Switching Power Supplies MCQs

1. What is the main advantage of a switching power supply compared to a linear power supply?
A) Higher efficiency
B) Lower cost
C) Smaller size
D) Lower electromagnetic interference
Answer: A) Higher efficiency

2. Which component in a switching power supply is responsible for converting DC voltage to high-frequency AC voltage?
A) Transformer
B) Diode
C) Capacitor
D) Inductor
Answer: A) Transformer

3. The duty cycle of a switching power supply refers to:
A) The ratio of on-time to total period
B) The maximum current it can supply
C) The frequency of the switching waveform
D) The efficiency of the power conversion
Answer: A) The ratio of on-time to total period

4. Which topology is commonly used in low-power switching power supplies due to its simplicity?
A) Flyback
B) Push-pull
C) Forward
D) Half-bridge
Answer: A) Flyback

5. The term “ripple voltage” in a switching power supply refers to:
A) The AC component superimposed on the DC output
B) The voltage drop across the diode
C) The voltage loss in the inductor
D) The voltage across the switching transistor
Answer: A) The AC component superimposed on the DC output

6. Which parameter is crucial for determining the maximum current output of a switching power supply?
A) Input voltage range
B) Output voltage regulation
C) Output capacitance
D) Power transistor rating
Answer: D) Power transistor rating

7. In a forward converter topology, which component is used to store energy during the switching cycle?
A) Transformer
B) Diode
C) Capacitor
D) Inductor
Answer: D) Inductor

8. The purpose of the snubber circuit in a switching power supply is to:
A) Filter out high-frequency noise
B) Protect the transformer from overcurrent
C) Prevent voltage spikes
D) Increase efficiency
Answer: C) Prevent voltage spikes

9. Which type of switching power supply topology typically provides galvanic isolation between input and output?
A) Buck
B) Boost
C) Flyback
D) SEPIC
Answer: C) Flyback

10. Which control method is commonly used in modern switching power supplies to regulate output voltage?
A) Pulse-width modulation (PWM)
B) Phase-locked loop (PLL)
C) Frequency modulation (FM)
D) Amplitude modulation (AM)
Answer: A) Pulse-width modulation (PWM)

11. The switching frequency of a power supply is primarily determined by:
A) The load current
B) The input voltage
C) The power transistor
D) The controller IC
Answer: D) The controller IC

12. A switching power supply operates in discontinuous conduction mode (DCM) when:
A) The load current is very high
B) The output voltage is regulated
C) The inductor current drops to zero during the switching cycle
D) The switching transistor is turned off
Answer: C) The inductor current drops to zero during the switching cycle

13. Which parameter is NOT typically a disadvantage of switching power supplies?
A) EMI generation
B) Complexity
C) Ripple voltage
D) High cost
Answer: D) High cost

14. The main advantage of a flyback converter over a forward converter is:
A) Higher efficiency
B) Lower EMI
C) Simpler design
D) Multiple outputs
Answer: D) Multiple outputs

15. Which component is essential for energy storage and transfer in a boost converter?
A) Transformer
B) Diode
C) Capacitor
D) Inductor
Answer: D) Inductor

16. The efficiency of a switching power supply is calculated as:
A) (Output power – Input power) / Output power
B) (Output power + Input power) / Input power
C) (Output power / Input power) × 100%
D) (Input power / Output power) × 100%
Answer: C) (Output power / Input power) × 100%

17. Which topology is known for its bidirectional capability, making it suitable for applications requiring both step-up and step-down conversions?
A) Flyback
B) SEPIC
C) Buck-boost
D) Push-pull
Answer: C) Buck-boost

18. In a half-bridge converter, how many switches are used?
A) One
B) Two
C) Three
D) Four
Answer: B) Two

19. The term “soft start” in switching power supplies refers to:
A) Gradually ramping up the output voltage
B) Reducing the switching frequency
C) Adding a snubber circuit
D) Improving the efficiency at low loads
Answer: A) Gradually ramping up the output voltage

20. Which type of control loop is used to regulate the output voltage of a switching power supply?
A) Current feedback
B) Voltage feedback
C) Phase-locked loop
D) Frequency modulation
Answer: B) Voltage feedback

21. The main advantage of a resonant converter compared to traditional switching converters is:
A) Higher efficiency
B) Lower output ripple
C) Smaller size
D) Lower cost
Answer: A) Higher efficiency

22. Which type of switching power supply is typically used in battery-operated devices to step up or step down the voltage?
A) Buck
B) Boost
C) Flyback
D) Push-pull
Answer: B) Boost

23. The primary purpose of the input filter in a switching power supply is to:
A) Prevent output voltage spikes
B) Reduce conducted EMI
C) Improve power factor
D) Stabilize the output voltage
Answer: B) Reduce conducted EMI

24. Which parameter is critical in determining the maximum output power of a switching power supply?
A) Input voltage range
B) Output voltage regulation
C) Output current rating
D) Switching frequency
Answer: C) Output current rating

25. Which component is used to rectify the AC output of the transformer in a flyback converter?
A) Diode
B) Capacitor
C) Inductor
D) Transformer
Answer: A) Diode

