Bridge Rectifier

Pre-Lab Information

Rectifiers are widely used in power supplies that provide the dc voltage necessary.

Materials and equipment Needed:

1. Materials:
   • One 120/24 V center-tapped transformer
   • Four diodes 1N4001
   • Two 2.2 kΩ resistors
   • One 100 μF, 50 V electrolytic capacitor (any voltage rating is fine since is simulation only)
   • One fuse (any rating is fine since is simulation only)
2. Equipment:
   • Oscilloscope

Procedure:

1. Connect the the bridge rectifier circuit shown in Figure 1. Notice that no terminal of the transformer secondary is at ground potential (some simulation software will not run if is not connected to the ground, check yours). The input voltage to the bridge, V_SEC, is not referenced to ground. In some simulation software the oscilloscope cannot be used to view both the input voltage and the load voltage at the same time. Check your circuit before run the simulation. Compute the expected peak output voltage. Then run the simulatoin and use a voltmeter to measure V_SEC (rms). Use the oscilloscope to measure the peak output voltage (V_LOAD) without a filter capacitor. Tabulate all data gathered.

Figure 1

1. Connect the 100 μF capacitor in parallel with the load resistor. Measure V_LOAD, the peak-to-peak ripple voltage, and the ripple frequency. Tabulate all data gathered and compare the results with and without the filter capacitor.
2. Simulate an open diode in the bridge by removing one diode from the circuit (choose yours). What happens to the output voltage, the ripple voltage and the ripple frequency?

Conclusion:

Write your detailed conclusion about this lab experiment.

Evaluation and Review Questions:

1. Compare a bridge rectifier circuit with full-wave rectifier center-tapped circuit which you did before. Which has the higher voltage output?
2. Explain how you could measure the ripple frequency to determine if a diode were open in a bridge rectifier circuit.
3. What is the maximum dc voltage you could expect to obtain from a transformer with a 12 V (rms) secondary using a bridge circuit with a filter capacitor?