Regulators based on powerful field-effect transistors. Transistor voltage regulator

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 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

SEVERAL SCHEMATIC DIAGRAMS OF POWER REGULATORS

POWER REGULATOR ON TRIAC

Features of the proposed device are the use of a D-trigger to build a generator synchronized with the mains voltage, and a method of controlling a triac using a single pulse, the duration of which is adjusted automatically. Unlike other methods of pulsed control of a triac, this method is not critical to the presence of an inductive component in the load. The generator pulses follow with a period of approximately 1.3 s.
The DD 1 microcircuit is powered by a current flowing through a protective diode located inside the microcircuit between its pins 3 and 14. It flows when the voltage at this pin, connected to the network through resistor R 4 and diode VD 5, exceeds the stabilization voltage of the zener diode VD 4 .

K. GAVRILOV, Radio, 2011, No. 2, p. 41

TWO-CHANNEL POWER CONTROL FOR HEATING DEVICES

The regulator contains two independent channels and allows you to maintain the required temperature for various loads: the temperature of a soldering iron tip, an electric iron, an electric heater, an electric stove, etc. The depth of regulation is 5...95% of the power of the supply network. The regulator circuit is powered by a rectified voltage of 9...11 V with transformer isolation from a 220 V network with low current consumption.

V.G. Nikitenko, O.V. Nikitenko, Radioamator, 2011, No. 4, p. 35

TRIAC POWER REGULATOR

A feature of this triac regulator is that the number of half-cycles of the mains voltage supplied to the load is even at any position of the control. As a result, a constant component of the consumed current is not formed and, therefore, there is no magnetization of the magnetic circuits of transformers and electric motors connected to the regulator. Power is regulated by changing the number of periods of alternating voltage applied to the load over a certain time interval. The regulator is designed to regulate the power of devices with significant inertia (heaters, etc.).
It is not suitable for adjusting the brightness of lighting, since the lamps will blink strongly.

V. KALASHNIK, N. CHEREMISINOVA, V. CHERNIKOV, Radiomir, 2011, No. 5, p. 17 - 18

INTERFERENCE-FREE VOLTAGE REGULATOR

Most voltage (power) regulators are made using thyristors according to a phase-pulse control circuit. It is known that such devices create a noticeable level of radio interference. The proposed regulator is free from this drawback. A feature of the proposed regulator is the control of the amplitude of the alternating voltage, in which the shape of the output signal is not distorted, unlike phase-pulse control.
The regulating element is a powerful transistor VT1 in the diagonal of the diode bridge VD1-VD4, connected in series with the load. The main disadvantage of the device is its low efficiency. When the transistor is closed, no current passes through the rectifier and the load. If control voltage is applied to the base of the transistor, it opens and current begins to flow through its collector-emitter section, diode bridge and load. The voltage at the regulator output (at the load) increases. When the transistor is open and in saturation mode, almost all the mains (input) voltage is applied to the load. The control signal is generated by a low-power power supply assembled on transformer T1, rectifier VD5 and smoothing capacitor C1.
The variable resistor R1 regulates the base current of the transistor, and therefore the amplitude of the output voltage. When the variable resistor slider is moved to the upper position in the diagram, the output voltage decreases, and to the lower position, it increases. Resistor R2 limits the maximum value of the control current. Diode VD6 protects the control unit in the event of breakdown of the collector junction of the transistor. The voltage regulator is mounted on a board made of foiled fiberglass laminate with a thickness of 2.5 mm. Transistor VT1 should be installed on a heat sink with an area of ​​at least 200 cm2. If necessary, diodes VD1-VD4 are replaced with more powerful ones, for example D245A, and are also placed on the heat sink.

