EET 3222 lab 7

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New York City College of Technology EET 3222 || Fall 2023 Lab #7 Discontinuous Buck Converter Prof. Fred bassali Jade Tse Date Due: November 26th, 2023

Table of Contents I. Objective … p. 1 II. Procedure … p. 1 III. Theoretical Calculations … p. 1 IV. Results … p. 2 V. Analysis … p. 3 VI. Conclusion … p. 4

Objective The objective of this lab experiment is to be able to simulate a forward converter circuit and compare them to out calculated results to see any difference. Procedure 1. Using Multisim, simulate the buck converter circuit (See attached) 2. Measure the output voltages for the duty ratios of D = 5% - 95% in 5% increments 3. Using Matlab, calculate the output voltages for the duty ratios of D = 5% - 95% in 5% increments (Use the appropriate equations for each case when the Buck converter is in continuous or discontinuous modes). 4. Using Multisim simulation find the value of the duty ratios of D for which is the mininimum value that the the current is still continuous and compare it with the theoretical value. 5. Plot the data point of paragraphs 2 and 3. (can use Matlab) 6. Measure peak-to-peak volatge ripple at D = 40% and compare it with theory Theoretical Calculations: ? = 40% ? 1 = −.4+ .4 2 +(8(200*10 −6 )/(20/10000) 2 =. 29 1 − ? = 1 −. 4 =. 6 1 − ? > ?1 𝑉 𝑜 = 𝑉 𝑠 ? ?+? 1 = 24 .4 .4+.29 = 13. 9

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△𝑉 𝑜 𝑉 𝑜 = 1−? 8𝐿?𝑓 = 1−.4 8(200*10 −6 )(1000*10 −6 )(10000 2 ) =. 375% ? = 80% 𝑉 𝑜 = 𝑉 𝑠 * ? = 24 *. 8 = 19. 2 Results: The following screenshots are imaged observed from oscilloscope by increasing the duty cycle from 0% to 95% with increments of 5% each. The top image is the current and the bottom screenshot shows the DC and DC component of the output voltage. D=5% D=10%

D=15% D=20% D=25%

D=30% D=35% D=40%

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D=45% D=50% D=55%

D=60% D=65% D=70%

D=75% D=80% D=85% D=90%

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D=95% Using Matlab: D 1-D D1 Current Vo (V) 0.05 0.95 0.4229 Discontinuous 2.5375 0.10 0.90 0.4000 Discontinuous 4.8000 0.15 0.85 0.3785 Discontinuous 6.8123 0.20 0.80 0.3583 Discontinuous 8.5982 0.25 0.75 0.3394 Discontinuous 10.1806 0.30 0.70 0.3217 Discontinuous 11.5812 0.35 0.65 0.3052 Discontinuous 12.8198 0.40 0.60 0.2899 Discontinuous 13.9151 0.45 0.55 0.2756 Discontinuous 14.8837 0.50 0.50 0.2623 Discontinuous 15.7409

0.55 0.45 0.2500 Discontinuous 16.5000 0.60 0.40 0.2385 Discontinuous 17.1732 0.65 0.35 0.2278 Discontinuous 17.7710 0.70 0.30 0.2179 Discontinuous 18.3028 0.75 0.25 0.2086 Discontinuous 18.7768 0.80 0.20 0.2000 Continuous 19.2000 0.85 0.15 0.1919 Continuous 20.4000 0.90 0.10 0.1844 Continuous 21.6000 0.95 0.05 0.1774 Continuous 22.8000 The duty ratios of D for which is the mininimum value that the the current is still continuous seems to be D=.8 or 80% duty cycle given this matlab result. Analysis: Looking at the output voltage at each duty cycle, our calculated values from matlab and the ones gained from multisim are pretty close with only a slight difference. Plotting the output voltage with their duty cycle we get these two graphs with the calculated values on the right, and the measured multisim results on the left

Comparing this two graphs, we can see the same similar trend up until a duty ratio of .8 where the trend seems to become a linear response. Our calculated duty ratio at 40% was .375%, the multisim result gave us about .294%. The percent difference is pretty substantial of about 22% when comparing the calculated result vs the simulated result. Conclusion: In conclusion, we were able to understand the property of a buck converter circuit and gain a deeper understanding of theoretical calculation vs simulated results for this converter. The results we gained showed that the theoretical followed closely similar results as the the simulated results with a bit of a discrepancy at duty cycle of 40%. Overall this lab gave a good understanding of buck converter.

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