4-3
Q3. What is the purpose of the filter section?
Q4. What is the purpose of the regulator section?
THE POWER TRANSFORMER
In some cases a power supply may not use a transformer; therefore, the power supply would be
connected directly to the source line voltage. This type of connection is used primarily because it is
economical. However, unless the power supply is completely insulated, it presents a dangerous shock
hazard to anyone who comes in contact with it. When a transformer is not being used, the return side of
the ac line is connected to the metal chassis. To remove this potential shock hazard and to have the option
of stepping up or stepping down the input voltage to the rectifier, a transformer must be used.
View A of figure 4-2 shows the schematic diagram for a STEP-UP transformer; view B shows a
STEP-DOWN transformer; and, view C shows a STEP-UP, CENTER-TAPPED transformer. The step-up
and step-down transformers were discussed in earlier NEETS modules, so only the center-tapped
transformer will be mentioned in this chapter. The primary purpose of the center-tapped transformer is to
provide two equal voltages to the conventional full-wave rectifier.
Figure 4-2A.—Common types of transformers. STEP-UP
Figure 4-2B.—Common types of transformers. STEP-DOWN
