4-94. Ideally, the output voltage should not change over the full range of operation. That
is, a 12-volt power supply should produce 12 volts at no load, at full load, and at all points
in between. In this case, the percent of regulation would be computed by using the
E no load - Efull load
Percent of Regulation =
E full load
12 - 12
= 0 x 100
Therefore, zero-percent load regulation is the ideal situation. It means that the output
voltage is constant under all load conditions. While you should strive for zero-percent load
regulation, in practical circuits you must settle for something less ideal. Even so, by using a
voltage regulator, you can hold the percent of regulation to a very low value.
4-95. You should know that the output of a power supply varies with changes in input
voltage and circuit load current requirements. Since many electronic types of equipment
require operating voltages and currents that must remain constant, some form of regulation
is necessary. Circuits that maintain power supply voltages or current outputs within
specified limits, or tolerances, are called REGULATORS. Depending on their specific
application, they are designated as DC voltage or DC current regulators.
4-96. Voltage regulator circuits are additions to basic power supply circuits that are
made up of rectifier and filter sections (see Figure 4-30). The purpose of the voltage
regulator is to provide an output voltage with little or no variation. Regulator circuits sense
changes in output voltages and compensate for the changes. Regulators that maintain
voltages within plus or minus ()0.1 percent are quite common.
Figure 4-30. Block Diagram of a Power Supply and Regulator
Series and Shunt Voltage Regulators
4-97. The two basic types of voltage regulators are classified as either SERIES or
SHUNT. The type depends on the location or position of the regulating element(s) in
relation to the circuit load resistance. Figure 4-31 shows these two basic types of voltage
regulators. In actual practice, the circuitry of regulating devices may be quite complex.
Broken lines have been used in the figure to highlight the differences between the series
and shunt regulators.
23 June 2005