radiocom.kunsan.ac.kr lecture malvino ch4 exam

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제4장 학습문제

제4장 Diode Circuits

Self Test

1. If N1/N2=2, and the primary voltage is 120V, what is the secondary voltage?

a. 0Vb. 30Vc. 60Vd. 480V

2. In a step-down transformer, which is larger?

a. primary voltageb. Secondary voltagec. Neitherd. No answer possible

3. A transformer has a turns tario of 2:1. What is the peak secondary voltage if 115Vrms is applied to the primary winding?

a. 57.5Vb. 81.3Vc. 230Vd. 325V

4. With a half-wave rectified voltage across the load resistor, load current flows for what part of a cycle?

a. 0°b. 90°c. 180°d. 360°

5. Suppose line voltage may be as low as 105Vrms or as high as 125Vrms in a half-wave rectifier. With a 5:1 step-down transformer,

the minimum peak load voltage is closest to

a. 21Vb. 25Vc. 29.7Vd. 35.4V

6. The voltage out of a bridge rectifier is a

a. Half-wave signalb. Full-wave signalc. Bridge-rectified signald. Sine wave

7. If the line voltage is 115Vrms, a turns ratio of 5:1 means the rms secondary voltage is closest to

a. 15Vb. 23Vc. 30Vd. 35V

8. What is the peak load voltage in a full-wave rectifier if the secondary voltage is 20Vrms?

a. 0Vb. 0.7Vc. 14.1Vd. 28.3V

9. We want a peak load voltage of 40V out of a bridge rectifier. What is the approximate rms value of secondary voltage?

a. 0V

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b. 14.4Vc. 28.3Vd. 56.6V

10. With a full-wave rectified voltage across the load resistor, load current flows for what part of a cycle?

a. 0°b. 90°c. 180°d. 360°

11. What is the peak load voltage out of a bridge rectifier for a secondary voltage of 12.6Vrms?(Use second approximation.)

a. 7.5Vb. 16.4Vc. 17.8Vd. 19.2V

12. If line frequency is 60Hz, the output frequency of a half-wave rectifier is

a. 30Hzb. 60Hzc. 120Hzd. 240Hz

13. If line frequency is 60Hz, the output frequency of a bridge rectifier is

a. 30Hzb. 60Hzc. 120Hzd. 240Hz

14. With the same secondary voltage and filter, which has the most ripple?

a. Half-wave rectifierb. Full-wave rectifierc. Bridge rectifierd. Impossible to say

15. With the same secondary voltage and filter, which produces the leaset load voltage?


16. If the filtered load current is 10mA, which of the following has a diode current of 10mA?


17. If the load current is 5mA and the filter capacitance is 1000uF, what is the peak-to-peak ripple out of a bridge rectifier?

a. 21.3pVb. 56.3nVc. 21.3mVd. 41.7mV

18. The diodes in a bridge rectifier each have a maximum dc current rating of 2A. This means the dc load current can have amaximum value of

a. 1Ab. 2Ac. 4Ad. 8A



19. What is the PIV across each diode of a bridge rectifier with a secondary voltage of 20Vrms?

a. 14.1Vb. 20Vc. 28.3Vd. 34V

20. If the secondary voltage increases in a bridge rectifier with a capacitor-input filter, the load voltage will

a. Decreaseb. Stay the samec. Increased. None of these

21. If the filter capacitance is increased, the ripple will

a. Decreaseb. Stay the samec. Increased. None of these

22. A circuit that removes positive or negative parts of a waveform is called a

a. Clamperb. Clipperc. Diode clampd. Limiter

23. A circuit that adds a positive or negative dc voltage to an input sine-wave is called a

a. Clamperb. Clipperc. Diode clampd. Limiter

24. For a clamper circuit to operate properly, its RLC time constant should be

a. Equal to the period T of the signalb. >10 times the period T of the signalc. >100 times the period T of the signald. <10 times the period T of the signal

25. Voltage multipliers are circuits best used to produce

a. Low voltage and low currentb. Low voltage and high currentc. High voltage and low currentd. High voltage and high current

Self Test Answers

문제번호 answer 문제번호 answer 문제번호 answer 문제번호 answer 문제번호 answer

1 b 2 a 3 b 4 c 5 c

6 b 7 b 8 c 9 c 10 d

11 b 12 b 13 c 14 a 15 b

16 a 17 d 18 c 19 c 20 c

21 a 22 b 23 a 24 c 25 c

Problems

1. What is the peak output voltage in Fig.4-36a if the diode is ideal?The average value? The dc value? Sketch the output waveform.



