Experiment #4:
Power Supply Circuits
Friday Group
Dr. Somnath
10-7-09
Ari Mahpour
Teddy Ariyatham
Jayson dela Cruz
Table of Contents
Objective ......................................................................................................................................... 3
Tools ............................................................................................................................................... 3
Theory ............................................................................................................................................. 4
Discussion and Results ................................................................................................................... 5
Part 1 ........................................................................................................................................... 5
Part 2 ........................................................................................................................................... 6
Part 3 ........................................................................................................................................... 7
Part 4 ........................................................................................................................................... 8
Part 6 ........................................................................................................................................... 9
Full Wave Rectifier ................................................................................................................. 9
Full Wave Rectifier with 100µF Capacitor........................................................................... 10
Part 8 ......................................................................................................................................... 11
Part 9 ......................................................................................................................................... 12
Conclusion .................................................................................................................................... 13
Objective
The purpose of this laboratory experiment is to explore the variaety of DC power supply
circuits. This will primarily be accomplished by passing an input through a rectifier, then filter,
then voltage regulator to get the desired output of the person’s choice. Throughout the
experiment a transformer will be used to replicate the output of an outlet’s sine wave (but
powered down). An in depth look at the theory behind the experiment is discussed in he
“Theory” portion of the laboratory report.
Tools
-
Oscilloscope
-
Functional generator
-
Power supply
-
Transformer
-
Diodes: D1N4002 and D1N746A (zener)
-
Capacitors: 100µF
-
Resistors: 100Ω, 510Ω, and 1kΩ
Theory
CENTER TAPPED TRANSFORMER
Figure 4.1a: PSPICE Model
12V
8V
4V
0V
-4V
-8V
-12V
0s
10ms
20ms
30ms
40ms
50ms
60ms
70ms
80ms
90ms
100ms
V(L3:1)
Time
Figure 4.1b: PSPICE Simulation
Figure 4.1 is a model of the Center-Tapped Transformer component from the
experiment. This transformer takes the 120V-rms 60kHz input from a regular wall outlet, and
outputs a 7.5V-rms 60kHz sin wave. This allows us to have a low voltage we can transform in
our lab experiment. The goal is to turn this sin wave in to a DC power supply using rectifiers,
filters, and regulators.
Discussion and Results
Part 1
Figure 4.5a: PSPICE Model
10V
5V
0V
-5V
-10V
0s
10ms
20ms
30ms
40ms
50ms
60ms
70ms
80ms
90ms
100ms
V(D1:2)
Time
Figure 4.5b: PSPICE Simulation
Figure 4.5 is a half wave rectifier using a regular diode. The diode allows current to pass
through one direction, but not the other direction. This results in a voltage across the resistor in
the positive region, but not in the negative region.
Part 2
Figure 4.6a: PSPICE Model
12V
8V
4V
0V
-4V
-8V
-12V
0s
V(C1:2)
10ms
V(D1:1)
20ms
30ms
40ms
50ms
60ms
70ms
80ms
90ms
100ms
Time
Figure 4.6b: PSPICE Simulation
Ripple = Vout amplitude/ Vout max
Vo max = 9.87890
Vo amp = 2.43906
Figure 4.6 is a very basic transformer using a half wave rectifier and a filter consisting of
a single capacitor. We can see that, because we are constantly charging the capacitor, the
capacitor voltage remains relatively high, with low amplitude. This is close to a real transformer
because as the capacitor amplitude reaches zero, we get a DC source voltage.
Part 3
Figure 4.7a: PSPICE Model
20V
Across Capacitor +
Resistor
10V
0V
-10V
-20V
10ms
V(L4:2)
20ms
V(C2:2)
30ms
40ms
50ms
60ms
70ms
80ms
90ms
100ms
Time
Figure 4.7b: PSPICE Simulation
12V
Across
Resistor
8V
4V
0V
-4V
-8V
-12V
10ms
V(L4:2)
20ms
V(R5:2)
30ms
40ms
50ms
60ms
70ms
80ms
Time
Figure 4.7c: PSPICE Simulation
90ms
100ms
Vo max = 9.81088
Vo amp = 2.75320
Figure 4.7 is the same circuit as Figure 4.6 except with an added resistor in series with
the capacitor. This allows the capacitor to hold charge for a longer period of time, which results
in a more DC voltage across the capacitor.
