Ideally, the output of most power supplies should be a constant voltage. Unfortunately, this is difficult to achieve. ...factors that can cause the output voltage to change. [is]...
is a change in the load resistance. In complex electronic equipment, the load can change as circuits are switched in and out.
These variations in load resistance tend to change the applied dc voltage because the power supply has a fixed internal resistance. If the load resistance decreases, the internal resistance of the power supply drops more voltage.
This causes a decrease in the voltage across the load.
Many circuits are designed to operate with a particular supply voltage. When the supply voltage changes, the operation of the circuit may be adversely affected.
Consequently, some types of equipment must have power supplies that produce the same output voltage regardless of changes in the load resistance or changes in the ac line voltage. This constant output voltage may be achieved by adding a circuit called the VOLTAGE REGULATOR at the output of the filter.
LOAD REGULATION
A commonly used FIGURE OF MERIT for a power supply is its
PERCENT OF REGULATION. The figure of merit gives us an indication of how much the
output voltage changes over a range of load resistance values. The percent of regulation aids in the determination of the type of load regulation needed. Percent of regulation is determined by the equation:
This equation compares the
change in output voltage at the two
loading extremes to the voltage produced at full loading. For example, assume that a power supply produces 12 volts when the load current is zero. If the output voltage drops to 10 volts when full load current flows, then the percent of regulation is:
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.
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