26. Which topology allows for seamless transition between step-up and step-down conversions without a change in polarity?
A) Buck
B) Boost
C) Buck-boost
D) Flyback
Answer: C) Buck-boost

27. The term “load regulation” in a switching power supply refers to:
A) The ability to maintain constant output voltage despite changes in load
B) Minimizing electromagnetic interference
C) Maximizing efficiency at full load
D) Adjusting the duty cycle of the switching waveform
Answer: A) The ability to maintain constant output voltage despite changes in load

28. Which parameter indicates the ability of a switching power supply to maintain a constant output voltage with varying input voltage?
A) Line regulation
B) Load regulation
C) Efficiency
D) Ripple voltage
Answer: A) Line regulation

29. A buck-boost converter is capable of:
A) Stepping up voltage only
B) Stepping down voltage only
C) Both stepping up and stepping down voltage
D) Generating multiple output voltages simultaneously
Answer: C) Both stepping up and stepping down voltage

30. Which control method is used in resonant converters to achieve high efficiency?
A) PWM
B) Phase control
C) Zero voltage switching (ZVS)
D) Hysteresis control
Answer: C) Zero voltage switching (ZVS)

31. The term “power factor correction (PFC)” in switching power supplies refers to:
A) Maximizing the power output
B) Reducing harmonic distortion in the input current
C) Improving efficiency at light loads
D) Stabilizing the output voltage
Answer: B) Reducing harmonic distortion in the input current

32. Which topology is preferred in applications requiring high power output due to its ability to handle large currents?
A) Buck
B) Boost
C) Full-bridge
D) Flyback
Answer: C) Full-bridge

33. Which component in a switching power supply stores energy during the on-time of the switching transistor?
A) Transformer
B) Capacitor
C) Inductor
D) Diode
Answer: C) Inductor

34. The primary advantage of a phase-shifted full-bridge converter is:
A) Higher efficiency
B) Lower EMI
C) Better thermal management
D) Simpler control circuitry
Answer: B) Lower EMI

35. Which type of feedback is essential for stable operation in a switching power supply?
A) Voltage feedback
B) Current feedback
C) Phase feedback
D) Frequency feedback
Answer: A) Voltage feedback

36. The term “duty cycle” in a switching power supply refers to:
A) The percentage of time the switching transistor is on
B) The ratio of inductance to capacitance
C) The frequency of the switching waveform
D) The efficiency of power conversion
Answer: A) The percentage of time the switching transistor is on

37. Which topology is known for its ability to provide both positive and negative output voltages?
A) Buck
B) Boost
C) Cuk
D) SEPIC
Answer: C) Cuk

38. Which component is used to store energy in a push-pull converter?
A) Transformer
B) Diode
C) Capacitor
D) Inductor
Answer: D) Inductor

39. The main advantage of a synchronous rectification in a switching power supply is:
A) Lower cost
B) Higher efficiency
C) Smaller size
D) Improved line regulation
Answer: B) Higher efficiency

40. Which topology is suitable for applications requiring very high step-down ratios?
A) Buck
B) Boost
C) Flyback
D) Forward
Answer: C) Flyback

41. In a resonant converter, the resonant frequency is primarily determined by:
A) The load resistance
B) The switching frequency
C) The inductance and capacitance values
D) The output voltage
Answer: C) The inductance and capacitance values

42. Which type of control method is used in LLC resonant converters?
A) PWM
B) Phase-shift control
C) Hysteresis control
D) Frequency modulation
Answer: B) Phase-shift control

43. The term “dropout voltage” in a switching regulator refers to:
A) The difference between the input and output voltages
B) The voltage loss across the inductor
C) The ripple voltage at the output
D) The maximum load current
Answer: A) The difference between the input and output voltages

44. Which topology is known for its ability to provide high efficiency at a wide range of input voltages?
A) Boost
B) SEPIC
C) Buck
D) Flyback
Answer: B) SEPIC

45. Which component is used to clamp voltage spikes in a switching power supply?
A) Zener diode
B) Varistor
C) MOV (Metal Oxide Varistor)
D) Schottky diode
Answer: C) MOV (Metal Oxide Varistor)

46. The term “steady-state error” in a switching power supply refers to:
A) The initial voltage overshoot upon power-on
B) The difference between actual and desired output voltage after reaching equilibrium
C) The time required for the output voltage to stabilize
D) The maximum load current the supply can handle
Answer: B) The difference between actual and desired output voltage after reaching equilibrium

47. Which parameter is most affected by the operating temperature of a switching power supply?
A) Efficiency
B) Ripple voltage
C) Load regulation
D) Line regulation
Answer: A) Efficiency

48. The term “dropout regulator” typically refers to:
A) A linear regulator
B) A switching regulator
C) A resonant converter
D) A buck-boost converter
Answer: A) A linear regulator

49. Which topology is commonly used in applications where the input voltage can be higher or lower than the desired output voltage?
A) Boost
B) Buck
C) SEPIC
D) Flyback
Answer: C) SEPIC

50. The term “dead time” in a switching power supply refers to:
A) The time period during which the transistor is off
B) The interval between two consecutive switching cycles
C) The time taken for the output voltage to stabilize
D) The delay in the control loop response
Answer: A) The time period during which the transistor is off

Switching Power Supplies MCQs

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