What is a Voltage Regulator?

A voltage regulator is a circuit that produces a fixed output voltage of a predetermined magnitude that remains constant regardless of input voltage or load conditions. It converts an unstable direct current voltage to a stable direct current voltage. Its power supply, which is made up of discrete components, offers a high output power and a wide range of adjustability. Integrated regulated power supply have become increasingly popular in recent years. Three-terminal series regulators are the most commonly used in low-power regulated power supplies. 78xx series, 79xx series, adjustable integrated voltage regulators, precise voltage reference integrated voltage regulators, and other integrated voltage regulators are commonly used in circuits.

How Does a Voltage Regulator Work? 

A voltage regulator is a circuit that generates and maintains a constant output voltage regardless of input voltage or load conditions. Voltage regulators (VRs) keep power supply voltages within a range that is compatible with the other electrical components. While most voltage regulators are used for DC/DC power conversion, some can also do AC/AC or AC/DC power conversion. The focus of this essay will be on DC/DC voltage regulators.

Classification of voltage regulators

Voltage regulators are classified into two types: linear voltage regulators and switching voltage regulators. A linear voltage regulator is a circuit that maintains a constant voltage and is classified into two types: low dropout and general dropout. Switching voltage regulators are a sort of switch mode power supply circuit that is meant to efficiently reduce dc voltage from a higher to a lower voltage. They are classified into step-down, step-up, and integrated types with opposing input and output polarity.

The voltage regulator is classified into three types based on the number of outlet terminals and usage: three-terminal fixed type, three-terminal adjustable type, multi-terminal adjustable type, and single-chip switch type.

On a single chip, the three-terminal fixed-type voltage regulator includes sampling resistors, compensating capacitors, protective circuits, high-power adjustment tubes, and other components. As a result, the entire integrated circuit block only has three terminals: input, output, and public. It is quite simple to use. Its downside is that the output voltage is fixed, necessitating the production of a range of goods with varying output voltages and current parameters.

To obtain different output voltages, the three-terminal adjustable integrated voltage regulator only requires two external resistors.

An early integrated voltage regulator is the multi-terminal adjustable kind. It is inconvenient to operate because to the low output power and numerous pins, but the precision is great and the price is low.

In recent years, the monolithic switch-type integrated regulated power supply has grown in popularity, and its efficiency is exceptionally good. Its operation differs from the previous three types. It is a converter that converts direct current (DC) to alternating current (AC) and then back to DC. There are typically two forms of pulse width modulation and pulse frequency modulation and the output voltage can be adjusted.

Typical Examples: LM317 & LM7805

The LM317 is a three-terminal positive-voltage regulator with an adjustable output voltage range of 1.25V to 37V that can deliver more than 1.5 A. It is useful for a wide range of applications, including local, on-card regulation. This device can also be used to create a programmable output regulator, or it can be used as a precision current regulator by attaching a fixed resistor between the adjustment and output.

The linear voltage regulator LM7805 offers over-voltage, over-current, and over-heat protection functions, resulting in an exceptionally steady performance. It is a 5V regulator with an output current of more than 1A and a good temperature coefficient. As a result, the product has numerous applications.

If you want to build a 5V power supply using a 7805, output currents of up to 1A can be generated from the IC if a suitable heat sink is used. A 9V transformer reduces the main voltage, a 1A bridge rectifies it, capacitor C1 filters it, and the 7805 regulates it to provide a constant 5V DC. Then test it by turning on the DC power source and adjusting the output voltage to around 8V or slightly higher. Alternatively, a 9V-12V battery can be used as a voltage source. When you set the voltage, keep an eye on the voltmeter panel. Prepare a DC voltmeter reading with a voltage range of 50V to measure the IC 7805 output voltage.

Applications of Voltage Regulators

Because the power dissipation of a linear regulator is exactly proportional to its output current for a given input and output voltage, typical efficiency can be as low as 50%. A switching regulator with optimal components can attain efficiency in the 90% range. The noise output of a linear regulator, on the other hand, is substantially lower than that of a switching regulator with the same output voltage and current requirements. A switching regulator can typically drive higher current loads than a linear regulator.

Limitations of Voltage Regulators

The primary advantage of linear regulators is their simplicity; nothing else has to be said. They do, however, have their own set of restrictions, as do all decent chips.

Linear regulators use feedback to reduce any superfluous voltage, much like a variable resistor. When drawing, the same current as the load is drawn. This squandered energy is transferred to heat, making these high-current regulators heated and inefficient.

For example, a 5V regulator with a 12V input and a 1A output has a power loss of (12V-5V)*1A, or 7W! That's a lot of lost energy for only 58 percent output!

As a result, regulators have poor energy efficiency when input-output voltage differentials or currents are large.

The input-output differential voltage problem can be solved by using more than one regulator in a succession of decreasing output voltages (up to the desired voltage value). Although the total power dissipation is the same as if only one regulator were used, the heat load is dispersed over all devices, lowering the overall operating temperature.

The power and efficiency limits can be handled by employing a switching supply, but the solution is application-dependent; there are no hard and fast rules for when to utilize which sort of power supply.