2. Repeat the preceding problem for Fig.4-36b.

3. What is the peak output voltage in Fig.4-36a using the second approximation of a diode?

The average value?The dc value?Sketch the output waveform.

4. Repeat the preceding problem for Fig.4-36b.

5. If a transformwer has a turns ratio of 6:1,

what is the rms secondary value?The peak secondary voltage?Assume a primary voltage of 120Vrms.

6. If a transformwer has a turns ratio of 1:12,

what is the rms secondary value?The peak secondary voltage?Assume a primary voltage of 120Vrms.

7. Calculate the peak output voltage and the dc output voltage in Fig.4-37 using an ideal diode.

8. Calculate the peak output voltage and the dc output voltage in Fig.4-37 using the second approximation.

9. A center-tapped transformer with 120V input has a turns ratio of 4:1.

What is the rms voltage across the upper half of the secondary winding?The peak voltage?What is the rms voltage across the lower half of the secondary winding?

10. What is the peak output voltage in Fig.4-38 if the diodes are ideal?




11. Repeat the preceding problem using the second approximation.

12. In Fig.4-39, what is the peak output voltage if the diodes are ideal?


13. repeat the preceding problem using the second approximation.

14. If the line voltage in Fig.4-39 varies from 105 to 125Vrms, what is the minimum dc output voltage? The maximum?

15. A half-wave signal with a peak of 20V is gthe input to a choke-input filter. If XL=1kΩ and XC=25Ω, what is the approximate peak-

to-peak ripple across the capacitor?

16. A full-wave signal with a peak of 14V is gthe input to a choke-input filter. If XL=2kΩ and XC=50Ω, what is the approximate peak-

to-peak ripple across the capacitor?

17. What is the dc output voltage and ripple in Fig.4-40a?

Sketch the output waveform.



18. In Fig.4-40b, calculate the dc output voltage and ripple.

19. What happens to the ripple in Fig.4-40a if the capacitance value is reduced to half?

20. In Fig.4-40a, what happens to the ripple if the resistance is reduced to 500Ω?

21. What is the dc output voltage in Fig.4-41?

The ripple?Sketch the output waveform.



22. If the line voltage decreases to 105V in Fig.4-41, what is the dc output voltage?

23. What is the peak inverse voltage in Fig.4-41?

24. If the turns ratio changes to 3:1 in Fig.4-41, what is the peak inverse voltage?

25. An F-25X replaces the transformer of Fig.4-41.

what is the approximate peak voltage across the secondary winding?The approximate dc output voltage?Is the transformer being operated at its rated output current?Will the dc output voltage be higher or lower than normal?

26. What is the primary current in Fig.4-41?

27. What is the average current through each diode in Fig.4-40a and 4-40b?

28. What is the average current through each diode of Fig.4-41?

29. If the filter capacitor in Fig.4-41 is open, what is the dc output voltage?

30. If only one diode in Fig.4-41 is open, what is the dc output voltage?

31. If somebody builds the circuit of Fig.4-41 with the electrolytic capacitor reversed, what kind of trouble is likely to happen?

32. If the load resistance of Fig.4-41 opens, what changes will occur in the output voltage?

33. In fig.4-42a, sketch the output waveform.

What is the maximum positive voltage?The maximum negative?



34. Repeat the preceding problem for Fig.4-42b

35. The diode clamp of Fig.4-42c protects the sensitive circuit. What are the limiting levels?

36. In Fig.4-42d, what is maximum positive output voltage?

Maximum negative output voltage?Sketch the output waveform.

37. If the sine wave of Fig.4-42d is only 20mV, the circuit will act as a diode clamp instead of a biased clipper. In this case, what is the



protected range of output voltage?

38. In fig4-43a, sketch the output waveform.

What is the maximum positive voltage?The maximum negative?

39. Repeat the preceding problem for Fig.4-43b

40. Sketch the output waveform of the clamper and final output in Fig.4-43c.

What is the dc output voltage with ideal diodes?To a second approximation?

