Q. What is meant by regulation?

The output of most power supplies should be a constant voltage. Unfortunately, this is difficult to achieve. There are two factors that can cause the output voltage to change.

· Change in AC Line Voltage

· Change in Load Resistance

First, the ac line voltage is not constant. The so-called 46 volts ac can vary from about 36 volts ac to 56 volts ac. This means that the peak ac voltage to which the rectifier responds can vary from about 40 volts to 50 volts. The ac line voltage alone can be responsible for nearly a 20 percent change in the dc output voltage.

The second factor that can change the dc output voltage is a change in the load resistance. In complex electronic equipment, the load can change as circuits are switched in and out. In a television receiver, the load on a particular power supply may depend on the brightness of the screen, the control settings, or even the channel selected. 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. There are many different types of regulators in use today.