Water heaters

Low voltage PWM controller for LEDs. LED driver ICs

When redesigning dashboards, there is a need to adjust the brightness of installed boards. This is especially necessary if you are driving for a long time in the dark. All the same, the LEDs shine juicier and brighter than conventional lamps, and even without a regulator, the work looks unfinished.

The issue is solved by buying a ready-made dimmer for adjusting LED strips or by a simple variable resistor installed in the network break. This is not our method. The regulator must be on PWM (pulse width modulator).

PWM adjustment is in the periodic switching on and off of the current through the LED for short periods of time. To avoid the flickering effect perceived by human vision, the frequency of this cycle should be at least 200 Hz.

One option for dimming LEDs is a simple device based on the popular 555 timer, which performs this operation using a PWM signal. The main component of the circuit is the 555 timer, which generates a PWM signal, the built-in generator changes the duty cycle of the pulses with a frequency of 200 Hz.

A variable resistor with the help of two pulse diodes adjusts the brightness. An important element of the circuit is a key field-effect transistor operating according to a common-source circuit. The dimmer circuit is capable of dimming from 5% to 95%.

Theory passed. Let's move on to practice.

Two conditions were set:
1. The circuit must be assembled on SMD components
2. Minimum dimensions.

Immediately there are difficulties in the selection of components. In my case, the main thing was to buy radio amateurs in Mecca - the Chip and Dip store and wait two weeks for delivery by the Russian Post. The rest is to look for local shops.

This is the most difficult, because. there are only a couple of them. I’ll say right away it didn’t work out the first time, I had to rack my brains with a field-effect transistor and redo / redraw / re-solder several times.

Based on the classic scheme:

Changes have been made to the schema:
1. Capacitances changed to 0.01uF and 0.1uF
2. Replaced transistor with IRF7413. Holds 30V 13A. Gorgeous!

First and second option.

Version 1 and version 2.

As can be seen in the second version, he also reduced the overall dimensions and replaced the field worker, capacity.

Comparison. For clarity of size.

Taking into account all the errors, I redid the circuit and slightly reduce the overall measurements.

Victory!

We connect a piece of the scale:

Maximum brightness

Chip NCP1014 is a PWM controller with a fixed conversion frequency and a built-in high-voltage switch. Additional internal blocks implemented as part of the microcircuit (see Fig. 1) allow it to meet the entire range of functional requirements for modern power supplies.

Rice. 1.

Series controllers NCP101X were discussed in detail in an article by Konstantin Staroverov in issue 3 of the journal for 2010, therefore, in the article we will confine ourselves to considering only the key features of the NCP1014 chip, and will focus on considering the calculation features and the mechanism of operation of the IP presented in the reference design.

Features of the NCP1014 controller

Integrated output 700V low on-resistance MOSFET (11Ω);
providing driver output current up to 450mA;
the ability to work at several fixed conversion frequencies - 65 and 100 kHz;
the conversion frequency varies within ± 3 ... 6% relative to its preset value, which allows you to "blur" the power of radiated interference within a certain frequency range and thereby reduce the EMI level;
the built-in high-voltage power supply system is able to ensure the operability of the microcircuit without the use of a transformer with a third auxiliary winding, which greatly simplifies the winding of the transformer. This feature is designated by the manufacturer as DSS ( Dynamic Self-Supply- autonomous dynamic power), however, its use limits the output power of the IP;
the ability to work with maximum efficiency at low load currents due to the PWM pulse skipping mode, which makes it possible to achieve low no-load power - no more than 100 mW when the microcircuit is powered from the third auxiliary winding of the transformer;
the transition to the pulse skipping mode occurs when the load current is reduced to a value of 0.25 from the nominal value, which eliminates the problem of generating acoustic noise even when using inexpensive pulse transformers;
implemented soft start function (1ms);
the voltage feedback output is directly connected to the output of the optocoupler;
a short circuit protection system with subsequent return to normal operation after its elimination has been implemented. The function allows you to track both directly a short circuit in the load, and the situation with an open feedback circuit in case of damage to the decoupling optocoupler;
built-in overheating protection mechanism.