Part 4
Figure 4.7d: PSPICE Model
15V
10V
0V
-10V
-15V
10.0ms
V(L4:2)
20.0ms
V(C2:2)
30.0ms
40.0ms
50.0ms
60.0ms
70.0ms
80.0ms
90.0ms
96.6ms
Time
Figure 4.7e: PSPICE Simulation
Vo max = 9.87910
Vo amp = 1.8997
In Figure 4.7dwe replace the 100uF capacitor with a 470uF capacitor. The results in the
output 4.7e show that, because the capacitor is capable of holding more charge, it discharges
slower than the 100uF capacitor. This results in even lower output amplitude.
Part 6
Full Wave Rectifier
Figure 4.8a: PSPICE Model
10V
5V
0V
-5V
-10V
10ms
V(D6:2)
20ms
30ms
40ms
50ms
60ms
70ms
80ms
90ms
100ms
Time
Figure 4.8b: PSPICE Simulation
Figure 4.8 is a test of a full wave rectifier. The diodes are placed in such a way that it
always directs current in one direction across the load resistor. This results in an output voltage
that is all in the positive region, with no cutoff regions.
Full Wave Rectifier with 100µF Capacitor
Figure 4.8c: PSPICE Model
12V
8V
4V
0V
-4V
-8V
-12V
60ms
V(D6:2)
70ms
V(D3:2,D5:1)
80ms
90ms
100ms
110ms
120ms
130ms
140ms
150ms
160ms
Time
Figure 4.8d: PSPICE Simulation
Vo max = 9.86250
Vo amp = 1.83936
In Figure 4.8c, we add a capacitor (filter) to the full wave rectifier. The capacitor is
charging during the entire output sin wave, resulting in a capacitor voltage with a very low
amplitude. The lower the output amplitude, the better transformer we have.
Part 8
Figure 4.9a: PSPICE Model
12V
8V
4V
0V
-4V
-8V
-12V
60ms
V(R8:1)
70ms
V(D3:2,D5:1)
80ms
90ms
100ms
110ms
120ms
130ms
140ms
150ms
160ms
Time
Figure 4.9b: PSPICE Simulation
Vo amp = 131.60563mV
Vo max= 7.26995V
In this circuit figure 4.9a, we’ve added another 100uF capacitor in parallel to the first,
increasing its effective capacitance to 200uF. As a result, the capacitors hold charge for a longer
period of time. The resulted figure 4.9b shows that the voltage is nearly a straight DC source
line. Our output voltage amplitude is in the low mV range.
Part 9
Figure 4.10a: PSPICE Model
20V
10V
0V
-10V
-20V
60ms
V(R8:1)
70ms
V(D3:2,D5:1)
80ms
90ms
100ms
110ms
120ms
130ms
140ms
150ms
160ms
Time
Figure 4.10b: PSPICE Simulation
Vo amp = 784.19399mV
Vo max= 7.63302
In the final circuit, Figure 4.10a, we added a voltage regulator stage to our transformer
in the form of a parallel zener diode. This zener diode regulates voltage by breaking down
(becoming a short) as soon as the voltage reaches a certain level. This creates a cutoff in the
output wave that further straightens out our DC output. This circuit could be further improved
by either adding another parallel capacitor, or increasing the single capacitor capacitance.
Conclusion
This laboratory experiment we learned many things including the use of a
transformer both in the physical and digital realm. Understanding and being able
to use parts such as transformers is an integral part to power systems. As the
world starts to move to the digital side of things, it is important for people in the
workplace and in the academic world to understand how to apply electrical
engineering concepts to the computer. Using PSPICE is the best way to
demonstrate one’s knowledge of circuit in the digital realm. In this particular
laboratory experiment, the laboratory manual starts to go into more, in depth
instructions on how to use PSPICE and take advantage of its many features. For
many labs to come, the student will find the laboratory manual to be a useful tool
in the process of learning PSPICE and all of its functions.