If the device is assembled without errors, it starts working immediately and requires virtually no setup. You just need to select resistor R2.
With the KT840B regulating transistor, the load power should not exceed 60 W. It can be replaced with devices: KT812B, KT824A, KT824B, KT828A, KT828B with a permissible power dissipation of 50 W; KT856A -75 W; KT834A, KT834B - 100 W; KT847A-125 W. The load power can be increased if regulating transistors of the same type are connected in parallel: the collectors and emitters are connected to each other, and the bases are connected to the variable resistor motor through separate diodes and resistors.
The device uses a small-sized transformer with a voltage on the secondary winding of 5...8 V. The KTs405E rectifier unit can be replaced with any other one or assembled from individual diodes with a permissible forward current of no less than the required base current of the regulating transistor. The same requirements apply to the VD6 diode. Capacitor C1 - oxide, for example, K50-6, K50-16, etc., with a rated voltage of at least 15 V. Variable resistor R1 - any with a rated dissipation power of 2 W. When installing and setting up the device, precautions should be taken: the regulator elements are under mains voltage. Note: To reduce distortion of the sine wave output voltage, try eliminating capacitor C1. A. Chekarov

Voltage regulator based on MOSFET transistors (IRF540, IRF840)

Oleg Belousov, Electrician, 201 2, No. 12, p. 64 - 66

Since the physical principle of operation of a field-effect transistor with an insulated gate differs from the operation of a thyristor and triac, it can be turned on and off repeatedly during the period of mains voltage. The switching frequency of powerful transistors in this circuit is chosen to be 1 kHz. The advantage of this circuit is its simplicity and the ability to change the duty cycle of the pulses, while slightly changing the pulse repetition rate.

In the author's design, the following pulse durations were obtained: 0.08 ms, with a repetition period of 1 ms, and 0.8 ms, with a repetition period of 0.9 ms, depending on the position of the resistor R2 slider.
You can turn off the voltage on the load by closing switch S 1, while a voltage close to the voltage at pin 7 of the microcircuit is set at the gates of the MOSFET transistors. With the toggle switch open, the voltage at the load in the author's copy of the device could be changed with resistor R 2 within the range of 18...214 V (measured by a TES 2712 type device).
The schematic diagram of such a regulator is shown in the figure below. The regulator uses a domestic K561LN2 microcircuit on two elements of which a generator with adjustable sensitivity is assembled, and four elements are used as current amplifiers.

To avoid interference via the 220 network, it is recommended to connect a choke wound on a ferrite ring with a diameter of 20...30 mm in series with the load until it is filled with 1 mm of wire.

Load current generator based on bipolar transistors (KT817, 2SC3987)

Butov A.L., Radioconstructor, 201 2, No. 7, p. 11 - 12

To check the functionality and configure power supplies, it is convenient to use a load simulator in the form of an adjustable current generator. Using such a device, you can not only quickly set up a power supply and voltage stabilizer, but also, for example, use it as a stable current generator for charging and discharging batteries, electrolysis devices, for electrochemical etching of printed circuit boards, as a current stabilizer for electric lamps, for “soft” start of commutator electric motors.
The device is a two-terminal device, does not require an additional power source and can be connected to the power supply circuit of various devices and actuators.
Current adjustment range from 0...0, 16 to 3 A, maximum power consumption (dissipation) 40 W, supply voltage range 3...30 V DC. The current consumption is regulated by variable resistor R6. The further to the left the slider of resistor R6 is in the diagram, the more current the device consumes. With open contacts of switch SA 1, resistor R6 can set the consumption current from 0.16 to 0.8 A. With closed contacts of this switch, the current is regulated in the range of 0.7... 3 A.

Current generator circuit board drawing

Car battery simulator (KT827)

V. MELNICHUK, Radiomir, 201 2, No. 1 2, p. 7 - 8

When converting computer switching power supplies (UPS) and chargers for car batteries, the finished products must be loaded with something during the setup process. Therefore, I decided to make an analogue of a powerful zener diode with an adjustable stabilization voltage, the circuits of which are shown in Fig. 1 . Resistor R 6 can be used to regulate the stabilization voltage from 6 to 16 V. A total of two such devices were made. In the first version, KT 803 is used as transistors VT 1 and VT 2.
The internal resistance of such a zener diode turned out to be too high. So, at a current of 2 A, the stabilization voltage was 12 V, and at 8 A - 16 V. In the second version, composite transistors KT827 were used. Here, at a current of 2 A, the stabilization voltage was 12 V, and at 10 A - 12.4 V.

