Chapter 6
Smoothing circuits and filters
By means of a smoothing circuit we can obtain continuous tension starting off of an alternate tension. Its practical use very extensive is given the great amount of electronic devices (most of these) that work with DC.
The basic element for the construction of rectifiers is the diode.
The rectifier simplest to realize is the one of average wave, which can be observed in the following figure:
We will analyze that he is what happens in each one of the intervals from the 1 to the 4.
In the first interval (1), the tension Versus is in the positive half-cycle, of this form we can suppose that she is positive in negative A and in B, receiving the diode direct polarization (+ anode and - cathode), allowing that the current circulates through him. If we measured the tension in the resistance, this one will practically be equal to the alternating current voltage of entrance Versus obtaining the indicated positive half-cycle with 1 in Vcc.
In interval 2 the polarity of the tension Versus has been reversed, of this form is negative in positive A and in B, polarizing to the diode in inverse sense consequently the same will not practically lead and will bring about a null tension in tips of the resistance, obtaining itself therefore the indicated null half-cycle with 2 in Vcc.
Continuing with the same analysis in intervals 3 and 4 the complete diagram for Vcc is obtained.
From this form we have obtained the tension Vcc, that Versus is rectified each average wave, having left to only pass the positive half-cycle of this one.
This rectified form of is not but advisable since a half-cycle of the signal of alternating is being wasted and if a later one is desired rectified to obtain continuous a pure one it will be very difficult to obtain given it the great asymmetry of this.
A better method is the one than it shows the following figure:
In this circuit two connected rectifying diodes with a transformer with intermediate taking have been used, which is connected to mass.
The form in which this rectifier works is very similar to the previous one, and the tensions in the different parts from the same are those that are in the figure:
As it is seen, to the D1 diode the V12 tension is applied to him and of the form already seen in the previous rectifier us dá an exit tension Versus as it is seen in the graph of Vs1.
To the D2 diode the V32 tension is applied to him and then we have the graficada tension Vs2 when coming out.
The tension of exit Versus is the sum of both and it is seen in the graph of Versus.
But this one continues being a method little used since it is due to have a transformer with intermediate taking.
The figure following sample the design of a rectifier who does not use a transformer with intermediate taking, thus is the one of greater use.
To this type of rectifiers rectifier denominates itself type bridge.
We have already seen the principle of the operation of the rectifiers, now we will see how to the rectified signal filters it to obtain continuous a pure one.
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