The NCP1014 controller is available in three package types - SOT-223, PDIP-7 and PDIP-7 GULLWING (see Figure 2) with the pinout shown in Figure 2. 3. The latest package is a special version of the PDIP-7 package with special pin molding, making it suitable for surface mounting.

Rice. 2.

Rice. 3.

Typical application diagram of NCP1014 controller in flyback ( flyback) converter is shown in Figure 4.

Rice. 4.

IP calculation method based on NCP1014 controller

Consider the method of step-by-step calculation of a flyback converter based on the NCP1014 using the example of a reference development of a power supply with an output power of up to 5 W to power a system of three LEDs connected in series. One-watt white LEDs with a normalization current of 350 mA and a voltage drop of 3.9 V were considered as LEDs.

first step is to determine the input, output and power characteristics of the developed IP:

input voltage range - Vac(min) = 85V, Vac(max) = 265V;
output parameters - Vout = 3x3.9V ≈ 11.75V, Iout = 350mA;
output power - Pout \u003d VoutxIout \u003d 11.75 Vx0.35 A ≈ 4.1 W
input power - Pin = Pout / h, where h is the estimated efficiency = 78%

Pin=4.1W/0.78=5.25W

DC input voltage range

Vdc(min) = Vdc(min) x 1.41 = 85 x 1.41 = 120V (dc)

Vdc(max) = Vdc(max) x 1.41 = 265 x 1.41 = 375V (dc)

average input current - Iin(avg) = Pin / Vdc(min) ≈ 5.25/120 ≈ 44mA
peak input current - Ipeak = 5xIin (avg) ≈ 220mA.

The first input link is a fuse and an EMI filter, and their selection is second step when designing IP. The fuse must be selected based on the value of the breaking current, and in the presented design, a fuse with a breaking current of 2 A was chosen. We will not delve into the procedure for calculating the input filter, but only note that the degree of suppression of common-mode and differential noise largely depends on the topology of the printed circuit board, as well as the proximity of the filter to the power connector.

third step is the calculation of parameters and selection of the diode bridge. The key parameters here are:

permissible reverse (blocking) diode voltage - VR ≥ Vdc (max) = 375V;
forward current of the diode - IF ≥ 1.5xIin (avg) = 1.5x0.044 = 66mA;
allowable overload current ( surge current), which can reach five times the average current:

IFSM ≥ 5 x IF = 5 x 0.066 = 330 mA.

fourth step is the calculation of the parameters of the input capacitor installed at the output of the diode bridge. The size of the input capacitor is determined by the peak value of the rectified input voltage and the specified level of input ripple. A larger input capacitor provides lower ripple values, but increases the inrush current of the power supply. In general, the capacitance of a capacitor is determined by the following formula:

Cin = Pin/, where

fac is the frequency of the AC mains (60 Hz for the design in question);

DV is the allowable ripple level (20% of Vdc (min) in our case).

Cin \u003d 5.25 / \u003d 17 uF.

In our case, we choose a 33uF aluminum electrolytic capacitor.

Fifth and main step is the calculation of the winding product - a pulse transformer. The calculation of the transformer is the most complex, important and "thin" part of the entire calculation of the power supply. The main functions of a transformer in a flyback converter are the accumulation of energy when the control key is closed and the current flows through its primary winding, and then its transfer to the secondary winding when the power to the primary part of the circuit is turned off.

Taking into account the input and output characteristics of the MT, calculated at the first step, as well as the requirements for ensuring the operation of the MT in the continuous current mode of the transformer, the maximum value of the duty cycle ( duty cycle) is equal to 48%. We will carry out all calculations of the transformer based on this value of the fill factor. Let us summarize the calculated and specified values of the key parameters:

controller operating frequency fop = 100 kHz
fill factor dmax= 48%
minimum input voltage Vin(min) = Vdc(min) - 20% = 96V
output power Pout= 4.1W
estimated value of efficiency h = 78%
peak input current Ipeak= 220mA

Now we can calculate the inductance of the primary winding of the transformer:

Lpri = Vin(min) x dmax/(Ipeak x fop) = 2.09 mH

The ratio of the number of turns of the windings is determined by the equation:

Npri / Nsec \u003d Vdc (min) x dmax / (Vout + V F x (1 - dmax)) ≈ 7

It remains for us to check the ability of the transformer to “pump” the required output power through itself. You can do this with the following equation:

Pin(core) = Lpri x I 2 peak x fop/2 ≥ Pout

Pin(core) = 2.09 mH x 0.22 2 x 100 kHz/2 = 5.05 W ≥ 4.1 W.

