BRIDGE RECTIFIER

Aim

To simulate and analyze the operation of a full bridge rectifier circuit, observe the output waveform, measure its performance parameters, and compare the results with theoretical predictions.

PRINCIPLE

A full-wave bridge rectifier converts alternating current (AC) into direct current (DC) by using four diodes arranged in a bridge formation. This configuration ensures that both the positive and negative halves of the AC input waveform are rectified. The diodes conduct alternately, depending on the input voltage polarity, resulting in a unidirectional current at the output

Simulation

1. Simulate the I-V characteristics of the diodes in a bridge full- wave rectifier.

2. Extract key parameters:

Reverse saturation current ( Is).

Forward voltage (Vf).

3. Analyze the effect of temperature variations on the rectifier's performance.

4. Compare simulated data with theoretical models and datasheet values.

COMPONENTS

Required Components:

Step-down transformer
Four diodes (e.g., 1N4007)
Load resistor
Capacitor (for smoothing)
Oscilloscope or multimeter

Procedure

1.Open LT Spice and create a new schematic

2. Select the required components:

- voltage source, transformer, diodes, resistor, and capacitor.

- Place the components on the schematic workspace.

3. Construct the bridge rectifier circuit using four diodes (D1, D2, D3, D4) in the configuration shown.

4. Connect the transformer (L1, L2) and load resistance ( R1 ) to the bridge rectifier circuit.

5. Place the capacitor ( C1 ) across the load to smooth the rectified output.

6. Set the voltage source ( V1 ) to a sine wave with ( 230V ) peak amplitude and

( 50Hz ) frequency.

7. Add simulation commands:

- For rectification analysis, use a transient simulation:

.trans 0 100ms.

8. Run the simulation to observe:

- Input waveform V(in) .

- Rectified output waveform V(out).

9. Measure current [I(load)] through ( R1 ) and voltage [ V(out)] across ( R1 ).

10. Record observations for different temperatures (e.g., 25°C, 50°C, 75°C).

Circuit

Table of observation

Nature of Graph

Result

1. The bridge full-wave rectifier successfully converted the AC input to a DC output.

2. The smoothing capacitor reduced ripple and provided a stable output voltage.

3. The output voltage and load current slightly decreased as the temperature increased, due to the thermal behavior of the diodes (increased forward voltage drop with temperature).

Conclusion

The simulation verified the functionality of a bridge full-wave rectifier:

- The output DC voltage closely follows the expected theoretical values.

- Temperature variations slightly affect diode characteristics, leading to small deviations in output voltage and current.

- The results align well with theoretical expectations, demonstrating the rectifier's ability to provide a consistent DC output.

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