lab4_203

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University of Massachusetts, Boston *

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365

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Electrical Engineering

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Jan 9, 2024

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pdf

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ENGIN 365 Lab 4: Diode Rectifier Circuits Objective: The purpose of this laboratory is to use basic diodes in circuits used to convert AC to DC. List of Equipment: 1. Tektronix AFG3022C Dual Channel Arbitrary Function Generator 2. Tektronix DPO 2004B Digital Oscilloscope 3. Tektronix DMM 4020 Digital Multimeter 4. Keithley 2230 Triple Channel DC Power Supply 5. Proto-board 6. Lab Component Kit 7. 1N4005 Diode (from component kit) 8. 1N5226 Zener Diode (from component kit) Introduction: The single most common application for diodes is in converting alternating current, AC, to direct current, DC, in a process called rectification. In this lab we will explore how to utilize the 1N4005 diode in circuits that perform rectification of AC voltages to DC voltages. Generally, AC voltage is taken from the wall outlet, where the voltage is then stepped down by using an AC transformer, as shown in Figure 1. After the transformer, a rectifier circuit, typically composed of 1 to 4 diodes, is used to convert the sinusoidal waveform to a pulsating signal with the same polarity. A filter circuit is then used to reduce the ripple of the pulsating signal to produce a nearly constant DC output. An additional voltage regulation stage is used to produce a usable DC voltage output with minimal fluctuations. Figure 1. Typical DC power supply. Pre-laboratory Exercise: 1. Half-wave rectifier a. Simulate in LTSPICE the half wave rectifier circuit shown in Figure 2; the AC source is an 8 V amplitude (16 V p-p ), 1 kHz sine wave. b. Determine the peak voltage across the 1 kΩ load resistor . What is the voltage drop across the diode at the peak? c. Determine the time-average DC voltage of this rectifier circuit. d. Add a 47 µF capacitor in parallel with the 1kΩ load resistor, run the simulation and measure the ripple voltage. Compare with theoretical value 𝑉 𝑟 = 𝑉 𝑝 (𝑓𝑅𝐶) ⁄ e. What is the frequency of the ripple?

2. Full-wave rectifier a. Simulate in LTSPICE the full-wave rectifier circuit shown in Figure 3; the AC source is an 8 V amplitude (16 V p-p ), 60 Hz sine wave. The diodes in Figure 3 are the D1N4002 diodes. b. Determine the peak voltage across the 1 kΩ load resistor. Wha t is the voltage drop across each diode in the bridge rectifier at the peak? c. Determine the time average DC voltage of this rectifier circuit. d. Add a 1000 µF capacitor in parallel with the 1kΩ load resistor, run the simulation and measure the ripple voltage. Compare with theoretical value 𝑉 𝑟 = 𝑉 𝑝 (2𝑓𝑅𝐶) ⁄ e. What is the frequency of the ripple? Lab Measurements: 1. Half-wave rectifier a. Assemble the circuit shown in Figure 2 with the 1N4005 diode. Using the function generator, supply an 8 V amplitude (16 V p-p ), 1 kHz sine wave to the circuit. b. Measure the voltage across the 1 kΩ load resistor. c. Determine the peak voltage and current across the load resistor. Compare the peak voltage with the theoretical value that you calculated and from the LTSPICE simulations in the pre-lab. d. Add a 47 µF electrolytic capacitor in parallel with the 1 kΩ load resistor. Measure the amplitude of the ripple and compare with the theoretical value from the pre- lab. Determine the frequency of the ripple voltage. e. What can be done to the circuit to reduce the ripple by a factor of 20? Test your answer by modifying the circuit and measuring the ripple again and compare with the theoretical value. f. Discuss your measurement results in the lab report. Figure 2. Half-wave rectifier.

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