Voltage Regulator

Most electronic equipment performs satis­factorily with some variations in supply voltage. However, operation of many circuits is sensitive to minimal changes in supply voltage. Thus, use of a voltage regulator is required. This chapter discusses the common types of elec­tronic voltage regulators. Also discussed are the electronic multimeter and the digital volt­meter.

Elec­tronic Voltage Regulators:

An electronic voltage regulator is connected between the power supply and load impedance to maintain the output voltage at a specific value. The regulator circuit reacts automatically within its design limits to compensate for devia­tions in output voltage due to changes in line voltage or variations in load impedance. Regulation of power supply output voltages using zener diodes and gas tubes has previously been discussed. While these devices are suit­able for circuit loads requiring small currents, they cannot regulate over a wide current range. Current handling capabilities, as well as percent of regulation, can be improved by using transis­tors or electron tubes in conjunction with the zener diode or gas tube. Depending upon their circuit relationship to the load impedance, electronic voltage regu­lators may be grouped into two general types. These are shunt regulators and series regu­lators. Series regulators are the most efficient, and therefore, are the most widely used.

The voltage reference generates a voltage level which is applied to the comparator circuit, which is generally error amplifier. The second input to the error amplifier is obtained through feedback network. Generally using the potential divider, the feedback signal is derived by sampling the output voltage. The error amplifier converts the difference between the output sample and the reference voltage into an error signal. This error signal in turn controls the active element of the regulator circuit, in order to compensate the change in the output voltage. Such an active element is generally a transistor. Thus the output voltage of the regulator is maintained constant.

Types of Voltage Regulators:

There are two types of voltage regulators available namely,

• Shunt voltage regulator
• Series voltage regulator

Each type provides a constant DC output voltage which is regulated. Let us discuss the functional block diagram and working principle of each of these two types of regulator circuits.

Questionnaire:

• What is voltage regulator?