It follows from the results that our transformer can pump the required power.

It can be seen that here we have given a far from complete calculation of the parameters of the transformer, but only determined its inductive characteristics and showed the sufficient power of the chosen solution. Many works have been written on the calculation of transformers, and the reader can find the calculation methods of interest to him, for example, in or. The coverage of these techniques is beyond the scope of this article.

The electrical circuit of the IP, corresponding to the calculations performed, is shown in Figure 5.

Rice. 5.

Now it's time to get acquainted with the features of the above solution, the calculation of which was not given above, but which are of great importance for the functioning of our IP and understanding the implementation features of the protective mechanisms implemented by the NCP1014 controller.

Features of the operation of the scheme that implements IP

The secondary part of the circuit consists of two main blocks - a block for transferring current to the load and a power supply for the feedback circuit.

When the control key is closed (direct mode), the feedback circuit power circuit operates, implemented on diode D6, current-setting resistor R3, capacitor C5 and zener diode D7, which, together with diode D8, sets the required supply voltage (5.1 V) of optocoupler and shunt regulator IC3.

During the reverse run, the energy stored in the transformer is transferred to the load through diode D10. At the same time, the storage capacitor C6 is charged, which smoothes the output ripples and provides a constant supply voltage to the load. The load current is set by resistor R6 and controlled by shunt regulator IC3.

IP has protection against load disconnection and load short circuit. Short circuit protection is provided by the TLV431 shunt regulator, the main role of which is the OS circuit regulator. A short circuit occurs under the condition of a short breakdown of all load LEDs (in the event of failure of one or two LEDs, their functions are taken over by parallel zener diodes D11 ... D13). The value of resistor R6 is selected so that at the operating load current (350 mA in our case) the voltage drop across it is less than 1.25 V. When a short circuit occurs, the current through R6 increases sharply, which leads to the opening of shunt IC3 and turn on optocoupler IC2 and forces the NCP1014 controller to reduce the output voltage.

The load shutdown protection mechanism is based on the inclusion of a Zener diode D9 in parallel with the load. Under conditions of opening of the load circuit and, as a result, an increase in the output voltage of the IP to 47 V, the zener diode D9 opens. This turns on the optocoupler and forces the controller to reduce the output voltage.

Interested in getting to know NCP1014 in person? - No problem!

For those who, before starting to develop their own IP based on NCP1014, want to make sure that this is a really simple, reliable and effective solution, ONSemiconductor produces several types of evaluation boards (see Table 1, Fig. 6; available for order through COMPEL).

Table 1. Overview of evaluation boards

Order code	Name	Short description
NCP1014LEDGTGEVB	8W LED driver with 0.8 power factor	The board is designed to demonstrate the possibility of building an LED driver with a power factor > 0.7 (Energy Star standard) without using an additional PFC chip. The output power (8 W) makes this solution ideal for powering structures like the Cree XLAMP MC-E containing four LEDs in series in one package.
NCP1014STBUCKGEVB	Non-inverting buck converter	The board is proof of the claim that the NCP1014 controller is enough to build a low price range power supply for harsh environments.

Rice. 6.

In addition, there are several more examples of the finished design of various IPs, in addition to those discussed in the article. This is a 5 W AC / DC adapter for cell phones, and another IP option for LED, as well as a large number of articles on the use of the NCP1014 controller, which you can find on the official website of ONSemiconductor - http://www.onsemi.com/.

COMPEL is the official distributor of ONSemiconductor and therefore on our website you can always find information on the availability and cost of chips manufactured by ONS, as well as order prototypes, including the NCP1014.

