Powerful PWM regulator. Digital PWM brushed motor speed controller Reversible PWM motor speed controller

When working with many different technologies, the question is often: how to manage the power that is available? What to do if it needs to be lowered or raised? The answer to these questions is a PWM regulator. What is he? Where is it used? And how to assemble such a device yourself?

What is pulse width modulation?

Without clarifying the meaning of this term, it makes no sense to continue. So, pulse-width modulation is the process of controlling the power that is supplied to the load, carried out by modifying the duty cycle of the pulses, which is done at a constant frequency. There are several types of pulse width modulation:

1. Analog.

2. Digital.

3. Binary (two-level).

4. Trinity (three-level).

What is a PWM regulator?

Now that we know what pulse width modulation is, we can talk about the main topic of the article. A PWM regulator is used to regulate the supply voltage and to prevent powerful inertial loads in automobiles and motorcycles. This may sound complicated and is best explained with an example. Let’s say you need to make the interior lighting lamps change their brightness not immediately, but gradually. The same applies to side lights, car headlights or fans. This desire can be realized by installing a transistor voltage regulator (parametric or compensation). But with a large current, it will generate extremely high power and will require the installation of additional large radiators or an addition in the form of a forced cooling system using a small fan removed from the computer device. As you can see, this path entails many consequences that will need to be overcome.

The real salvation from this situation was the PWM regulator, which operates on powerful field-effect power transistors. They can switch high currents (up to 160 Amps) with only 12-15V gate voltage. It should be noted that the resistance of an open transistor is quite low, and thanks to this, the level of power dissipation can be significantly reduced. To create your own PWM regulator, you will need a control circuit that can provide a voltage difference between the source and gate within the range of 12-15V. If this cannot be achieved, the channel resistance will greatly increase and the power dissipation will increase significantly. And this, in turn, can cause the transistor to overheat and fail.

A whole range of microcircuits for PWM regulators are produced that can withstand an increase in input voltage to a level of 25-30V, despite the fact that the power supply will be only 7-14V. This will allow the output transistor to be turned on in the circuit along with the common drain. This, in turn, is necessary to connect a load with a common minus. Examples include the following samples: L9610, L9611, U6080B ... U6084B. Most loads do not draw more than 10 amps of current, so they cannot cause voltage sags. And as a result, you can use simple circuits without modification in the form of an additional unit that will increase the voltage. And it is precisely these samples of PWM regulators that will be discussed in the article. They can be built on the basis of an asymmetrical or standby multivibrator. It’s worth talking about the PWM engine speed controller. More on this later.

Scheme No. 1

This PWM controller circuit was assembled using CMOS chip inverters. It is a rectangular pulse generator that operates on 2 logic elements. Thanks to the diodes, the time constant of discharge and charge of the frequency-setting capacitor changes separately here. This allows you to change the duty cycle of the output pulses, and as a result, the value of the effective voltage that is present at the load. In this circuit, it is possible to use any inverting CMOS elements, as well as NOR and AND. Examples include K176PU2, K561LN1, K561LA7, K561LE5. You can use other types, but before that you will have to think carefully about how to correctly group their inputs so that they can perform the assigned functionality. The advantages of the scheme are the accessibility and simplicity of the elements. Disadvantages are the difficulty (almost impossibility) of modification and imperfection regarding changing the output voltage range.

Scheme No. 2

It has better characteristics than the first sample, but is more difficult to implement. Can regulate the effective load voltage in the range of 0-12V, to which it changes from an initial value of 8-12V. The maximum current depends on the type of field-effect transistor and can reach significant values. Given that the output voltage is proportional to the control input, this circuit can be used as part of a control system (to maintain the temperature level).

Reasons for the spread

What attracts car enthusiasts to a PWM controller? It should be noted that there is a desire to increase efficiency when constructing secondary ones for electronic equipment. Thanks to this property, this technology can also be found in the manufacture of computer monitors, displays in phones, laptops, tablets and similar equipment, and not just in cars. It should also be noted that this technology is significantly inexpensive when used. Also, if you decide not to buy, but to assemble a PWM controller yourself, you can save money when improving your own car.