However, when regulating more powerful consumers, for example electric boilers, triac power regulators become unsuitable - they will create too much interference on the network. To solve this problem, it is better to use regulators with a longer period of ON-OFF modes, which clearly eliminates the occurrence of interference. One of the diagram options is shown.

I. NECHAYEV, Kursk

This regulator allows you to control the amount of heat generated by the electric heater. The principle of its operation is based on changing the number of periods of the mains voltage supplied to the heater, with switching on and off occurring at moments close to the transition of the instantaneous value of the mains voltage through zero. Therefore, the regulator creates virtually no switching interference. Unfortunately, it is not suitable for dimming incandescent lamps, which will flicker noticeably.

The device diagram is shown in Fig. 1.

As switching elements, it uses field-effect transistors IRF840 with a permissible drain-source voltage of 500 V, a drain current of 8 A at a case temperature of 25 ° C and 5 A at a temperature of 100 ° C, a pulse current of 32 A, an open channel resistance of 0.85 Ohm and dissipated power of 125 W. Each transistor contains an internal protective diode connected parallel to the channel in reverse polarity (cathode to drain). This allows you to connect two transistors in back-to-back series to switch alternating voltage.

Elements DD1.1, DD1.2 are used to assemble a generator of adjustable duty cycle pulses running at a frequency of approximately 1 Hz. On DD1.3, DD1.4 - voltage comparator. DD2.1 is a D-trigger, and DD1.5, DD1.6 are buffer stages. Quenching resistor R2, diodes VD3 and VD4, zener diode VD6, capacitor C2 form a parametric voltage stabilizer. Diodes VD5, VD7 suppress voltage surges at the gates of transistors VT1, VT2.

Timing diagrams of signals at various points of the regulator are shown in Fig. 2.

The positive half-wave of the mains voltage, passing through diodes VD3, VD4 and resistor R2, charges capacitor C2 to the stabilization voltage of the zener diode VD6. The voltage at the anode of diode VD4 is a sinusoid limited from below by a zero value, and from above by the stabilization voltage of the zener diode VD6 plus the forward voltage drop across the diode itself. The comparator on elements DD1.3, DD1.4 makes the voltage drops steeper. The pulses generated by it are supplied to the synchronization input (pin 11) of the DD2.1 trigger, and to its input D (pin 9) - pulses with a frequency of approximately 1 Hz from the output of the generator on elements DD1.1, DD1.2.

The output pulses of the trigger are fed through elements DD1.5 and DD1.6 connected in parallel (to reduce the output resistance) to the gates of transistors VT1 and VT2. They differ from generator pulses by “tying” time differences to the network voltage crossing a level close to zero, in the direction from plus to minus. Therefore, the opening and closing of transistors occurs only at the moments of such intersections (which guarantees a low level of interference) and always for an integer number of periods of the mains voltage. As the variable resistor R1 changes the duty cycle of the generator pulses, the ratio of the duration of the on and off state of the heater, and therefore the average amount of heat generated by it, also changes.

Field-effect transistors can be replaced with others that are suitable for the permissible voltage and current, but must be equipped with protective diodes. K561 series microcircuits, if necessary, are replaced with functional analogues of the 564 series or imported ones. Zener diode D814D - any medium power with a stabilization voltage of 10...15 V.

Most of the device parts are placed on a printed circuit board made of single-sided foil fiberglass, shown in Fig. 3.

When the heater power is more than 500 W, transistors VT1 and VT2 must be equipped with heat sinks.

The board is installed in a housing made of insulating material, on the wall of which a socket XS1 and a variable resistor R1 are mounted. A handle made of insulating material must be placed on the resistor axis.

When setting up the regulator, check the voltage on capacitor C2 throughout the entire power adjustment range. If it changes noticeably, the value of resistor R2 will have to be reduced.
Radio No. 4 2005.

Triac power regulator.

Choke L1 is any noise-suppressing device used in such devices, corresponding to the load. You can, in principle, do without it, especially if the load is inductive in nature. Capacitors CI, C2 - for a voltage of at least 250 V. Diodes VD1...VD4 - any silicon for a reverse voltage of at least 300 V.