Conclusion

The use of the NCP1014 controller manufactured by ONS makes it possible to develop high-performance AC/DC converters for supplying loads with a stabilized current. Proper use of the key features of the controller makes it possible to ensure the safety of the final power supply in the conditions of an open or short circuit of the load with a minimum number of additional electronic components.

Literature

1. Konstantin Staroverov "The use of NCP101X / 102X controllers in the development of medium-power network power supplies", Electronics News magazine, No. 3, 2010, ss. 7-10.

4. Mac Raymond. Switching power supplies. Theoretical foundations of design and guidance on practical application / Per. from English. Pryanichnikova S.V., M.: Dodeka-XXI Publishing House, 2008, - 272 p.: ill.

5. Vdovin S.S. Design of pulse transformers, L .: Energoatomizdat, 1991, - 208 p.: ill.

6. TND329-D. "5W Cellular Phone CCCV AC-DC Adepter"/ http://www.onsemi.com/pub_link/Collateral/TND329-D.PDF.

7. TND371-D. "Offline LED Driver Intended for ENERGY STAR"/ http://www.onsemi.com/pub_link/Collateral/TND371-D.PDF.

Obtaining technical information, ordering samples, delivery - e-mail:

NCP4589 - LDO Regulator
with automatic energy saving

NCP4589 - new 300mA CMOS LDO regulator from ON Semiconductor. The NCP4589 switches to low current mode at low current load and automatically switches back to "fast" mode as soon as the output load exceeds 3 mA.

The NCP4589 can be put into permanent fast operation mode by forced mode selection (special input control).

Key Features of NCP4589:

Operating range of input voltages: 1.4 ... 5.25V
Output voltage range: 0.8…4.0V (in 0.1V increments)
Input current in three modes:

Low Power Mode - 1.0µA at V OUT< 1,85 В

Fast Mode - 55µA

Power saving mode - 0.1 uA

Minimum voltage drop: 230mV at I OUT = 300mA, V OUT = 2.8V
High voltage ripple rejection: 70dB at 1kHz (in fast mode).

NCP4620 Wide Range LDO Regulator

NCP4620 - This is a CMOS LDO regulator for 150mA from ON Semiconductor with an input voltage range of 2.6 to 10 V. The device has a high output accuracy - about 1% - with a low temperature coefficient of ±80 ppm/°C.

The NCP4620 has overheat protection and an Enable input, and is available with a standard output and an Auto Discharge output.

Key Features of NCP4620:

Operating input voltage range from 2.6 to 10V (max. 12V)
Output fixed voltage range from 1.2 to 6.0V (100mV steps)
Direct minimum voltage drop - 165mV (at 100mA)
Power supply ripple suppression - 70dB
Chip power off when overheated up to 165°C

This article describes how to assemble a simple but effective LED brightness control based on PWM dimming () LED lighting.

LEDs (light emitting diodes) are very sensitive components. If the supply current or voltage exceeds the allowable value, it can lead to their failure or significantly reduce the service life.

Usually, the current is limited using a resistor connected in series with the LED, or by a circuit current regulator (). Increasing the current on the LED increases its intensity, and reducing the current reduces it. One way to control the brightness of the glow is to use a variable resistor () to dynamically change the brightness.

But this is only applicable to a single LED, since even in one batch there may be diodes with different luminous intensity and this will affect the uneven glow of a group of LEDs.

Pulse width modulation. A much more efficient method of regulating the brightness of the glow by applying (PWM). With PWM, groups of LEDs are supplied with the recommended current, while at the same time dimming is possible by supplying power at a high frequency. Changing the period causes a change in brightness.

The duty cycle can be thought of as the ratio of the power on and off times supplied to the LED. For example, if we consider a cycle of one second and at the same time the LED will be 0.1 seconds off, and 0.9 seconds on, it turns out that the glow will be about 90% of the nominal value.

Description of PWM dimmer

The easiest way to achieve this high frequency switching is to use a IC, one of the most common and most versatile ICs ever made. The PWM controller circuit shown below is designed to be used as a dimmer to power LEDs (12 volts) or a speed controller for a 12 volt DC motor.

