Experiment 2

The George Washington University
School of Engineering and Applied Science
Department of Electrical and Computer Engineering
ECE 20 - Summer 2000
Experiment # 2

Solid State Diodes
Applications I

Equipment:
You must make up a complete equipment list and have you instructor review it before you start.

Components:

D1 through D4 - 1N4002
T1 - 12.6 - 16.0 Volt Center Tapped Transformer
RL - 16 k Ohm
C1 - C2 - capacitors, to be determined by your voltage doubler design
R2 resistor, to be determined by your voltage doubler design

Objectives:

To measure the output characteristics of your transformer
To build and safely test a half wave rectifier
To build and safely test a full wave rectifier
To build and safely test a bridge rectifier
To design, build and test a voltage doubler

CAUTION!
BE CAREFUL DURING THIS EXPERIMENT!
HAZARDOUS VOLTAGES WILL
BE PRESENT WHEN YOU PERFORM
YOUR MEASUREMENTS!

1.- Types of Positive Voltage Rectifiers (HW)

a. Draw and label the following types of positive voltage rectifiers (use ORCAD schematic module):

Figure #1 -- Half Wave Rectifier
Figure #2 – Full Wave Rectifier and
Figure #3 -- Bridge Rectifier.

Please read the textbook in Chapter 3 under "Diode as a Rectifier" to help you design these circuits.

b. Designate the transformer as T1, the load as RL and the rectifier diodes as D1, D2, D3 and D4.

c. Using ORCAD, run a transient simulation for each circuit. Plot 5 complete cycles of the Vin and Vout for each circuit.

d. Indicate in the different regions of each of the output signal plots the function performed by each of the diodes of the
corresponding rectifier, and any relevant details.

2.- The Turns Ratio

WARNING:
Connect the oscilloscope only to the secondary! Never connect the scope to the primary!
The negative lead on the scope probe is ground. If you connect this lead to the primary,
you will cause 120 Vrms at 20 Amps to short through your probe to ground!

a. Transformer Primary Voltage, V1 is given as 110 V_rms.Use the oscilloscope to measure Transformer Secondary
Voltage (V2) in rms.

b. Express the primary voltage (V1) and secondary voltage (V2) in
     i) V_rms
     ii)V_peak
     iii)V_{peak
to peak}
     iv)V_avg.

You can get all the measurement from the Digital oscilloscope. Place this information in Table # 1.
Determine the turns ratio (V1/V2) of T1 and place this info in Table #1.

c. Using digital oscilloscope, print out the Vout of secondary winding. Label this plot Figure A - Unloaded
Transformer Secondary Waveform. Then disconnect Transformer from the AC outlet.

3.- Testing Positive Rectifiers

WARNING - Hazardous voltages will be present during
these experiments! Please be very careful.

Construct the circuit shown in Figure #1. Test the circuit for a possible short to ground with an ohm meter. Correct any wiring errors and test again. Connect T1 to an AC outlet. Measure and print the waveform across RL. Disconnect T1 from the AC outlet! Plot and label the waveform Figure 1A -- Wave Form Across RL In Half Wave Rectifier.

Label the axis and any details in the plot.

Construct the circuit shown in Figure #2. Test the circuit for a possible short to ground with an ohm meter. Correct any wiring errors and test again. Connect T1 to an AC outlet. Measure and print the waveform across RL. Disconnect T1 from the AC outlet! Plot and label the waveform Figure 2A -- Wave Form Across RL In Full Wave Rectifier.

Label the axis and any details in the plot.

Construct the circuit shown in Figure #3. Test the circuit for a possible short to ground with an ohm meter. Correct any wiring errors and test again. Connect T1 to an AC outlet. Measure and print the waveform across RL. Disconnect T1 from the AC outlet! Plot and label the waveform Figure 3A -- Wave Form Across RL In Bridge Rectifier.

Label the axis and any details in the plot.

4.- Voltage Doubler Design

WARNING - Hazardous voltages will be present during this experiment.

(HW) Design and build a voltage doubler that has the specifications below.

Input: 12 Vpeak (Transformer Secondary Voltage)

Output: 24 V_DC

Type of Load: resistive
Power to Load: 100 mWDC

Please read the textbook in Chapter 3 under "Clamping Circuit/Voltage Doubler" to help you designing this circuit. Draw and label the schematic Figure # 4 - Voltage Doubler (use ORCAD schematic module). Run a transient simulation, and print out these output plots:
i) 5 complete cycles of the Vin
ii) Vout accross each of the diodes
iii) Vout accross each of the capacitors.

Be sure that your design guarantees that steady state is reached in less than 5 cycles.

Build the design in part (a). Check the POLARITY of every components in your circuit. Make sure you have the correct polarity for everything before you are making any measurement. Using digital oscilloscope, print out the Vin and Vout of the voltage doubler. Label this as Figure #4B - Voltage Doubler Vin/Vout. Make sure you label the axis.

5.- Analysis of results

Compare the measured results of each type of positive rectifier to those obtained using ORCAD. Provide explanation if the measured results are different from ORCAD simulation.

Explain the detail characteristics of each positive rectifier and possible application. The example of detail characteristic is the different PIV for different rectifiers.

Which one is better, Full Wave or Bridge Rectifier? Explain.

Provide one possible application of Voltage Doubler circuit.