Conclusion

Well, you now know what a PWM power regulator is, how it works, and you can even assemble similar devices yourself. Therefore, if you want to experiment with the capabilities of your car, there is only one thing to say about this - do it. Moreover, you can not only use the diagrams presented here, but also significantly modify them if you have the appropriate knowledge and experience. But even if everything doesn’t work out the first time, you can gain a very valuable thing - experience. Who knows where it might come in handy next and how important its presence will be.

Smooth engine operation, without jerks or power surges, is the key to its durability. To control these indicators, an electric motor speed controller is used for 220V, 12V and 24V; all of these frequencies can be made with your own hands or you can buy a ready-made unit.

Why do you need a speed controller?

An engine speed controller, a frequency converter, is a device with a powerful transistor, which is necessary to invert the voltage, as well as to ensure smooth stopping and starting of an asynchronous motor using PWM. PWM – wide-pulse control of electrical devices. It is used to create a specific sinusoid of alternating and direct current.

The simplest example of a converter is a conventional voltage stabilizer. But the device under discussion has a much wider range of operation and power.

Frequency converters are used in any device that is powered by electrical energy. Governors provide extremely precise electrical motor control so that engine speed can be adjusted up or down, maintaining revs at the desired level, and protecting instruments from sudden revving. In this case, the electric motor uses only the energy needed to operate, instead of running it at full power.

Why do you need a speed controller for an asynchronous electric motor:

1. To save energy. By controlling the speed of the motor, the smoothness of its start and stop, strength and speed, you can achieve significant savings in personal funds. As an example, reducing speed by 20% can result in energy savings of 50%.
2. The frequency converter can be used to control process temperature, pressure or without the use of a separate controller;
3. No additional controller required for soft start;
4. Maintenance costs are significantly reduced.

The device is often used for a welding machine (mainly for semi-automatic machines), an electric stove, a number of household appliances (vacuum cleaner, sewing machine, radio, washing machine), home heater, various ship models, etc.

Operating principle of the speed controller

The speed controller is a device consisting of the following three main subsystems:

1. AC motor;
2. Main drive controller;
3. Drive and additional parts.

When the AC motor is started at full power, current is transferred with the full power of the load, this is repeated 7-8 times. This current bends the motor windings and generates heat that will be generated for a long time. This can significantly reduce engine longevity. In other words, the converter is a kind of step inverter that provides double energy conversion.

Depending on the incoming voltage, the frequency regulator of the speed of a three-phase or single-phase electric motor rectifies the current of 220 or 380 volts. This action is carried out using a rectifying diode, which is located at the energy input. Next, the current is filtered using capacitors. Next, PWM is generated, the electrical circuit is responsible for this. Now the windings of the induction motor are ready to transmit the pulse signal and integrate them into the desired sine wave. Even with a microelectric motor, these signals are issued, literally, in batches.

How to choose a regulator

There are several characteristics by which you need to choose a speed controller for a car, machine electric motor, or household needs:

1. Control type. For commutator motors, there are regulators with a vector or scalar control system. The former are more often used, but the latter are considered more reliable;
2. Power. This is one of the most important factors for choosing an electrical frequency converter. It is necessary to select a frequency generator with a power that corresponds to the maximum permissible on the protected device. But for a low-voltage motor it is better to choose a regulator more powerful than the permissible watt value;
3. Voltage. Naturally, everything here is individual, but if possible, you need to buy a speed controller for an electric motor, the circuit diagram of which has a wide range of permissible voltages;
4. Frequency range. Frequency conversion is the main task of this device, so try to choose a model that will best suit your needs. Let's say, for a manual router, 1000 Hertz will be enough;
5. According to other characteristics. This is the warranty period, the number of inputs, the size (there is a special attachment for desktop machines and hand tools).

At the same time, you also need to understand that there is a so-called universal rotation regulator. This is a frequency converter for brushless motors.

There are two parts in this circuit - one is logical, where the microcontroller is located on the chip, and the second is power. Basically, such an electrical circuit is used for a powerful electric motor.

Video: electric motor speed controller with SHIRO V2

How to make a homemade engine speed controller

You can make a simple triac motor speed controller, its diagram is presented below, and the price consists only of parts sold in any electrical store.

To work, we need a powerful triac of the BT138-600 type, it is recommended by a radio engineering magazine.

