. So, here are 14 schemes for every taste:
This converter operates at a frequency of 50 kHz, galvanic isolation is provided by transformer T1, which is wound on a K10x6x4.5 ring made of 2000NM ferrite and contains: primary winding - 2x10 turns, secondary winding - 2x70 turns of PEV-0.2 wire. Transistors can be replaced with KT501B. Almost no current is consumed from the battery when there is no load.
Transformer T1 is wound on a ferrite ring with a diameter of 7 mm, and contains two windings of 25 turns of wire PEV = 0.3.
Push-pull unstabilized converter based on a multivibrator (VT1 and VT2) and a power amplifier (VT3 and VT4). The output voltage is selected by the number of turns of the secondary winding pulse transformer T1.
Stabilizing type converter based on the MAX631 microcircuit from MAXIM. Generation frequency 40...50 kHz, storage element - inductor L1.
You can use one of the two chips separately, for example the second one, to multiply the voltage from two batteries.
Typical circuit for connecting a pulse boost stabilizer on the MAX1674 microcircuit from MAXIM. Operation is maintained at an input voltage of 1.1 volts. Efficiency - 94%, load current - up to 200 mA.
Allows you to obtain two different stabilized voltages with an efficiency of 50...60% and a load current of up to 150 mA in each channel. Capacitors C2 and C3 are energy storage devices.
8. Switching boost stabilizer on the MAX1724EZK33 chip from MAXIM
Typical circuit diagram for connecting a specialized microcircuit from MAXIM. It remains operational at an input voltage of 0.91 volts, has a small-sized SMD housing and provides a load current of up to 150 mA with an efficiency of 90%.
A typical circuit for connecting a pulsed step-down stabilizer on a widely available TEXAS microcircuit. Resistor R3 regulates the output voltage within +2.8…+5 volts. Resistor R1 sets the short circuit current, which is calculated by the formula: Is(A)= 0.5/R1(Ohm)
Integrated voltage inverter, efficiency - 98%.
Two isolated voltage converters DA1 and DA2, connected in a “non-isolated” circuit with a common ground.
The inductance of the primary winding of transformer T1 is 22 μH, the ratio of turns of the primary winding to each secondary is 1: 2.5.
Typical circuit of a stabilized boost converter on a MAXIM microcircuit.
