How to design Basic Shunt Regulator and its working principle

A shunt voltage regulator is a fundamental yet effective circuit for maintaining a stable output voltage by diverting excess current to ground. Here we explains the working principle of a basic shunt regulator, complete with a circuit diagram and calculations for current and voltage. By the end, you'll understand how this simple 5V voltage regular design can regulate electrical power efficiently in your projects. It can be useful to power your Arduino and other electronics circuits.

Overview of the Circuit

The following schematic diagram represents a linear power supply with a basic shunt voltage regulator.

The system uses an AC power supply as the input, which is rectified, filtered, and regulated to produce a stable DC power supply for the load. This type of low-voltage power supply is ideal for small-scale electronics requiring stable voltage.

Key Components and Functions

1. Power Source: The circuit begins with an AC power supply connected to a power adapter. It converts AC into a pulsating DC using a full-bridge rectifier consisting of diodes $D_1$ and $D_2$ (1N4001). This is the foundation of the electric power supply circuit.

2. Input Filter: Capacitor $C_1$(470 µF) smooths the pulsating DC, providing a relatively stable unregulated DC power supply.

3. Low-Pass Filter: The resistor \(R_1\)(160 Ω) and capacitor $C_2$(100 µF) form a low-pass filter, reducing ripples further for a clean energy supply.

4. Voltage Regulator:

   • The series resistor $R_s$(120 Ω) limits the current flowing into the shunt regulator circuit.
   • The zener diode $D_4$(1N749A) maintains a reference voltage of 4.3V.
   • The transistor $Q_1$(2N2222N) stabilizes the output voltage by shunting excess current to ground.
   • The load resistor $R_L$(220 Ω) consumes the regulated power.

   The circuit provides a stable output voltage of 5.0V, making it suitable as a power supply unit (PSU) for small devices.

Circuit Operation

1. Voltage Regulation: The zener diode clamps the voltage to 4.3V. Adding the base-emitter voltage ($V_{BE}$) of the transistor ($\sim 0.7 \, \text{V}$) gives the final output voltage:

   $$V_{out} = V_z + V_{BE} = 4.3 \, \text{V} + 0.7 \, \text{V} = 5.0 \, \text{V}.$$

2. Current Regulation: The series resistor $R_s$ limits the total current. Excess current not required by the load is shunted through the transistor $Q_1$ to maintain stability.

Calculations

1. Output Voltage ($V_{out}$):

2. Series Resistor Current ($I_s$):

where:

• $V_{in} = 11.5 \, \text{V}$,
• $V_{out} = 5.0 \, \text{V}$,
• $R_s = 120 \, \Omega$.

3. Load Current ($I_L$):

where:

• $V_{out} = 5.0 \, \text{V}$,
• $R_L = 220 \, \Omega$.

4. Collector Current ($I_c$):

Applications

• As a programmable power supply for low-power devices.
• As a battery charger with additional modifications.
• In DIY projects requiring a low-cost linear power supply.

If you're interested in building similar circuits, check out these guides:

• DIY 5V Regulated Power Supply
• Simple Series Voltage Regulator Design

Advantages and Limitations

Advantages:

1. Simple design with minimal components.
2. Effective for low-power applications.

Limitations:

1. Inefficient at high input currents as excess current is dissipated as heat.
2. Unsuitable for high-power applications due to heat dissipation issues.

For more efficient power systems, consider a switching power supply or a modular power supply.

Explore Related Topics

• Learn about LM317-based Battery Chargers.
• Discover DIY Transformer Design for small power inverters and converters.
• Find out how to build a Reverse Polarity Protection Circuit.

This basic shunt regulator serves as an excellent introduction to voltage regulation for enthusiasts and professionals alike.