4-30
Figure 4-27.—Full-wave rectifier with an LC choke-input filter.
When the XC of a filter capacitor is decreased, it provides less opposition to the flow of ac. The
greater the ac flow through the capacitor, the lower the flow through the load. Conversely, the larger the
XL of the choke, the greater the amount of ac ripple developed across the choke; consequently, less ripple
is developed across the load and better filtering is obtained.
Q21. In an LC choke-input filter, what prevents the rapid charging of the capacitor?
Q22. What is the range of values usually chosen for a choke?
Q23. If the impedance of the choke is increased, will the ripple amplitude increase or decrease?
FAILURE ANALYSIS OF AN LC CHOKE-INPUT FILTER.—The filter capacitors are subject
to open circuits, short circuits, and excessive leakage; the series inductor is subject to open windings and,
occasionally, shorted turns or a short circuit to the core.