41. Calculate the dc output voltage in Fig.4-44a.



42. What is the trippler output in Fig.4-44b?

43. What is the quadrupler output in Fig.4-44c?

Critical Thinking

44. If one of the diodes in Fig.4-41 shorts, what will the probable result be?



45. The power supply of Fig.4-45 has two output voltages. What are their approximate values?

46. A surge resistor of 4.7Ω is added to Fig.4-45. what is the maximum possible value of surge current?

47. A full-wave voltage has a peak value of 15V. Somebody hands you a book of trigonometry tables, so that you can look up tha valueof a sine wave at intgervals of 1°. Describe how you could prove that the average value of a full-wave signal is 63.6 percent of the peakvalue.

48. For the switch position shown in Fig.4-46, what is the output voltage?

If the switch is thrown to the other position, what is the output voltage?

49. If Vin is 40Vrms in Fig.4-47 and the time constant RC is very large compared to the period of the source voltage, what does Vout

equal? Why?



Troubleshooting

50. Figure 4-48 shows a bridge rectifier circuit with normal circuit values and eight troubles - T1∼T8. Find all eight troubles.

troubleshooting

V1 V2 VL VR f RL C1 F1

ok 115 12.7 18 0.3 120 1k ok ok

T1 115 12.7 11.4 18 120 1k ∞ ok

T2 115 12.7 17.7 0.6 60 1k ok ok

T3 0 0 0 0 0 0 ok ∞

T4 115 12.7 0 0 0 1k ok ok

T5 0 0 0 0 0 1k ok ∞

T6 115 12.7 18 0 0 ∞ ok ok

T7 115 0 0 0 0 1k ok ok

T8 0 0 0 0 0 1k 0 ∞

Job Interview Questions

1.Here's a pencil and paper. Tell me how a bridge rectifier with a capacitor-input filgter works. In your explanation, I expect to see a schematic diagram andwaveforms at different points in the circuit.

2.Suppose there's a bridge rectifier with a capacitor-input filter on my lab bench. It's not working. Tell me how you would troubleshoot it. Indicate the kind ofinstruments you would use and how you would isolate common troubles.



3. Excessive current or voltage can destroy the diodes in a power supply. Draw a bridge rectifier with a capacitor-input filter and tell me how current or voltagecan destroy a diode. do the same for excessive reverse voltage.

4. Tell me everything you know about clippers, clampers, and diode clamps. Show me typical waveforms, clipping levels, clamping levels, and protection levels.

5.I want you to tell me how a peak-to-peak detector works. Then, I want you to tell me in what ways a voltage doubler is similar to a peak-to-peak detectorand in what ways it differs from a peak-to-peak detector.

6.What is the advantage of using a bridge rectifier in a power supply as opposed to using a half-wave or a full-wave rectifier? Why is the bridge rectifier moreefficient than the others?

7. In what power-supply application might I prefer to use an LC-type filter instead of the RC-type? Why?

8. What is the relationship between a half-wave rectifier and a full-wave rectifier?

9. Under what circumstances is it appropriate to use a voltage multiplier as part of a power supply?

10.A dc power supply is supposed to have an output of 5V. You measure exactly 5V out of this supply using a dc voltmeter. Is it possible for the power supplyto still have a problem? If so, how would you troubleshoot it?

11. Why would I use a voltage multiplier instead of a transformer with a higher turns ratio and an ordinary rectifier?

12. List the advantages and disadvantages of the RC filter and LC filter.

13.While troubleshooting a power supply, you find a resistor burned black. A measurement shows that the resistor is open. Should you replace the resistor andturn the supply back on? If not, what should you do next?

14. For a bridge rectifier, list three possible faults and what the symptoms of each would be.

사용한 프로그램 예 제

MultiSim

변압기 권선비

반파 정류회로

전파 정류회로

브리지 전파 정류회로

양 클램퍼 회로

음 클램퍼 회로

양 클리퍼 회로

음 클리퍼 회로

2배압 정류기 회로 피크-피크 검출기 회로

3배압 정류기 회로

4배압 정류기 회로

OrCAD/PSpice

변압기 권선비

반파 정류회로

전파 정류회로

브리지 전파 정류회로

양 클램퍼 회로

음 클램퍼 회로

양 클리퍼 회로

음 클리퍼 회로

피크-피크 검출기 회로

diode datasheet 1N4001-1N4007 Datasheet

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radiocom.kunsan.ac.kr lecture malvino ch4 exam

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