Rectifiers:
Almost all electronic circuits require a dc source of
power. For portable low power systems batteries may be used.
More frequently, however, electronic equipment is energized by
a power supply, a piece of equipment which converts the alter-
nating waveform from the power lines into an essentially direct
voltage.
Objective
To study the characteristics of halfwave rectifier with and without filter and to calculate the following parameters.
Ripple factor
Rectification efficiency
Theory
A device, such as the semiconductor diode, which is
capable of converting a sinusoidal input waveform (whose average value is zero) into a unidirectional (though not constant) waveform, with a nonzero average component, is called a rectifier. The basic circuit for half-wave rectification is shown below.
In a rectifier circuit the input is a sinusiodal wave
\( v_i = V_m sin(wt) \)
has a peak value V m which is very large compared with the cutin
voltage \( V_T \) of the diode, we assume in the following discussion
that \( V_\gamma = 0 \), (The condition \( V_I \neq 0 \) is treated. With the diode idealized to be a resistance \( R_f \) in the ON state and an open circuit in the OFF state, the current \( i \) in the diode or load \( R_L \) is given in
\( i = I_m sin(α) \qquad \quad if \quad 0 ≤ \alpha ≤ \pi \)
\( i =0 \qquad \qquad \qquad if \quad π ≤ \alpha ≤ 2\pi \)
where \(\alpha = \omega t \) and
\( I_m =\frac{V_m}{R_f+R_L} \)
Note that the output current is unidirectional. We
now calculate this nonzero value of the average current.
Sinusoidal voltage \( v_i \) Diode
and Load Voltage \(i\)
The voltage \( v_i \) is in figure and
the rectified diode voltage is in figure below
.
The input \( v_i \) and the rectified output \( v_o \) togeter in figure below
where \(V_{rms} = \) rms value of input,
\( V_{dc} = \) Average value of input and
\( V_m = \) peak value of output.
Ripple factor
\( r = \frac{V_{r,rms}}{V_{dc}} \)
where \( V_{r,rms} \) is the rms value of the ac component. Since
\( {V_{rms}}^2 = {V_{r,rms}}^2+{V_{dc}}^2 \)
\( r =\sqrt{ (\frac{V_{rms}}{V_{dc}})^2-1}=1.21 \)
Pre-Quiz
What a retifier do?
A half wave rectifier is defined as a type of rectifier that only allows ______________ of an AC voltage waveform to pass, blocking the other ____________.
Half wave rectifier is used in
Simulation
Instructions
Observe the circuit diagram of the halfwave rectifier
Click on the Power Button.
Select the Amplitide(A) of the input sine wave signal(Vi).
Select the frequency of the signal(f) for the input signal(Vi).
Select the "Channel 1" to observe the input signal on graph
Select the "Channel 2" to observe the rectified output signal on graph
Select the "Dual" to observe the input signal and rectified output signal on graph
Change the values of A, f to observe the variation in the input and output signals.
Hover on the graph to observe the value of the Vi and Vo at that instatnt of time T.
Save the graph if you are done with your experiment.
Note:
Ideal diode is considered
Make sure always Input Signal Amplitude>0 v
Make sure always Input Signal Frequency>0 Hz
Load resistance \( R=1k \Omega \)
To change the values just scroll by hovering on it.
