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.