Transistors VT1, VT2 are also, in principle, any silicon with the appropriate type of conductivity.

This circuit works with any type of triacs for the appropriate voltage. The most powerful one we were able to test was TS142-80-10.

Radio amateur 8/97

Step power regulator.

The proposed device is distinguished by accessible parts with a small number and uncritical ratings. Step regulation: 2/2, 2/3, 2/4, 3/7, 3/8, 3/9 and 3/10 of the full load power.

The regulator diagram is shown in Fig. 1.

It consists of a power unit (diodes VD2, VD6, zener diode VD1, resistor R3, capacitor C1), a control unit (resistors R1, R2, R4, R5, switch SA1, decimal counter DD1, diodes VD3-VD5) and a power unit on the field transistor VT1 and diode bridge VD7-VD10, it also includes resistor R6.

Suppose switch SA1 is set to position 2/3. During the first positive half-cycle of the mains voltage, diodes VD2 and VD6 are open. The current flowing through the zener diode VD1 forms a pulse with an amplitude of 15 V with a steep rise and fall. This pulse charges capacitor C1 through diode VD2, and through resistor R1 enters the CN input of counter DD1. At the edge of this pulse, a high level will be set at output 1 of the counter, which, through diode VD4 and resistor R4, will go to the gate of field-effect transistor VT1 and open it. As a result, a positive half-wave of current flows through the load.

During the negative half-cycle, the diodes VD2 and VD6 are closed, but the voltage of the charged capacitor C1 (it is then recharged by each positive half-cycle) continues to power the counter DD1, the state of which does not change. Transistor VT1 remains open, and current continues to flow through the load.

With the beginning of the next positive half-cycle, the level at output 1 of the counter will become low, and at output 2 - high. Transistor VT2, whose gate-source voltage has become zero, will be closed, and the load will be disconnected from the network for the entire period.

In the third positive half-cycle, the high level set at output 3 will flow through switch SA1 to the R input of the counter, which will immediately go into its initial state with a high level at output 0 and low at all other outputs. The voltage supplied through diode VD3 and resistor R4 to the gate of transistor VT1 will open it. At the end of this period the cycle will repeat. In other positions of switch SA1, the device operates similarly, only the number of periods during which the load is connected to the network and disconnected from it changes.

The regulator almost does not create radio interference, since the switching of the counter, and with it the opening and closing of the transistor VT1, occurs at moments when the instantaneous value of the mains voltage is very close to zero - it does not exceed the stabilization voltage of the zener diode VD1. Resistor R6 suppresses voltage surges that occur when switching an inductive load, which reduces the likelihood of breakdown of transistor VT1.

The regulator is assembled on a printed circuit board made of one-sided foil-coated PCB (Fig. 2).

It is designed for MLT resistors and similar ones with the power indicated on the diagram, and the resistor ratings may differ several times from those indicated. Capacitor C1 - K50-35 or other oxide. The KS515G zener diode can be replaced with KS515Zh or KS508B, the KD257B diodes with imported 1N5404, and the KP740 transistor with IRF740.

Switch SA1 is a P2G-3 11P1N biscuits, of which only seven positions are used. The switch terminals are connected by flexible wires to unmarked contact pads located on the printed circuit board around the DD1 chip.

It is advisable to check the assembled device by connecting it to the network through an isolation transformer with a voltage on the secondary winding of 20...30 V and replacing the actual load with a 1.5...3 kOhm resistor. Only after making sure that it works correctly, connect it to the network directly. After this, it is dangerous to touch any elements of the device (except for the insulated switch handle) - they are under mains voltage.

The regulator has been tested with loads up to 600 W. Field-effect transistor VT1, due to the low resistance of the open channel, heats up very little, however, it is advisable to provide it with a small heat sink.

The presented regulator is designed to regulate the temperature of a soldering iron tip for a rated voltage from 100 to 220 V, but can also work with other loads. A powerful switching field-effect transistor IRF840 is used as a regulating element.

This transistor has a high drain-source operating voltage of up to 500 V and a drain current of up to 8 A at a case temperature of 25 ° C (5 A at 100 ° C). The pulse current can reach 32 A, the permissible gate-source voltage is ±20 V, the power dissipation is 125 W, the open channel resistance is 0.85 Ohm, and the closed channel current is only 25 μA. To control the transistor, very little static power is required, making the controller very economical.

