Page 86 - Understanding Automotive Electronics

2735 | CH 3 Page 73 Tuesday, March 10, 1998 11:03 AM

ELECTRONICS FUNDAMENTALS 3

Figure 3.1
Diode
Characteristics

FPO

convert the ac voltage into a dc voltage for use with automotive alternators to
provide dc current for battery charging.
The use of a capacitor to The input voltage V of Figure 3.1c is ac; the output voltage V has a dc
in
out
store charge and resist component and a time-varying component, as shown in Figure 3.1d. The
voltage changes smooths output voltage of the half-wave rectifier can be smoothed by adding a capacitor,
the rippling or pulsating which is represented by the dotted lines in Figure 3.1c. Since the capacitor
output of a half-wave stores a charge and opposes voltage changes, it discharges (supplies current) to
rectifier. the load resistance R when V is going negative from its peak voltage. The
in
capacitor is recharged when V comes back to its positive peak and current is
in
supplied to the load by the V . The result is V that is more nearly a smooth,
in
out
steady dc voltage, as shown by the dotted lines between the peaks of Figure
3.1d.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 73