Study the bridge rectifier and calculate the output signal parameters of the bridge rectifier with the help of C.R.O. (80 Marks)

Introduction

A bridge rectifier is an electronic circuit used to convert alternating current (AC) into direct current (DC). It uses four diodes arranged in a bridge configuration. The output of a bridge rectifier is a pulsating DC waveform which can be observed and measured using a Cathode Ray Oscilloscope (C.R.O.).

Definition

A bridge rectifier is a full-wave rectifier circuit that converts both half cycles of AC input into DC output using four diodes.

Circuit Components

• Step-down Transformer
• Four Diodes (D1, D2, D3, D4)
• Load Resistor (RL)
• C.R.O.
• Connecting Wires

Working Principle

During the positive half cycle of AC input, two diodes conduct and allow current through the load in one direction. During the negative half cycle, the other two diodes conduct and again current flows in the same direction through the load. Thus, both half cycles are converted into pulsating DC.

Waveform Observation using C.R.O.

The CRO is used to observe the input AC waveform and the output rectified waveform. The output waveform appears as a series of positive pulses representing full-wave rectification.

Measurement of Output Parameters

1. Peak Voltage (Vp)

Measured from CRO by counting vertical divisions and multiplying with volt/div.

Vp = Divisions × Volt/div

2. RMS Voltage (Vrms)

Vrms = Vp / √2

3. Average Voltage (Vdc)

Vdc = (2Vp) / π

4. Ripple Factor (γ)

γ = √[(Vrms / Vdc)² − 1]

5. Frequency

f = 1 / Time Period

Procedure

1. Connect the bridge rectifier circuit properly.
2. Apply AC input through transformer.
3. Connect CRO probes across input and output.
4. Switch ON the supply.
5. Observe input waveform (sine wave).
6. Observe output waveform (full-wave rectified).
7. Measure vertical and horizontal divisions.
8. Calculate parameters using formulas.

Advantages

• High efficiency
• Uses both half cycles
• No center-tapped transformer required

Disadvantages

• More diodes required
• Voltage drop across diodes

Applications

• Power supplies
• Battery charging
• DC circuits

Precautions

• Check diode polarity
• Ensure proper connections
• Avoid high voltage on CRO

Result

The bridge rectifier was studied and output parameters were calculated successfully using CRO.

Conclusion

The bridge rectifier efficiently converts AC into DC. CRO helps in analyzing waveform and calculating important parameters.