A simple circuit for regulating and stabilizing voltage is shown in the picture above; even a novice in electronics can assemble it. For example, 50 volts are supplied to the input, and at the output we get 15.7 volts or another value up to 27V.
The main radio component of this device is a field-effect (MOSFET) transistor, which can be used as IRLZ24/32/44 and others like it. They are most commonly produced by IRF and Vishay in TO-220 and D2Pak packages. It costs about $0.58 UAH at retail; on ebay 10psc can be purchased for $3 ($0.3 per piece). Such a powerful transistor has three terminals: drain, source and gate; it has the following structure: metal-dielectric (silicon dioxide SiO2)-semiconductor. The TL431 stabilizer chip in the TO-92 package provides the ability to adjust the value of the output electrical voltage. I left the transistor itself on the radiator and soldered it to the board using wires.
The input voltage for this circuit can be from 6 to 50 volts. At the output we get 3-27V with the ability to regulate with a 33k substring resistor. The output current is quite large, up to 10 Amps, depending on the radiator.
Smoothing capacitors C1, C2 can have a capacity of 10-22 μF, C3 4.7 μF. Without them, the circuit will still work, but not as well as it should. Do not forget about the voltage of electrolytic capacitors at the input and output; I took all of them designed for 50 Volts.
The power that can be dissipated by this cannot be more than 50 watts. The field-effect transistor must be installed on a radiator, the recommended surface area of which is at least 200 square centimeters (0.02 m2). Don’t forget about thermal paste or rubber backing so that the heat transfers better.
It is possible to use a 33k substring resistor like WH06-1, WH06-2; they have fairly precise resistance adjustment, this is what they look like, imported and Soviet.
For convenience, it is better to solder two pads onto the board rather than wires, which are easily torn off.
Discuss the article VOLTAGE STABILIZER ON A FIELD TRANSISTOR
The LM317 is more suitable than ever for the design of simple, regulated sources and electronics with a variety of output characteristics, both variable output voltage and fixed voltage output. electric shock loads.
To facilitate the calculation of the required output parameters, there is a specialized LM317 calculator, which can be downloaded from the link at the end of the article along with the LM317 datasheet.
Technical characteristics of the stabilizer LM317:
- Providing output voltage from 1.2 to 37 V.
- Load current up to 1.5 A.
- Availability of protection against possible short circuit.
- Reliable protection of the microcircuit from overheating.
- Output voltage error 0.1%.
This inexpensive integrated circuit is available in TO-220, ISOWATT220, TO-3, and also D2PAK packages.
Purpose of the microcircuit pins:
Online calculator LM317
Below is an online calculator for calculating a voltage stabilizer based on LM317. In the first case, based on the required output voltage and the resistance of resistor R1, resistor R2 is calculated. In the second case, knowing the resistances of both resistors (R1 and R2), you can calculate the voltage at the output of the stabilizer.
For a calculator for calculating the current stabilizer on LM317, see.
Examples of application of the LM317 stabilizer (connection circuits)
Current stabilizer
The current stabilizer can be used in circuits of various battery chargers or regulated power supplies. The standard charger circuit is shown below.
This connection circuit uses a direct current charging method. As can be seen from the diagram, the charge current depends on the resistance of resistor R1. The value of this resistance ranges from 0.8 Ohm to 120 Ohm, which corresponds to a charging current from 10 mA to 1.56 A:
5 Volt power supply with electronic switching
Below is a diagram of a 15 volt power supply with soft start. The required smoothness of switching on the stabilizer is set by the capacitance of capacitor C2:
Switching circuit with adjustable output voltage
Hello dear readers. I've been wanting to try this pattern for a long time powerful, adjustable voltage stabilizer, the diagram of which is presented in the book “Microcircuits for linear power supplies and their application”, Dodeka Publishing House, 1998. The diagram is shown in Figure 1.
Figure 2 shows the circuit that I assembled. It does not contain a diode, resistor 2 and capacitor 2. Resistor R2 is necessary to close the leakage currents of powerful transistors. You can learn more about installing additional elements in the above-mentioned book. Here is a short excerpt from this book.
Data of the tested stabilizer
Input voltage………………………. 22V
Output voltage……………………. 14.15V
Current……………………………………………………... 0... 5A
Output voltage dip………. 0.05V
I did not measure the ripple voltage, since I powered the stabilizer from a DC power supply.
