Linear Voltage Regulators

A voltage regulator is used to regulate voltage levels. When a steady, reliable voltage is needed, then the voltage regulator is the preferred device. It generates a fixed output voltage that remains constant for any changes in an input voltage or load conditions. It acts as a buffer for protecting components from damages. A voltage regulator is a device with a simple feed-forward design and it uses negative feedback control loops. There are mainly two types of voltage regulators: Linear voltage regulators and switching voltage regulators; these are used in wider applications. The linear voltage regulator is the easiest type of voltage regulator. It is available in two types, which are compact and used in low power, low voltage systems. Let us discuss different types of voltage regulators.

There are two types of linear voltage regulators:

  • Series
  • Shunt



Series Voltage Regulator

The amount of current drawn is effectively used by the load; this is the main advantage of the series voltage regulator. Even when the load does not require any current, the series regulator does not draw full current. Therefore, a series regulator is considerably more efficient than shunt voltage regulator.

      Series Voltage Regulator Circuit Series Voltage Regulator Circuit



Applications of Series Regulators:

  • Use in all power supplies to electronic gadgets to regulate voltage and save the device from damage
  • Used with the alternator of internal combustion engines to regulate the alternator output.
  • Used for electronics circuits to supply a precise amount of voltage



Shunt Voltage Regulator

A shunt voltage regulator works by providing a path from the supply voltage to ground through a variable resistance. The current through the shunt regulator has diverted away from the load and flows uselessly to the ground, making this form usually less efficient than the series regulator. It is, however, simpler, sometimes consisting of just a voltage-reference diode, and is used in very low-powered circuits wherein the wasted current is too small to be of concern. This form is very common for voltage reference circuits. A shunt regulator can usually only sink (absorb) current.



Applications of Shunt Regulators :

Shunt regulators are used in:

  • Low Output Voltage Switching Power Supplies
  • Current Source and Sink Circuits
  • Error Amplifiers
  • Adjustable Voltage or Current Linear and Switching Power Supplies
  • Voltage Monitoring
  • Analog and Digital Circuits that require
  • Precision current limiters


Advantages of Linear Voltage Regulators



The advantages of Linear Voltage Regulators are as follows:

  • Implementation of Linear Voltage Regulators is very simple and they are easy to use.
  • In spite of their power dissipation, linear voltage regulators are robust in over current protection and thermal protection.
  • Adjustable Voltage regulators require a very few external components to achieve its operation. Fixed voltage regulators require almost no external components (may be a couple of bypass capacitors).
  • At low cost you have a wide range of voltage and current selection.



Disadvantages of Linear Voltage Regulators



The disadvantage of Linear Voltage regulators are as follows:

  • Usually, linear voltage regulators are step down only i.e. the output voltage is always less than the input voltage.
  • When operating from AC mains supply, a step-down transformer is required to bring the voltage to an operable level. Hence, they are usually bulky.
  • As the regulation is done by dissipating excess power as heat, they tend to become extremely hot and the use of a heat sink is unavoidable.
  • Also, the efficiency of linear regulators is usually very less, somewhere between 20% to 60%.


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