In this circuit, the resistors to the LEDs need to be adjusted to provide a forward current of 25mA. As a result, the total current of the three lines of LEDs will be 75mA. The transistor must be rated for a current of at least 75 mA, but it is better to take it with a margin.

This dimmer circuit is dimmable from 5% to 95%, but by using germanium diodes instead of , the range can be extended from 1% to 99% of the nominal value.

In some cases, for example, in flashlights or home lighting fixtures, it becomes necessary to adjust the brightness of the glow. It would seem that it’s easier: just change the current through the LED by increasing or decreasing. But in this case, a significant part of the energy will be consumed on the limiting resistor, which is completely unacceptable for autonomous power supply from batteries or accumulators.

In addition, the color of the glow of the LEDs will change: for example, white color when the current drops below the nominal value (for most LEDs 20mA) will have a slightly greenish tint. Such a change in color in some cases is completely useless. Imagine that these LEDs illuminate the screen of a TV or computer monitor.

In these cases, apply PWM - regulation (width - pulse). Its meaning is that it periodically lights up and goes out. In this case, the current remains nominal throughout the entire flash time, so the luminescence spectrum is not distorted. If the LED is white, then green shades will not appear.

In addition, with this method of power control, energy losses are minimal, the efficiency of circuits with PWM control is very high, reaching more than 90 percent.

The principle of PWM - regulation is quite simple, and is shown in Figure 1. A different ratio of the time of the lit and extinguished state is perceived by the eye as: like in a movie - frames shown separately in turn are perceived as a moving image. It all depends on the projection frequency, which will be discussed a little later.

Figure 1. The principle of PWM - regulation

The figure shows the signal diagrams at the output of the PWM control device (or master oscillator). Zero and one are indicated: a logical one (high level) causes the LED to glow, a logical zero (low level), respectively, extinction.

Although everything can be the other way around, since it all depends on the circuitry of the output key, turning on the LED can be done at a low level and turning it off, just high. In this case, a physically logical one will have a low voltage level, and a logical zero will be high.

In other words, a logical one causes some event or process to turn on (in our case, the LED lights up), and a logical zero should turn off this process. That is, not always a high level at the output of a digital microcircuit is a LOGICAL unit, it all depends on how a particular circuit is built. This is so, for information. But for now, we will assume that the key is controlled by a high level, and it simply cannot be otherwise.

Frequency and width of control pulses

Note that the pulse period (or frequency) remains unchanged. But, in general, the pulse frequency does not affect the brightness of the glow, therefore, there are no special requirements for frequency stability. Only the duration (WIDTH), in this case, of a positive pulse changes, due to which the whole mechanism of pulse-width modulation works.

The duration of the control pulses in Figure 1 is expressed in %%. This is the so-called "duty cycle" or, in English terminology, DUTY CYCLE. It is expressed as the ratio of the duration of the control pulse to the pulse repetition period.

In Russian terminology, it is usually used "duty cycle" - the ratio of the repetition period to the time of the impulse A. Thus, if the fill factor is 50%, then the duty cycle will be equal to 2. There is no fundamental difference here, therefore, you can use any of these values, to whom it is more convenient and understandable.

Here, of course, one could give formulas for calculating the duty cycle and DUTY CYCLE, but in order not to complicate the presentation, we will do without formulas. Last but not least, Ohm's law. There's nothing you can do about it: "You don't know Ohm's law, stay at home!" If anyone is interested in these formulas, they can always be found on the Internet.

PWM frequency for dimmer

As mentioned a little higher, there are no special requirements for the stability of the PWM pulse frequency: well, it “floats” a little, and that’s okay. PWM controllers have a similar frequency instability, by the way, quite large, which does not interfere with their use in many designs. In this case, it is only important that this frequency does not fall below a certain value.

And what should be the frequency, and how unstable can it be? Do not forget that we are talking about dimmers. In film technology, there is a term "critical flicker frequency". This is the frequency at which individual pictures displayed one after the other are perceived as a moving picture. For the human eye, this frequency is 48 Hz.

This is precisely the reason why the frame rate on film was 24fps (the television standard is 25fps). To increase this frequency to the critical one, film projectors use a two-bladed obturator (shutter) that overlaps each displayed frame twice.

