What is the Difference Between Regulated and Unregulated Power Supply? Definitions and Formulas

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Difference Between Regulated and Unregulated Power Supply

The key difference between Regulated and unregulated power Supplies is based on how they control voltage. A regulated power supply acts like a steady stream, providing a consistent supply voltage regardless of input fluctuations or device usage. The unregulated power supply is more like the pressure (voltage) can change depending on the source and how much current is flowing. Regulated power supplies are better for sensitive electrical appliances, while unregulated power supply ones are cheaper and simpler for low-power applications that can tolerate some voltage fluctuations. Keep reading to learn about the difference between regulated and unregulated power supply real-life applications and formulas used to apply.

What is a Regulated Power Supply?

A Regulated power supply is a device that takes electrical input, typically AC known as Alternating Current, and converts it into a smooth, steady DC known as Direct Current output at a specific voltage. The main important thing about it is that it keeps this output voltage steady even if:

  • The incoming AC voltage fluctuates slightly.
  • The device plugged into the power supply draws more or less current.
Regulated Power Supply
Regulated Power Supply

This stable voltage is crucial for many electronic devices to function properly and avoid damage. Here’s a breakdown of how it works.

  1. Conversion: The power supply first converts the AC input to a bumpy DC using a rectifier.
  2. Smoothing: A capacitor helps smooth out these fluctuations, but some variations (ripple) remain.
  3. Regulation: A voltage regulator circuit actively monitors and adjusts the output voltage to ensure it stays constant at the desired voltage level.

Regulated power supplies are essential for powering various electronic devices, including Computers, Laptops, TVs, Smartphones, Lab Instruments, and many other electronic devices. They provide a reliable and stable power source, preventing malfunctions and protecting delicate components from voltage spikes or drops.

What is an Unregulated Power Supply?

An Unregulated power supply is a device that converts AC (Alternating Current) to DC (Direct Current) for powering electronic devices. However, unlike its regulated counterpart, it doesn’t have a built-in mechanism to maintain a perfectly constant voltage output that varies with changes in input voltage, load current, and temperature.

Here’s a breakdown of how it works and its main characteristics:


  • Takes AC input (usually household voltage).
  • Converts it to a pulsating DC voltage using a rectifier (like a diode).
  • Filters the pulsating DC with a capacitor (smooths out some fluctuations).
  • Delivers the DC output to the connected device.
Unregulated Power Supply
Unregulated Power Supply

It is suitable for low-power applications where slight voltage variations are acceptable e.g., some LED lights, and basic motors. It’s not recommended for sensitive electronics that require a very stable voltage for proper operation like computers and smartphones. It works well for low-power applications that don’t need perfect voltage stability.

Also Read: Difference Between Parallel and Perpendicular

What is the Difference Between Regulated and Unregulated Power Supply?

The table summarises the key differences between Regulated and Unregulated Power Supply.

ParticularRegulated Power Supply
Unregulated Power Supply
Voltage StabilityMaintains constant voltage output despite fluctuations in input or load.
Voltage output varies with changes in input voltage and load.
Voltage RegulationUtilizes components such as voltage regulators to ensure stable output voltage.Does not use voltage regulation components, leading to voltage fluctuations.
EfficiencyGenerally more efficient due to regulation circuitry, minimizing wasted energy.Can be less efficient, especially under varying load conditions.
ComplexityTypically more complex due to additional regulation circuitry.Less complex as it lacks regulation components.
CostGenerally more expensive due to additional components and complexity.Usually more affordable due to simpler design.
ApplicationsCommonly used in sensitive electronic devices where stable voltage is crucial (e.g., computers, and medical equipment).Suitable for less critical applications where voltage fluctuations are tolerable (e.g., basic household appliances).

Difference Between Regulated and Unregulated Power Supply Formulas

There isn’t a single formula for either regulated or unregulated power supply. However, there are some key concepts and calculations involved in their design.

Unregulated Power Supply

  • Transformer Turns Ratio: This formula helps determine the AC voltage output from the transformer based on the input voltage and the ratio of turns on the primary and secondary windings. 
Vout = Vin x (NSecondary/Nprimary)

Where Vout = output voltage, Vin = input voltage, Nsecondary = number of turns on the secondary coil, and Nprimary = number of turns on the primary coil.

  • Peak DC Voltage from Rectifier: This is an approximation for the pulsating DC voltage after rectification. It’s roughly 0.318 times the peak AC voltage (considering a single-diode rectifier). 
Vdc = 0.318 x Vpeak (AC)


  • Vdc = Approximate peak DC voltage
  • Vpeak (AC) = Peak voltage of the AC input

Regulated Power Supply (Additional Considerations)

  • Capacitor Selection: Choosing the right capacitor value is crucial for smoothing the rectified DC voltage. This involves calculations considering:
    • Ripple voltage tolerance (how much fluctuation is acceptable)
    • Desired output current
    • Operating frequency

These formulas depend on specific component datasheets and desired performance.

  • Voltage Regulator Characteristics: Voltage regulators use various techniques (like pass transistors or feedback loops) to maintain a constant output voltage. Understanding these goes beyond basic formulas. Datasheets for specific voltage regulator ICs will provide relevant performance parameters.

Unregulated supplies involve simpler calculations for transformer turns ratio and estimating peak DC voltage. Regulated supplies require more in-depth analysis for filtering and voltage regulation, relying on component specifications and datasheets.

Application of Difference Between Regulated and Unregulated Power Supply in Real-Life

Here’s a breakdown of how regulated and unregulated power supplies are used in real life.

Regulated Power Supply

  • Computers and Laptops: Stable voltage is crucial for processors, memory, and other sensitive components.
  • Smartphones and Tablets: Consistent voltage delivery is essential for smooth operation and battery charging.
  • TVs and Monitors: Regulated supplies provide clean power for displays and internal circuits.
  • Medical Equipment: Ensuring precise voltage is critical for accurate readings and safe operation.
  • Lab Instruments: Regulated power supplies guarantee consistent power for scientific experiments and measurements.

Unregulated Power Supply

  • LED Lighting (with current control): Some LED lights can tolerate slight voltage variations and use unregulated supplies with current-limiting circuits for safety.
  • Basic Motors: Motors used in toys or simple appliances may function with unregulated power as long as voltage fluctuations aren’t significant.
  • DIY Projects: Hobbyists might use unregulated supplies for low-power experiments where precise voltage isn’t critical.

Also Read: Difference Between Differentiation and Integration

Similarities Between Regulated and Unregulated Power Supply

Both regulated and unregulated power supplies take electricity, usually AC from the wall outlet, and convert it into a usable form for electronic devices. They both typically have a transformer to step the voltage up or down, and a capacitor to help smooth out the flow of electricity. That’s like having a water pump that adjusts pressure and a tank to even out the flow of water.

The main difference is how steady the voltage is. Imagine the water pressure again. A regulated power supply is like a fancy pump that keeps the pressure exactly the same no matter how much water is being used. An unregulated power supply is more basic – the pressure might change a little if more water is being used.


What is the difference between unregulated and regulated?

The major difference between regulated and uncontrolled power supplies is that regulated power supplies have steady output voltages while unregulated power supplies have output voltages that change based on external factors like temperature, load current, and input voltage.

Why use a regulated power supply?

It keeps the voltage fixed no matter how much current the load uses, as long as the limits that were set are not pushed too far.

What is the efficiency of the unregulated power supply?

Because it is easy, an uncontrolled power source lasts a long time and works about 60% of the time.

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