TC 9-62
Figure 4-23. Half-wave Rectifier with an LC Choke-input Filter
4-59. Redraw the filter circuit so that you can see the voltage divider action (see Figure
4-24, view (A). Remember, the 165 volts peak-to-peak 60 Hz provided by the rectifier
consists of both an AC and a DC component. In Figure 4-24, you can see that the capacitor
(C1) offers the least opposition (265 ohms) to the AC component. Therefore, the greatest
amount of AC will flow through C1 (the heavy line indicates the AC current flow through
the capacitor). So, the capacitor bypasses, or shunts, most of the AC around the load.
Figure 4-24. AC Component in an LC Choke-input Filter
Figure 4-24, view (B)), you will have a total resistance of 258 ohms. To compute this, use
the following formula:
(R1) (R 2)
RT =
R1 + R 2
You now have a voltage divider (see Figure 4-25). Notice that because of the impedance
ratios, a large amount of ripple voltage is dropped across L1 and a substantially smaller
amount is dropped across C1 and RL. You can further increase the ripple voltage across L1
4-22
TC 9-62
23 June 2005
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