In amateur narrow-film 8mm projectors, the projection frequency was 16 frames / sec, so the obturator had as many as three blades. The same purpose in television is served by the fact that the image is shown in half-frames: first even, and then odd lines of the image. The result is a flicker frequency of 50 Hz.

The operation of the LED in PWM mode is a separate flash of adjustable duration. In order for these flashes to be perceived by the eye as a continuous glow, their frequency must in no way be less than the critical one. Any higher, but no lower. This factor should be taken into account when creating PWM - controllers for lamps.

By the way, just as an interesting fact: scientists have somehow determined that the critical frequency for the eye of a bee is 800 Hz. Therefore, the bee will see the movie on the screen as a sequence of separate images. In order for her to see a moving image, the projection frequency will need to be increased to eight hundred fields per second!

To control the actual LED is used. Recently, the most widely used for this purpose are those that allow switching significant power (the use of conventional bipolar transistors for these purposes is considered simply indecent).

Such a need, (powerful MOSFET - transistor) arises with a large number of LEDs, for example, with, which will be discussed a little later. If the power is low - when using one or two LEDs, you can use low-power switches, and if possible, connect the LEDs directly to the outputs of the microcircuits.

Figure 2 shows a functional diagram of a PWM controller. Resistor R2 is conditionally shown as a control element in the diagram. By rotating its knob, you can change the duty cycle of the control pulses within the required limits, and, consequently, the brightness of the LEDs.

Figure 2. Functional diagram of the PWM controller

The figure shows three strings of LEDs connected in series with terminating resistors. Approximately the same connection is used in LED strips. The longer the tape, the more LEDs, the greater the current consumption.

It is in these cases that powerful ones will be required, the allowable drain current of which should be slightly more than the current consumed by the tape. The last requirement is met quite easily: for example, the IRL2505 transistor has a drain current of about 100A, a drain voltage of 55V, while its size and price are quite attractive for use in various designs.

PWM master oscillators

A microcontroller can be used as a master PWM oscillator (most often in industrial conditions), or a circuit made on microcircuits with a low degree of integration. If it is planned to make a small number of PWM controllers at home, and there is no experience in creating microcontroller devices, then it is better to make a controller on what is currently at hand.

These can be logic circuits of the K561 series, integrated timer, as well as specialized circuits designed for. In this role, you can even make it work by assembling an adjustable generator on it, but this is, perhaps, "for the love of art." Therefore, only two schemes will be considered below: the most common on the 555 timer, and on the UC3843 UPS controller.

Schematic of the master oscillator on the timer 555

Figure 3. Schematic of the master oscillator

This circuit is a conventional square wave generator whose frequency is set by capacitor C1. The capacitor is charged through the circuit "Output - R2 - RP1-C1 - common wire". In this case, a high-level voltage must be present at the output, which is equivalent to the output being connected to the positive pole of the power source.

The capacitor is discharged along the circuit "C1 - VD2 - R2 - Output - common wire" at a time when there is a low level voltage at the output - the output is connected to a common wire. It is this difference in the charge-discharge paths of the time-setting capacitor that provides pulses with adjustable width.

It should be noted that diodes, even of the same type, have different parameters. In this case, their electrical capacitance plays a role, which changes under the action of voltage across the diodes. Therefore, along with the change in the duty cycle of the output signal, its frequency also changes.

The main thing is that it does not become less than the critical frequency, which was mentioned a little higher. Otherwise, instead of a uniform glow with different brightness, individual flashes will be visible.

Approximately (again, the diodes are to blame), the frequency of the generator can be determined by the formula shown below.

The frequency of the PWM generator on the timer 555.

If we substitute the capacitance of the capacitor in farads and the resistance in ohms into the formula, then the result should be in hertz Hz: you can’t get away from the SI system! This assumes that the slider of the variable resistor RP1 is in the middle position (in the formula RP1 / 2), which corresponds to the output signal of the meander shape. In Figure 2, this is exactly the part where the pulse duration is 50%, which is equivalent to a signal with a duty cycle of 2.

