e x a m p l e 4.13
half-wave
rectifier
re-examined
As another example of piecewise linear analysis, we re-examine the half-wave rectifier
circuit for a sinusoidal input previously analyzed using graphical analysis in Section 4.10.
This time around, we will use a piecewise linear model for the diode, but use the same
graphical approach of Section 4.10.
Thus we start with the same circuit topology as in Figure 4.21a, except that the diode
is modeled using its piecewise linear approximation, the ideal diode, as shown in
Figure 4.32a. Assuming as before a ten-volt sinusoidal input voltage, as might be typical
in power supplies, we draw a succession of load lines on the piecewise linear characteristics, Figure 4.32b, for representative values of the input wave, and plot the output voltage
point by point. The desired output voltage is vR , which in the graph is the horizontal
E = E o cos ( ωt )
+
-
R
+
vR
-
(a)
iD
Slope = -1/R
F I G U R E 4.32 Half-wave
rectifier: ideal diode piecewise
linear analysis.
vR
(b)
E
vD
vR
(c)
t
214a
distance from the operation point intersection to the input voltage. The resulting output
wave is shown in Figure 4.32c.
Comparison with the previous analysis, Section 4.10 and Figure 4.21, indicates that
at least for this problem, the simple ‘‘ideal diode’’ approximation yields a reasonably
accurate answer. As one would expect, the error mainly derives from the neglect of the
0.6-V drop across the diode. Clearly, the error would be more objectionable if the input
sinusoid had been of one volt peak rather than 10 volts.
214b