PWM controller: principle of operation and scope
The very principle of pulse-width simulation(PWM) has been known for a long time, but it was applied relatively recently in various schemes. It is the key to the operation of many devices used in various fields: uninterruptible power supplies of various capacities, frequency converters, voltage regulation systems, current or speed, laboratory frequency converters, etc. He perfectly showed himself in the automotive industry and in production as an element for controlling the operation of both service and powerful electric motors. The PWM regulator has proven itself in various circuits.
Let's look at some practicalexamples showing how it is possible to regulate the speed of rotation of the electric motor by means of electronic circuits incorporating a PWM controller. Suppose that you need to change the speed of the electric motor in the heating system of the cabin of your car. It's quite a useful improvement, is not it? Especially in the off-season, when you want to adjust the temperature in the cabin smoothly. The DC motor installed in this system allows you to vary the speed, but you need to affect its EMF. With the help of modern electronic elements this task is easy to perform. For this, a powerful field-effect transistor is switched on in the engine power circuit. Manages it, as you may have guessed, a PWM regulator. With it, you can change the speed of the motor in a wide range.
How does the PWM regulator operate in circuitsalternating current? In this case, a somewhat different control scheme is used, but the principle of operation remains the same. As an example, we can consider the operation of a frequency converter. Such devices are widely used in industry to regulate the speed of engines. To begin with, the three-phase voltage is rectified with the help of the Larionov bridge and partially smoothed out. And only then it is fed to a powerful bipolar assembly or a module based on FETs. It is controlled by a PWM voltage regulator assembled on the basis of a microcontroller. It also forms control impulses, their width and frequency, which is necessary for forming a certain speed of the electric motor.
Unfortunately, in addition to good operationalcharacteristics, in circuits where a PWM controller is used, there are usually strong interference in the power circuit. This is due to the presence of inductance in the windings of the motors and the line itself. They struggle with this variety of circuit solutions: they install powerful network filters in alternating current circuits or put a reverse diode parallel to the motor in circuits of permanent power supply.
Such schemes are quite highreliability in work and are innovative in the field of controlling electric drives of various capacities. They are compact enough and well manageable. The latest modifications of such devices are widely used in manufacturing.