PWM master oscillator on a UC3843 chip

Its scheme is shown in Figure 4.

Figure 4. Schematic of the PWM master oscillator on the UC3843 chip

The UC3843 chip is a control PWM controller for switching power supplies and is used, for example, in ATX format computer sources. In this case, the typical scheme for its inclusion has been somewhat changed towards simplification. To control the width of the output pulse, a control voltage of positive polarity is applied to the input of the circuit, then a PWM pulse signal is obtained at the output.

In the simplest case, the control voltage can be applied using a variable resistor with a resistance of 22 ... 100 KΩ. If necessary, control voltage can be obtained, for example, from an analog light sensor made on a photoresistor: the darker it is outside the window, the brighter it is in the room.

The control voltage affects the PWM output in such a way that when it is reduced, the output pulse width increases, which is not at all surprising. After all, the original purpose of the UC3843 microcircuit is to stabilize the voltage of the power supply: if the output voltage drops, and with it the regulating voltage, then measures must be taken (increase the width of the output pulse) to slightly increase the output voltage.

Regulating voltage in power supplies is generated, as a rule, using zener diodes. More often than not, this or something similar.

With the ratings of the parts indicated in the diagram, the generator frequency is about 1 kHz, and unlike the generator on the 555 timer, it does not “float” when the duty cycle of the output signal changes - taking care of the frequency of switching power supplies.

To regulate a significant power, for example, an LED strip, a key stage on a MOSFET transistor should be connected to the output, as shown in Figure 2.

We could talk more about PWM controllers, but for now let's stop there, and in the next article we will look at various ways to connect LEDs. After all, not all methods are equally good, there are those that should be avoided, and there are simply plenty of errors when connecting LEDs.

The simplest LED dimmer circuit presented in this article can be successfully applied in car tuning, and just to increase comfort in the car at night, for example, to illuminate the instrument panel, glove compartments, and so on. To assemble this product, you do not need technical knowledge, just be careful and accurate.
The voltage of 12 volts is considered completely safe for people. If you use an LED strip in your work, then we can assume that you will not suffer from a fire either, since the strip practically does not heat up and cannot catch fire from overheating. But accuracy in work is needed, so as not to allow a short circuit in the mounted device and as a result of a fire, which means to save your property.
Transistor T1, depending on the brand, can regulate the brightness of LEDs with a total power of up to 100 watts, provided that it is installed on a cooling radiator of the appropriate area.
The operation of the transistor T1 can be compared with the operation of an ordinary water tap, and the potentiometer R1 with its handle. The more you turn, the more water flows. So here. The more you turn off the potentiometer, the more current flows. You twist it - it flows less and the LEDs shine less.

Regulator circuit

For this scheme, we need not numerous details.
Transistor T1. You can apply KT819 with any letter. KT729. 2N5490. 2N6129. 2N6288. 2SD1761. BD293. BD663. BD705. BD709. BD953. These transistors need to be selected depending on how much LED power you plan to control. Depending on the power of the transistor is also its price.
Potentiometer R1 can be any type of resistance from three to twenty kilos. A three kiloohm potentiometer will only slightly reduce the brightness of the LEDs. Ten kilo-ohm - will reduce almost to zero. Twenty - will adjust from the middle of the scale. Choose what suits you best.
If you use an LED strip, then you do not have to bother with the calculation of the damping resistance (in the R2 and R3 diagrams) using the formulas, because these resistances are already built into the tape during manufacture and all you need is to connect it to a voltage of 12 volts. Just need to buy a tape specifically for a voltage of 12 volts. If you connect a tape, then exclude the resistances R2 and R3.
They also produce LED assemblies designed for 12 volt power supply, and LED bulbs for cars. In all these devices, during manufacture, quenching resistors or power drivers are built in and they are directly connected to the on-board network of the machine. If you are only taking the first steps in electronics, then it is better to use just such devices.
So, we have decided on the components of the circuit, it's time to start assembling.

We fasten the transistor to the cooling radiator with a bolt through a heat-conducting insulating gasket (so that there is no electrical contact between the radiator and the vehicle's on-board network, in order to avoid a short circuit).