3  Check List

This is the guide for your submission for the lab. The questions are repeated elsewhere though the lab document and collected here for your convenience.

Put all the answers, plots, and oscilloscope screenshots in a single PDF document and upload to Gradescope.

3.1 Tasks

3.1.1 Measuring Components

  1. Using the AD2 measure the capacitance and ESR of three capacitors: 16ZLH680MEFC10X12.5 (electrolytic) A758EK107M1CAAE018 (polymer electrolytic), CL31A106MAHNNNE (ceramic)
  2. (Post Lab) You are considering using the capacitors for output filtering of a boost converter with a 50% duty cycle and a 0.5A output current. Assume the inductor has negligible ripple. Which capacitor would provide the lowest voltage ripple at 10KHz? At 2MHz?
  3. (Post Lab) You need to select one of the capacitors for filtering the 120Hz ripple from a rectified AC transformer. Assuming you could use multiple of the (more costly) ceramic or polymer electrolytic capacitors to match the capacitance of the electrolytic capacitor, would the lower ESR of either of the capacitors lead to any significant benefit?

3.1.2 Capacitor Networks

  1. Draw the equivalent circuit diagram of the circuit shown in Figure 4.5, including the inductance of the copper tape traces and capacitor ESL.
  2. Construct the copper tape circuit shown in Figure 4.5. Any package size SMD ceramic capacitor can be used. For the polymer electrolytic capacitor use the part you used for the first part of the lab. Measure the impedance of the network with the AD2 from 1kHz to 10MHz and save the plot.
  3. From the measured impedance curve and resonant frequencies of your circuit calculate the values of the inductances in your equivalent circuit diagram.
  4. At what frequency does the capacitor network have the highest impedance compared to either capacitor in isolation? How many times higher is the impedance?
  5. What circuit values could you change to reduce the maximum impedance of the parallel resonant peak?

3.1.3 System Transfer Functions and Loop Stability

  1. Provide the plot of the measured TL431 and best fit modeled TL431 gain. What are your extracted values of \(K\), \(\omega_1\) and \(\omega_2\)?
  2. Using your model of the system find a capacitor value that causes the TL431 output to oscillate. What is the value of the capacitor? What is the modeled phase margin with this capacitor?
  3. Capture an oscilloscope waveform of the TL431 shunt regulator oscillating with a capacitive load. What is the frequency of oscillation? How does it compare to the modeled crossover frequency and why may it differ?
  4. Provide a picture of your copper tape circuits.
  5. (Post Lab) If you added a voltage divider between the cathode and reference pin of the TL431 to regulate at an output voltage greater than \(2.5~V\) how would this impact the crossover frequency of the open loop transfer function?

3.1.4 Feedback

Please provide feedback to help make future labs better! Anonymous feedback can be provided via this google form or included in your lab submission. Feedback is strongly appreciated but feel free to skip answering any feedback questions.

  1. Approximately how many hours did this lab take?
  2. Is there anything that you think should be removed from the lab? If so, what?
  3. Is there anything that you wish the lab included or elaborated more on? If so, what?
  4. What is the most useful thing that you learned from this lab?