- Voltage Regulator Definition: A voltage regulator is defined as a device that keeps the voltage level within suitable limits to protect connected equipment.
- Linear Voltage Regulator: This type adjusts resistance to maintain a steady output voltage and includes series and shunt types.
- Shunt Voltage Regulator: A shunt voltage regulator diverts excess current to the ground, ensuring stable voltage across the load.
- Zener Diode as Voltage Regulator: Zener diodes provide a reference voltage and are used in series and shunt voltage regulators.
- Switching Voltage Regulator: These regulators switch on and off quickly to control voltage efficiently, allowing for step-up, step-down, and inverting outputs.
What is Voltage Regulation
A voltage regulator is an electronic device that keeps the power supply voltage within safe limits for the connected equipment. It holds the voltage source output inside the range the load accepts.
A voltage regulator controls the voltage level, no matter the changes in input voltage or load. It protects devices from damage and can regulate both AC and DC voltages, depending on its design.
Types of Voltage Regulators
There are two main types of voltage regulators available:
- Linear Voltage Regulators
- Switching Voltage Regulators
These can be further classified into more specific voltage regulators, as discussed below.
Linear Voltage Regulator
A linear voltage regulator acts as a voltage divider built around an FET operating in its Ohmic region. It holds a steady output by varying its resistance with the load. Two main types exist:
- Series voltage regulator
- Shunt voltage regulator
Series Voltage Regulator
A variable element sits in series with the connected load, and the regulator holds a steady output by varying that element’s resistance with the load. Two types are described below.
Discrete Transistor Series Voltage Regulator
In the block diagram, an unregulated input first reaches a controller that adjusts the voltage delivered toward the output. A sampling circuit measures the output, and a comparator checks that sample against a reference voltage, feeding the difference back to the controller.
The comparator circuit sends a control signal to the controller if the output voltage changes. The controller then adjusts the voltage to keep it within the acceptable range, ensuring a stable output.
Zener Diode as Voltage Regulator
When a Zener diode supplies the reference, the circuit becomes a Zener-controlled transistor series voltage regulator, also called an emitter-follower regulator. The series pass transistor connects with its collector-emitter path in series with the load (see figure below). The transistor is the variable element, and the Zener diode provides the reference voltage.
Shunt Voltage Regulator
The shunt voltage regulator diverts current away from the load to ground through a variable resistance. In other words, it absorbs current, which makes it less efficient than the series voltage regulator. Its applications include error amplifiers, voltage monitoring and precision current limiters. Two types are described below.
Discrete Transistor Shunt Voltage Regulator
The controller shunts part of the current from the unregulated input away from the load, and the regulation appears across the load.
Whenever a load variation raises or lowers the output voltage, the comparator signals the controller, which shunts the extra current away from the load to hold the output steady.
Zener Controlled Transistor Shunt Voltage Regulator
Here, the unregulated voltage is directly proportional to the voltage drop that occurs across the series resistance. That drop relates to the current delivered to the load, and the output voltage relates to the transistor base-emitter voltage (VBE) and the Zener diode.
| Advantages of Linear Voltage Regulator | Disadvantages of Linear Voltage Regulator |
| Design is very simple | Low efficiency |
| Less output ripple | Space requirement is large |
| Response time is fast | Voltage cannot be increased |
| Less noise | A heat sink is sometimes required |
Switching Voltage Regulator
This regulator switches a series device on and off rapidly. As with the linear types, a feedback mechanism controls how much charge reaches the load, and the switch duty cycle sets that quantity. With this voltage regulator the output can exceed the input, or its polarity can be opposite to the input.
This is a highly efficient voltage regulator. Three common topologies are the buck (step-down), boost (step-up) and buck-boost (step-down, step-up or inverting) regulators. A simplified circuit diagram of a switching voltage regulator is shown below.
| Advantages of Switching Voltage Regulator | Disadvantages of Switching Voltage Regulator |
| Efficiency is very high. | Complex design |
| Size and weight are very low. | Expensive |
| Boost or buck or inverting or buck/boost is possible. | Noise is high |
| Less heat to dissipate | Transient recovery time is time-consuming |
Application of Voltage Regulators
The applications for voltage regulators include:
- Power distribution system
- Automobile alternator
- Power station generator plant
- Computer power supplies