And so I applied 22V to the input, and using resistor R5 set the output voltage to 14V - more precisely, it was 14.15. When the load current increased to 5A, the output voltage decreased to 14.1V, which corresponds to a voltage drop of 50mV, which is not bad.
When the voltage drop across the stabilizer itself is 10V and the current through powerful transistors is 5A, i.e. the power released to them in the form of heat is 50 W, a radiator of this size heats up to a temperature of 80 (in photo 1 it’s actually 75 - then the temperature rose) degrees.
For silicon it’s like “good morning.” But after running the stabilizer at this temperature for about an hour, one of the KT829A suddenly died (breakdown of the k-e, but when the temperature dropped, all the properties of the transistor were restored, for me this is not an isolated case in my practice, which is why I always test my crafts at high and low temperatures, if they are expected to work with possible climate change), had to be replaced. My transistors are all used, soldered from old TVs. Resistors located in the emitters of powerful transistors are more needed to control the collector currents of these transistors than to equalize them. For me, the spread of these currents from transistor to transistor changed significantly, which required the selection of transistors. For example, the current of one transistor was 1.64A, and the other was 0.63A. So, these supposedly equalizing resistors in the emitter circuits can be safely removed after selecting the transistors. The stabilizer is mounted using a hinged method directly on the radiator (see photo 2). When installing the stabilizer, certain conditions must be observed.
1. The wire going from resistor R5 to ground must be soldered directly to the output terminal of the unit.
2. Capacitors C1 and C2 are installed in close proximity to the stabilizer chip.
3. It is best to solder resistor R4 directly to the corresponding pins of the microcircuit.
4. C1 and C2 are better than tantalum.
After assembling the stabilizer, be sure to check the output voltage of the stabilizer with an oscilloscope - it may self-excite. If an excitation occurs, then strong heating of C1 and C2 is possible, up to an explosion. When you turn it on for the first time, always quickly feel the electrolytes with your fingers to see if their temperature increases. The stabilizer works normally with an input voltage of 34V, while the output voltage should be no more than 24V (depends on the value of resistor R5 and is calculated using the formula).
The current can reach 10A if two fans are used for forced airflow. In general, I’m already thinking about making myself a laboratory power supply based on this stabilizer, supplementing it with protection and indication systems, and, of course, a voltmeter and ammeter. Good luck to everyone. Goodbye K.V.Yu.
Printed circuit board with components and instructions in the package. In amateur radio practice, a power source is often needed that is simple in design, small in size, and has a high load capacity. This kit will allow you to assemble an adjustable voltage stabilizer with a wide range of output voltage (3...27V) and output current up to 10 A.
Printed circuit board with components and instructions in the package.
In amateur radio practice, a power source is often needed that is simple in design, small in size, and has a high load capacity. This kit will allow you to assemble an adjustable voltage stabilizer with a wide range of output voltage (3...27V) and output current up to 10 A.
The circuit consists of a powerful field-effect transistor Q1, connected as a drain follower, and a reference voltage source assembled on a TL431 chip, which has high thermal stability over the entire temperature range. The output voltage is set by a divider consisting of R2, R3 and R4. If the device needs to be used as a stabilizer with a fixed output voltage, then R3 must be replaced with a jumper. Then, the output voltage is calculated by the formula:
U OUT = U REF × (1+R2/R4) - U GS,Where: U REF- reference voltage TL431 - 2.5 V;
UGS- gate-source threshold voltage (1…2 V).
The transistor must be installed on a radiator with a surface area comparable to the power dissipation, which can be calculated using the formula:
P q = (U IN - U OUT) × I LOAD,Where: Pq- power dissipation of the transistor;
U IN, U OUT- input and output voltages, respectively;
I NAGR- load current.
Characteristics:
Supply voltage: 6...50 V;
. Output voltage: 3...27 V;
. Maximum output current: 10 A.
Contents of delivery:
Printed circuit board;
. A set of radio components;
. User manual.
Notes:
In the case where the load is inductive in nature, it is additionally necessary to install a diode parallel to the load that dampens the reverse emissions of the EMF. The capacity of additional capacitors is selected at the rate of 1000 μF per 1 A of load current;
The maximum power dissipated by the transistor should not exceed 50 W. The device does not have short circuit protection, and if the load current or power dissipation value is exceeded, transistor Q1 may fail.