The load is connected in series with the control element. Since the transistor contains a built-in protective diode connected in parallel to the channel (cathode to drain), regulation of the power consumed by the load can be changed from 50 to 100% of the nominal value, which is quite enough for a soldering iron.

A pulse generator controlling the transistor is assembled using logic elements DD1.1-DD1.4, resistors R1-R4, capacitor C1 and diode VD2. In this case, elements DD1.1, DD1.2 and resistor R4 are connected according to the Schmitt trigger circuit, and elements DD1.3, DD1.4 connected in parallel represent a buffer-inverter. The driver is powered by the parametric voltage stabilizer R5VD1.

Diode VD3 is a decoupling diode; it prevents capacitor C2 from discharging during negative half-cycles of the mains voltage, thereby maintaining a stable supply voltage for the microcircuit. Diodes VD4, VD5 protect the output of the logical elements of the buffer from pulsed network noise from the field-effect transistor VT1.

With a positive half-wave of the mains voltage (plus - on the right terminal of resistor R5 in the diagram), the zener diode VD1 will be about 10V and capacitor C2 will charge through the diode VD3 to approximately 9 V. This voltage is used to power the DD1 microcircuit. At the same time, capacitor C1 is charged relatively slowly through resistors R1, R2. When the voltage on it reaches a level of 30...40% of the supply voltage of the microcircuit, the Schmitt trigger will switch, the high level at the output of the DD1.1 element will change to a low level, a high level (about 9 V) will appear at the buffer output, so the field-effect transistor VT1 will open from this moment the voltage is applied to the load.

The negative half-wave of the mains voltage passes through the protective diode of the field-effect transistor freely to the load, although the transistor is closed. Since the zener diode is turned on in the forward direction, there will be a voltage across it of about 0.7 V and capacitor C1 will quickly discharge through the diode VD2. A low level appears at the input of the Schmitt trigger, the trigger switches to its previous state, and the low level at the output of the buffer closes the transistor.

The greater the resistance of resistor R1, the slower capacitor C1 charges and the later the transistor opens from the moment the positive half-wave appears. Thus, by changing the resistance of resistor R1, you can adjust the effective voltage across the load.

In addition to those indicated in the diagram, you can use K561LA7, . Zener diode D814V can be replaced with D814G, KS510A; diodes KD522B to KD102B, KD103A, KD503A, KD510A, KD521A. Variable resistor - SPO-0.15, SP4-1a.

Do not forget that the device parts are under mains voltage! This requires thoughtful design and caution during operation.

When setting up a regulator, it may be necessary to select a variable resistor R1 or capacitor C1 so that the power control is smooth, without “dead zones”. At this time, it is convenient to use a low-power incandescent lamp as a load.

The regulator can operate with a lower supply voltage, up to 30 V. In this case, it is necessary to select resistor R5 such that the supply voltage of the microcircuit is stable. If it is less than the stabilization voltage of the zener diode, then gradually, in steps of no more than 10%, reduce the resistance of resistor R5 until the voltage is restored to the normal level.

If the load current of the regulator exceeds 2 Amps, the transistor will have to be removed from the board and installed on a heat sink. It should be noted that the described regulator loads the network asymmetrically, i.e., for the positive and negative half-waves of the mains voltage, the power consumption is different. Operating such a network load if its power exceeds 50 W is prohibited by state regulations.

To ensure symmetrical load of the regulator, it is enough to connect it to the network through a bridge rectifier assembled from diodes of the appropriate power (the positive terminal of the bridge must be connected to the right terminal of resistor R5 according to the diagram). In this case, a pulsating unipolar current will flow through the load, but for heating devices and incandescent lamps this does not matter.

In addition, it will be necessary to ensure that capacitor C1 is discharged at the end of each half-cycle. To do this, you need to shunt the zener diode VD1 with a resistor with a resistance of 10 kOhm (check during setup). It should be as large as possible, but such that in the position of the resistor R1 motor, corresponding to the minimum power in the load, the transistor does not open.