In the described circuit, the speed will be adjusted using potentiometer P1. Parameter P1 determines the phase of the incoming pulse signal, which in turn opens the triac. This scheme can be used both in field farming and at home. You can use this regulator for sewing machines, fans, tabletop drilling machines.

The principle of operation is simple: at the moment when the motor slows down a little, its inductance drops, and this increases the voltage in R2-P1 and C3, which in turn leads to a longer opening of the triac.

A thyristor feedback regulator works a little differently. It allows energy to flow back into the energy system, which is very economical and beneficial. This electronic device involves the inclusion of a powerful thyristor in the electrical circuit. His diagram looks like this:

Here, to supply direct current and rectify, a control signal generator, an amplifier, a thyristor, and a speed stabilization circuit are required.

It is convenient to regulate the supply voltage of powerful consumers using regulators with pulse-width modulation. The advantage of such regulators is that the output transistor operates in switch mode, which means it has two states - open or closed. It is known that the greatest heating of the transistor occurs in a half-open state, which leads to the need to install it on a large area radiator and save it from overheating.

I propose a simple PWM regulator circuit. The device is powered from a 12V DC voltage source. With the specified instance of the transistor, it can withstand current up to 10A.

Let's consider the operation of the device: A multivibrator with an adjustable duty cycle is assembled on transistors VT1 and VT2. The pulse repetition rate is about 7 kHz. From the collector of transistor VT2, pulses are sent to key transistor VT3, which controls the load. The duty cycle is regulated by variable resistor R4. When the slider of this resistor is in the extreme left position, see the top diagram, the pulses at the output of the device are narrow, which indicates the minimum output power of the regulator. In the extreme right position, see the bottom diagram, the pulses are wide, the regulator operates at full power.

Diagram of PWM operation in KT1

Using this regulator, you can control 12 V household incandescent lamps, a DC motor with an insulated housing. If the regulator is used in a car, where the minus is connected to the body, the connection should be made through a pnp transistor, as shown in the figure.
Details: Almost any low-frequency transistors can operate in the generator, for example KT315, KT3102. Key transistor IRF3205, IRF9530. We can replace the pnp transistor P210 with KT825, and the load can be connected to a current of up to 20A!

And in conclusion, it should be said that this regulator has been working in my car with an interior heating engine for more than two years.

List of radioelements

Another electronic device with wide application.
It is a powerful PWM (PWM) controller with smooth manual control. It operates at a constant voltage of 10-50V (it is better not to go beyond the range of 12-40V) and is suitable for regulating the power of various consumers (lamps, LEDs, motors, heaters) with a maximum current consumption of 40A.

Sent in a standard padded envelope




The case is held together with latches that break easily, so open it carefully.


Inside the circuit board and the removed regulator knob


The printed circuit board is double-sided fiberglass, soldering and installation are neat. Connection via a powerful terminal block.




Ventilation slots in the case are ineffective, because... almost completely covered by the printed circuit board.


When assembled it looks something like this


The actual dimensions are slightly larger than stated: 123x55x40mm

Schematic diagram of the device


The declared PWM frequency is 12kHz. The actual frequency varies in the range of 12-13kHz when adjusting the output power.
If necessary, the PWM operating frequency can be reduced by soldering the desired capacitor in parallel with C5 (initial capacitance 1nF). It is not advisable to increase the frequency, because switching losses will increase.
The variable resistor has a built-in switch in the leftmost position that allows you to turn off the device. There is also a red LED on the board that lights up when the regulator is operating.
For some reason, the markings on the PWM controller chip have been carefully erased, although it’s easy to guess that it’s an analogue of NE555 :)
The regulation range is close to the stated 5-100%
Element CW1 looks like a current stabilizer in the diode body, but I’m not sure exactly...
As with most power regulators, regulation is carried out via the negative conductor. There is no short circuit protection.
There are initially no markings on the mosfets and diode assembly; they are located on individual radiators with thermal paste.
The regulator can operate on an inductive load, because At the output there is an assembly of protective Schottky diodes, which suppresses the self-induction EMF.
A test with a current of 20A showed that the radiators heat up slightly and can draw more, presumably up to 30A. The measured total resistance of the open channels of field workers is only 0.002 Ohm (drops 0.04V at a current of 20A).
If you reduce the PWM frequency, you will pull out all the declared 40A. Sorry I can't check...

You can draw your own conclusions, I liked the device :)