Single Phase Rectifiers

ATTENTION: During this experiment, do not touch any part of the circuit while energized. The AC source is only grounded as shown in Fig. 1 and 2 when the function generator is a source. Do NOT ground the VARIAC.

1. AC Source Setup

For this experiment, two AC sources are used; a variable transformer (VARIAC) at a low frequency of 60 Hz and a function generator with 10 V peak sinusoidal output and 1 kHz frequency.

1. Before starting, connect the differential probe to one scope channel, and a regular probe to the other channel.
2. Adjust the buttons on the probes as follows: differential probe at 20X (or 1/20) and the regular probe at 10X. Do not forget to turn ON the differential probe.
3. On each channel's menu on the scope, set the probe to be at 10X. For the differential probe, manually multiply any measurements or results by two to reach the 20X desired.
4. To set up the function generator, make sure the 50 Ω OUTPUT is connected to a BNC-to-alligator cable.
   1. Connect the alligator clips to a regular scope probe to observe the function generator output.
   2. Set the output to be a sinusoid at 10 V peak and 1 kHz frequency with zero DC offset.
   3. Observe the function generator output and adjust its settings to achieve the desired output waveform.
   4. Once your signal is set, disconnect the BNC connector but keep the function generator ON to maintain its settings. Disconnect the scope probe from the generator output.
5. To setup the VARIAC, make sure the VARIAC output (looks like a regular receptacle) is not connected to any cable.
   1. Keep the VARIAC OFF and make sure its knob is set to zero.
   2. Slowly adjust the VARIAC knob to 5% output. This should yield around 10V peak voltage.

Half-Wave Rectifier

2. Resistive Load with High Frequency Input

1. Use the function generator as the AC source but keep it disconnected from the circuit for now.
2. On the proto board, build the circuit shown in Fig.1. The diode (D) is 2A01G-T rated for 50 V and 2 A while the load resistor (R) is 51 Ω.
   1. Make sure the diode polarity is correct. The dash on the diode is at the cathode.
3. Before connecting the differential probe to the circuit, tie the probe's terminals together and adjust its measured waveform on the screen to show zero offset voltage.
   1. Connect the differential voltage probe across the load resistor to observe the output voltage V_out.
   2. Connect a regular probe across the AC side to observe the input voltage V_in.
   3. Connect the function generator to the circuit.
4. Adjust the time base on the scope to show V_in and V_out for up to four fundamental cycles of V_in. Make a copy of the waveforms.
   1. Zoom in at the diode turn-off region and make a copy of the waveforms.
5. Disconnect the function generator and remove the differential probe for load modifications. Keep the rest of the circuit and connections as they are.

Figure 1: Half-wave rectifier with resistive load

3. Resistive-Inductive Load with High Frequency Input

1. Using the same circuit in Fig. 1, connect a 4.7 mH inductor (L) in series with the resistive load as shown in Fig. 2.
2. Connect the differential voltage probe across the load resistor to observe the resistor voltage V_out which has the same waveform shape as the R-L load current I_out.
3. Turn the function generator output ON.
4. Adjust the time base on the scope to show V_in and V_out for up to four fundamental cycles of V_in. Make a copy of the waveforms.
   1. Zoom in at the diode turn-off region and observe the delay in the turn-off time. Make a copy of the waveforms.
   2. Turn the function generator output OFF and disconnect it from the circuit.
   3. Remove the inductor L and keep the rest of the circuit as it is.

Figure 2: Half-wave rectifier with R-L load

4. Resistive Load with Low Frequency Input

1. Make sure the VARIAC output is at 5% and disconnected from the circuit. Connect the differential probe across the VARIAC, turn the VARIAC ON and slightly adjust its output to achieve 10 V peak.
   1. Capture the waveform on the scope to use as your reference input voltage observation.
   2. Turn the VARIAC OFF but do not change its voltage setting.
2. Using the same circuit from Fig. 1, i.e. with the inductor disconnected and the resistor being the only load, connect the VARIAC output using the plug-banana cable.
3. Connect the differential voltage probe across the load resistor to observe the output voltage, V_out.
4. Turn ON the VARIAC output. Stay away from the circuit and observe the waveforms on the scope. If you need to debug your circuit, power the VARIAC OFF first.
5. Adjust the time base on the scope to show V_out for up to four fundamental cycles. Make a copy of the waveform.
   1. Zoom in at the diode turn-off region and make a copy of the waveforms.
6. Turn OFF the VARIAC and disassemble your circuit. Do NOT change the VARIAC voltage setting.

Full-Wave Rectifier

5. Resistive Load

1. On the proto board, build the circuit shown in Fig. 3.
   1. Make sure the diode polarity is correct. The dash on the diode is at the cathode.
2. Once the circuit is ready, connect the VARIAC output as the AC source.
3. Connect the differential voltage probe across the load resistor to observe the output voltage V_out.
4. Turn ON the VARIAC output. Stay away from the circuit and observe the waveforms on the scope. If you need to debug your circuit, power the VARIAC OFF first.
5. Adjust the time base on the scope to show V_out for up to four fundamental cycles of V_in. Make a copy of the waveforms.
   1. Measure the peak-to-peak value of V_out by using the cursors.
6. Keep the probe connections as they are and Turn OFF the VARIAC and disassemble your circuit.
   1. Do NOT change the VARIAC voltage setting.

Figure 3. Full-wave rectifier with resistive load.

6. Resistive Load with Filtering Capacitor

1. Using the same circuit in Fig. 3, connect an electrolytic capacitor (C) in parallel with the resistive load as shown in Fig. 4.
   1. Make sure the capacitor polarity is correct with the ( - ) terminal connected to negative side of the load.
2. Turn ON the VARIAC output. Stay away from the circuit and observe the waveforms on the scope. Before debugging the circuit, power the VARIAC OFF.
3. Adjust the time base on the scope to show V_out for up to four fundamental cycles of VIN. Make a copy of the waveforms.
   1. Measure the peak-to-peak value of V_out by using the cursors and the AC coupling option for that channel (AC coupling eliminates the DC offset of a signal).
4. Return this to DC coupling once the measurement is made.
5. Turn OFF the VARIAC.
6. Disassemble the circuit and clean up the bench.

Figure 4. Full-wave rectifier with resistive load and capacitive filtering