Initially, the task was to make a simple and compact power regulator for a network soldering iron operating on an alternating voltage of 220 volts, and after some searching, the circuit that was once published in the magazine Radio 2-3\92 (author - I. Nechaev) was taken as a basis. Kursk).

Schematic diagram of the 220V regulator

An interesting feature of this circuit is that its output can produce a voltage greater than its input. This may be necessary, for example, if for some reason you need to increase the rated power of your soldering iron. For example, if you need to desolder/solder some massive part, but the temperature of the soldering iron tip is not sufficient for this. The voltage increase occurs due to its conversion from alternating to direct (after rectification by the diode bridge and smoothing the voltage ripple of capacitor C1). Thus, after the rectifier, we can get a constant voltage of up to 45 volts. On the first two elements of the K176LA7 microcircuit, a conventional generator with the ability to adjust the duty cycle of the pulses is assembled, and on two more of its elements there is an amplifying buffer cascade. The frequency of the generator with the elements C3, R2, R3 indicated in the diagram is about 1500 Hz, and the duty cycle of the pulses can be adjusted by resistor R4 from 1.05 to 20. These pulses, through a buffer cascade and resistor R5, are sent to an electronic switch on transistors and from it to load (soldering iron). The load voltage is approximately 40...45V depending on the power of the step-down transformer at the input and the power consumption of the soldering iron).

There is also a version of the same circuit, but slightly modified to be able to work with a 220 volt load. The operating principle of this circuit is the same, but a field-effect transistor is used as a key and, accordingly, the ratings of some elements are slightly changed to ensure the circuit operates with voltage:

Here, the “key” on transistor VT1 is also controlled by the pulse width method. And you can also regulate the voltage on your soldering iron within a fairly wide range, from the maximum (about 300 volts) to the minimum level (tens of volts). The adjustment limits of the output voltage can be narrowed to the limits you need if you connect resistors in series with the diodes VD6, VD7, as in the previous circuit. The values ​​of these resistors can range from units to 100 kOhm and are selected (if necessary) during setup. Both schemes do not require any other settings and are not critical to the details used.

I assembled and tested the second circuit for a 220 volt soldering iron. Instead of the filter capacitor C1, a nominal value of 25 µF x 400 V was installed (large capacitors were simply not available), and C2 was increased to 47 µF x 16 V and C3 - 150 pF (the generator frequency was about 30 kHz, which is much higher, than in the first circuit. But the circuit worked quite normally and, to be honest, I did not try to increase this capacity or change the frequency). The printed circuit board was drawn by hand:

The microcircuit here can be replaced with another from the K561, K176 series or a similar imported one, containing at least four inverters/elements “AND-NOT” or “OR-NOT” (K561LE5, K176LE5, K561LN2, CD4001, CD4011 ...). I installed the transistor type BUZ90. When connecting a load of up to 100 watts (I tried it with a regular incandescent lamp), the transistor did not heat up at all and a heat sink was not required (the circuit was assembled for a 40-watt soldering iron). But resistor R1 got very hot, so it had to be replaced by two two-watt 47 kOhm resistors connected in parallel. And still, they heat up quite noticeably during operation, so I had to make a number of small holes in the case at the location of these resistors for ventilation:

The Zener diode was supplied D814G (any voltage can be used for a voltage of 6 - 14 volts and a current of about 20 mA, depending on the power supply range and current consumption of the chip used), variable resistor R2 - 220 kOhm. Instead of 1N4148 diodes, you can use KD522 or KD521. Electrolytic capacitors must have an operating voltage no less than that required by the circuit. As a simple indicator of operation, an LED was used (any low power is possible), connected parallel to the output in series with a quenching resistor. The resistor value is selected during setup depending on the type of LED and the required brightness of its glow (the anode of the LED is connected to the “+” terminal of the circuit output).

The entire circuit, as you can see, easily fits into the adapter/charger case. It can also be used as, for example, a dimmer for an incandescent lamp. The brightness is adjusted smoothly and no “flickering” of the lamp was noticed.

Checking the operation of the regulator

The material was sent by Andrey Baryshev.