Construction and Testing of a Step-Up DC Chopper Circuit

Experiment No:

Experiment Name:

Construction and Testing of a Step-Up DC Chopper Circuit

Aim:

To design, construct, and test a step-up (boost) DC-DC converter and verify the effect of varying the duty cycle on the output voltage.

Theory:

A step-up chopper, also known as a boost converter, is a type of DC-DC converter used to increase (boost) a lower DC input voltage to a higher output voltage. It works on the principle of energy storage in an inductor and controlled switching using a semiconductor device like a MOSFET.

• Switch ON: Current flows through the inductor and stores energy in its magnetic field.
• Switch OFF: The inductor opposes the sudden drop in current by reversing polarity, forcing current through the diode to the load, thereby boosting the voltage.
• The output voltage is always greater than the input voltage.
• The amount of voltage boost depends on the duty cycle (D) of the PWM signal.

       Vo​=Vin​​ / 1−D

Where:

• Vo​: Output voltage
• Vin​: Input voltage
• D: Duty cycle (0 < D < 1)

Apparatus:

DC Power Supply
Inductor
Capacitor
Diode
MOSFET
PWM Source
Load Resistor
Multimeter/DSO

 

Circuit Diagram:

 

Procedure:

1. Assemble the boost converter circuit on a breadboard or PCB.
2. Connect the input power supply (e.g., 5V DC).
3. Apply a PWM signal to the MOSFET gate using Arduino/function generator.
4. Start with a low duty cycle (e.g., 20%) and gradually increase it up to ~70%.
5. Measure and record the output voltage at each step.
6. Ensure all components are operating within safe limits.

Observation Table:

Duty Cycle (%)	Input Voltage (V)	Output Voltage (V)
20	5.0	6.3
30	5.0	7.1
40	5.0	8.4
50	5.0	10.0
60	5.0	12.6
70	5.0	16.8

 

Result:

• Output voltage increases with an increase in duty cycle.
• The circuit successfully steps up the input voltage as per the theoretical equation.

 

Discussion:

• The experimental output closely matches theoretical values.
• Minor differences are due to diode voltage drops, switching losses, and inductor resistance.
• Boost converters are efficient and widely used in modern electronics where higher voltage is needed from a low voltage source.